App architecture modifications.

Now GUI and the app itself is divided into two different binaries.
The app also provides system tray icon.
Whereas the GUI can be used to configure the app.

app/src/audio.rs

@@ -0,0 +1,86 @@
+mod rodio;
+mod kira;
+
+use std::cmp::Ordering;
+use std::path::PathBuf;
+use once_cell::sync::OnceCell;
+
+use crate::{config, DB, SOUND_DIR};
+use crate::config::structs::AudioType;
+
+static AUDIO_TYPE: OnceCell<AudioType> = OnceCell::new();
+
+
+pub fn init() -> Result<(), ()> {
+    if !AUDIO_TYPE.get().is_none() {return Ok(());} // already initialized
+
+    // set default audio type
+    // @TODO. Make it configurable?
+    AUDIO_TYPE.set(config::DEFAULT_AUDIO_TYPE).unwrap();
+
+    // load given audio backend
+    match AUDIO_TYPE.get().unwrap() {
+        AudioType::Rodio => {
+            // Init Rodio
+            info!("Initializing Rodio audio backend.");
+
+            match rodio::init() {
+                Ok(_) => {
+                    info!("Successfully initialized Rodio audio backend.");
+                },
+                Err(msg) => {
+                    error!("Failed to initialize Rodio audio backend.");
+
+                    return Err(())
+                }
+            }
+        },
+        AudioType::Kira => {
+            // Init Kira
+            info!("Initializing Kira audio backend.");
+
+            match kira::init() {
+                Ok(_) => {
+                    info!("Successfully initialized Kira audio backend.");
+                },
+                Err(msg) => {
+                    error!("Failed to initialize Kira audio backend.");
+
+                    return Err(())
+                }
+            }
+        }
+    }
+
+    Ok(())
+}
+
+pub fn play_sound(filename: &PathBuf) {
+    info!("Playing {}", filename.display());
+
+    match AUDIO_TYPE.get().unwrap() {
+        AudioType::Rodio => {
+            rodio::play_sound(filename, true);
+        },
+        AudioType::Kira => {
+            kira::play_sound(filename)
+        }
+    }
+}
+
+pub fn get_sound_directory() -> Option<PathBuf> {
+    let voice = DB.get().unwrap().voice.as_str();
+    let voice_path = SOUND_DIR.join(voice);
+
+    match voice_path.exists() && voice_path.cmp(&SOUND_DIR) != Ordering::Equal {
+        true => Some(voice_path),
+        _ => {
+            let default_voice_path = SOUND_DIR.join(config::DEFAULT_VOICE);
+
+            match default_voice_path.exists() {
+                true => Some(default_voice_path),
+                _ => None
+            }
+        }
+    }
+}