Add the library trait

src/lib.rs

@@ -4,6 +4,7 @@ use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
 pub mod database;
+pub mod library;
 
 /// [MusicBrainz Identifier](https://musicbrainz.org/doc/MusicBrainz_Identifier) (MBID).
 pub type Mbid = Uuid;

src/library/mod.rs

@@ -0,0 +1,17 @@
+use std::path::Path;
+
+use crate::ReleaseGroup;
+
+/// Options for refining library queries.
+pub struct Query {
+    albumartist: Option<String>,
+    artist: Option<String>,
+    album: Option<String>,
+    track: Option<u32>,
+    title: Option<String>,
+}
+
+/// Trait for interacting with the music library.
+pub trait Library {
+    fn list(&self, album: bool, path: Path, format: &str, query: Query) -> Vec<ReleaseGroup>;
+}