Move common utilities

src/sources/common.rs

@@ -1,3 +1,5 @@
+use std::collections::BTreeMap;
+
 /// Struct for a song.
 #[derive(Debug, Default)]
 pub(crate) struct Song {
@@ -10,3 +12,16 @@ pub(crate) struct Song {
     track: Option<String>,
     composer: Option<String>,
 }
+
+/// SongTags is a representation of the tags associated with a
+/// song. This is a BTreeMap with two Strings.
+pub(crate) type SongTags = BTreeMap<String, String>;
+
+/// This function takes tags of SongTags type, and a tag to retrieve.
+pub(crate) fn get_tag(tags: &SongTags, tag: &str) -> Option<String> {
+    return if let Some(x) = tags.get(tag) {
+        Some(x.to_string())
+    } else {
+        None
+    }
+}