Generic json database backend

src/collection/mod.rs

@@ -94,6 +94,7 @@ mod tests {
     use mockall::predicate;
 
     use crate::{
+        collection::Collection,
         database::{self, MockDatabase},
         library::{self, MockLibrary, Query},
         tests::COLLECTION,
@@ -122,7 +123,7 @@ mod tests {
             .expect_write()
             .with(predicate::eq(database_input))
             .times(1)
-            .return_once(|_| database_result);
+            .return_once(|_: &Collection| database_result);
 
         let mut collection_manager = MhCollectionManager::new(library, database);
 
@@ -164,7 +165,7 @@ mod tests {
         database
             .expect_write()
             .times(1)
-            .return_once(|_| database_result);
+            .return_once(|_: &Collection| database_result);
 
         let mut collection_manager = MhCollectionManager::new(library, database);
 

src/database/json.rs

@@ -3,7 +3,8 @@
 use std::fs;
 use std::path::{Path, PathBuf};
 
-use crate::collection::Collection;
+use serde::de::DeserializeOwned;
+use serde::Serialize;
 
 #[cfg(test)]
 use mockall::automock;
@@ -27,25 +28,25 @@ pub trait JsonDatabaseBackend {
 }
 
 /// JSON database.
-pub struct JsonDatabase {
-    backend: Box<dyn JsonDatabaseBackend + Send + Sync>,
+pub struct JsonDatabase<JDB> {
+    backend: JDB,
 }
 
-impl JsonDatabase {
+impl<JDB: JsonDatabaseBackend> JsonDatabase<JDB> {
     /// Create a new JSON database with the provided backend, e.g. [`JsonDatabaseFileBackend`].
-    pub fn new(backend: Box<dyn JsonDatabaseBackend + Send + Sync>) -> Self {
+    pub fn new(backend: JDB) -> Self {
         JsonDatabase { backend }
     }
 }
 
-impl Database for JsonDatabase {
-    fn read(&self, collection: &mut Collection) -> Result<(), Error> {
+impl<JDB: JsonDatabaseBackend> Database for JsonDatabase<JDB> {
+    fn read<D: DeserializeOwned>(&self, collection: &mut D) -> Result<(), Error> {
         let serialized = self.backend.read()?;
         *collection = serde_json::from_str(&serialized)?;
         Ok(())
     }
 
-    fn write(&mut self, collection: &Collection) -> Result<(), Error> {
+    fn write<S: Serialize>(&mut self, collection: &S) -> Result<(), Error> {
         let serialized = serde_json::to_string(&collection)?;
         self.backend.write(&serialized)?;
         Ok(())
@@ -162,9 +163,7 @@ mod tests {
             .times(1)
             .return_once(|_| Ok(()));
 
-        JsonDatabase::new(Box::new(backend))
-            .write(&write_data)
-            .unwrap();
+        JsonDatabase::new(backend).write(&write_data).unwrap();
     }
 
     #[test]
@@ -176,9 +175,7 @@ mod tests {
         backend.expect_read().times(1).return_once(|| result);
 
         let mut read_data: Vec<Artist> = vec![];
-        JsonDatabase::new(Box::new(backend))
-            .read(&mut read_data)
-            .unwrap();
+        JsonDatabase::new(backend).read(&mut read_data).unwrap();
 
         assert_eq!(read_data, expected);
     }
@@ -197,7 +194,7 @@ mod tests {
             .return_once(|_| Ok(()));
         backend.expect_read().times(1).return_once(|| result);
 
-        let mut database = JsonDatabase::new(Box::new(backend));
+        let mut database = JsonDatabase::new(backend);
 
         let write_data = COLLECTION.to_owned();
         let mut read_data: Vec<Artist> = vec![];

src/database/mod.rs

@@ -2,11 +2,11 @@
 
 use std::fmt;
 
+use serde::{de::DeserializeOwned, Serialize};
+
 #[cfg(test)]
 use mockall::automock;
 
-use crate::collection::Collection;
-
 pub mod json;
 
 /// Error type for database calls.
@@ -39,8 +39,8 @@ impl From<std::io::Error> for Error {
 #[cfg_attr(test, automock)]
 pub trait Database {
     /// Read collection from the database.
-    fn read(&self, collection: &mut Collection) -> Result<(), Error>;
+    fn read<D: DeserializeOwned + 'static>(&self, collection: &mut D) -> Result<(), Error>;
 
     /// Write collection to the database.
-    fn write(&mut self, collection: &Collection) -> Result<(), Error>;
+    fn write<S: Serialize + 'static>(&mut self, collection: &S) -> Result<(), Error>;
 }

src/main.rs

@@ -45,9 +45,7 @@ fn main() {
         BeetsLibraryCommandExecutor::default().config(opt.beets_config_file_path.as_deref()),
     );
 
-    let database = JsonDatabase::new(Box::new(JsonDatabaseFileBackend::new(
-        &opt.database_file_path,
-    )));
+    let database = JsonDatabase::new(JsonDatabaseFileBackend::new(&opt.database_file_path));
 
     let collection_manager = MhCollectionManager::new(beets, database);
 

tests/database/json.rs

@@ -20,7 +20,7 @@ fn write() {
     let file = NamedTempFile::new().unwrap();
 
     let backend = JsonDatabaseFileBackend::new(file.path());
-    let mut database = JsonDatabase::new(Box::new(backend));
+    let mut database = JsonDatabase::new(backend);
 
     let write_data = COLLECTION.to_owned();
     database.write(&write_data).unwrap();
@@ -34,7 +34,7 @@ fn write() {
 #[test]
 fn read() {
     let backend = JsonDatabaseFileBackend::new(&*DATABASE_TEST_FILE);
-    let database = JsonDatabase::new(Box::new(backend));
+    let database = JsonDatabase::new(backend);
 
     let mut read_data: Vec<Artist> = vec![];
     database.read(&mut read_data).unwrap();
@@ -48,7 +48,7 @@ fn reverse() {
     let file = NamedTempFile::new().unwrap();
 
     let backend = JsonDatabaseFileBackend::new(file.path());
-    let mut database = JsonDatabase::new(Box::new(backend));
+    let mut database = JsonDatabase::new(backend);
 
     let write_data = COLLECTION.to_owned();
     database.write(&write_data).unwrap();