Add trait to decouple file from json

src/database/json.rs

@@ -1,46 +1,39 @@
 //! Module for storing MusicHoard data in a JSON file database.
 
-use std::fs::File;
+use std::fs::{read_to_string, write};
-use std::io::{Read, Write};
+use std::path::PathBuf;
-use std::path::Path;
 
 use serde::de::DeserializeOwned;
 use serde::Serialize;
 
 use super::{DatabaseRead, DatabaseWrite};
 
+/// Trait for the JSON database backend.
+pub trait DatabaseJsonBackend {
+    /// Read the JSON string from the backend.
+    fn read(&self) -> Result<String, std::io::Error>;
+
+    /// Write the JSON string to the backend.
+    fn write(&mut self, json: &str) -> Result<(), std::io::Error>;
+}
+
 /// A JSON file database.
 pub struct DatabaseJson {
-    database_file: File,
+    backend: Box<dyn DatabaseJsonBackend>,
 }
 
 impl DatabaseJson {
-    /// Create a read-only database instance. If the JSON file does not exist, an error is returned.
+    pub fn new(backend: Box<dyn DatabaseJsonBackend>) -> Self {
-    pub fn reader(path: &Path) -> Result<Self, std::io::Error> {
+        DatabaseJson { backend }
-        Ok(Self {
-            database_file: File::open(path)?,
-        })
-    }
-
-    /// Create a write-only database instance. If the file does not exist, it is created, if it does
-    /// exist, it is truncated.
-    pub fn writer(path: &Path) -> Result<Self, std::io::Error> {
-        Ok(Self {
-            database_file: File::create(path)?,
-        })
     }
 }
 
 impl DatabaseRead for DatabaseJson {
-    fn read<D>(&mut self, collection: &mut D) -> Result<(), std::io::Error>
+    fn read<D>(&self, collection: &mut D) -> Result<(), std::io::Error>
     where
         D: DeserializeOwned,
     {
-        // Read entire file to memory as for now this is faster than a buffered read from disk:
+        let serialized = self.backend.read()?;
-        // https://github.com/serde-rs/json/issues/160
-        let mut serialized = String::new();
-        self.database_file.read_to_string(&mut serialized)?;
-
         *collection = serde_json::from_str(&serialized)?;
         Ok(())
     }
@@ -52,21 +45,54 @@ impl DatabaseWrite for DatabaseJson {
         S: Serialize,
     {
         let serialized = serde_json::to_string(&collection)?;
-        self.database_file.write_all(serialized.as_bytes())?;
+        self.backend.write(&serialized)?;
         Ok(())
     }
 }
 
+pub struct DatabaseJsonFile {
+    path: PathBuf,
+}
+
+impl DatabaseJsonFile {
+    /// Create a database instance that will read/write to the provided path.
+    pub fn new(path: PathBuf) -> Self {
+        DatabaseJsonFile { path }
+    }
+}
+
+impl DatabaseJsonBackend for DatabaseJsonFile {
+    fn read(&self) -> Result<String, std::io::Error> {
+        // Read entire file to memory as for now this is faster than a buffered read from disk:
+        // https://github.com/serde-rs/json/issues/160
+        read_to_string(&self.path)
+    }
+
+    fn write(&mut self, json: &str) -> Result<(), std::io::Error> {
+        write(&self.path, json)
+    }
+}
+
 #[cfg(test)]
 mod tests {
-    use std::path::Path;
-    use tempfile::NamedTempFile;
-
     use super::*;
 
     use crate::{Album, AlbumId, Track};
 
-    const TEST_FILENAME: &str = "tests/files/database_json_test.json";
+    struct DatabaseJsonTest {
+        json: String,
+    }
+
+    impl DatabaseJsonBackend for DatabaseJsonTest {
+        fn read(&self) -> Result<String, std::io::Error> {
+            Ok(self.json.clone())
+        }
+
+        fn write(&mut self, json: &str) -> Result<(), std::io::Error> {
+            assert_eq!(self.json, json);
+            Ok(())
+        }
+    }
 
     fn test_data() -> Vec<Album> {
         vec![
@@ -109,55 +135,91 @@ mod tests {
         ]
     }
 
+    fn album_to_json(album: &Album) -> String {
+        let album_id_artist = &album.id.artist;
+        let album_id_year = album.id.year;
+        let album_id_title = &album.id.title;
+
+        let mut album_tracks: Vec<String> = vec![];
+        for track in album.tracks.iter() {
+            let track_number = track.number;
+            let track_title = &track.title;
+
+            let mut track_artist: Vec<String> = vec![];
+            for artist in track.artist.iter() {
+                track_artist.push(format!("\"{artist}\""))
+            }
+            let track_artist = track_artist.join(",");
+
+            album_tracks.push(format!(
+                "{{\
+                 \"number\":{track_number},\
+                 \"title\":\"{track_title}\",\
+                 \"artist\":[{track_artist}]\
+                 }}"
+            ));
+        }
+        let album_tracks = album_tracks.join(",");
+
+        format!(
+            "{{\
+             \"id\":{{\
+             \"artist\":\"{album_id_artist}\",\
+             \"year\":{album_id_year},\
+             \"title\":\"{album_id_title}\"\
+             }},\"tracks\":[{album_tracks}]\
+             }}"
+        )
+    }
+
+    fn albums_to_json(albums: &Vec<Album>) -> String {
+        let mut albums_strings: Vec<String> = vec![];
+        for album in albums.iter() {
+            albums_strings.push(album_to_json(album));
+        }
+        let albums_json = albums_strings.join(",");
+        format!("[{albums_json}]")
+    }
+
     #[test]
     fn write() {
         let write_data = test_data();
-        let temp_file = NamedTempFile::new().unwrap();
+        let backend = DatabaseJsonTest {
-        DatabaseJson::writer(temp_file.path())
+            json: albums_to_json(&write_data),
-            .unwrap()
+        };
+
+        DatabaseJson::new(Box::new(backend))
             .write(&write_data)
             .unwrap();
-
-        let mut write_data_str = String::new();
-        File::open(temp_file.path())
-            .unwrap()
-            .read_to_string(&mut write_data_str)
-            .unwrap();
-
-        let mut test_data_str = String::new();
-        File::open(TEST_FILENAME)
-            .unwrap()
-            .read_to_string(&mut test_data_str)
-            .unwrap();
-
-        assert_eq!(write_data_str, test_data_str);
     }
 
     #[test]
     fn read() {
+        let expected = test_data();
+        let backend = DatabaseJsonTest {
+            json: albums_to_json(&expected),
+        };
+
         let mut read_data: Vec<Album> = vec![];
-        DatabaseJson::reader(Path::new(TEST_FILENAME))
+        DatabaseJson::new(Box::new(backend))
-            .unwrap()
             .read(&mut read_data)
             .unwrap();
-        assert_eq!(read_data, test_data());
+
+        assert_eq!(read_data, expected);
     }
 
     #[test]
     fn reverse() {
+        let expected = test_data();
+        let backend = DatabaseJsonTest {
+            json: albums_to_json(&expected),
+        };
+        let mut database = DatabaseJson::new(Box::new(backend));
+
         let write_data = test_data();
         let mut read_data: Vec<Album> = vec![];
-
+        database.write(&write_data).unwrap();
-        let temp_file = NamedTempFile::new().unwrap();
+        database.read(&mut read_data).unwrap();
-
-        DatabaseJson::writer(temp_file.path())
-            .unwrap()
-            .write(&write_data)
-            .unwrap();
-        DatabaseJson::reader(temp_file.path())
-            .unwrap()
-            .read(&mut read_data)
-            .unwrap();
 
         assert_eq!(write_data, read_data);
     }

src/database/mod.rs

@@ -8,7 +8,7 @@ pub mod json;
 /// Trait for database reads.
 pub trait DatabaseRead {
     /// Read collection from the database.
-    fn read<D>(&mut self, collection: &mut D) -> Result<(), std::io::Error>
+    fn read<D>(&self, collection: &mut D) -> Result<(), std::io::Error>
     where
         D: DeserializeOwned;
 }

src/library/beets.rs

@@ -80,7 +80,7 @@ impl QueryArgsBeets for Query {
 /// Trait for invoking beets commands.
 pub trait BeetsExecutor {
     /// Invoke beets with the provided arguments.
-    fn exec(&mut self, arguments: Vec<String>) -> Result<Vec<String>, Error>;
+    fn exec(&mut self, arguments: &[String]) -> Result<Vec<String>, Error>;
 }
 
 /// Struct for interacting with the music library via beets.
@@ -106,7 +106,7 @@ impl Beets {
 impl Library for Beets {
     fn list(&mut self, query: &Query) -> Result<Vec<Album>, Error> {
         let cmd = Self::list_cmd_and_args(query);
-        let output = self.executor.exec(cmd)?;
+        let output = self.executor.exec(&cmd)?;
         Self::list_to_albums(output)
     }
 }
@@ -209,7 +209,7 @@ impl Default for SystemExecutor {
 }
 
 impl BeetsExecutor for SystemExecutor {
-    fn exec(&mut self, arguments: Vec<String>) -> Result<Vec<String>, Error> {
+    fn exec(&mut self, arguments: &[String]) -> Result<Vec<String>, Error> {
         let output = Command::new(&self.bin).args(arguments).output()?;
         let output = std::str::from_utf8(&output.stdout)?;
         Ok(output.split('\n').map(|s| s.to_string()).collect())
@@ -226,10 +226,8 @@ mod tests {
     }
 
     impl BeetsExecutor for TestExecutor {
-        fn exec(&mut self, arguments: Vec<String>) -> Result<Vec<String>, Error> {
+        fn exec(&mut self, arguments: &[String]) -> Result<Vec<String>, Error> {
-            if self.arguments.is_some() {
+            assert_eq!(&self.arguments.take().unwrap(), arguments);
-                assert_eq!(self.arguments.take().unwrap(), arguments);
-            }
             self.output.take().unwrap()
         }
     }
@@ -303,6 +301,14 @@ mod tests {
         strings
     }
 
+    fn albums_to_beets_string(albums: &Vec<Album>) -> Vec<String> {
+        let mut strings = vec![];
+        for album in albums.iter() {
+            strings.append(&mut album_to_beets_string(album));
+        }
+        strings
+    }
+
     #[test]
     fn test_query() {
         let query = Query::new()
@@ -341,10 +347,7 @@ mod tests {
     #[test]
     fn test_list_ordered() {
         let expected = test_data();
-        let mut output = vec![];
+        let output = albums_to_beets_string(&expected);
-        for album in expected.iter() {
-            output.append(&mut album_to_beets_string(album));
-        }
 
         let executor = TestExecutor {
             arguments: Some(vec!["ls".to_string(), Beets::LIST_FORMAT_ARG.to_string()]),
@@ -359,10 +362,7 @@ mod tests {
     #[test]
     fn test_list_unordered() {
         let mut expected = test_data();
-        let mut output = vec![];
+        let mut output = albums_to_beets_string(&expected);
-        for album in expected.iter() {
-            output.append(&mut album_to_beets_string(album));
-        }
         let last = output.len() - 1;
         output.swap(0, last);
 
@@ -391,10 +391,7 @@ mod tests {
         expected[1].id.year = expected[0].id.year;
         expected[1].id.title = expected[0].id.title.clone();
 
-        let mut output = vec![];
+        let output = albums_to_beets_string(&expected);
-        for album in expected.iter() {
-            output.append(&mut album_to_beets_string(album));
-        }
 
         let executor = TestExecutor {
             arguments: Some(vec!["ls".to_string(), Beets::LIST_FORMAT_ARG.to_string()]),

tests/files/database_json_test.json

@@ -1 +0,0 @@
-[{"id":{"artist":"Artist A","year":1998,"title":"Release group A"},"tracks":[{"number":1,"title":"Track A.1","artist":["Artist A.A"]},{"number":2,"title":"Track A.2","artist":["Artist A.A"]},{"number":3,"title":"Track A.3","artist":["Artist A.A","Artist A.B"]}]},{"id":{"artist":"Artist B","year":2008,"title":"Release group B"},"tracks":[{"number":1,"title":"Track B.1","artist":["Artist B.A"]}]}]