Clean up private helper methods

src/library/beets.rs

@@ -78,15 +78,39 @@ pub struct Beets {
     executor: Box<dyn BeetsExecutor>,
 }
 
+impl Beets {
+    pub fn new(executor: Box<dyn BeetsExecutor>) -> Beets {
+        Beets { executor }
+    }
+}
+
+trait LibraryPrivate {
+    const CMD_LIST: &'static str;
+    const SEPARATOR: &'static str;
+    const LIST_FORMAT: &'static str;
+
+    fn list_cmd_and_args(query: &Query) -> Vec<String>;
+    fn list_to_albums(list_output: Vec<String>) -> Result<Vec<Album>, Error>;
+}
+
+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)?;
+        Self::list_to_albums(output)
+    }
+}
+
 macro_rules! separator {
     () => {
         "-*^-"
     };
 }
 
-impl Beets {
-    const SEPARATOR: &str = separator!();
-    const LIST_FORMAT: &str = concat!(
+impl LibraryPrivate for Beets {
+    const CMD_LIST: &'static str = "ls";
+    const SEPARATOR: &'static str = separator!();
+    const LIST_FORMAT: &'static str = concat!(
         "--format=",
         "$albumartist",
         separator!(),
@@ -101,8 +125,11 @@ impl Beets {
         "$artist"
     );
 
-    pub fn new(executor: Box<dyn BeetsExecutor>) -> Beets {
-        Beets { executor }
+    fn list_cmd_and_args(query: &Query) -> Vec<String> {
+        let mut cmd: Vec<String> = vec![String::from(Self::CMD_LIST)];
+        cmd.push(Self::LIST_FORMAT.to_string());
+        cmd.append(&mut query.to_args());
+        cmd
     }
 
     fn list_to_albums(list_output: Vec<String>) -> Result<Vec<Album>, Error> {
@@ -147,22 +174,11 @@ impl Beets {
                 });
             }
         }
+
         Ok(albums)
     }
 }
 
-impl Library for Beets {
-    fn list(&mut self, query: &Query) -> Result<Vec<Album>, Error> {
-        let mut arguments: Vec<String> = vec![String::from("ls")];
-        arguments.push(Self::LIST_FORMAT.to_string());
-        arguments.append(&mut query.to_args());
-
-        let output = self.executor.exec(arguments)?;
-
-        Self::list_to_albums(output)
-    }
-}
-
 pub struct SystemExecutor {
     bin: String,
 }