Add database-library merge (#59)

Closes #48

Reviewed-on: https://git.wojciechkozlowski.eu/wojtek/musichoard/pulls/59

.gitignore

@@ -1,2 +1,3 @@
 /target
 /codecov
+database.json

src/database/json/mod.rs

@@ -6,13 +6,19 @@ use serde::Serialize;
 #[cfg(test)]
 use mockall::automock;
 
-use super::{Error, IDatabase};
+use super::{IDatabase, LoadError, SaveError};
 
 pub mod backend;
 
-impl From<serde_json::Error> for Error {
-    fn from(err: serde_json::Error) -> Error {
-        Error::SerDeError(err.to_string())
+impl From<serde_json::Error> for LoadError {
+    fn from(err: serde_json::Error) -> LoadError {
+        LoadError::SerDeError(err.to_string())
+    }
+}
+
+impl From<serde_json::Error> for SaveError {
+    fn from(err: serde_json::Error) -> SaveError {
+        SaveError::SerDeError(err.to_string())
     }
 }
 
@@ -40,13 +46,13 @@ impl<JDB: IJsonDatabaseBackend> JsonDatabase<JDB> {
 }
 
 impl<JDB: IJsonDatabaseBackend> IDatabase for JsonDatabase<JDB> {
-    fn read<D: DeserializeOwned>(&self, collection: &mut D) -> Result<(), Error> {
+    fn load<D: DeserializeOwned>(&self, collection: &mut D) -> Result<(), LoadError> {
         let serialized = self.backend.read()?;
         *collection = serde_json::from_str(&serialized)?;
         Ok(())
     }
 
-    fn write<S: Serialize>(&mut self, collection: &S) -> Result<(), Error> {
+    fn save<S: Serialize>(&mut self, collection: &S) -> Result<(), SaveError> {
         let serialized = serde_json::to_string(&collection)?;
         self.backend.write(&serialized)?;
         Ok(())
@@ -61,7 +67,7 @@ mod tests {
 
     use super::*;
 
-    use crate::{tests::COLLECTION, Artist, ArtistId, Format};
+    use crate::{tests::COLLECTION, Artist, ArtistId, Collection, Format};
 
     fn artist_to_json(artist: &Artist) -> String {
         let album_artist = &artist.id.name;
@@ -73,8 +79,8 @@ mod tests {
 
             let mut tracks: Vec<String> = vec![];
             for track in album.tracks.iter() {
-                let track_number = track.number;
-                let track_title = &track.title;
+                let track_number = track.id.number;
+                let track_title = &track.id.title;
 
                 let mut track_artist: Vec<String> = vec![];
                 for artist in track.artist.iter() {
@@ -89,8 +95,7 @@ mod tests {
 
                 tracks.push(format!(
                     "{{\
-                     \"number\":{track_number},\
-                     \"title\":\"{track_title}\",\
+                     \"id\":{{\"number\":{track_number},\"title\":\"{track_title}\"}},\
                      \"artist\":[{track_artist}],\
                      \"quality\":{{\"format\":\"{track_format}\",\"bitrate\":{track_bitrate}}}\
                      }}"
@@ -128,7 +133,7 @@ mod tests {
     }
 
     #[test]
-    fn write() {
+    fn save() {
         let write_data = COLLECTION.to_owned();
         let input = artists_to_json(&write_data);
 
@@ -139,11 +144,11 @@ mod tests {
             .times(1)
             .return_once(|_| Ok(()));
 
-        JsonDatabase::new(backend).write(&write_data).unwrap();
+        JsonDatabase::new(backend).save(&write_data).unwrap();
     }
 
     #[test]
-    fn read() {
+    fn load() {
         let expected = COLLECTION.to_owned();
         let result = Ok(artists_to_json(&expected));
 
@@ -151,7 +156,7 @@ mod tests {
         backend.expect_read().times(1).return_once(|| result);
 
         let mut read_data: Vec<Artist> = vec![];
-        JsonDatabase::new(backend).read(&mut read_data).unwrap();
+        JsonDatabase::new(backend).load(&mut read_data).unwrap();
 
         assert_eq!(read_data, expected);
     }
@@ -174,14 +179,25 @@ mod tests {
 
         let write_data = COLLECTION.to_owned();
         let mut read_data: Vec<Artist> = vec![];
-        database.write(&write_data).unwrap();
-        database.read(&mut read_data).unwrap();
+        database.save(&write_data).unwrap();
+        database.load(&mut read_data).unwrap();
 
         assert_eq!(write_data, read_data);
     }
 
     #[test]
-    fn errors() {
+    fn load_errors() {
+        let json = String::from("");
+        let serde_err = serde_json::from_str::<Collection>(&json);
+        assert!(serde_err.is_err());
+
+        let serde_err: LoadError = serde_err.unwrap_err().into();
+        assert!(!serde_err.to_string().is_empty());
+        assert!(!format!("{:?}", serde_err).is_empty());
+    }
+
+    #[test]
+    fn save_errors() {
         let mut object = HashMap::<ArtistId, String>::new();
         object.insert(
             ArtistId {
@@ -192,7 +208,7 @@ mod tests {
         let serde_err = serde_json::to_string(&object);
         assert!(serde_err.is_err());
 
-        let serde_err: Error = serde_err.unwrap_err().into();
+        let serde_err: SaveError = serde_err.unwrap_err().into();
         assert!(!serde_err.to_string().is_empty());
         assert!(!format!("{:?}", serde_err).is_empty());
     }

src/database/mod.rs

@@ -13,36 +13,62 @@ pub mod json;
 /// Trait for interacting with the database.
 #[cfg_attr(test, automock)]
 pub trait IDatabase {
-    /// Read collection from the database.
-    fn read<D: DeserializeOwned + 'static>(&self, collection: &mut D) -> Result<(), Error>;
+    /// Load collection from the database.
+    fn load<D: DeserializeOwned + 'static>(&self, collection: &mut D) -> Result<(), LoadError>;
 
-    /// Write collection to the database.
-    fn write<S: Serialize + 'static>(&mut self, collection: &S) -> Result<(), Error>;
+    /// Save collection to the database.
+    fn save<S: Serialize + 'static>(&mut self, collection: &S) -> Result<(), SaveError>;
 }
 
 /// Error type for database calls.
 #[derive(Debug)]
-pub enum Error {
-    /// The database experienced an I/O error.
+pub enum LoadError {
+    /// The database experienced an I/O read error.
     IoError(String),
-    /// The database experienced a (de)serialisation error.
+    /// The database experienced a deserialisation error.
     SerDeError(String),
 }
 
-impl fmt::Display for Error {
+impl fmt::Display for LoadError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
-            Self::IoError(ref s) => write!(f, "the database experienced an I/O error: {s}"),
+            Self::IoError(ref s) => write!(f, "the database experienced an I/O read error: {s}"),
             Self::SerDeError(ref s) => {
-                write!(f, "the database experienced a (de)serialisation error: {s}")
+                write!(f, "the database experienced a deserialisation error: {s}")
             }
         }
     }
 }
 
-impl From<std::io::Error> for Error {
-    fn from(err: std::io::Error) -> Error {
-        Error::IoError(err.to_string())
+impl From<std::io::Error> for LoadError {
+    fn from(err: std::io::Error) -> LoadError {
+        LoadError::IoError(err.to_string())
+    }
+}
+
+/// Error type for database calls.
+#[derive(Debug)]
+pub enum SaveError {
+    /// The database experienced an I/O write error.
+    IoError(String),
+    /// The database experienced a serialisation error.
+    SerDeError(String),
+}
+
+impl fmt::Display for SaveError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Self::IoError(ref s) => write!(f, "the database experienced an I/O write error: {s}"),
+            Self::SerDeError(ref s) => {
+                write!(f, "the database experienced a serialisation error: {s}")
+            }
+        }
+    }
+}
+
+impl From<std::io::Error> for SaveError {
+    fn from(err: std::io::Error) -> SaveError {
+        SaveError::IoError(err.to_string())
     }
 }
 
@@ -50,11 +76,15 @@ impl From<std::io::Error> for Error {
 mod tests {
     use std::io;
 
-    use super::Error;
+    use super::{LoadError, SaveError};
 
     #[test]
     fn errors() {
-        let io_err: Error = io::Error::new(io::ErrorKind::Interrupted, "error").into();
+        let io_err: LoadError = io::Error::new(io::ErrorKind::Interrupted, "error").into();
+        assert!(!io_err.to_string().is_empty());
+        assert!(!format!("{:?}", io_err).is_empty());
+
+        let io_err: SaveError = io::Error::new(io::ErrorKind::Interrupted, "error").into();
         assert!(!io_err.to_string().is_empty());
         assert!(!format!("{:?}", io_err).is_empty());
     }

src/lib.rs

@@ -3,10 +3,16 @@
 pub mod database;
 pub mod library;
 
-use std::fmt;
+use std::{
+    cmp::Ordering,
+    collections::{HashMap, HashSet},
+    fmt,
+    iter::Peekable,
+    mem,
+};
 
 use database::IDatabase;
-use library::{ILibrary, Query};
+use library::{ILibrary, Item, Query};
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
@@ -27,17 +33,42 @@ pub struct Quality {
     pub bitrate: u32,
 }
 
+/// The track identifier.
+#[derive(Clone, Debug, Deserialize, Serialize, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct TrackId {
+    pub number: u32,
+    pub title: String,
+}
+
 /// A single track on an album.
 #[derive(Clone, Debug, Deserialize, Serialize, PartialEq, Eq)]
 pub struct Track {
-    pub number: u32,
-    pub title: String,
+    pub id: TrackId,
     pub artist: Vec<String>,
     pub quality: Quality,
 }
 
+impl PartialOrd for Track {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        self.id.partial_cmp(&other.id)
+    }
+}
+
+impl Ord for Track {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.id.cmp(&other.id)
+    }
+}
+
+impl Merge for Track {
+    fn merge(self, other: Self) -> Self {
+        assert_eq!(self.id, other.id);
+        self
+    }
+}
+
 /// The album identifier.
-#[derive(Clone, Debug, Deserialize, Serialize, PartialEq, Eq, Hash)]
+#[derive(Clone, Debug, Deserialize, Serialize, PartialEq, PartialOrd, Ord, Eq, Hash)]
 pub struct AlbumId {
     pub year: u32,
     pub title: String,
@@ -50,8 +81,28 @@ pub struct Album {
     pub tracks: Vec<Track>,
 }
 
+impl PartialOrd for Album {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        self.id.partial_cmp(&other.id)
+    }
+}
+
+impl Ord for Album {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.id.cmp(&other.id)
+    }
+}
+
+impl Merge for Album {
+    fn merge(mut self, other: Self) -> Self {
+        assert_eq!(self.id, other.id);
+        self.tracks = MergeSorted::new(self.tracks.into_iter(), other.tracks.into_iter()).collect();
+        self
+    }
+}
+
 /// The artist identifier.
-#[derive(Clone, Debug, Deserialize, Serialize, PartialEq, Eq, Hash)]
+#[derive(Clone, Debug, Deserialize, Serialize, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct ArtistId {
     pub name: String,
 }
@@ -63,9 +114,79 @@ pub struct Artist {
     pub albums: Vec<Album>,
 }
 
+impl PartialOrd for Artist {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        self.id.partial_cmp(&other.id)
+    }
+}
+
+impl Ord for Artist {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.id.cmp(&other.id)
+    }
+}
+
+impl Merge for Artist {
+    fn merge(mut self, other: Self) -> Self {
+        assert_eq!(self.id, other.id);
+        self.albums = MergeSorted::new(self.albums.into_iter(), other.albums.into_iter()).collect();
+        self
+    }
+}
+
 /// The collection type. Currently, a collection is a list of artists.
 pub type Collection = Vec<Artist>;
 
+trait Merge {
+    fn merge(self, other: Self) -> Self;
+}
+
+struct MergeSorted<L, R>
+where
+    L: Iterator<Item = R::Item>,
+    R: Iterator,
+{
+    left: Peekable<L>,
+    right: Peekable<R>,
+}
+
+impl<L, R> MergeSorted<L, R>
+where
+    L: Iterator<Item = R::Item>,
+    R: Iterator,
+{
+    fn new(left: L, right: R) -> MergeSorted<L, R> {
+        MergeSorted {
+            left: left.peekable(),
+            right: right.peekable(),
+        }
+    }
+}
+
+impl<L, R> Iterator for MergeSorted<L, R>
+where
+    L: Iterator<Item = R::Item>,
+    R: Iterator,
+    L::Item: Ord + Merge,
+{
+    type Item = L::Item;
+
+    fn next(&mut self) -> Option<L::Item> {
+        let which = match (self.left.peek(), self.right.peek()) {
+            (Some(l), Some(r)) => l.cmp(r),
+            (Some(_), None) => Ordering::Less,
+            (None, Some(_)) => Ordering::Greater,
+            (None, None) => return None,
+        };
+
+        match which {
+            Ordering::Less => self.left.next(),
+            Ordering::Equal => Some(self.left.next().unwrap().merge(self.right.next().unwrap())),
+            Ordering::Greater => self.right.next(),
+        }
+    }
+}
+
 /// Error type for `musichoard`.
 #[derive(Debug, PartialEq, Eq)]
 pub enum Error {
@@ -92,8 +213,14 @@ impl From<library::Error> for Error {
     }
 }
 
-impl From<database::Error> for Error {
-    fn from(err: database::Error) -> Error {
+impl From<database::LoadError> for Error {
+    fn from(err: database::LoadError) -> Error {
+        Error::DatabaseError(err.to_string())
+    }
+}
+
+impl From<database::SaveError> for Error {
+    fn from(err: database::SaveError) -> Error {
         Error::DatabaseError(err.to_string())
     }
 }
@@ -117,18 +244,119 @@ impl<LIB: ILibrary, DB: IDatabase> MusicHoard<LIB, DB> {
     }
 
     pub fn rescan_library(&mut self) -> Result<(), Error> {
-        self.collection = self.library.list(&Query::new())?;
+        let items = self.library.list(&Query::new())?;
+        let mut library = Self::items_to_artists(items);
+        Self::sort(&mut library);
+
+        let collection = mem::take(&mut self.collection);
+        self.collection = Self::merge(library, collection);
+
+        Ok(())
+    }
+
+    pub fn load_from_database(&mut self) -> Result<(), Error> {
+        let mut database: Collection = vec![];
+        self.database.load(&mut database)?;
+        Self::sort(&mut database);
+
+        let collection = mem::take(&mut self.collection);
+        self.collection = Self::merge(collection, database);
+
         Ok(())
     }
 
     pub fn save_to_database(&mut self) -> Result<(), Error> {
-        self.database.write(&self.collection)?;
+        self.database.save(&self.collection)?;
         Ok(())
     }
 
     pub fn get_collection(&self) -> &Collection {
         &self.collection
     }
+
+    fn sort(collection: &mut [Artist]) {
+        collection.sort_unstable();
+        for artist in collection.iter_mut() {
+            artist.albums.sort_unstable();
+            for album in artist.albums.iter_mut() {
+                album.tracks.sort_unstable();
+            }
+        }
+    }
+
+    fn merge(primary: Vec<Artist>, secondary: Vec<Artist>) -> Vec<Artist> {
+        MergeSorted::new(primary.into_iter(), secondary.into_iter()).collect()
+    }
+
+    fn items_to_artists(items: Vec<Item>) -> Vec<Artist> {
+        let mut artists: Vec<Artist> = vec![];
+        let mut album_ids = HashMap::<ArtistId, HashSet<AlbumId>>::new();
+
+        for item in items.into_iter() {
+            let artist_id = ArtistId {
+                name: item.album_artist,
+            };
+
+            let album_id = AlbumId {
+                year: item.album_year,
+                title: item.album_title,
+            };
+
+            let track = Track {
+                id: TrackId {
+                    number: item.track_number,
+                    title: item.track_title,
+                },
+                artist: item.track_artist,
+                quality: Quality {
+                    format: item.track_format,
+                    bitrate: item.track_bitrate,
+                },
+            };
+
+            let artist = if album_ids.contains_key(&artist_id) {
+                // Assume results are in some order which means they will likely be grouped by
+                // artist. Therefore, we look from the back since the last inserted artist is most
+                // likely the one we are looking for.
+                artists
+                    .iter_mut()
+                    .rev()
+                    .find(|a| a.id == artist_id)
+                    .unwrap()
+            } else {
+                album_ids.insert(artist_id.clone(), HashSet::<AlbumId>::new());
+                artists.push(Artist {
+                    id: artist_id.clone(),
+                    albums: vec![],
+                });
+                artists.last_mut().unwrap()
+            };
+
+            if album_ids[&artist_id].contains(&album_id) {
+                // Assume results are in some order which means they will likely be grouped by
+                // album. Therefore, we look from the back since the last inserted album is most
+                // likely the one we are looking for.
+                let album = artist
+                    .albums
+                    .iter_mut()
+                    .rev()
+                    .find(|a| a.id == album_id)
+                    .unwrap();
+                album.tracks.push(track);
+            } else {
+                album_ids
+                    .get_mut(&artist_id)
+                    .unwrap()
+                    .insert(album_id.clone());
+                artist.albums.push(Album {
+                    id: album_id,
+                    tracks: vec![track],
+                });
+            }
+        }
+
+        artists
+    }
 }
 
 #[cfg(test)]
@@ -146,13 +374,245 @@ mod tests {
 
     pub static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| collection!());
 
+    pub fn artist_to_items(artist: &Artist) -> Vec<Item> {
+        let mut items = vec![];
+
+        for album in artist.albums.iter() {
+            for track in album.tracks.iter() {
+                items.push(Item {
+                    album_artist: artist.id.name.clone(),
+                    album_year: album.id.year,
+                    album_title: album.id.title.clone(),
+                    track_number: track.id.number,
+                    track_title: track.id.title.clone(),
+                    track_artist: track.artist.clone(),
+                    track_format: track.quality.format,
+                    track_bitrate: track.quality.bitrate,
+                });
+            }
+        }
+
+        items
+    }
+
+    pub fn artists_to_items(artists: &[Artist]) -> Vec<Item> {
+        let mut items = vec![];
+        for artist in artists.iter() {
+            items.append(&mut artist_to_items(artist));
+        }
+        items
+    }
+
     #[test]
-    fn read_get_write() {
+    fn merge_track() {
+        let left = Track {
+            id: TrackId {
+                number: 04,
+                title: String::from("a title"),
+            },
+            artist: vec![String::from("left artist")],
+            quality: Quality {
+                format: Format::Flac,
+                bitrate: 1411,
+            },
+        };
+        let right = Track {
+            id: left.id.clone(),
+            artist: vec![String::from("right artist")],
+            quality: Quality {
+                format: Format::Mp3,
+                bitrate: 320,
+            },
+        };
+
+        let merged = left.clone().merge(right);
+        assert_eq!(left, merged);
+    }
+
+    #[test]
+    fn merge_album_no_overlap() {
+        let left = COLLECTION[0].albums[0].to_owned();
+        let mut right = COLLECTION[0].albums[1].to_owned();
+        right.id = left.id.clone();
+
+        let mut expected = left.clone();
+        expected.tracks.append(&mut right.tracks.clone());
+        expected.tracks.sort_unstable();
+
+        let merged = left.clone().merge(right);
+        assert_eq!(expected, merged);
+    }
+
+    #[test]
+    fn merge_album_overlap() {
+        let mut left = COLLECTION[0].albums[0].to_owned();
+        let mut right = COLLECTION[0].albums[1].to_owned();
+        right.id = left.id.clone();
+        left.tracks.push(right.tracks[0].clone());
+        left.tracks.sort_unstable();
+
+        let mut expected = left.clone();
+        expected.tracks.append(&mut right.tracks.clone());
+        expected.tracks.sort_unstable();
+        expected.tracks.dedup();
+
+        let merged = left.clone().merge(right);
+        assert_eq!(expected, merged);
+    }
+
+    #[test]
+    fn merge_artist_no_overlap() {
+        let left = COLLECTION[0].to_owned();
+        let mut right = COLLECTION[1].to_owned();
+        right.id = left.id.clone();
+
+        let mut expected = left.clone();
+        expected.albums.append(&mut right.albums.clone());
+        expected.albums.sort_unstable();
+
+        let merged = left.clone().merge(right);
+        assert_eq!(expected, merged);
+    }
+
+    #[test]
+    fn merge_artist_overlap() {
+        let mut left = COLLECTION[0].to_owned();
+        let mut right = COLLECTION[1].to_owned();
+        right.id = left.id.clone();
+        left.albums.push(right.albums[0].clone());
+        left.albums.sort_unstable();
+
+        let mut expected = left.clone();
+        expected.albums.append(&mut right.albums.clone());
+        expected.albums.sort_unstable();
+        expected.albums.dedup();
+
+        let merged = left.clone().merge(right);
+        assert_eq!(expected, merged);
+    }
+
+    #[test]
+    fn merge_collection_no_overlap() {
+        let half: usize = COLLECTION.len() / 2;
+
+        let left = COLLECTION[..half].to_owned();
+        let right = COLLECTION[half..].to_owned();
+
+        let mut expected = COLLECTION.to_owned();
+        expected.sort_unstable();
+
+        let merged = MusicHoard::<MockILibrary, MockIDatabase>::merge(left.clone(), right);
+        assert_eq!(expected, merged);
+    }
+
+    #[test]
+    fn merge_collection_overlap() {
+        let half: usize = COLLECTION.len() / 2;
+
+        let left = COLLECTION[..(half + 1)].to_owned();
+        let right = COLLECTION[half..].to_owned();
+
+        let mut expected = COLLECTION.to_owned();
+        expected.sort_unstable();
+
+        let merged = MusicHoard::<MockILibrary, MockIDatabase>::merge(left.clone(), right);
+        assert_eq!(expected, merged);
+    }
+
+    #[test]
+    fn rescan_library_ordered() {
+        let mut library = MockILibrary::new();
+        let database = MockIDatabase::new();
+
+        let library_input = Query::new();
+        let library_result = Ok(artists_to_items(&COLLECTION));
+
+        library
+            .expect_list()
+            .with(predicate::eq(library_input))
+            .times(1)
+            .return_once(|_| library_result);
+
+        let mut music_hoard = MusicHoard::new(library, database);
+
+        music_hoard.rescan_library().unwrap();
+        assert_eq!(music_hoard.get_collection(), &*COLLECTION);
+    }
+
+    #[test]
+    fn rescan_library_unordered() {
+        let mut library = MockILibrary::new();
+        let database = MockIDatabase::new();
+
+        let library_input = Query::new();
+        let mut library_result = Ok(artists_to_items(&COLLECTION));
+
+        // Swap the last item with the first.
+        let last = library_result.as_ref().unwrap().len() - 1;
+        library_result.as_mut().unwrap().swap(0, last);
+
+        library
+            .expect_list()
+            .with(predicate::eq(library_input))
+            .times(1)
+            .return_once(|_| library_result);
+
+        let mut music_hoard = MusicHoard::new(library, database);
+
+        music_hoard.rescan_library().unwrap();
+        assert_eq!(music_hoard.get_collection(), &*COLLECTION);
+    }
+
+    #[test]
+    fn rescan_library_album_title_year_clash() {
+        let mut library = MockILibrary::new();
+        let database = MockIDatabase::new();
+
+        let mut expected = COLLECTION.to_owned();
+        expected[0].albums[0].id.year = expected[1].albums[0].id.year;
+        expected[0].albums[0].id.title = expected[1].albums[0].id.title.clone();
+
+        let library_input = Query::new();
+        let library_result = Ok(artists_to_items(&expected));
+
+        library
+            .expect_list()
+            .with(predicate::eq(library_input))
+            .times(1)
+            .return_once(|_| library_result);
+
+        let mut music_hoard = MusicHoard::new(library, database);
+
+        music_hoard.rescan_library().unwrap();
+        assert_eq!(music_hoard.get_collection(), &expected);
+    }
+
+    #[test]
+    fn load_database() {
+        let library = MockILibrary::new();
+        let mut database = MockIDatabase::new();
+
+        database
+            .expect_load()
+            .times(1)
+            .return_once(|coll: &mut Collection| {
+                *coll = COLLECTION.to_owned();
+                Ok(())
+            });
+
+        let mut music_hoard = MusicHoard::new(library, database);
+
+        music_hoard.load_from_database().unwrap();
+        assert_eq!(music_hoard.get_collection(), &*COLLECTION);
+    }
+
+    #[test]
+    fn rescan_get_save() {
         let mut library = MockILibrary::new();
         let mut database = MockIDatabase::new();
 
         let library_input = Query::new();
-        let library_result = Ok(COLLECTION.to_owned());
+        let library_result = Ok(artists_to_items(&COLLECTION));
 
         let database_input = COLLECTION.to_owned();
         let database_result = Ok(());
@@ -164,7 +624,7 @@ mod tests {
             .return_once(|_| library_result);
 
         database
-            .expect_write()
+            .expect_save()
             .with(predicate::eq(database_input))
             .times(1)
             .return_once(|_: &Collection| database_result);
@@ -199,22 +659,46 @@ mod tests {
     }
 
     #[test]
-    fn database_error() {
+    fn database_load_error() {
         let library = MockILibrary::new();
         let mut database = MockIDatabase::new();
 
-        let database_result = Err(database::Error::IoError(String::from("I/O error")));
+        let database_result = Err(database::LoadError::IoError(String::from("I/O error")));
 
         database
-            .expect_write()
+            .expect_load()
+            .times(1)
+            .return_once(|_: &mut Collection| database_result);
+
+        let mut music_hoard = MusicHoard::new(library, database);
+
+        let actual_err = music_hoard.load_from_database().unwrap_err();
+        let expected_err = Error::DatabaseError(
+            database::LoadError::IoError(String::from("I/O error")).to_string(),
+        );
+
+        assert_eq!(actual_err, expected_err);
+        assert_eq!(actual_err.to_string(), expected_err.to_string());
+    }
+
+    #[test]
+    fn database_save_error() {
+        let library = MockILibrary::new();
+        let mut database = MockIDatabase::new();
+
+        let database_result = Err(database::SaveError::IoError(String::from("I/O error")));
+
+        database
+            .expect_save()
             .times(1)
             .return_once(|_: &Collection| database_result);
 
         let mut music_hoard = MusicHoard::new(library, database);
 
         let actual_err = music_hoard.save_to_database().unwrap_err();
-        let expected_err =
-            Error::DatabaseError(database::Error::IoError(String::from("I/O error")).to_string());
+        let expected_err = Error::DatabaseError(
+            database::SaveError::IoError(String::from("I/O error")).to_string(),
+        );
 
         assert_eq!(actual_err, expected_err);
         assert_eq!(actual_err.to_string(), expected_err.to_string());

src/library/beets/mod.rs

@@ -1,17 +1,12 @@
 //! Module for interacting with the music library via
 //! [beets](https://beets.readthedocs.io/en/stable/).
 
-use std::{
-    collections::{HashMap, HashSet},
-    str,
-};
-
 #[cfg(test)]
 use mockall::automock;
 
-use crate::{Album, AlbumId, Artist, ArtistId, Format, Quality, Track};
+use crate::Format;
 
-use super::{Error, Field, ILibrary, Query};
+use super::{Error, Field, ILibrary, Item, Query};
 
 pub mod executor;
 
@@ -92,7 +87,7 @@ pub struct BeetsLibrary<BLE> {
 
 trait ILibraryPrivate {
     fn list_cmd_and_args(query: &Query) -> Vec<String>;
-    fn list_to_artists<S: AsRef<str>>(list_output: &[S]) -> Result<Vec<Artist>, Error>;
+    fn list_to_items<S: AsRef<str>>(list_output: &[S]) -> Result<Vec<Item>, Error>;
 }
 
 impl<BLE: IBeetsLibraryExecutor> BeetsLibrary<BLE> {
@@ -104,10 +99,10 @@ impl<BLE: IBeetsLibraryExecutor> BeetsLibrary<BLE> {
 }
 
 impl<BLE: IBeetsLibraryExecutor> ILibrary for BeetsLibrary<BLE> {
-    fn list(&mut self, query: &Query) -> Result<Vec<Artist>, Error> {
+    fn list(&mut self, query: &Query) -> Result<Vec<Item>, Error> {
         let cmd = Self::list_cmd_and_args(query);
         let output = self.executor.exec(&cmd)?;
-        Self::list_to_artists(&output)
+        Self::list_to_items(&output)
     }
 }
 
@@ -119,9 +114,8 @@ impl<BLE: IBeetsLibraryExecutor> ILibraryPrivate for BeetsLibrary<BLE> {
         cmd
     }
 
-    fn list_to_artists<S: AsRef<str>>(list_output: &[S]) -> Result<Vec<Artist>, Error> {
-        let mut artists: Vec<Artist> = vec![];
-        let mut album_ids = HashMap::<ArtistId, HashSet<AlbumId>>::new();
+    fn list_to_items<S: AsRef<str>>(list_output: &[S]) -> Result<Vec<Item>, Error> {
+        let mut items: Vec<Item> = vec![];
 
         for line in list_output.iter().map(|s| s.as_ref()) {
             if line.is_empty() {
@@ -138,69 +132,31 @@ impl<BLE: IBeetsLibraryExecutor> ILibraryPrivate for BeetsLibrary<BLE> {
             let album_title = split[2].to_string();
             let track_number = split[3].parse::<u32>()?;
             let track_title = split[4].to_string();
-            let track_artist = split[5].to_string();
-            let track_format = split[6].to_string();
-            let track_bitrate = split[7].trim_end_matches("kbps").parse::<u32>()?;
-
-            let artist_id = ArtistId { name: album_artist };
-
-            let album_id = AlbumId {
-                year: album_year,
-                title: album_title,
-            };
-
-            let track = Track {
-                number: track_number,
-                title: track_title,
-                artist: track_artist.split("; ").map(|s| s.to_owned()).collect(),
-                quality: Quality {
-                    format: match track_format.as_ref() {
+            let track_artist = split[5]
+                .to_string()
+                .split("; ")
+                .map(|s| s.to_owned())
+                .collect();
+            let track_format = match split[6].to_string().as_str() {
                 TRACK_FORMAT_FLAC => Format::Flac,
                 TRACK_FORMAT_MP3 => Format::Mp3,
                 _ => return Err(Error::Invalid(line.to_string())),
-                    },
-                    bitrate: track_bitrate,
-                },
             };
+            let track_bitrate = split[7].trim_end_matches("kbps").parse::<u32>()?;
 
-            let artist = if album_ids.contains_key(&artist_id) {
-                // Beets returns results in order so we look from the back.
-                artists
-                    .iter_mut()
-                    .rev()
-                    .find(|a| a.id == artist_id)
-                    .unwrap()
-            } else {
-                album_ids.insert(artist_id.clone(), HashSet::<AlbumId>::new());
-                artists.push(Artist {
-                    id: artist_id.clone(),
-                    albums: vec![],
-                });
-                artists.last_mut().unwrap()
-            };
-
-            if album_ids[&artist_id].contains(&album_id) {
-                // Beets returns results in order so we look from the back.
-                let album = artist
-                    .albums
-                    .iter_mut()
-                    .rev()
-                    .find(|a| a.id == album_id)
-                    .unwrap();
-                album.tracks.push(track);
-            } else {
-                album_ids
-                    .get_mut(&artist_id)
-                    .unwrap()
-                    .insert(album_id.clone());
-                artist.albums.push(Album {
-                    id: album_id,
-                    tracks: vec![track],
+            items.push(Item {
+                album_artist,
+                album_year,
+                album_title,
+                track_number,
+                track_title,
+                track_artist,
+                track_format,
+                track_bitrate,
             });
         }
-        }
 
-        Ok(artists)
+        Ok(items)
     }
 }
 
@@ -208,45 +164,34 @@ impl<BLE: IBeetsLibraryExecutor> ILibraryPrivate for BeetsLibrary<BLE> {
 mod tests {
     use mockall::predicate;
 
-    use crate::tests::COLLECTION;
+    use crate::tests::{artists_to_items, COLLECTION};
 
     use super::*;
 
-    fn artist_to_beets_string(artist: &Artist) -> Vec<String> {
-        let mut strings = vec![];
-
-        let album_artist = &artist.id.name;
-
-        for album in artist.albums.iter() {
-            let album_year = &album.id.year;
-            let album_title = &album.id.title;
-
-            for track in album.tracks.iter() {
-                let track_number = &track.number;
-                let track_title = &track.title;
-                let track_artist = &track.artist.join("; ");
-                let track_format = match track.quality.format {
+    fn item_to_beets_string(item: &Item) -> String {
+        format!(
+            "{album_artist}{sep}{album_year}{sep}{album_title}{sep}\
+             {track_number}{sep}{track_title}{sep}\
+             {track_artist}{sep}{track_format}{sep}{track_bitrate}kbps",
+            album_artist = item.album_artist,
+            album_year = item.album_year,
+            album_title = item.album_title,
+            track_number = item.track_number,
+            track_title = item.track_title,
+            track_artist = item.track_artist.join("; "),
+            track_format = match item.track_format {
                 Format::Flac => TRACK_FORMAT_FLAC,
                 Format::Mp3 => TRACK_FORMAT_MP3,
-                };
-                let track_bitrate = track.quality.bitrate;
-
-                strings.push(format!(
-                    "{album_artist}{0}{album_year}{0}{album_title}{0}\
-                     {track_number}{0}{track_title}{0}\
-                     {track_artist}{0}{track_format}{0}{track_bitrate}kbps",
-                    LIST_FORMAT_SEPARATOR,
-                ));
-            }
+            },
+            track_bitrate = item.track_bitrate,
+            sep = LIST_FORMAT_SEPARATOR,
+        )
     }
 
-        strings
-    }
-
-    fn artists_to_beets_string(artists: &[Artist]) -> Vec<String> {
+    fn items_to_beets_strings(items: &[Item]) -> Vec<String> {
         let mut strings = vec![];
-        for artist in artists.iter() {
-            strings.append(&mut artist_to_beets_string(artist));
+        for item in items.iter() {
+            strings.push(item_to_beets_string(item));
         }
         strings
     }
@@ -311,72 +256,15 @@ mod tests {
         let mut beets = BeetsLibrary::new(executor);
         let output = beets.list(&Query::new()).unwrap();
 
-        let expected: Vec<Artist> = vec![];
+        let expected: Vec<Item> = vec![];
         assert_eq!(output, expected);
     }
 
     #[test]
-    fn test_list_ordered() {
+    fn test_list() {
         let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
-        let expected = COLLECTION.to_owned();
-        let result = Ok(artists_to_beets_string(&expected));
-
-        let mut executor = MockIBeetsLibraryExecutor::new();
-        executor
-            .expect_exec()
-            .with(predicate::eq(arguments))
-            .times(1)
-            .return_once(|_| result);
-
-        let mut beets = BeetsLibrary::new(executor);
-        let output = beets.list(&Query::new()).unwrap();
-
-        assert_eq!(output, expected);
-    }
-
-    #[test]
-    fn test_list_unordered() {
-        let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
-        let mut expected = COLLECTION.to_owned();
-        let mut output = artists_to_beets_string(&expected);
-        let last = output.len() - 1;
-        output.swap(0, last);
-        let result = Ok(output);
-
-        // Putting the last track first will make the entire artist come first in the output.
-        expected.rotate_right(1);
-
-        // Same applies to that artists' albums.
-        expected[0].albums.rotate_right(1);
-
-        // Same applies to that album's tracks.
-        expected[0].albums[0].tracks.rotate_right(1);
-
-        // And the original first album's (now the first album of the second artist) tracks first
-        // track comes last.
-        expected[1].albums[0].tracks.rotate_left(1);
-
-        let mut executor = MockIBeetsLibraryExecutor::new();
-        executor
-            .expect_exec()
-            .with(predicate::eq(arguments))
-            .times(1)
-            .return_once(|_| result);
-
-        let mut beets = BeetsLibrary::new(executor);
-        let output = beets.list(&Query::new()).unwrap();
-
-        assert_eq!(output, expected);
-    }
-
-    #[test]
-    fn test_list_album_title_year_clash() {
-        let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
-        let mut expected = COLLECTION.to_owned();
-        expected[0].albums[0].id.year = expected[1].albums[0].id.year;
-        expected[0].albums[0].id.title = expected[1].albums[0].id.title.clone();
-        let output = artists_to_beets_string(&expected);
-        let result = Ok(output);
+        let expected = artists_to_items(&COLLECTION);
+        let result = Ok(items_to_beets_strings(&expected));
 
         let mut executor = MockIBeetsLibraryExecutor::new();
         executor
@@ -422,15 +310,15 @@ mod tests {
         let mut beets = BeetsLibrary::new(executor);
         let output = beets.list(&query).unwrap();
 
-        let expected: Vec<Artist> = vec![];
+        let expected: Vec<Item> = vec![];
         assert_eq!(output, expected);
     }
 
     #[test]
     fn invalid_data_split() {
         let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
-        let expected = COLLECTION.to_owned();
-        let mut output = artists_to_beets_string(&expected);
+        let expected = artists_to_items(&COLLECTION);
+        let mut output = items_to_beets_strings(&expected);
         let invalid_string = output[2]
             .split(LIST_FORMAT_SEPARATOR)
             .map(|s| s.to_owned())
@@ -455,8 +343,8 @@ mod tests {
     #[test]
     fn invalid_data_format() {
         let arguments = vec!["ls".to_string(), LIST_FORMAT_ARG.to_string()];
-        let expected = COLLECTION.to_owned();
-        let mut output = artists_to_beets_string(&expected);
+        let expected = artists_to_items(&COLLECTION);
+        let mut output = items_to_beets_strings(&expected);
         let mut invalid_string = output[2]
             .split(LIST_FORMAT_SEPARATOR)
             .map(|s| s.to_owned())

src/library/mod.rs

@@ -5,7 +5,7 @@ use std::{collections::HashSet, fmt, num::ParseIntError, str::Utf8Error};
 #[cfg(test)]
 use mockall::automock;
 
-use crate::Artist;
+use crate::Format;
 
 #[cfg(feature = "library-beets")]
 pub mod beets;
@@ -14,7 +14,20 @@ pub mod beets;
 #[cfg_attr(test, automock)]
 pub trait ILibrary {
     /// List lirbary items that match the a specific query.
-    fn list(&mut self, query: &Query) -> Result<Vec<Artist>, Error>;
+    fn list(&mut self, query: &Query) -> Result<Vec<Item>, Error>;
+}
+
+/// An item from the library. An item corresponds to an individual file (usually a single track).
+#[derive(Debug, PartialEq, Eq)]
+pub struct Item {
+    pub album_artist: String,
+    pub album_year: u32,
+    pub album_title: String,
+    pub track_number: u32,
+    pub track_title: String,
+    pub track_artist: Vec<String>,
+    pub track_format: Format,
+    pub track_bitrate: u32,
 }
 
 /// Individual fields that can be queried on.

src/main.rs

@@ -1,6 +1,8 @@
+use std::fs::OpenOptions;
 use std::path::PathBuf;
 use std::{ffi::OsString, io};
 
+use musichoard::Collection;
 use ratatui::{backend::CrosstermBackend, Terminal};
 use structopt::StructOpt;
 
@@ -57,9 +59,28 @@ fn with<LIB: ILibrary, DB: IDatabase>(lib: LIB, db: DB) {
 }
 
 fn main() {
-    // Create the application.
     let opt = Opt::from_args();
 
+    // Create an empty database file if it does not exist.
+    match OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .open(&opt.database_file_path)
+    {
+        Ok(f) => {
+            drop(f);
+            JsonDatabase::new(JsonDatabaseFileBackend::new(&opt.database_file_path))
+                .save::<Collection>(&vec![])
+                .expect("failed to create empty database");
+        }
+        Err(e) => match e.kind() {
+            io::ErrorKind::AlreadyExists => {}
+            _ => panic!("failed to access database file"),
+        },
+    }
+
+    // Create the application.
+    let db_exec = JsonDatabaseFileBackend::new(&opt.database_file_path);
     if let Some(uri) = opt.beets_ssh_uri {
         let uri = uri.into_string().expect("invalid SSH URI");
         let beets_config_file_path = opt
@@ -70,11 +91,9 @@ fn main() {
         let lib_exec = BeetsLibrarySshExecutor::new(uri)
             .expect("failed to initialise beets")
             .config(beets_config_file_path);
-        let db_exec = JsonDatabaseFileBackend::new(&opt.database_file_path);
         with(BeetsLibrary::new(lib_exec), JsonDatabase::new(db_exec));
     } else {
         let lib_exec = BeetsLibraryProcessExecutor::default().config(opt.beets_config_file_path);
-        let db_exec = JsonDatabaseFileBackend::new(&opt.database_file_path);
         with(BeetsLibrary::new(lib_exec), JsonDatabase::new(db_exec));
     }
 }

src/testlib.rs

@@ -13,8 +13,10 @@ macro_rules! collection {
                         },
                         tracks: vec![
                             Track {
+                                id: TrackId {
                                     number: 1,
                                     title: "track a.a.1".to_string(),
+                                },
                                 artist: vec!["artist a.a.1".to_string()],
                                 quality: Quality {
                                     format: Format::Flac,
@@ -22,8 +24,10 @@ macro_rules! collection {
                                 },
                             },
                             Track {
+                                id: TrackId {
                                     number: 2,
                                     title: "track a.a.2".to_string(),
+                                },
                                 artist: vec![
                                     "artist a.a.2.1".to_string(),
                                     "artist a.a.2.2".to_string(),
@@ -34,8 +38,10 @@ macro_rules! collection {
                                 },
                             },
                             Track {
+                                id: TrackId {
                                     number: 3,
                                     title: "track a.a.3".to_string(),
+                                },
                                 artist: vec!["artist a.a.3".to_string()],
                                 quality: Quality {
                                     format: Format::Flac,
@@ -51,8 +57,10 @@ macro_rules! collection {
                         },
                         tracks: vec![
                             Track {
+                                id: TrackId {
                                     number: 1,
                                     title: "track a.b.1".to_string(),
+                                },
                                 artist: vec!["artist a.b.1".to_string()],
                                 quality: Quality {
                                     format: Format::Flac,
@@ -60,8 +68,10 @@ macro_rules! collection {
                                 },
                             },
                             Track {
+                                id: TrackId {
                                     number: 2,
                                     title: "track a.b.2".to_string(),
+                                },
                                 artist: vec!["artist a.b.2".to_string()],
                                 quality: Quality {
                                     format: Format::Flac,
@@ -84,8 +94,10 @@ macro_rules! collection {
                         },
                         tracks: vec![
                             Track {
+                                id: TrackId {
                                     number: 1,
                                     title: "track b.a.1".to_string(),
+                                },
                                 artist: vec!["artist b.a.1".to_string()],
                                 quality: Quality {
                                     format: Format::Mp3,
@@ -93,8 +105,10 @@ macro_rules! collection {
                                 },
                             },
                             Track {
+                                id: TrackId {
                                     number: 2,
                                     title: "track b.a.2".to_string(),
+                                },
                                 artist: vec![
                                     "artist b.a.2.1".to_string(),
                                     "artist b.a.2.2".to_string(),
@@ -113,8 +127,10 @@ macro_rules! collection {
                         },
                         tracks: vec![
                             Track {
+                                id: TrackId {
                                     number: 1,
                                     title: "track b.b.1".to_string(),
+                                },
                                 artist: vec!["artist b.b.1".to_string()],
                                 quality: Quality {
                                     format: Format::Flac,
@@ -122,8 +138,10 @@ macro_rules! collection {
                                 },
                             },
                             Track {
+                                id: TrackId {
                                     number: 2,
                                     title: "track b.b.2".to_string(),
+                                },
                                 artist: vec![
                                     "artist b.b.2.1".to_string(),
                                     "artist b.b.2.2".to_string(),
@@ -149,8 +167,10 @@ macro_rules! collection {
                         },
                         tracks: vec![
                             Track {
+                                id: TrackId {
                                     number: 1,
                                     title: "track c.a.1".to_string(),
+                                },
                                 artist: vec!["artist c.a.1".to_string()],
                                 quality: Quality {
                                     format: Format::Mp3,
@@ -158,8 +178,10 @@ macro_rules! collection {
                                 },
                             },
                             Track {
+                                id: TrackId {
                                     number: 2,
                                     title: "track c.a.2".to_string(),
+                                },
                                 artist: vec![
                                     "artist c.a.2.1".to_string(),
                                     "artist c.a.2.2".to_string(),
@@ -178,8 +200,10 @@ macro_rules! collection {
                         },
                         tracks: vec![
                             Track {
+                                id: TrackId {
                                     number: 1,
                                     title: "track c.b.1".to_string(),
+                                },
                                 artist: vec!["artist c.b.1".to_string()],
                                 quality: Quality {
                                     format: Format::Flac,
@@ -187,8 +211,10 @@ macro_rules! collection {
                                 },
                             },
                             Track {
+                                id: TrackId {
                                     number: 2,
                                     title: "track c.b.2".to_string(),
+                                },
                                 artist: vec![
                                     "artist c.b.2.1".to_string(),
                                     "artist c.b.2.2".to_string(),

src/tui/event.rs

@@ -2,11 +2,14 @@ use crossterm::event::{KeyEvent, MouseEvent};
 use std::fmt;
 use std::sync::mpsc;
 
+use super::ui::UiError;
+
 #[derive(Debug)]
 pub enum EventError {
     Send(Event),
     Recv,
     Io(std::io::Error),
+    Ui(String),
 }
 
 impl fmt::Display for EventError {
@@ -17,6 +20,9 @@ impl fmt::Display for EventError {
             Self::Io(ref e) => {
                 write!(f, "an I/O error was triggered during event handling: {e}")
             }
+            Self::Ui(ref s) => {
+                write!(f, "the UI returned an error during event handling: {s}")
+            }
         }
     }
 }
@@ -33,6 +39,12 @@ impl From<mpsc::RecvError> for EventError {
     }
 }
 
+impl From<UiError> for EventError {
+    fn from(err: UiError) -> EventError {
+        EventError::Ui(err.to_string())
+    }
+}
+
 #[derive(Clone, Copy, Debug)]
 pub enum Event {
     Key(KeyEvent),
@@ -90,6 +102,8 @@ mod tests {
 
     use crossterm::event::{KeyCode, KeyEvent, KeyEventKind, KeyEventState, KeyModifiers};
 
+    use crate::tui::ui::UiError;
+
     use super::{Event, EventChannel, EventError};
 
     #[test]
@@ -133,13 +147,16 @@ mod tests {
         }));
         let recv_err = EventError::Recv;
         let io_err = EventError::Io(io::Error::new(io::ErrorKind::Interrupted, "interrupted"));
+        let ui_err: EventError = UiError::Lib(String::from("lib error")).into();
 
         assert!(!send_err.to_string().is_empty());
         assert!(!recv_err.to_string().is_empty());
         assert!(!io_err.to_string().is_empty());
+        assert!(!ui_err.to_string().is_empty());
 
         assert!(!format!("{:?}", send_err).is_empty());
         assert!(!format!("{:?}", recv_err).is_empty());
         assert!(!format!("{:?}", io_err).is_empty());
+        assert!(!format!("{:?}", ui_err).is_empty());
     }
 }

src/tui/handler.rs

@@ -14,7 +14,8 @@ pub trait IEventHandler<UI> {
 }
 
 trait IEventHandlerPrivate<UI> {
-    fn handle_key_event(ui: &mut UI, key_event: KeyEvent);
+    fn handle_key_event(ui: &mut UI, key_event: KeyEvent) -> Result<(), EventError>;
+    fn quit(ui: &mut UI) -> Result<(), EventError>;
 }
 
 pub struct EventHandler {
@@ -31,7 +32,7 @@ impl EventHandler {
 impl<UI: IUi> IEventHandler<UI> for EventHandler {
     fn handle_next_event(&self, ui: &mut UI) -> Result<(), EventError> {
         match self.events.recv()? {
-            Event::Key(key_event) => Self::handle_key_event(ui, key_event),
+            Event::Key(key_event) => Self::handle_key_event(ui, key_event)?,
             Event::Mouse(_) => {}
             Event::Resize(_, _) => {}
         };
@@ -40,16 +41,16 @@ impl<UI: IUi> IEventHandler<UI> for EventHandler {
 }
 
 impl<UI: IUi> IEventHandlerPrivate<UI> for EventHandler {
-    fn handle_key_event(ui: &mut UI, key_event: KeyEvent) {
+    fn handle_key_event(ui: &mut UI, key_event: KeyEvent) -> Result<(), EventError> {
         match key_event.code {
             // Exit application on `ESC` or `q`.
             KeyCode::Esc | KeyCode::Char('q') => {
-                ui.quit();
+                Self::quit(ui)?;
             }
             // Exit application on `Ctrl-C`.
             KeyCode::Char('c') | KeyCode::Char('C') => {
                 if key_event.modifiers == KeyModifiers::CONTROL {
-                    ui.quit();
+                    Self::quit(ui)?;
                 }
             }
             // Category change.
@@ -69,6 +70,14 @@ impl<UI: IUi> IEventHandlerPrivate<UI> for EventHandler {
             // Other keys.
             _ => {}
         }
+
+        Ok(())
+    }
+
+    fn quit(ui: &mut UI) -> Result<(), EventError> {
+        ui.quit();
+        ui.save()?;
+        Ok(())
     }
 }
 // GRCOV_EXCL_STOP

src/tui/lib.rs

@@ -3,24 +3,26 @@ use musichoard::{database::IDatabase, library::ILibrary, Collection, MusicHoard}
 #[cfg(test)]
 use mockall::automock;
 
-use super::Error;
-
 #[cfg_attr(test, automock)]
 pub trait IMusicHoard {
-    fn rescan_library(&mut self) -> Result<(), Error>;
+    fn rescan_library(&mut self) -> Result<(), musichoard::Error>;
+    fn load_from_database(&mut self) -> Result<(), musichoard::Error>;
+    fn save_to_database(&mut self) -> Result<(), musichoard::Error>;
     fn get_collection(&self) -> &Collection;
 }
 
-impl From<musichoard::Error> for Error {
-    fn from(err: musichoard::Error) -> Error {
-        Error::Lib(err.to_string())
-    }
-}
-
 // GRCOV_EXCL_START
 impl<LIB: ILibrary, DB: IDatabase> IMusicHoard for MusicHoard<LIB, DB> {
-    fn rescan_library(&mut self) -> Result<(), Error> {
-        Ok(MusicHoard::rescan_library(self)?)
+    fn rescan_library(&mut self) -> Result<(), musichoard::Error> {
+        MusicHoard::rescan_library(self)
+    }
+
+    fn load_from_database(&mut self) -> Result<(), musichoard::Error> {
+        MusicHoard::load_from_database(self)
+    }
+
+    fn save_to_database(&mut self) -> Result<(), musichoard::Error> {
+        MusicHoard::save_to_database(self)
     }
 
     fn get_collection(&self) -> &Collection {

src/tui/mod.rs

@@ -25,6 +25,12 @@ pub enum Error {
     ListenerPanic,
 }
 
+impl From<musichoard::Error> for Error {
+    fn from(err: musichoard::Error) -> Error {
+        Error::Lib(err.to_string())
+    }
+}
+
 impl From<io::Error> for Error {
     fn from(err: io::Error) -> Error {
         Error::Io(err.to_string())
@@ -174,13 +180,18 @@ mod tests {
         Terminal::new(backend).unwrap()
     }
 
-    pub fn ui(collection: Collection) -> Ui<MockIMusicHoard> {
+    pub fn music_hoard(collection: Collection) -> MockIMusicHoard {
         let mut music_hoard = MockIMusicHoard::new();
 
+        music_hoard.expect_load_from_database().returning(|| Ok(()));
         music_hoard.expect_rescan_library().returning(|| Ok(()));
         music_hoard.expect_get_collection().return_const(collection);
 
-        Ui::new(music_hoard).unwrap()
+        music_hoard
+    }
+
+    pub fn ui(collection: Collection) -> Ui<MockIMusicHoard> {
+        Ui::new(music_hoard(collection)).unwrap()
     }
 
     fn listener() -> MockIEventListener {

src/tui/ui.rs

@@ -1,3 +1,5 @@
+use std::fmt;
+
 use musichoard::{Album, Artist, Collection, Format, Track};
 use ratatui::{
     backend::Backend,
@@ -9,10 +11,31 @@ use ratatui::{
 
 use super::{lib::IMusicHoard, Error};
 
+#[derive(Debug)]
+pub enum UiError {
+    Lib(String),
+}
+
+impl fmt::Display for UiError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Self::Lib(ref s) => write!(f, "the musichoard library returned an error: {s}"),
+        }
+    }
+}
+
+impl From<musichoard::Error> for UiError {
+    fn from(err: musichoard::Error) -> UiError {
+        UiError::Lib(err.to_string())
+    }
+}
+
 pub trait IUi {
     fn is_running(&self) -> bool;
     fn quit(&mut self);
 
+    fn save(&mut self) -> Result<(), UiError>;
+
     fn increment_category(&mut self);
     fn decrement_category(&mut self);
 
@@ -404,7 +427,7 @@ impl<'a, 'b> TrackState<'a, 'b> {
         let list = List::new(
             tracks
                 .iter()
-                .map(|id| ListItem::new(id.title.as_str()))
+                .map(|tr| ListItem::new(tr.id.title.as_str()))
                 .collect::<Vec<ListItem>>(),
         );
 
@@ -415,9 +438,9 @@ impl<'a, 'b> TrackState<'a, 'b> {
              Artist: {}\n\
              Quality: {}",
             track
-                .map(|t| t.number.to_string())
+                .map(|t| t.id.number.to_string())
                 .unwrap_or_else(|| "".to_string()),
-            track.map(|t| t.title.as_str()).unwrap_or(""),
+            track.map(|t| t.id.title.as_str()).unwrap_or(""),
             track
                 .map(|t| t.artist.join("; "))
                 .unwrap_or_else(|| "".to_string()),
@@ -440,6 +463,7 @@ impl<'a, 'b> TrackState<'a, 'b> {
 
 impl<MH: IMusicHoard> Ui<MH> {
     pub fn new(mut music_hoard: MH) -> Result<Self, Error> {
+        music_hoard.load_from_database()?;
         music_hoard.rescan_library()?;
         let selection = Selection::new(Some(music_hoard.get_collection()));
         Ok(Ui {
@@ -531,6 +555,11 @@ impl<MH: IMusicHoard> IUi for Ui<MH> {
         self.running = false;
     }
 
+    fn save(&mut self) -> Result<(), UiError> {
+        self.music_hoard.save_to_database()?;
+        Ok(())
+    }
+
     fn increment_category(&mut self) {
         self.selection.increment_category();
     }
@@ -603,6 +632,22 @@ mod tests {
 
     use super::*;
 
+    pub fn music_hoard(collection: Collection) -> MockIMusicHoard {
+        let mut music_hoard = MockIMusicHoard::new();
+
+        music_hoard
+            .expect_load_from_database()
+            .times(1)
+            .return_once(|| Ok(()));
+        music_hoard
+            .expect_rescan_library()
+            .times(1)
+            .return_once(|| Ok(()));
+        music_hoard.expect_get_collection().return_const(collection);
+
+        music_hoard
+    }
+
     #[test]
     fn test_track_selection() {
         let tracks = &COLLECTION[0].albums[0].tracks;
@@ -757,17 +802,7 @@ mod tests {
 
     #[test]
     fn ui_running() {
-        let mut music_hoard = MockIMusicHoard::new();
-
-        music_hoard
-            .expect_rescan_library()
-            .times(1)
-            .return_once(|| Ok(()));
-        music_hoard
-            .expect_get_collection()
-            .return_const(COLLECTION.to_owned());
-
-        let mut ui = Ui::new(music_hoard).unwrap();
+        let mut ui = Ui::new(music_hoard(COLLECTION.to_owned())).unwrap();
         assert!(ui.is_running());
 
         ui.quit();
@@ -775,18 +810,23 @@ mod tests {
     }
 
     #[test]
-    fn ui_modifiers() {
-        let mut music_hoard = MockIMusicHoard::new();
+    fn ui_save() {
+        let mut music_hoard = music_hoard(COLLECTION.to_owned());
 
         music_hoard
-            .expect_rescan_library()
+            .expect_save_to_database()
             .times(1)
             .return_once(|| Ok(()));
-        music_hoard
-            .expect_get_collection()
-            .return_const(COLLECTION.to_owned());
 
         let mut ui = Ui::new(music_hoard).unwrap();
+
+        let result = ui.save();
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn ui_modifiers() {
+        let mut ui = Ui::new(music_hoard(COLLECTION.to_owned())).unwrap();
         assert!(ui.is_running());
 
         assert_eq!(ui.selection.active, Category::Artist);
@@ -875,17 +915,10 @@ mod tests {
 
     #[test]
     fn app_no_tracks() {
-        let mut music_hoard = MockIMusicHoard::new();
         let mut collection = COLLECTION.to_owned();
         collection[0].albums[0].tracks = vec![];
 
-        music_hoard
-            .expect_rescan_library()
-            .times(1)
-            .return_once(|| Ok(()));
-        music_hoard.expect_get_collection().return_const(collection);
-
-        let mut app = Ui::new(music_hoard).unwrap();
+        let mut app = Ui::new(music_hoard(collection)).unwrap();
         assert!(app.is_running());
 
         assert_eq!(app.selection.active, Category::Artist);
@@ -911,17 +944,10 @@ mod tests {
 
     #[test]
     fn app_no_albums() {
-        let mut music_hoard = MockIMusicHoard::new();
         let mut collection = COLLECTION.to_owned();
         collection[0].albums = vec![];
 
-        music_hoard
-            .expect_rescan_library()
-            .times(1)
-            .return_once(|| Ok(()));
-        music_hoard.expect_get_collection().return_const(collection);
-
-        let mut app = Ui::new(music_hoard).unwrap();
+        let mut app = Ui::new(music_hoard(collection)).unwrap();
         assert!(app.is_running());
 
         assert_eq!(app.selection.active, Category::Artist);
@@ -960,16 +986,7 @@ mod tests {
 
     #[test]
     fn app_no_artists() {
-        let mut music_hoard = MockIMusicHoard::new();
-        let collection = vec![];
-
-        music_hoard
-            .expect_rescan_library()
-            .times(1)
-            .return_once(|| Ok(()));
-        music_hoard.expect_get_collection().return_const(collection);
-
-        let mut app = Ui::new(music_hoard).unwrap();
+        let mut app = Ui::new(music_hoard(vec![])).unwrap();
         assert!(app.is_running());
 
         assert_eq!(app.selection.active, Category::Artist);
@@ -1042,4 +1059,13 @@ mod tests {
 
         terminal.draw(|frame| ui.render(frame)).unwrap();
     }
+
+    #[test]
+    fn errors() {
+        let ui_err: UiError = musichoard::Error::DatabaseError(String::from("get rekt")).into();
+
+        assert!(!ui_err.to_string().is_empty());
+
+        assert!(!format!("{:?}", ui_err).is_empty());
+    }
 }

tests/database/json.rs

@@ -16,14 +16,14 @@ static DATABASE_TEST_FILE: Lazy<PathBuf> =
     Lazy::new(|| fs::canonicalize("./tests/files/database/database.json").unwrap());
 
 #[test]
-fn write() {
+fn save() {
     let file = NamedTempFile::new().unwrap();
 
     let backend = JsonDatabaseFileBackend::new(file.path());
     let mut database = JsonDatabase::new(backend);
 
     let write_data = COLLECTION.to_owned();
-    database.write(&write_data).unwrap();
+    database.save(&write_data).unwrap();
 
     let expected = fs::read_to_string(&*DATABASE_TEST_FILE).unwrap();
     let actual = fs::read_to_string(file.path()).unwrap();
@@ -32,12 +32,12 @@ fn write() {
 }
 
 #[test]
-fn read() {
+fn load() {
     let backend = JsonDatabaseFileBackend::new(&*DATABASE_TEST_FILE);
     let database = JsonDatabase::new(backend);
 
     let mut read_data: Vec<Artist> = vec![];
-    database.read(&mut read_data).unwrap();
+    database.load(&mut read_data).unwrap();
 
     let expected = COLLECTION.to_owned();
     assert_eq!(read_data, expected);
@@ -51,10 +51,10 @@ fn reverse() {
     let mut database = JsonDatabase::new(backend);
 
     let write_data = COLLECTION.to_owned();
-    database.write(&write_data).unwrap();
+    database.save(&write_data).unwrap();
 
     let mut read_data: Vec<Artist> = vec![];
-    database.read(&mut read_data).unwrap();
+    database.load(&mut read_data).unwrap();
 
     assert_eq!(write_data, read_data);
 }

tests/lib.rs

@@ -1,7 +1,7 @@
 mod database;
 mod library;
 
-use musichoard::{Album, AlbumId, Artist, ArtistId, Format, Quality, Track};
+use musichoard::{Album, AlbumId, Artist, ArtistId, Format, Quality, Track, TrackId};
 use once_cell::sync::Lazy;
 
 static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
@@ -17,8 +17,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                 },
                 tracks: vec![
                     Track {
+                        id: TrackId {
                             number: 01,
                             title: String::from("Az’"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -26,8 +28,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 02,
                             title: String::from("Arkaim"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -35,8 +39,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 03,
                             title: String::from("Bol’no mne"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -44,8 +50,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 04,
                             title: String::from("Leshiy"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -53,8 +61,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 05,
                             title: String::from("Zakliatie"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -62,8 +72,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 06,
                             title: String::from("Predok"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -71,8 +83,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 07,
                             title: String::from("Nikogda"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -80,8 +94,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 08,
                             title: String::from("Tam za tumanami"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -89,8 +105,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 09,
                             title: String::from("Potomok"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -98,8 +116,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 10,
                             title: String::from("Slovo"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -107,8 +127,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 11,
                             title: String::from("Odna"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -116,8 +138,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 12,
                             title: String::from("Vo moiom sadochke…"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -125,8 +149,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 13,
                             title: String::from("Stenka na stenku"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -134,8 +160,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 14,
                             title: String::from("Zimushka"),
+                        },
                         artist: vec![String::from("Аркона")],
                         quality: Quality {
                             format: Format::Flac,
@@ -157,8 +185,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                     },
                     tracks: vec![
                         Track {
+                            id: TrackId {
                                 number: 01,
                                 title: String::from("Samon"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -166,8 +196,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 02,
                                 title: String::from("Primordial Breath"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -175,8 +207,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 03,
                                 title: String::from("Inis Mona"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -184,8 +218,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 04,
                                 title: String::from("Gray Sublime Archon"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -193,8 +229,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 05,
                                 title: String::from("Anagantios"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -202,8 +240,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 06,
                                 title: String::from("Bloodstained Ground"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -211,8 +251,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 07,
                                 title: String::from("The Somber Lay"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -220,8 +262,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 08,
                                 title: String::from("Slanias Song"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -229,8 +273,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 09,
                                 title: String::from("Giamonios"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -238,8 +284,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 10,
                                 title: String::from("Tarvos"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -247,8 +295,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 11,
                                 title: String::from("Calling the Rain"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -256,8 +306,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 12,
                                 title: String::from("Elembivos"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -273,8 +325,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                     },
                     tracks: vec![
                         Track {
+                            id: TrackId {
                                 number: 01,
                                 title: String::from("Verja Urit an Bitus"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -282,8 +336,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 02,
                                 title: String::from("Uis Elveti"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -291,8 +347,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 03,
                                 title: String::from("Ôrô"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -300,8 +358,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 04,
                                 title: String::from("Lament"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -309,8 +369,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 05,
                                 title: String::from("Druid"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -318,8 +380,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 06,
                                 title: String::from("Jêzaïg"),
+                            },
                             artist: vec![String::from("Eluveitie")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -341,8 +405,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                 },
                 tracks: vec![
                     Track {
+                        id: TrackId {
                             number: 01,
                             title: String::from("Intro = Chaos"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -350,8 +416,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 02,
                             title: String::from("Modlitwa"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -359,8 +427,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 03,
                             title: String::from("Długa droga z piekła"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -368,8 +438,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 04,
                             title: String::from("Synowie ognia"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -377,8 +449,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 05,
                             title: String::from("1902"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -386,8 +460,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 06,
                             title: String::from("Krew za krew"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -395,8 +471,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 07,
                             title: String::from("Kulminacja"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -404,8 +482,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 08,
                             title: String::from("Judasz"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -413,8 +493,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 09,
                             title: String::from("Więzy"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -422,8 +504,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 10,
                             title: String::from("Zagubione dusze"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -431,8 +515,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 11,
                             title: String::from("Linia życia"),
+                        },
                         artist: vec![String::from("Frontside")],
                         quality: Quality {
                             format: Format::Flac,
@@ -453,8 +539,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                 },
                 tracks: vec![
                     Track {
+                        id: TrackId {
                             number: 01,
                             title: String::from("Unbreakable"),
+                        },
                         artist: vec![String::from("Heaven’s Basement")],
                         quality: Quality {
                             format: Format::Mp3,
@@ -462,8 +550,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 02,
                             title: String::from("Guilt Trips and Sins"),
+                        },
                         artist: vec![String::from("Heaven’s Basement")],
                         quality: Quality {
                             format: Format::Mp3,
@@ -471,8 +561,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 03,
                             title: String::from("The Long Goodbye"),
+                        },
                         artist: vec![String::from("Heaven’s Basement")],
                         quality: Quality {
                             format: Format::Mp3,
@@ -480,8 +572,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 04,
                             title: String::from("Close Encounters"),
+                        },
                         artist: vec![String::from("Heaven’s Basement")],
                         quality: Quality {
                             format: Format::Mp3,
@@ -489,8 +583,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 05,
                             title: String::from("Paranoia"),
+                        },
                         artist: vec![String::from("Heaven’s Basement")],
                         quality: Quality {
                             format: Format::Mp3,
@@ -498,8 +594,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 06,
                             title: String::from("Let Me Out of Here"),
+                        },
                         artist: vec![String::from("Heaven’s Basement")],
                         quality: Quality {
                             format: Format::Mp3,
@@ -507,8 +605,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                         },
                     },
                     Track {
+                        id: TrackId {
                             number: 07,
                             title: String::from("Leeches"),
+                        },
                         artist: vec![String::from("Heaven’s Basement")],
                         quality: Quality {
                             format: Format::Mp3,
@@ -530,8 +630,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                     },
                     tracks: vec![
                         Track {
+                            id: TrackId {
                                 number: 01,
                                 title: String::from("Fight Fire with Fire"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -539,8 +641,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 02,
                                 title: String::from("Ride the Lightning"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -548,8 +652,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 03,
                                 title: String::from("For Whom the Bell Tolls"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -557,8 +663,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 04,
                                 title: String::from("Fade to Black"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -566,8 +674,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 05,
                                 title: String::from("Trapped under Ice"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -575,8 +685,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 06,
                                 title: String::from("Escape"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -584,8 +696,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 07,
                                 title: String::from("Creeping Death"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -593,8 +707,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 08,
                                 title: String::from("The Call of Ktulu"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -610,8 +726,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                     },
                     tracks: vec![
                         Track {
+                            id: TrackId {
                                 number: 01,
                                 title: String::from("The Ecstasy of Gold"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -619,8 +737,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 02,
                                 title: String::from("The Call of Ktulu"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -628,8 +748,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 03,
                                 title: String::from("Master of Puppets"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -637,8 +759,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 04,
                                 title: String::from("Of Wolf and Man"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -646,8 +770,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 05,
                                 title: String::from("The Thing That Should Not Be"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -655,8 +781,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 06,
                                 title: String::from("Fuel"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -664,8 +792,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 07,
                                 title: String::from("The Memory Remains"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -673,8 +803,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 08,
                                 title: String::from("No Leaf Clover"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -682,8 +814,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 09,
                                 title: String::from("Hero of the Day"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -691,8 +825,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 10,
                                 title: String::from("Devil’s Dance"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -700,8 +836,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 11,
                                 title: String::from("Bleeding Me"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -709,8 +847,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 12,
                                 title: String::from("Nothing Else Matters"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -718,8 +858,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 13,
                                 title: String::from("Until It Sleeps"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -727,8 +869,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 14,
                                 title: String::from("For Whom the Bell Tolls"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -736,8 +880,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 15,
                                 title: String::from("−Human"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -745,8 +891,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 16,
                                 title: String::from("Wherever I May Roam"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -754,8 +902,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 17,
                                 title: String::from("Outlaw Torn"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -763,8 +913,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 18,
                                 title: String::from("Sad but True"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -772,8 +924,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 19,
                                 title: String::from("One"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -781,8 +935,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 20,
                                 title: String::from("Enter Sandman"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,
@@ -790,8 +946,10 @@ static COLLECTION: Lazy<Vec<Artist>> = Lazy::new(|| {
                             },
                         },
                         Track {
+                            id: TrackId {
                                 number: 21,
                                 title: String::from("Battery"),
+                            },
                             artist: vec![String::from("Metallica")],
                             quality: Quality {
                                 format: Format::Flac,

tests/library/beets.rs

@@ -9,7 +9,7 @@ use once_cell::sync::Lazy;
 use musichoard::{
     library::{
         beets::{executor::BeetsLibraryProcessExecutor, BeetsLibrary},
-        Field, ILibrary, Query,
+        Field, ILibrary, Item, Query,
     },
     Artist,
 };
@@ -32,6 +32,35 @@ static BEETS_TEST_CONFIG: Lazy<Arc<Mutex<BeetsLibrary<BeetsLibraryProcessExecuto
         )))
     });
 
+fn artist_to_items(artist: &Artist) -> Vec<Item> {
+    let mut items = vec![];
+
+    for album in artist.albums.iter() {
+        for track in album.tracks.iter() {
+            items.push(Item {
+                album_artist: artist.id.name.clone(),
+                album_year: album.id.year,
+                album_title: album.id.title.clone(),
+                track_number: track.id.number,
+                track_title: track.id.title.clone(),
+                track_artist: track.artist.clone(),
+                track_format: track.quality.format,
+                track_bitrate: track.quality.bitrate,
+            });
+        }
+    }
+
+    items
+}
+
+fn artists_to_items(artists: &[Artist]) -> Vec<Item> {
+    let mut items = vec![];
+    for artist in artists.iter() {
+        items.append(&mut artist_to_items(artist));
+    }
+    items
+}
+
 #[test]
 fn test_no_config_list() {
     let beets_arc = BEETS_EMPTY_CONFIG.clone();
@@ -39,7 +68,7 @@ fn test_no_config_list() {
 
     let output = beets.list(&Query::new()).unwrap();
 
-    let expected: Vec<Artist> = vec![];
+    let expected: Vec<Item> = vec![];
     assert_eq!(output, expected);
 }
 
@@ -61,7 +90,7 @@ fn test_full_list() {
 
     let output = beets.list(&Query::new()).unwrap();
 
-    let expected: Vec<Artist> = COLLECTION.to_owned();
+    let expected: Vec<Item> = artists_to_items(&COLLECTION);
     assert_eq!(output, expected);
 }
 
@@ -74,7 +103,7 @@ fn test_album_artist_query() {
         .list(Query::new().include(Field::AlbumArtist(String::from("Аркона"))))
         .unwrap();
 
-    let expected: Vec<Artist> = COLLECTION[0..1].to_owned();
+    let expected: Vec<Item> = artists_to_items(&COLLECTION[0..1]);
     assert_eq!(output, expected);
 }
 
@@ -87,7 +116,7 @@ fn test_album_title_query() {
         .list(&Query::new().include(Field::AlbumTitle(String::from("Slovo"))))
         .unwrap();
 
-    let expected: Vec<Artist> = COLLECTION[0..1].to_owned();
+    let expected: Vec<Item> = artists_to_items(&COLLECTION[0..1]);
     assert_eq!(output, expected);
 }
 
@@ -100,6 +129,6 @@ fn test_exclude_query() {
         .list(&Query::new().exclude(Field::AlbumArtist(String::from("Аркона"))))
         .unwrap();
 
-    let expected: Vec<Artist> = COLLECTION[1..].to_owned();
+    let expected: Vec<Item> = artists_to_items(&COLLECTION[1..]);
     assert_eq!(output, expected);
 }