Added file extension constant and updated constants module (#17)

Reviewed-on: phoenix/icarus-models#17
Co-authored-by: KD <kundeng94@gmail.com>
Co-committed-by: KD <kundeng94@gmail.com>

src/constants.rs

@@ -1,5 +1,14 @@
+pub mod file_extensions {
+    pub mod audio {
         pub const DEFAULTMUSICEXTENSION: &str = FLACEXTENSION;
         pub const FLACEXTENSION: &str = ".flac";
         pub const WAVEXTENSION: &str = ".wav";
         pub const MPTHREEEXTENSION: &str = ".mp3";
+    }
+
+    pub mod image {
         pub const JPGEXTENSION: &str = ".jpg";
+        pub const JPEGEXTENSION: &str = ".jpeg";
+        pub const PNGEXTENSION: &str = ".png";
+    }
+}

src/song.rs

@@ -128,12 +128,18 @@ impl Song {
 
         let file_extension = match typ {
             types::MusicTypes::DefaultMusicExtension => {
-                String::from(constants::DEFAULTMUSICEXTENSION)
+                String::from(constants::file_extensions::audio::DEFAULTMUSICEXTENSION)
             }
 
-            types::MusicTypes::WavExtension => String::from(constants::WAVEXTENSION),
+            types::MusicTypes::WavExtension => {
-            types::MusicTypes::FlacExtension => String::from(constants::FLACEXTENSION),
+                String::from(constants::file_extensions::audio::WAVEXTENSION)
-            types::MusicTypes::MPThreeExtension => String::from(constants::MPTHREEEXTENSION),
+            }
+            types::MusicTypes::FlacExtension => {
+                String::from(constants::file_extensions::audio::FLACEXTENSION)
+            }
+            types::MusicTypes::MPThreeExtension => {
+                String::from(constants::file_extensions::audio::MPTHREEEXTENSION)
+            }
         };
 
         if randomize {