src/core/interface/musicbrainz/mod.rs

@@ -2,15 +2,11 @@
 
 use std::{fmt, num};
 
-// TODO: #[cfg(test)]
-// TODO: use mockall::automock;
-
 use uuid::{self, Uuid};
 
 use crate::collection::album::Album;
 
 /// Trait for interacting with the MusicBrainz API.
-// TODO: #[cfg_attr(test, automock)]
 pub trait IMusicBrainz {
     fn lookup_artist_release_groups(&mut self, mbid: &Mbid) -> Result<Vec<Album>, Error>;
     fn search_release_group(
@@ -20,7 +16,7 @@ pub trait IMusicBrainz {
     ) -> Result<Vec<Match<Album>>, Error>;
 }
 
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub struct Match<T> {
     pub score: u8,
     pub item: T,

src/external/musicbrainz/api/mod.rs

@@ -150,6 +150,7 @@ struct SearchReleaseGroup {
     title: String,
     first_release_date: String,
     primary_type: SerdeAlbumPrimaryType,
+    secondary_types: Option<Vec<SerdeAlbumSecondaryType>>,
 }
 
 impl TryFrom<SearchReleaseGroup> for Match<Album> {
@@ -160,7 +161,10 @@ impl TryFrom<SearchReleaseGroup> for Match<Album> {
             entity.title,
             AlbumDate::from_mb_date(&entity.first_release_date)?,
             Some(entity.primary_type.into()),
-            vec![],
+            entity
+                .secondary_types
+                .map(|v| v.into_iter().map(|st| st.into()).collect())
+                .unwrap_or_default(),
         );
         let mbref = MbAlbumRef::from_uuid_str(entity.id)
             .map_err(|err| Error::MbidParse(err.to_string()))?;
@@ -229,7 +233,7 @@ pub enum SerdeAlbumSecondaryTypeDef {
     FieldRecording,
 }
 
-#[derive(Debug, Deserialize)]
+#[derive(Clone, Debug, Deserialize)]
 pub struct SerdeAlbumSecondaryType(
     #[serde(with = "SerdeAlbumSecondaryTypeDef")] AlbumSecondaryType,
 );
@@ -320,6 +324,7 @@ mod tests {
             title: String::from("an album"),
             first_release_date: String::from("1986-04"),
             primary_type: SerdeAlbumPrimaryType(AlbumPrimaryType::Album),
+            secondary_types: Some(vec![SerdeAlbumSecondaryType(AlbumSecondaryType::Live)]),
         };
         let response = ResponseSearchReleaseGroup {
             release_groups: vec![release_group],
@@ -350,7 +355,7 @@ mod tests {
             AlbumId::new("an album"),
             (1986, 4),
             Some(AlbumPrimaryType::Album),
-            vec![],
+            vec![AlbumSecondaryType::Live],
         );
         album.set_musicbrainz_ref(
             MbAlbumRef::from_uuid_str("11111111-1111-1111-1111-111111111111").unwrap(),

src/main.rs

@@ -16,6 +16,7 @@ use musichoard::{
             executor::{ssh::BeetsLibrarySshExecutor, BeetsLibraryProcessExecutor},
             BeetsLibrary,
         },
+        musicbrainz::api::{client::MusicBrainzApiClient, MusicBrainzApi},
     },
     interface::{
         database::{IDatabase, NullDatabase},
@@ -26,6 +27,12 @@ use musichoard::{
 
 use tui::{App, EventChannel, EventHandler, EventListener, Tui, Ui};
 
+const MUSICHOARD_HTTP_USER_AGENT: &str = concat!(
+    "MusicHoard/",
+    env!("CARGO_PKG_VERSION"),
+    " ( musichoard@thenineworlds.net )"
+);
+
 #[derive(StructOpt)]
 struct Opt {
     #[structopt(flatten)]
@@ -74,7 +81,11 @@ fn with<Database: IDatabase, Library: ILibrary>(builder: MusicHoardBuilder<Datab
     let listener = EventListener::new(channel.sender());
     let handler = EventHandler::new(channel.receiver());
 
-    let app = App::new(music_hoard);
+    let client = MusicBrainzApiClient::new(MUSICHOARD_HTTP_USER_AGENT)
+        .expect("failed to initialise HTTP client");
+    let api = Box::new(MusicBrainzApi::new(client));
+
+    let app = App::new(music_hoard, api);
     let ui = Ui;
 
     // Run the TUI application.

src/tui/app/machine/browse.rs

@@ -1,6 +1,10 @@
+use std::{thread, time};
+
+use musichoard::collection::musicbrainz::IMusicBrainzRef;
+
 use crate::tui::{
     app::{
-        machine::{App, AppInner, AppMachine},
+        machine::{matches::AppMatchesInfo, App, AppInner, AppMachine},
         selection::{Delta, ListSelection},
         AppPublic, AppState, IAppInteractBrowse,
     },
@@ -81,6 +85,45 @@ impl<MH: IMusicHoard> IAppInteractBrowse for AppMachine<MH, AppBrowse> {
         AppMachine::search(self.inner, orig).into()
     }
 
+    fn fetch_musicbrainz(mut self) -> Self::APP {
+        let coll = self.inner.music_hoard.get_collection();
+        let artist = match self.inner.selection.state_artist(coll) {
+            Some(artist_state) => &coll[artist_state.index],
+            None => {
+                return AppMachine::error(self.inner, "cannot fetch: no artist selected").into()
+            }
+        };
+
+        let arid = match artist.musicbrainz {
+            Some(ref mbid) => mbid.mbid(),
+            None => {
+                return AppMachine::error(self.inner, "cannot fetch: missing artist MBID").into()
+            }
+        };
+
+        let mut artist_album_matches = vec![];
+        let mut album_iter = artist.albums.iter().peekable();
+        while let Some(album) = album_iter.next() {
+            if album.musicbrainz.is_some() {
+                continue;
+            }
+
+            match self.inner.mb_api.search_release_group(arid, album) {
+                Ok(matches) => artist_album_matches.push(AppMatchesInfo {
+                    matching: album.clone(),
+                    matches,
+                }),
+                Err(err) => return AppMachine::error(self.inner, err.to_string()).into(),
+            }
+
+            if album_iter.peek().is_some() {
+                thread::sleep(time::Duration::from_secs(1));
+            }
+        }
+
+        AppMachine::matches(self.inner, artist_album_matches).into()
+    }
+
     fn no_op(self) -> Self::APP {
         self.into()
     }
@@ -88,10 +131,17 @@ impl<MH: IMusicHoard> IAppInteractBrowse for AppMachine<MH, AppBrowse> {
 
 #[cfg(test)]
 mod tests {
+    use mockall::{predicate, Sequence};
+    use musichoard::collection::album::Album;
+
     use crate::tui::{
         app::{
-            machine::tests::{inner, music_hoard},
-            Category, IAppInteract,
+            machine::tests::{inner, inner_with_mb, music_hoard},
+            Category, IAppAccess, IAppInteract, IAppInteractMatches,
+        },
+        lib::external::musicbrainz::{
+            self,
+            api::{Match, Mbid, MockIMusicBrainz},
         },
         testmod::COLLECTION,
     };
@@ -168,6 +218,104 @@ mod tests {
         app.unwrap_search();
     }
 
+    #[test]
+    fn fetch_musicbrainz() {
+        let mut mb_api = Box::new(MockIMusicBrainz::new());
+
+        let arid: Mbid = "11111111-1111-1111-1111-111111111111".try_into().unwrap();
+        let album_1 = COLLECTION[1].albums[0].clone();
+        let album_4 = COLLECTION[1].albums[3].clone();
+
+        let album_match_1_1 = Match::new(100, album_1.clone());
+        let album_match_1_2 = Match::new(50, album_4.clone());
+        let album_match_4_1 = Match::new(100, album_4.clone());
+        let album_match_4_2 = Match::new(30, album_1.clone());
+        let matches_1 = vec![album_match_1_1.clone(), album_match_1_2.clone()];
+        let matches_4 = vec![album_match_4_1.clone(), album_match_4_2.clone()];
+
+        let result_1: Result<Vec<Match<Album>>, musicbrainz::api::Error> = Ok(matches_1.clone());
+        let result_4: Result<Vec<Match<Album>>, musicbrainz::api::Error> = Ok(matches_4.clone());
+
+        // Other albums have an MBID and so they will be skipped.
+        let mut seq = Sequence::new();
+
+        mb_api
+            .expect_search_release_group()
+            .with(predicate::eq(arid.clone()), predicate::eq(album_1.clone()))
+            .times(1)
+            .in_sequence(&mut seq)
+            .return_once(|_, _| result_1);
+        mb_api
+            .expect_search_release_group()
+            .with(predicate::eq(arid.clone()), predicate::eq(album_4.clone()))
+            .times(1)
+            .in_sequence(&mut seq)
+            .return_once(|_, _| result_4);
+
+        let browse = AppMachine::browse(inner_with_mb(music_hoard(COLLECTION.to_owned()), mb_api));
+
+        // Use the second artist for this test.
+        let browse = browse.increment_selection(Delta::Line).unwrap_browse();
+        let mut app = browse.fetch_musicbrainz();
+
+        let public = app.get();
+        assert!(matches!(public.state, AppState::Matches(_)));
+
+        let public_matches = public.state.unwrap_matches();
+
+        assert_eq!(public_matches.matching, Some(&album_1));
+        assert_eq!(public_matches.matches, Some(matches_1.as_slice()));
+
+        let mut app = app.unwrap_matches().select();
+
+        let public = app.get();
+        assert!(matches!(public.state, AppState::Matches(_)));
+
+        let public_matches = public.state.unwrap_matches();
+
+        assert_eq!(public_matches.matching, Some(&album_4));
+        assert_eq!(public_matches.matches, Some(matches_4.as_slice()));
+
+        let app = app.unwrap_matches().select();
+        app.unwrap_browse();
+    }
+
+    #[test]
+    fn fetch_musicbrainz_no_artist() {
+        let browse = AppMachine::browse(inner(music_hoard(vec![])));
+        let app = browse.fetch_musicbrainz();
+        app.unwrap_error();
+    }
+
+    #[test]
+    fn fetch_musicbrainz_no_mbid() {
+        let browse = AppMachine::browse(inner(music_hoard(COLLECTION.to_owned())));
+
+        // Use the fourth artist for this test as they have no MBID.
+        let browse = browse.increment_selection(Delta::Line).unwrap_browse();
+        let browse = browse.increment_selection(Delta::Line).unwrap_browse();
+        let browse = browse.increment_selection(Delta::Line).unwrap_browse();
+        let app = browse.fetch_musicbrainz();
+        app.unwrap_error();
+    }
+
+    #[test]
+    fn fetch_musicbrainz_api_error() {
+        let mut mb_api = Box::new(MockIMusicBrainz::new());
+
+        let error = Err(musicbrainz::api::Error::RateLimit);
+
+        mb_api
+            .expect_search_release_group()
+            .times(1)
+            .return_once(|_, _| error);
+
+        let browse = AppMachine::browse(inner_with_mb(music_hoard(COLLECTION.to_owned()), mb_api));
+
+        let app = browse.fetch_musicbrainz();
+        app.unwrap_error();
+    }
+
     #[test]
     fn no_op() {
         let browse = AppMachine::browse(inner(music_hoard(vec![])));

src/tui/app/machine/matches.rs

@@ -0,0 +1,295 @@
+use std::cmp;
+
+use musichoard::{collection::album::Album, interface::musicbrainz::Match};
+
+use crate::tui::{
+    app::{
+        machine::{App, AppInner, AppMachine},
+        AppPublic, AppPublicMatches, AppState, IAppInteractMatches, WidgetState,
+    },
+    lib::IMusicHoard,
+};
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct AppMatchesInfo {
+    pub matching: Album,
+    pub matches: Vec<Match<Album>>,
+}
+
+pub struct AppMatches {
+    matches_info_vec: Vec<AppMatchesInfo>,
+    index: Option<usize>,
+    state: WidgetState,
+}
+
+impl<MH: IMusicHoard> AppMachine<MH, AppMatches> {
+    pub fn matches(inner: AppInner<MH>, matches_info_vec: Vec<AppMatchesInfo>) -> Self {
+        let mut index = None;
+        let mut state = WidgetState::default();
+        if let Some(matches_info) = matches_info_vec.first() {
+            index = Some(0);
+            if !matches_info.matches.is_empty() {
+                state.list.select(Some(0));
+            }
+        }
+
+        AppMachine {
+            inner,
+            state: AppMatches {
+                matches_info_vec,
+                index,
+                state,
+            },
+        }
+    }
+}
+
+impl<MH: IMusicHoard> From<AppMachine<MH, AppMatches>> for App<MH> {
+    fn from(machine: AppMachine<MH, AppMatches>) -> Self {
+        AppState::Matches(machine)
+    }
+}
+
+impl<'a, MH: IMusicHoard> From<&'a mut AppMachine<MH, AppMatches>> for AppPublic<'a> {
+    fn from(machine: &'a mut AppMachine<MH, AppMatches>) -> Self {
+        let (matching, matches) = match machine.state.index {
+            Some(index) => (
+                Some(&machine.state.matches_info_vec[index].matching),
+                Some(machine.state.matches_info_vec[index].matches.as_slice()),
+            ),
+            None => (None, None),
+        };
+
+        AppPublic {
+            inner: (&mut machine.inner).into(),
+            state: AppState::Matches(AppPublicMatches {
+                matching,
+                matches,
+                state: &mut machine.state.state,
+            }),
+        }
+    }
+}
+
+impl<MH: IMusicHoard> IAppInteractMatches for AppMachine<MH, AppMatches> {
+    type APP = App<MH>;
+
+    fn prev_match(mut self) -> Self::APP {
+        if let Some(list_index) = self.state.state.list.selected() {
+            let result = list_index.saturating_sub(1);
+            self.state.state.list.select(Some(result));
+        }
+
+        self.into()
+    }
+
+    fn next_match(mut self) -> Self::APP {
+        if let Some(list_index) = self.state.state.list.selected() {
+            let result = list_index.saturating_add(1);
+            let to = cmp::min(
+                result,
+                self.state.matches_info_vec[self.state.index.unwrap()]
+                    .matches
+                    .len()
+                    .saturating_sub(1),
+            );
+            self.state.state.list.select(Some(to));
+        }
+
+        self.into()
+    }
+
+    fn select(mut self) -> Self::APP {
+        self.state.index = self.state.index.map(|i| i.saturating_add(1));
+        self.state.state = WidgetState::default();
+        if let Some(index) = self.state.index {
+            if let Some(matches_info) = self.state.matches_info_vec.get(index) {
+                if !matches_info.matches.is_empty() {
+                    self.state.state.list.select(Some(0));
+                }
+                return self.into();
+            }
+        }
+
+        AppMachine::browse(self.inner).into()
+    }
+
+    fn abort(self) -> Self::APP {
+        AppMachine::browse(self.inner).into()
+    }
+
+    fn no_op(self) -> Self::APP {
+        self.into()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use musichoard::collection::album::{AlbumDate, AlbumId, AlbumPrimaryType, AlbumSecondaryType};
+
+    use crate::tui::app::{
+        machine::tests::{inner, music_hoard},
+        IAppAccess,
+    };
+
+    use super::*;
+
+    fn matches_info_vec() -> Vec<AppMatchesInfo> {
+        let album_1 = Album::new(
+            AlbumId::new("Album 1"),
+            AlbumDate::new(Some(1990), Some(5), None),
+            Some(AlbumPrimaryType::Album),
+            vec![AlbumSecondaryType::Live, AlbumSecondaryType::Compilation],
+        );
+
+        let album_1_1 = album_1.clone();
+        let album_match_1_1 = Match {
+            score: 100,
+            item: album_1_1,
+        };
+
+        let mut album_1_2 = album_1.clone();
+        album_1_2.id.title.push_str(" extra title part");
+        album_1_2.secondary_types.pop();
+        let album_match_1_2 = Match {
+            score: 100,
+            item: album_1_2,
+        };
+
+        let matches_info_1 = AppMatchesInfo {
+            matching: album_1.clone(),
+            matches: vec![album_match_1_1.clone(), album_match_1_2.clone()],
+        };
+
+        let album_2 = Album::new(
+            AlbumId::new("Album 2"),
+            AlbumDate::new(Some(2001), None, None),
+            Some(AlbumPrimaryType::Album),
+            vec![],
+        );
+
+        let album_2_1 = album_1.clone();
+        let album_match_2_1 = Match {
+            score: 100,
+            item: album_2_1,
+        };
+
+        let matches_info_2 = AppMatchesInfo {
+            matching: album_2.clone(),
+            matches: vec![album_match_2_1.clone()],
+        };
+
+        vec![matches_info_1, matches_info_2]
+    }
+
+    #[test]
+    fn create_empty() {
+        let matches = AppMachine::matches(inner(music_hoard(vec![])), vec![]);
+
+        let widget_state = WidgetState::default();
+
+        assert_eq!(matches.state.matches_info_vec, vec![]);
+        assert_eq!(matches.state.index, None);
+        assert_eq!(matches.state.state, widget_state);
+
+        let mut app = matches.no_op();
+        let public = app.get();
+        let public_matches = public.state.unwrap_matches();
+
+        assert_eq!(public_matches.matching, None);
+        assert_eq!(public_matches.matches, None);
+        assert_eq!(public_matches.state, &widget_state);
+    }
+
+    #[test]
+    fn create_nonempty() {
+        let matches_info_vec = matches_info_vec();
+        let matches = AppMachine::matches(inner(music_hoard(vec![])), matches_info_vec.clone());
+
+        let mut widget_state = WidgetState::default();
+        widget_state.list.select(Some(0));
+
+        assert_eq!(matches.state.matches_info_vec, matches_info_vec);
+        assert_eq!(matches.state.index, Some(0));
+        assert_eq!(matches.state.state, widget_state);
+
+        let mut app = matches.no_op();
+        let public = app.get();
+        let public_matches = public.state.unwrap_matches();
+
+        assert_eq!(public_matches.matching, Some(&matches_info_vec[0].matching));
+        assert_eq!(
+            public_matches.matches,
+            Some(matches_info_vec[0].matches.as_slice())
+        );
+        assert_eq!(public_matches.state, &widget_state);
+    }
+
+    #[test]
+    fn matches_flow() {
+        let matches_info_vec = matches_info_vec();
+        let matches = AppMachine::matches(inner(music_hoard(vec![])), matches_info_vec.clone());
+
+        let mut widget_state = WidgetState::default();
+        widget_state.list.select(Some(0));
+
+        assert_eq!(matches.state.matches_info_vec, matches_info_vec);
+        assert_eq!(matches.state.index, Some(0));
+        assert_eq!(matches.state.state, widget_state);
+
+        let matches = matches.prev_match().unwrap_matches();
+
+        assert_eq!(matches.state.index, Some(0));
+        assert_eq!(matches.state.state.list.selected(), Some(0));
+
+        let matches = matches.next_match().unwrap_matches();
+
+        assert_eq!(matches.state.index, Some(0));
+        assert_eq!(matches.state.state.list.selected(), Some(1));
+
+        let matches = matches.next_match().unwrap_matches();
+
+        assert_eq!(matches.state.index, Some(0));
+        assert_eq!(matches.state.state.list.selected(), Some(1));
+
+        let matches = matches.select().unwrap_matches();
+
+        assert_eq!(matches.state.index, Some(1));
+        assert_eq!(matches.state.state.list.selected(), Some(0));
+
+        // And it's done
+        matches.select().unwrap_browse();
+    }
+
+    #[test]
+    fn matches_abort() {
+        let matches_info_vec = matches_info_vec();
+        let matches = AppMachine::matches(inner(music_hoard(vec![])), matches_info_vec.clone());
+
+        let mut widget_state = WidgetState::default();
+        widget_state.list.select(Some(0));
+
+        assert_eq!(matches.state.matches_info_vec, matches_info_vec);
+        assert_eq!(matches.state.index, Some(0));
+        assert_eq!(matches.state.state, widget_state);
+
+        matches.abort().unwrap_browse();
+    }
+
+    #[test]
+    fn matches_select_empty() {
+        let matches = AppMachine::matches(inner(music_hoard(vec![])), vec![]);
+
+        assert_eq!(matches.state.matches_info_vec, vec![]);
+        assert_eq!(matches.state.index, None);
+
+        matches.select().unwrap_browse();
+    }
+
+    #[test]
+    fn no_op() {
+        let matches = AppMachine::matches(inner(music_hoard(vec![])), vec![]);
+        let app = matches.no_op();
+        app.unwrap_matches();
+    }
+}

src/tui/app/machine/mod.rs

@@ -2,18 +2,20 @@ mod browse;
 mod critical;
 mod error;
 mod info;
+mod matches;
 mod reload;
 mod search;
 
 use crate::tui::{
     app::{selection::Selection, AppPublic, AppPublicInner, AppState, IAppAccess, IAppInteract},
-    lib::IMusicHoard,
+    lib::{external::musicbrainz::api::IMusicBrainz, IMusicHoard},
 };
 
 use browse::AppBrowse;
 use critical::AppCritical;
 use error::AppError;
 use info::AppInfo;
+use matches::AppMatches;
 use reload::AppReload;
 use search::AppSearch;
 
@@ -22,6 +24,7 @@ pub type App<MH> = AppState<
     AppMachine<MH, AppInfo>,
     AppMachine<MH, AppReload>,
     AppMachine<MH, AppSearch>,
+    AppMachine<MH, AppMatches>,
     AppMachine<MH, AppError>,
     AppMachine<MH, AppCritical>,
 >;
@@ -34,13 +37,14 @@ pub struct AppMachine<MH: IMusicHoard, STATE> {
 pub struct AppInner<MH: IMusicHoard> {
     running: bool,
     music_hoard: MH,
+    mb_api: Box<dyn IMusicBrainz>,
     selection: Selection,
 }
 
 impl<MH: IMusicHoard> App<MH> {
-    pub fn new(mut music_hoard: MH) -> Self {
+    pub fn new(mut music_hoard: MH, mb_api: Box<dyn IMusicBrainz>) -> Self {
         let init_result = Self::init(&mut music_hoard);
-        let inner = AppInner::new(music_hoard);
+        let inner = AppInner::new(music_hoard, mb_api);
         match init_result {
             Ok(()) => AppMachine::browse(inner).into(),
             Err(err) => AppMachine::critical(inner, err.to_string()).into(),
@@ -56,6 +60,7 @@ impl<MH: IMusicHoard> App<MH> {
         match self {
             AppState::Browse(browse) => &browse.inner,
             AppState::Info(info) => &info.inner,
+            AppState::Matches(matches) => &matches.inner,
             AppState::Reload(reload) => &reload.inner,
             AppState::Search(search) => &search.inner,
             AppState::Error(error) => &error.inner,
@@ -67,6 +72,7 @@ impl<MH: IMusicHoard> App<MH> {
         match self {
             AppState::Browse(browse) => &mut browse.inner,
             AppState::Info(info) => &mut info.inner,
+            AppState::Matches(matches) => &mut matches.inner,
             AppState::Reload(reload) => &mut reload.inner,
             AppState::Search(search) => &mut search.inner,
             AppState::Error(error) => &mut error.inner,
@@ -80,6 +86,7 @@ impl<MH: IMusicHoard> IAppInteract for App<MH> {
     type IS = AppMachine<MH, AppInfo>;
     type RS = AppMachine<MH, AppReload>;
     type SS = AppMachine<MH, AppSearch>;
+    type MS = AppMachine<MH, AppMatches>;
     type ES = AppMachine<MH, AppError>;
     type CS = AppMachine<MH, AppCritical>;
 
@@ -92,7 +99,9 @@ impl<MH: IMusicHoard> IAppInteract for App<MH> {
         self
     }
 
-    fn state(self) -> AppState<Self::BS, Self::IS, Self::RS, Self::SS, Self::ES, Self::CS> {
+    fn state(
+        self,
+    ) -> AppState<Self::BS, Self::IS, Self::RS, Self::SS, Self::MS, Self::ES, Self::CS> {
         self
     }
 }
@@ -102,6 +111,7 @@ impl<MH: IMusicHoard> IAppAccess for App<MH> {
         match self {
             AppState::Browse(browse) => browse.into(),
             AppState::Info(info) => info.into(),
+            AppState::Matches(matches) => matches.into(),
             AppState::Reload(reload) => reload.into(),
             AppState::Search(search) => search.into(),
             AppState::Error(error) => error.into(),
@@ -111,11 +121,12 @@ impl<MH: IMusicHoard> IAppAccess for App<MH> {
 }
 
 impl<MH: IMusicHoard> AppInner<MH> {
-    pub fn new(music_hoard: MH) -> Self {
+    pub fn new(music_hoard: MH, mb_api: Box<dyn IMusicBrainz>) -> Self {
         let selection = Selection::new(music_hoard.get_collection());
         AppInner {
             running: true,
             music_hoard,
+            mb_api,
             selection,
         }
     }
@@ -136,12 +147,12 @@ mod tests {
 
     use crate::tui::{
         app::{AppState, IAppInteract, IAppInteractBrowse},
-        lib::MockIMusicHoard,
+        lib::{external::musicbrainz::api::MockIMusicBrainz, MockIMusicHoard},
     };
 
     use super::*;
 
-    impl<BS, IS, RS, SS, ES, CS> AppState<BS, IS, RS, SS, ES, CS> {
+    impl<BS, IS, RS, SS, MS, ES, CS> AppState<BS, IS, RS, SS, MS, ES, CS> {
         pub fn unwrap_browse(self) -> BS {
             match self {
                 AppState::Browse(browse) => browse,
@@ -170,6 +181,13 @@ mod tests {
             }
         }
 
+        pub fn unwrap_matches(self) -> MS {
+            match self {
+                AppState::Matches(matches) => matches,
+                _ => panic!(),
+            }
+        }
+
         pub fn unwrap_error(self) -> ES {
             match self {
                 AppState::Error(error) => error,
@@ -203,21 +221,32 @@ mod tests {
         music_hoard
     }
 
+    fn mb_api() -> Box<MockIMusicBrainz> {
+        Box::new(MockIMusicBrainz::new())
+    }
+
     pub fn inner(music_hoard: MockIMusicHoard) -> AppInner<MockIMusicHoard> {
-        AppInner::new(music_hoard)
+        AppInner::new(music_hoard, mb_api())
+    }
+
+    pub fn inner_with_mb(
+        music_hoard: MockIMusicHoard,
+        mb_api: Box<MockIMusicBrainz>,
+    ) -> AppInner<MockIMusicHoard> {
+        AppInner::new(music_hoard, mb_api)
     }
 
     #[test]
     fn state_browse() {
-        let mut app = App::new(music_hoard_init(vec![]));
+        let mut app = App::new(music_hoard_init(vec![]), mb_api());
         assert!(app.is_running());
 
         let state = app.state();
-        matches!(state, AppState::Browse(_));
+        assert!(matches!(state, AppState::Browse(_)));
         app = state;
 
         let public = app.get();
-        matches!(public.state, AppState::Browse(_));
+        assert!(matches!(public.state, AppState::Browse(_)));
 
         let app = app.force_quit();
         assert!(!app.is_running());
@@ -225,17 +254,17 @@ mod tests {
 
     #[test]
     fn state_info() {
-        let mut app = App::new(music_hoard_init(vec![]));
+        let mut app = App::new(music_hoard_init(vec![]), mb_api());
         assert!(app.is_running());
 
         app = app.unwrap_browse().show_info_overlay();
 
         let state = app.state();
-        matches!(state, AppState::Info(_));
+        assert!(matches!(state, AppState::Info(_)));
         app = state;
 
         let public = app.get();
-        matches!(public.state, AppState::Info(_));
+        assert!(matches!(public.state, AppState::Info(_)));
 
         let app = app.force_quit();
         assert!(!app.is_running());
@@ -243,17 +272,17 @@ mod tests {
 
     #[test]
     fn state_reload() {
-        let mut app = App::new(music_hoard_init(vec![]));
+        let mut app = App::new(music_hoard_init(vec![]), mb_api());
         assert!(app.is_running());
 
         app = app.unwrap_browse().show_reload_menu();
 
         let state = app.state();
-        matches!(state, AppState::Reload(_));
+        assert!(matches!(state, AppState::Reload(_)));
         app = state;
 
         let public = app.get();
-        matches!(public.state, AppState::Reload(_));
+        assert!(matches!(public.state, AppState::Reload(_)));
 
         let app = app.force_quit();
         assert!(!app.is_running());
@@ -261,17 +290,35 @@ mod tests {
 
     #[test]
     fn state_search() {
-        let mut app = App::new(music_hoard_init(vec![]));
+        let mut app = App::new(music_hoard_init(vec![]), mb_api());
         assert!(app.is_running());
 
         app = app.unwrap_browse().begin_search();
 
         let state = app.state();
-        matches!(state, AppState::Search(_));
+        assert!(matches!(state, AppState::Search(_)));
         app = state;
 
         let public = app.get();
-        matches!(public.state, AppState::Search(""));
+        assert!(matches!(public.state, AppState::Search("")));
+
+        let app = app.force_quit();
+        assert!(!app.is_running());
+    }
+
+    #[test]
+    fn state_matches() {
+        let mut app = App::new(music_hoard_init(vec![]), mb_api());
+        assert!(app.is_running());
+
+        app = AppMachine::matches(app.unwrap_browse().inner, vec![]).into();
+
+        let state = app.state();
+        assert!(matches!(state, AppState::Matches(_)));
+        app = state;
+
+        let public = app.get();
+        assert!(matches!(public.state, AppState::Matches(_)));
 
         let app = app.force_quit();
         assert!(!app.is_running());
@@ -279,17 +326,17 @@ mod tests {
 
     #[test]
     fn state_error() {
-        let mut app = App::new(music_hoard_init(vec![]));
+        let mut app = App::new(music_hoard_init(vec![]), mb_api());
         assert!(app.is_running());
 
         app = AppMachine::error(app.unwrap_browse().inner, "get rekt").into();
 
         let state = app.state();
-        matches!(state, AppState::Error(_));
+        assert!(matches!(state, AppState::Error(_)));
         app = state;
 
         let public = app.get();
-        matches!(public.state, AppState::Error("get rekt"));
+        assert!(matches!(public.state, AppState::Error("get rekt")));
 
         app = app.force_quit();
         assert!(!app.is_running());
@@ -297,17 +344,17 @@ mod tests {
 
     #[test]
     fn state_critical() {
-        let mut app = App::new(music_hoard_init(vec![]));
+        let mut app = App::new(music_hoard_init(vec![]), mb_api());
         assert!(app.is_running());
 
         app = AppMachine::critical(app.unwrap_browse().inner, "get rekt").into();
 
         let state = app.state();
-        matches!(state, AppState::Critical(_));
+        assert!(matches!(state, AppState::Critical(_)));
         app = state;
 
         let public = app.get();
-        matches!(public.state, AppState::Critical("get rekt"));
+        assert!(matches!(public.state, AppState::Critical("get rekt")));
 
         app = app.force_quit();
         assert!(!app.is_running());
@@ -323,7 +370,7 @@ mod tests {
             .return_once(|| Err(musichoard::Error::LibraryError(String::from("get rekt"))));
         music_hoard.expect_get_collection().return_const(vec![]);
 
-        let app = App::new(music_hoard);
+        let app = App::new(music_hoard, mb_api());
         assert!(app.is_running());
         app.unwrap_critical();
     }

src/tui/app/mod.rs

@@ -4,13 +4,17 @@ mod selection;
 pub use machine::App;
 pub use selection::{Category, Delta, Selection, WidgetState};
 
-use musichoard::collection::Collection;
+use musichoard::{
+    collection::{album::Album, Collection},
+    interface::musicbrainz::Match,
+};
 
-pub enum AppState<BS, IS, RS, SS, ES, CS> {
+pub enum AppState<BS, IS, RS, SS, MS, ES, CS> {
     Browse(BS),
     Info(IS),
     Reload(RS),
     Search(SS),
+    Matches(MS),
     Error(ES),
     Critical(CS),
 }
@@ -20,6 +24,7 @@ pub trait IAppInteract {
     type IS: IAppInteractInfo<APP = Self>;
     type RS: IAppInteractReload<APP = Self>;
     type SS: IAppInteractSearch<APP = Self>;
+    type MS: IAppInteractMatches<APP = Self>;
     type ES: IAppInteractError<APP = Self>;
     type CS: IAppInteractCritical<APP = Self>;
 
@@ -27,7 +32,9 @@ pub trait IAppInteract {
     fn force_quit(self) -> Self;
 
     #[allow(clippy::type_complexity)]
-    fn state(self) -> AppState<Self::BS, Self::IS, Self::RS, Self::SS, Self::ES, Self::CS>;
+    fn state(
+        self,
+    ) -> AppState<Self::BS, Self::IS, Self::RS, Self::SS, Self::MS, Self::ES, Self::CS>;
 }
 
 pub trait IAppInteractBrowse {
@@ -46,6 +53,8 @@ pub trait IAppInteractBrowse {
 
     fn begin_search(self) -> Self::APP;
 
+    fn fetch_musicbrainz(self) -> Self::APP;
+
     fn no_op(self) -> Self::APP;
 }
 
@@ -79,6 +88,18 @@ pub trait IAppInteractSearch {
     fn no_op(self) -> Self::APP;
 }
 
+pub trait IAppInteractMatches {
+    type APP: IAppInteract;
+
+    fn prev_match(self) -> Self::APP;
+    fn next_match(self) -> Self::APP;
+    fn select(self) -> Self::APP;
+
+    fn abort(self) -> Self::APP;
+
+    fn no_op(self) -> Self::APP;
+}
+
 pub trait IAppInteractError {
     type APP: IAppInteract;
 
@@ -109,9 +130,16 @@ pub struct AppPublicInner<'app> {
     pub selection: &'app mut Selection,
 }
 
-pub type AppPublicState<'app> = AppState<(), (), (), &'app str, &'app str, &'app str>;
+pub struct AppPublicMatches<'app> {
+    pub matching: Option<&'app Album>,
+    pub matches: Option<&'app [Match<Album>]>,
+    pub state: &'app mut WidgetState,
+}
 
-impl<BS, IS, RS, SS, ES, CS> AppState<BS, IS, RS, SS, ES, CS> {
+pub type AppPublicState<'app> =
+    AppState<(), (), (), &'app str, AppPublicMatches<'app>, &'app str, &'app str>;
+
+impl<BS, IS, RS, SS, MS, ES, CS> AppState<BS, IS, RS, SS, MS, ES, CS> {
     pub fn is_search(&self) -> bool {
         matches!(self, AppState::Search(_))
     }

src/tui/handler.rs

@@ -6,7 +6,7 @@ use mockall::automock;
 use crate::tui::{
     app::{
         AppState, Delta, IAppInteract, IAppInteractBrowse, IAppInteractCritical, IAppInteractError,
-        IAppInteractInfo, IAppInteractReload, IAppInteractSearch,
+        IAppInteractInfo, IAppInteractMatches, IAppInteractReload, IAppInteractSearch,
     },
     event::{Event, EventError, EventReceiver},
 };
@@ -22,6 +22,7 @@ trait IEventHandlerPrivate<APP: IAppInteract> {
     fn handle_info_key_event(app: <APP as IAppInteract>::IS, key_event: KeyEvent) -> APP;
     fn handle_reload_key_event(app: <APP as IAppInteract>::RS, key_event: KeyEvent) -> APP;
     fn handle_search_key_event(app: <APP as IAppInteract>::SS, key_event: KeyEvent) -> APP;
+    fn handle_matches_key_event(app: <APP as IAppInteract>::MS, key_event: KeyEvent) -> APP;
     fn handle_error_key_event(app: <APP as IAppInteract>::ES, key_event: KeyEvent) -> APP;
     fn handle_critical_key_event(app: <APP as IAppInteract>::CS, key_event: KeyEvent) -> APP;
 }
@@ -69,6 +70,9 @@ impl<APP: IAppInteract> IEventHandlerPrivate<APP> for EventHandler {
             AppState::Search(search) => {
                 <Self as IEventHandlerPrivate<APP>>::handle_search_key_event(search, key_event)
             }
+            AppState::Matches(matches) => {
+                <Self as IEventHandlerPrivate<APP>>::handle_matches_key_event(matches, key_event)
+            }
             AppState::Error(error) => {
                 <Self as IEventHandlerPrivate<APP>>::handle_error_key_event(error, key_event)
             }
@@ -102,6 +106,7 @@ impl<APP: IAppInteract> IEventHandlerPrivate<APP> for EventHandler {
                     app.no_op()
                 }
             }
+            KeyCode::Char('f') | KeyCode::Char('F') => app.fetch_musicbrainz(),
             // Othey keys.
             _ => app.no_op(),
         }
@@ -156,6 +161,19 @@ impl<APP: IAppInteract> IEventHandlerPrivate<APP> for EventHandler {
         }
     }
 
+    fn handle_matches_key_event(app: <APP as IAppInteract>::MS, key_event: KeyEvent) -> APP {
+        match key_event.code {
+            // Abort.
+            KeyCode::Esc | KeyCode::Char('q') | KeyCode::Char('Q') => app.abort(),
+            // Select.
+            KeyCode::Up => app.prev_match(),
+            KeyCode::Down => app.next_match(),
+            KeyCode::Enter => app.select(),
+            // Othey keys.
+            _ => app.no_op(),
+        }
+    }
+
     fn handle_error_key_event(app: <APP as IAppInteract>::ES, _key_event: KeyEvent) -> APP {
         // Any key dismisses the error.
         app.dismiss_error()

src/tui/lib.rs

@@ -1,6 +1,6 @@
 use musichoard::{
-    collection::Collection, interface::database::IDatabase, interface::library::ILibrary,
-    IMusicHoardBase, IMusicHoardDatabase, IMusicHoardLibrary, MusicHoard,
+    collection::Collection, interface, IMusicHoardBase, IMusicHoardDatabase, IMusicHoardLibrary,
+    MusicHoard,
 };
 
 #[cfg(test)]
@@ -14,7 +14,9 @@ pub trait IMusicHoard {
 }
 
 // GRCOV_EXCL_START
-impl<Database: IDatabase, Library: ILibrary> IMusicHoard for MusicHoard<Database, Library> {
+impl<Database: interface::database::IDatabase, Library: interface::library::ILibrary> IMusicHoard
+    for MusicHoard<Database, Library>
+{
     fn rescan_library(&mut self) -> Result<(), musichoard::Error> {
         <Self as IMusicHoardLibrary>::rescan_library(self)
     }
@@ -28,3 +30,45 @@ impl<Database: IDatabase, Library: ILibrary> IMusicHoard for MusicHoard<Database
     }
 }
 // GRCOV_EXCL_STOP
+
+pub mod external {
+    pub mod musicbrainz {
+        pub mod api {
+            use musichoard::{
+                collection::album::Album,
+                external::musicbrainz::api::{IMusicBrainzApiClient, MusicBrainzApi},
+                interface,
+            };
+
+            #[cfg(test)]
+            use mockall::automock;
+
+            pub type Match<T> = interface::musicbrainz::Match<T>;
+            pub type Mbid = interface::musicbrainz::Mbid;
+            pub type Error = interface::musicbrainz::Error;
+
+            #[cfg_attr(test, automock)]
+            pub trait IMusicBrainz {
+                fn search_release_group(
+                    &mut self,
+                    arid: &Mbid,
+                    album: &Album,
+                ) -> Result<Vec<Match<Album>>, Error>;
+            }
+
+            // GRCOV_EXCL_START
+            impl<Mbc: IMusicBrainzApiClient> IMusicBrainz for MusicBrainzApi<Mbc> {
+                fn search_release_group(
+                    &mut self,
+                    arid: &Mbid,
+                    album: &Album,
+                ) -> Result<Vec<Match<Album>>, Error> {
+                    <Self as interface::musicbrainz::IMusicBrainz>::search_release_group(
+                        self, arid, album,
+                    )
+                }
+            }
+            // GRCOV_EXCL_STOP
+        }
+    }
+}

src/tui/mod.rs

@@ -173,6 +173,7 @@ mod testmod;
 mod tests {
     use std::{io, thread};
 
+    use lib::external::musicbrainz::api::MockIMusicBrainz;
     use ratatui::{backend::TestBackend, Terminal};
 
     use musichoard::collection::Collection;
@@ -201,7 +202,7 @@ mod tests {
     }
 
     fn app(collection: Collection) -> App<MockIMusicHoard> {
-        App::new(music_hoard(collection))
+        App::new(music_hoard(collection), Box::new(MockIMusicBrainz::new()))
     }
 
     fn listener() -> MockIEventListener {

src/tui/ui.rs

@@ -1,11 +1,14 @@
 use std::collections::HashMap;
 
-use musichoard::collection::{
-    album::{Album, AlbumDate, AlbumPrimaryType, AlbumSecondaryType, AlbumSeq, AlbumStatus},
-    artist::Artist,
-    musicbrainz::IMusicBrainzRef,
-    track::{Track, TrackFormat, TrackQuality},
-    Collection,
+use musichoard::{
+    collection::{
+        album::{Album, AlbumDate, AlbumPrimaryType, AlbumSecondaryType, AlbumSeq, AlbumStatus},
+        artist::Artist,
+        musicbrainz::IMusicBrainzRef,
+        track::{Track, TrackFormat, TrackQuality},
+        Collection,
+    },
+    interface::musicbrainz::Match,
 };
 use ratatui::{
     layout::{Alignment, Rect},
@@ -501,6 +504,7 @@ impl Minibuffer<'_> {
                     Paragraph::new("m: show info overlay"),
                     Paragraph::new("g: show reload menu"),
                     Paragraph::new("ctrl+s: search artist"),
+                    Paragraph::new("f: fetch musicbrainz"),
                 ],
                 columns,
             },
@@ -525,6 +529,13 @@ impl Minibuffer<'_> {
                 ],
                 columns,
             },
+            AppState::Matches(public) => Minibuffer {
+                paragraphs: vec![
+                    Paragraph::new(Minibuffer::display_matching_info(public.matching)),
+                    Paragraph::new("q: abort"),
+                ],
+                columns: 2,
+            },
             AppState::Error(_) => Minibuffer {
                 paragraphs: vec![Paragraph::new(
                     "Press any key to dismiss the error message...",
@@ -547,6 +558,17 @@ impl Minibuffer<'_> {
 
         mb
     }
+
+    fn display_matching_info(matching: Option<&Album>) -> String {
+        match matching {
+            Some(matching) => format!(
+                "Matching: {} | {}",
+                AlbumState::display_album_date(&matching.date),
+                &matching.id.title
+            ),
+            None => String::from("Matching: nothing"),
+        }
+    }
 }
 
 struct ReloadMenu;
@@ -621,6 +643,18 @@ impl Ui {
         state.height = area.height.saturating_sub(2) as usize;
     }
 
+    fn render_overlay_list_widget(
+        title: &str,
+        list: List,
+        state: &mut WidgetState,
+        active: bool,
+        area: Rect,
+        frame: &mut Frame,
+    ) {
+        frame.render_widget(Clear, area);
+        Self::render_list_widget(title, list, state, active, area, frame);
+    }
+
     fn render_info_widget(
         title: &str,
         paragraph: Paragraph,
@@ -792,6 +826,41 @@ impl Ui {
         }
     }
 
+    fn display_match_string(match_album: &Match<Album>) -> String {
+        format!(
+            "{:010} | {} [{}] ({}%)",
+            AlbumState::display_album_date(&match_album.item.date),
+            &match_album.item.id.title,
+            AlbumState::display_type(
+                &match_album.item.primary_type,
+                &match_album.item.secondary_types
+            ),
+            match_album.score,
+        )
+    }
+
+    fn build_match_list(matches: &[Match<Album>]) -> List {
+        List::new(
+            matches
+                .iter()
+                .map(Ui::display_match_string)
+                .map(ListItem::new)
+                .collect::<Vec<ListItem>>(),
+        )
+    }
+
+    fn render_matches_overlay(
+        matching: Option<&Album>,
+        matches: Option<&[Match<Album>]>,
+        state: &mut WidgetState,
+        frame: &mut Frame,
+    ) {
+        let area = OverlayBuilder::default().build(frame.size());
+        let matching_string = Minibuffer::display_matching_info(matching);
+        let list = matches.map(|m| Ui::build_match_list(m)).unwrap_or_default();
+        Self::render_overlay_list_widget(&matching_string, list, state, true, area, frame)
+    }
+
     fn render_reload_overlay(frame: &mut Frame) {
         let area = OverlayBuilder::default()
             .with_width(OverlaySize::Value(39))
@@ -827,6 +896,9 @@ impl IUi for Ui {
         Self::render_main_frame(collection, selection, &state, frame);
         match state {
             AppState::Info(_) => Self::render_info_overlay(collection, selection, frame),
+            AppState::Matches(public) => {
+                Self::render_matches_overlay(public.matching, public.matches, public.state, frame)
+            }
             AppState::Reload(_) => Self::render_reload_overlay(frame),
             AppState::Error(msg) => Self::render_error_overlay("Error", msg, frame),
             AppState::Critical(msg) => Self::render_error_overlay("Critical Error", msg, frame),
@@ -837,10 +909,10 @@ impl IUi for Ui {
 
 #[cfg(test)]
 mod tests {
-    use musichoard::collection::artist::ArtistId;
+    use musichoard::collection::{album::AlbumId, artist::ArtistId};
 
     use crate::tui::{
-        app::{AppPublic, AppPublicInner, Delta},
+        app::{AppPublic, AppPublicInner, AppPublicMatches, Delta},
         testmod::COLLECTION,
         tests::terminal,
     };
@@ -860,6 +932,11 @@ mod tests {
                     AppState::Info(()) => AppState::Info(()),
                     AppState::Reload(()) => AppState::Reload(()),
                     AppState::Search(s) => AppState::Search(s),
+                    AppState::Matches(ref mut m) => AppState::Matches(AppPublicMatches {
+                        matching: m.matching,
+                        matches: m.matches,
+                        state: m.state,
+                    }),
                     AppState::Error(s) => AppState::Error(s),
                     AppState::Critical(s) => AppState::Critical(s),
                 },
@@ -870,6 +947,18 @@ mod tests {
     fn draw_test_suite(collection: &Collection, selection: &mut Selection) {
         let mut terminal = terminal();
 
+        let album = Album::new(
+            AlbumId::new("An Album"),
+            AlbumDate::new(Some(1990), Some(5), None),
+            Some(AlbumPrimaryType::Album),
+            vec![AlbumSecondaryType::Live, AlbumSecondaryType::Compilation],
+        );
+
+        let album_match = Match {
+            score: 80,
+            item: album.clone(),
+        };
+
         let mut app = AppPublic {
             inner: AppPublicInner {
                 collection,
@@ -888,6 +977,26 @@ mod tests {
         app.state = AppState::Search("");
         terminal.draw(|frame| Ui::render(&mut app, frame)).unwrap();
 
+        let album_matches = [album_match.clone(), album_match.clone()];
+        let mut widget_state = WidgetState::default();
+        widget_state.list.select(Some(0));
+
+        app.state = AppState::Matches(AppPublicMatches {
+            matching: Some(&album),
+            matches: Some(&album_matches),
+            state: &mut widget_state,
+        });
+        terminal.draw(|frame| Ui::render(&mut app, frame)).unwrap();
+
+        let mut widget_state = WidgetState::default();
+
+        app.state = AppState::Matches(AppPublicMatches {
+            matching: None,
+            matches: None,
+            state: &mut widget_state,
+        });
+        terminal.draw(|frame| Ui::render(&mut app, frame)).unwrap();
+
         app.state = AppState::Error("get rekt scrub");
         terminal.draw(|frame| Ui::render(&mut app, frame)).unwrap();