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/rodio.rs

@@ -0,0 +1,76 @@
+/*
+    Abandoned temporary.
+    Problems with blocking behaviour.
+    Possible fixes are running rodio in a separate thread or smthng.
+*/
+
+use std::fs::File;
+use std::path::PathBuf;
+use std::io::BufReader;
+use once_cell::sync::OnceCell;
+
+use rodio::{Decoder, OutputStream, OutputStreamHandle, Sink};
+
+// static STREAM: OnceCell<OutputStream> = OnceCell::new();
+static STREAM_HANDLE: OnceCell<OutputStreamHandle> = OnceCell::new();
+static SINK: OnceCell<Sink> = OnceCell::new();
+
+pub fn init() -> Result<(), ()> {
+    if !STREAM_HANDLE.get().is_none() {return Ok(());} // already initialized
+
+    // get output stream handle to the default physical sound device
+    match OutputStream::try_default() {
+        Ok(out) => {
+            // divide
+            let (_stream, stream_handle) = out;
+
+            // create sink
+            let sink;
+            match Sink::try_new(&stream_handle) {
+                Ok(s) => {
+                    info!("Sink initialized.");
+                    sink = s;
+                },
+                Err(msg) => {
+                    error!("Cannot create sink.\nError details: {}", msg);
+
+                    // failed
+                    return Err(())
+                }
+            }
+
+            // store
+            // STREAM.set(_stream).unwrap();
+            STREAM_HANDLE.set(stream_handle);
+            SINK.set(sink);
+
+            // success
+            Ok(())
+        },
+        Err(msg) => {
+            error!("Failed to initialize audio stream.\nError details: {}", msg);
+
+            // failed
+            Err(())
+        }
+    }
+}
+
+pub fn play_sound(filename: &PathBuf, sleep: bool) {
+    // Load a sound from a file, using a path relative to Cargo.toml
+    // let filepath = format!("{PUBLIC_PATH}/sound/{filename}.wav");
+    let file = BufReader::new(File::open(&filename).unwrap());
+
+    // Decode that sound file into a source
+    let source = Decoder::new(file).unwrap();
+
+    // Play the sound directly on the device
+    // STREAM_HANDLE.get().unwrap().play_raw(source.convert_samples());
+    SINK.get().unwrap().append(source);
+
+    if sleep {
+        // The sound plays in a separate thread. This call will block the current thread until the sink
+        // has finished playing all its queued sounds.
+        SINK.get().unwrap().sleep_until_end();
+    }
+}