Import in separate crate and change source ID calculation

import/src/session.rs

@@ -0,0 +1,91 @@
+use crate::{disc, folder};
+use crate::error::Result;
+use futures_channel::oneshot;
+use std::path::PathBuf;
+use std::thread;
+use std::sync::Arc;
+
+/// Interface for importing audio tracks from a medium or folder.
+pub struct ImportSession {
+    /// A string identifying the source as specific as possible across platforms and formats.
+    pub(super) source_id: String,
+
+    /// The tracks that are available on the source.
+    pub(super) tracks: Vec<ImportTrack>,
+
+    /// A closure that has to be called to copy the tracks if set.
+    pub(super) copy: Option<Box<dyn Fn() -> Result<()> + Send + Sync>>,
+}
+
+impl ImportSession {
+    /// Create a new import session for a audio CD.
+    pub async fn audio_cd() -> Result<Arc<Self>> {
+        let (sender, receiver) = oneshot::channel();
+
+        thread::spawn(move || {
+            let result = disc::new();
+            let _ = sender.send(result);
+        });
+
+        Ok(Arc::new(receiver.await??))
+    }
+
+    /// Create a new import session for a folder.
+    pub async fn folder(path: PathBuf) -> Result<Arc<Self>> {
+        let (sender, receiver) = oneshot::channel();
+
+        thread::spawn(move || {
+            let result = folder::new(path);
+            let _ = sender.send(result);
+        });
+
+        Ok(Arc::new(receiver.await??))
+    }
+
+    /// Get a string identifying the source as specific as possible across platforms and mediums.
+    pub fn source_id(&self) -> &str {
+        &self.source_id
+    }
+
+    /// Get the tracks that are available on the source.
+    pub fn tracks(&self) -> &[ImportTrack] {
+        &self.tracks
+    }
+
+    /// Copy the tracks to their advertised locations, if neccessary.
+    pub async fn copy(self: &Arc<Self>) -> Result<()> {
+        if self.copy.is_some() {
+            let clone = Arc::clone(self);
+            let (sender, receiver) = oneshot::channel();
+
+            thread::spawn(move || {
+                let copy = clone.copy.as_ref().unwrap();
+                sender.send(copy()).unwrap();
+            });
+
+            receiver.await?
+        } else {
+            Ok(())
+        }
+    }
+}
+
+/// A track on an import source.
+#[derive(Clone, Debug)]
+pub struct ImportTrack {
+    /// The track number.
+    pub number: u32,
+
+    /// A human readable identifier for the track. This will be used to present the track for
+    /// selection.
+    pub name: String,
+
+    /// The path to the file where the corresponding audio file is. This file is only required to
+    /// exist, once the import was successfully completed. This will not be the actual file within
+    /// the user's music library, but the temporary location from which it can be copied to the
+    /// music library.
+    pub path: PathBuf,
+
+    /// The track's duration in milliseconds.
+    pub duration: u64,
+}