src/tui/app/selection/album.rs

@@ -0,0 +1,306 @@
+use std::cmp;
+
+use musichoard::collection::{album::{Album, AlbumId}, track::Track};
+
+use crate::tui::app::selection::{
+    track::{IdSelectTrack, TrackSelection},
+    Delta, SelectionState, WidgetState,
+};
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct AlbumSelection {
+    pub state: WidgetState,
+    pub track: TrackSelection,
+}
+
+impl AlbumSelection {
+    pub fn initialise(albums: &[Album]) -> Self {
+        let mut selection = AlbumSelection {
+            state: WidgetState::default(),
+            track: TrackSelection::initialise(&[]),
+        };
+        selection.reinitialise(albums, None);
+        selection
+    }
+
+    pub fn reinitialise(&mut self, albums: &[Album], album: Option<IdSelectAlbum>) {
+        if let Some(album) = album {
+            let result = albums.binary_search_by(|a| a.get_sort_key().cmp(&album.album_id));
+            match result {
+                Ok(index) => self.reinitialise_with_index(albums, index, album.track),
+                Err(index) => self.reinitialise_with_index(albums, index, None),
+            }
+        } else {
+            self.reinitialise_with_index(albums, 0, None)
+        }
+    }
+
+    fn reinitialise_with_index(
+        &mut self,
+        albums: &[Album],
+        index: usize,
+        active_track: Option<IdSelectTrack>,
+    ) {
+        if albums.is_empty() {
+            self.state.list.select(None);
+            self.track = TrackSelection::initialise(&[]);
+        } else if index >= albums.len() {
+            let end = albums.len() - 1;
+            self.state.list.select(Some(end));
+            self.track = TrackSelection::initialise(&albums[end].tracks);
+        } else {
+            self.state.list.select(Some(index));
+            self.track.reinitialise(&albums[index].tracks, active_track);
+        }
+    }
+
+    pub fn selected(&self) -> Option<usize> {
+        self.state.list.selected()
+    }
+
+    pub fn selected_track(&self) -> Option<usize> {
+        self.track.selected()
+    }
+
+    pub fn select(&mut self, albums: &[Album], to: Option<usize>) {
+        match to {
+            Some(to) => self.select_to(albums, to),
+            None => self.state.list.select(None),
+        }
+    }
+
+    pub fn select_track(&mut self, albums: &[Album], to: Option<usize>) {
+        if let Some(index) = self.state.list.selected() {
+            self.track.select(&albums[index].tracks, to);
+        }
+    }
+
+    fn select_to(&mut self, albums: &[Album], mut to: usize) {
+        to = cmp::min(to, albums.len() - 1);
+        if self.state.list.selected() != Some(to) {
+            self.state.list.select(Some(to));
+            self.track = TrackSelection::initialise(&albums[to].tracks);
+        }
+    }
+
+    pub fn selection_state<'a>(&self, list: &'a [Album]) -> Option<SelectionState<'a, Album>> {
+        let selected = self.state.list.selected();
+        selected.map(|index| SelectionState { list, index })
+    }
+
+    pub fn state_tracks<'a>(&self, albums: &'a [Album]) -> Option<SelectionState<'a, Track>> {
+        let selected = self.state.list.selected();
+        selected.and_then(|index| self.track.selection_state(&albums[index].tracks))
+    }
+
+    pub fn reset(&mut self, albums: &[Album]) {
+        if self.state.list.selected() != Some(0) {
+            self.reinitialise(albums, None);
+        }
+    }
+
+    pub fn reset_track(&mut self, albums: &[Album]) {
+        if let Some(index) = self.state.list.selected() {
+            self.track.reset(&albums[index].tracks);
+        }
+    }
+
+    pub fn increment(&mut self, albums: &[Album], delta: Delta) {
+        self.increment_by(albums, delta.as_usize(&self.state));
+    }
+
+    pub fn increment_track(&mut self, albums: &[Album], delta: Delta) {
+        if let Some(index) = self.state.list.selected() {
+            self.track.increment(&albums[index].tracks, delta);
+        }
+    }
+
+    fn increment_by(&mut self, albums: &[Album], by: usize) {
+        if let Some(index) = self.state.list.selected() {
+            let mut result = index.saturating_add(by);
+            if result >= albums.len() {
+                result = albums.len() - 1;
+            }
+            if self.state.list.selected() != Some(result) {
+                self.state.list.select(Some(result));
+                self.track = TrackSelection::initialise(&albums[result].tracks);
+            }
+        }
+    }
+
+    pub fn decrement(&mut self, albums: &[Album], delta: Delta) {
+        self.decrement_by(albums, delta.as_usize(&self.state));
+    }
+
+    pub fn decrement_track(&mut self, albums: &[Album], delta: Delta) {
+        if let Some(index) = self.state.list.selected() {
+            self.track.decrement(&albums[index].tracks, delta);
+        }
+    }
+
+    fn decrement_by(&mut self, albums: &[Album], by: usize) {
+        if let Some(index) = self.state.list.selected() {
+            let result = index.saturating_sub(by);
+            if self.state.list.selected() != Some(result) {
+                self.state.list.select(Some(result));
+                self.track = TrackSelection::initialise(&albums[result].tracks);
+            }
+        }
+    }
+}
+
+pub struct IdSelectAlbum {
+    album_id: AlbumId,
+    track: Option<IdSelectTrack>,
+}
+
+impl IdSelectAlbum {
+    pub fn get(albums: &[Album], selection: &AlbumSelection) -> Option<Self> {
+        selection.state.list.selected().map(|index| {
+            let album = &albums[index];
+            IdSelectAlbum {
+                album_id: album.get_sort_key().clone(),
+                track: IdSelectTrack::get(&album.tracks, &selection.track),
+            }
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tui::testmod::COLLECTION;
+
+    use super::*;
+
+
+    #[test]
+    fn album_selection() {
+        let albums = &COLLECTION[0].albums;
+        assert!(albums.len() > 1);
+
+        let mut empty = AlbumSelection::initialise(&[]);
+        assert_eq!(empty.state.list.selected(), None);
+        assert_eq!(empty.track.state.list.selected(), None);
+
+        empty.increment(albums, Delta::Line);
+        assert_eq!(empty.state.list.selected(), None);
+        assert_eq!(empty.track.state.list.selected(), None);
+
+        empty.decrement(albums, Delta::Line);
+        assert_eq!(empty.state.list.selected(), None);
+        assert_eq!(empty.track.state.list.selected(), None);
+
+        let mut sel = AlbumSelection::initialise(albums);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.track.state.list.selected(), Some(0));
+
+        sel.increment_track(albums, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.track.state.list.selected(), Some(1));
+
+        // Verify that decrement that doesn't change index does not reset track.
+        sel.decrement(albums, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.track.state.list.selected(), Some(1));
+
+        sel.increment(albums, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(1));
+        assert_eq!(sel.track.state.list.selected(), Some(0));
+
+        sel.decrement(albums, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.track.state.list.selected(), Some(0));
+
+        for _ in 0..(albums.len() + 5) {
+            sel.increment(albums, Delta::Line);
+        }
+        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
+        assert_eq!(sel.track.state.list.selected(), Some(0));
+
+        sel.increment_track(albums, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
+        assert_eq!(sel.track.state.list.selected(), Some(1));
+
+        // Verify that increment that doesn't change index does not reset track.
+        sel.increment(albums, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
+        assert_eq!(sel.track.state.list.selected(), Some(1));
+    }
+
+    #[test]
+    fn album_delta_page() {
+        let albums = &COLLECTION[1].albums;
+        assert!(albums.len() > 1);
+
+        let empty = AlbumSelection::initialise(&[]);
+        assert_eq!(empty.state.list.selected(), None);
+
+        let mut sel = AlbumSelection::initialise(albums);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.track.state.list.selected(), Some(0));
+
+        assert!(albums.len() >= 4);
+        sel.state.height = 3;
+
+        sel.increment_track(albums, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.track.state.list.selected(), Some(1));
+
+        // Verify that decrement that doesn't change index does not reset track.
+        sel.decrement(albums, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.track.state.list.selected(), Some(1));
+
+        sel.increment(albums, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(2));
+        assert_eq!(sel.track.state.list.selected(), Some(0));
+
+        sel.decrement(albums, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.track.state.list.selected(), Some(0));
+
+        for _ in 0..(albums.len() + 5) {
+            sel.increment(albums, Delta::Page);
+        }
+        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
+        assert_eq!(sel.track.state.list.selected(), Some(0));
+
+        sel.increment_track(albums, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
+        assert_eq!(sel.track.state.list.selected(), Some(1));
+
+        // Verify that increment that doesn't change index does not reset track.
+        sel.increment(albums, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
+        assert_eq!(sel.track.state.list.selected(), Some(1));
+    }
+
+    #[test]
+    fn album_reinitialise() {
+        let albums = &COLLECTION[0].albums;
+        assert!(albums.len() > 1);
+
+        let mut sel = AlbumSelection::initialise(albums);
+        sel.state.list.select(Some(albums.len() - 1));
+        sel.track.state.list.select(Some(1));
+
+        // Re-initialise.
+        let expected = sel.clone();
+        let active_album = IdSelectAlbum::get(albums, &sel);
+        sel.reinitialise(albums, active_album);
+        assert_eq!(sel, expected);
+
+        // Re-initialise out-of-bounds.
+        let mut expected = sel.clone();
+        expected.decrement(albums, Delta::Line);
+        let active_album = IdSelectAlbum::get(albums, &sel);
+        sel.reinitialise(&albums[..(albums.len() - 1)], active_album);
+        assert_eq!(sel, expected);
+
+        // Re-initialise empty.
+        let expected = AlbumSelection::initialise(&[]);
+        let active_album = IdSelectAlbum::get(albums, &sel);
+        sel.reinitialise(&[], active_album);
+        assert_eq!(sel, expected);
+    }
+}

src/tui/app/selection/artist.rs

@@ -0,0 +1,338 @@
+use std::cmp;
+
+use musichoard::collection::{
+    album::Album,
+    artist::{Artist, ArtistId},
+    track::Track,
+};
+
+use crate::tui::app::selection::{
+    album::{AlbumSelection, IdSelectAlbum},
+    Delta, SelectionState, WidgetState,
+};
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct ArtistSelection {
+    pub state: WidgetState,
+    pub album: AlbumSelection,
+}
+
+impl ArtistSelection {
+    pub fn initialise(artists: &[Artist]) -> Self {
+        let mut selection = ArtistSelection {
+            state: WidgetState::default(),
+            album: AlbumSelection::initialise(&[]),
+        };
+        selection.reinitialise(artists, None);
+        selection
+    }
+
+    pub fn reinitialise(&mut self, artists: &[Artist], active: Option<IdSelectArtist>) {
+        if let Some(active) = active {
+            let result = artists.binary_search_by(|a| a.get_sort_key().cmp(&active.artist_id));
+            match result {
+                Ok(index) => self.reinitialise_with_index(artists, index, active.album),
+                Err(index) => self.reinitialise_with_index(artists, index, None),
+            }
+        } else {
+            self.reinitialise_with_index(artists, 0, None)
+        }
+    }
+
+    fn reinitialise_with_index(
+        &mut self,
+        artists: &[Artist],
+        index: usize,
+        active_album: Option<IdSelectAlbum>,
+    ) {
+        if artists.is_empty() {
+            self.state.list.select(None);
+            self.album = AlbumSelection::initialise(&[]);
+        } else if index >= artists.len() {
+            let end = artists.len() - 1;
+            self.state.list.select(Some(end));
+            self.album = AlbumSelection::initialise(&artists[end].albums);
+        } else {
+            self.state.list.select(Some(index));
+            self.album
+                .reinitialise(&artists[index].albums, active_album);
+        }
+    }
+
+    pub fn selected(&self) -> Option<usize> {
+        self.state.list.selected()
+    }
+
+    pub fn selected_album(&self) -> Option<usize> {
+        self.album.selected()
+    }
+
+    pub fn selected_track(&self) -> Option<usize> {
+        self.album.selected_track()
+    }
+
+    pub fn select(&mut self, artists: &[Artist], to: Option<usize>) {
+        match to {
+            Some(to) => self.select_to(artists, to),
+            None => self.state.list.select(None),
+        }
+    }
+
+    pub fn select_album(&mut self, artists: &[Artist], to: Option<usize>) {
+        if let Some(index) = self.state.list.selected() {
+            self.album.select(&artists[index].albums, to);
+        }
+    }
+
+    pub fn select_track(&mut self, artists: &[Artist], to: Option<usize>) {
+        if let Some(index) = self.state.list.selected() {
+            self.album.select_track(&artists[index].albums, to);
+        }
+    }
+
+    fn select_to(&mut self, artists: &[Artist], mut to: usize) {
+        to = cmp::min(to, artists.len() - 1);
+        if self.state.list.selected() != Some(to) {
+            self.state.list.select(Some(to));
+            self.album = AlbumSelection::initialise(&artists[to].albums);
+        }
+    }
+
+    pub fn selection_state<'a>(&self, list: &'a [Artist]) -> Option<SelectionState<'a, Artist>> {
+        let selected = self.state.list.selected();
+        selected.map(|index| SelectionState { list, index })
+    }
+
+    pub fn state_album<'a>(&self, artists: &'a [Artist]) -> Option<SelectionState<'a, Album>> {
+        let selected = self.state.list.selected();
+        selected.and_then(|index| self.album.selection_state(&artists[index].albums))
+    }
+
+    pub fn state_track<'a>(&self, artists: &'a [Artist]) -> Option<SelectionState<'a, Track>> {
+        let selected = self.state.list.selected();
+        selected.and_then(|index| self.album.state_tracks(&artists[index].albums))
+    }
+
+    pub fn reset(&mut self, artists: &[Artist]) {
+        if self.state.list.selected() != Some(0) {
+            self.reinitialise(artists, None);
+        }
+    }
+
+    pub fn reset_album(&mut self, artists: &[Artist]) {
+        if let Some(index) = self.state.list.selected() {
+            self.album.reset(&artists[index].albums);
+        }
+    }
+
+    pub fn reset_track(&mut self, artists: &[Artist]) {
+        if let Some(index) = self.state.list.selected() {
+            self.album.reset_track(&artists[index].albums);
+        }
+    }
+
+    pub fn increment(&mut self, artists: &[Artist], delta: Delta) {
+        self.increment_by(artists, delta.as_usize(&self.state));
+    }
+
+    pub fn increment_album(&mut self, artists: &[Artist], delta: Delta) {
+        if let Some(index) = self.state.list.selected() {
+            self.album.increment(&artists[index].albums, delta);
+        }
+    }
+
+    pub fn increment_track(&mut self, artists: &[Artist], delta: Delta) {
+        if let Some(index) = self.state.list.selected() {
+            self.album.increment_track(&artists[index].albums, delta);
+        }
+    }
+
+    fn increment_by(&mut self, artists: &[Artist], by: usize) {
+        if let Some(index) = self.state.list.selected() {
+            let result = index.saturating_add(by);
+            self.select_to(artists, result);
+        }
+    }
+
+    pub fn decrement(&mut self, artists: &[Artist], delta: Delta) {
+        self.decrement_by(artists, delta.as_usize(&self.state));
+    }
+
+    pub fn decrement_album(&mut self, artists: &[Artist], delta: Delta) {
+        if let Some(index) = self.state.list.selected() {
+            self.album.decrement(&artists[index].albums, delta);
+        }
+    }
+
+    pub fn decrement_track(&mut self, artists: &[Artist], delta: Delta) {
+        if let Some(index) = self.state.list.selected() {
+            self.album.decrement_track(&artists[index].albums, delta);
+        }
+    }
+
+    fn decrement_by(&mut self, artists: &[Artist], by: usize) {
+        if let Some(index) = self.state.list.selected() {
+            let result = index.saturating_sub(by);
+            if self.state.list.selected() != Some(result) {
+                self.state.list.select(Some(result));
+                self.album = AlbumSelection::initialise(&artists[result].albums);
+            }
+        }
+    }
+}
+
+pub struct IdSelectArtist {
+    artist_id: ArtistId,
+    album: Option<IdSelectAlbum>,
+}
+
+impl IdSelectArtist {
+    pub fn get(artists: &[Artist], selection: &ArtistSelection) -> Option<Self> {
+        selection.state.list.selected().map(|index| {
+            let artist = &artists[index];
+            IdSelectArtist {
+                artist_id: artist.get_sort_key().clone(),
+                album: IdSelectAlbum::get(&artist.albums, &selection.album),
+            }
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tui::testmod::COLLECTION;
+
+    use super::*;
+
+
+    #[test]
+    fn artist_selection() {
+        let artists = &COLLECTION;
+        assert!(artists.len() > 1);
+
+        let mut empty = ArtistSelection::initialise(&[]);
+        assert_eq!(empty.state.list.selected(), None);
+        assert_eq!(empty.album.state.list.selected(), None);
+
+        empty.increment(artists, Delta::Line);
+        assert_eq!(empty.state.list.selected(), None);
+        assert_eq!(empty.album.state.list.selected(), None);
+
+        empty.decrement(artists, Delta::Line);
+        assert_eq!(empty.state.list.selected(), None);
+        assert_eq!(empty.album.state.list.selected(), None);
+
+        let mut sel = ArtistSelection::initialise(artists);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.album.state.list.selected(), Some(0));
+
+        sel.increment_album(artists, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.album.state.list.selected(), Some(1));
+
+        // Verify that decrement that doesn't change index does not reset album.
+        sel.decrement(artists, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.album.state.list.selected(), Some(1));
+
+        sel.increment(artists, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(1));
+        assert_eq!(sel.album.state.list.selected(), Some(0));
+
+        sel.decrement(artists, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.album.state.list.selected(), Some(0));
+
+        for _ in 0..(artists.len() + 5) {
+            sel.increment(artists, Delta::Line);
+        }
+        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
+        assert_eq!(sel.album.state.list.selected(), Some(0));
+
+        sel.increment_album(artists, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
+        assert_eq!(sel.album.state.list.selected(), Some(1));
+
+        // Verify that increment that doesn't change index does not reset album.
+        sel.increment(artists, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
+        assert_eq!(sel.album.state.list.selected(), Some(1));
+    }
+
+    #[test]
+    fn artist_delta_page() {
+        let artists = &COLLECTION;
+        assert!(artists.len() > 1);
+
+        let empty = ArtistSelection::initialise(&[]);
+        assert_eq!(empty.state.list.selected(), None);
+
+        let mut sel = ArtistSelection::initialise(artists);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.album.state.list.selected(), Some(0));
+
+        assert!(artists.len() >= 4);
+        sel.state.height = 3;
+
+        sel.increment_album(artists, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.album.state.list.selected(), Some(1));
+
+        // Verify that decrement that doesn't change index does not reset album.
+        sel.decrement(artists, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.album.state.list.selected(), Some(1));
+
+        sel.increment(artists, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(2));
+        assert_eq!(sel.album.state.list.selected(), Some(0));
+
+        sel.decrement(artists, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(0));
+        assert_eq!(sel.album.state.list.selected(), Some(0));
+
+        for _ in 0..(artists.len() + 5) {
+            sel.increment(artists, Delta::Page);
+        }
+        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
+        assert_eq!(sel.album.state.list.selected(), Some(0));
+
+        sel.increment_album(artists, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
+        assert_eq!(sel.album.state.list.selected(), Some(1));
+
+        // Verify that increment that doesn't change index does not reset album.
+        sel.increment(artists, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
+        assert_eq!(sel.album.state.list.selected(), Some(1));
+    }
+
+    #[test]
+    fn artist_reinitialise() {
+        let artists = &COLLECTION;
+        assert!(artists.len() > 1);
+
+        let mut sel = ArtistSelection::initialise(artists);
+        sel.state.list.select(Some(artists.len() - 1));
+        sel.album.state.list.select(Some(1));
+
+        // Re-initialise.
+        let expected = sel.clone();
+        let active_artist = IdSelectArtist::get(artists, &sel);
+        sel.reinitialise(artists, active_artist);
+        assert_eq!(sel, expected);
+
+        // Re-initialise out-of-bounds.
+        let mut expected = sel.clone();
+        expected.decrement(artists, Delta::Line);
+        let active_artist = IdSelectArtist::get(artists, &sel);
+        sel.reinitialise(&artists[..(artists.len() - 1)], active_artist);
+        assert_eq!(sel, expected);
+
+        // Re-initialise empty.
+        let expected = ArtistSelection::initialise(&[]);
+        let active_artist = IdSelectArtist::get(artists, &sel);
+        sel.reinitialise(&[], active_artist);
+        assert_eq!(sel, expected);
+    }
+}

src/tui/app/selection/mod.rs

@@ -1,11 +1,11 @@
-use musichoard::collection::{
-    album::{Album, AlbumId},
-    artist::{Artist, ArtistId},
-    track::{Track, TrackId},
-    Collection,
-};
+mod album;
+mod artist;
+mod track;
+
+use musichoard::collection::{album::Album, artist::Artist, track::Track, Collection};
 use ratatui::widgets::ListState;
-use std::cmp;
+
+use artist::{ArtistSelection, IdSelectArtist};
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Category {
@@ -31,21 +31,9 @@ pub struct Selection {
     pub artist: ArtistSelection,
 }
 
-#[derive(Clone, Debug, PartialEq)]
-pub struct ArtistSelection {
-    pub state: WidgetState,
-    pub album: AlbumSelection,
-}
-
-#[derive(Clone, Debug, PartialEq)]
-pub struct AlbumSelection {
-    pub state: WidgetState,
-    pub track: TrackSelection,
-}
-
-#[derive(Clone, Debug, PartialEq)]
-pub struct TrackSelection {
-    pub state: WidgetState,
+pub struct SelectionState<'a, T> {
+    pub list: &'a [T],
+    pub index: usize,
 }
 
 pub enum Delta {
@@ -62,11 +50,6 @@ impl Delta {
     }
 }
 
-pub struct SelectionState<'a, T> {
-    pub list: &'a [T],
-    pub index: usize,
-}
-
 impl Selection {
     pub fn new(artists: &[Artist]) -> Self {
         Selection {
@@ -214,393 +197,6 @@ impl Selection {
     }
 }
 
-impl ArtistSelection {
-    fn initialise(artists: &[Artist]) -> Self {
-        let mut selection = ArtistSelection {
-            state: WidgetState::default(),
-            album: AlbumSelection::initialise(&[]),
-        };
-        selection.reinitialise(artists, None);
-        selection
-    }
-
-    fn reinitialise(&mut self, artists: &[Artist], active: Option<IdSelectArtist>) {
-        if let Some(active) = active {
-            let result = artists.binary_search_by(|a| a.get_sort_key().cmp(&active.artist_id));
-            match result {
-                Ok(index) => self.reinitialise_with_index(artists, index, active.album),
-                Err(index) => self.reinitialise_with_index(artists, index, None),
-            }
-        } else {
-            self.reinitialise_with_index(artists, 0, None)
-        }
-    }
-
-    fn reinitialise_with_index(
-        &mut self,
-        artists: &[Artist],
-        index: usize,
-        active_album: Option<IdSelectAlbum>,
-    ) {
-        if artists.is_empty() {
-            self.state.list.select(None);
-            self.album = AlbumSelection::initialise(&[]);
-        } else if index >= artists.len() {
-            let end = artists.len() - 1;
-            self.state.list.select(Some(end));
-            self.album = AlbumSelection::initialise(&artists[end].albums);
-        } else {
-            self.state.list.select(Some(index));
-            self.album
-                .reinitialise(&artists[index].albums, active_album);
-        }
-    }
-
-    fn selected(&self) -> Option<usize> {
-        self.state.list.selected()
-    }
-
-    fn selected_album(&self) -> Option<usize> {
-        self.album.selected()
-    }
-
-    fn selected_track(&self) -> Option<usize> {
-        self.album.selected_track()
-    }
-
-    fn select(&mut self, artists: &[Artist], to: Option<usize>) {
-        match to {
-            Some(to) => self.select_to(artists, to),
-            None => self.state.list.select(None),
-        }
-    }
-
-    fn select_album(&mut self, artists: &[Artist], to: Option<usize>) {
-        if let Some(index) = self.state.list.selected() {
-            self.album.select(&artists[index].albums, to);
-        }
-    }
-
-    fn select_track(&mut self, artists: &[Artist], to: Option<usize>) {
-        if let Some(index) = self.state.list.selected() {
-            self.album.select_track(&artists[index].albums, to);
-        }
-    }
-
-    fn select_to(&mut self, artists: &[Artist], mut to: usize) {
-        to = cmp::min(to, artists.len() - 1);
-        if self.state.list.selected() != Some(to) {
-            self.state.list.select(Some(to));
-            self.album = AlbumSelection::initialise(&artists[to].albums);
-        }
-    }
-
-    fn selection_state<'a>(&self, list: &'a [Artist]) -> Option<SelectionState<'a, Artist>> {
-        let selected = self.state.list.selected();
-        selected.map(|index| SelectionState { list, index })
-    }
-
-    fn state_album<'a>(&self, artists: &'a [Artist]) -> Option<SelectionState<'a, Album>> {
-        let selected = self.state.list.selected();
-        selected.and_then(|index| self.album.selection_state(&artists[index].albums))
-    }
-
-    fn state_track<'a>(&self, artists: &'a [Artist]) -> Option<SelectionState<'a, Track>> {
-        let selected = self.state.list.selected();
-        selected.and_then(|index| self.album.state_tracks(&artists[index].albums))
-    }
-
-    fn reset(&mut self, artists: &[Artist]) {
-        if self.state.list.selected() != Some(0) {
-            self.reinitialise(artists, None);
-        }
-    }
-
-    fn reset_album(&mut self, artists: &[Artist]) {
-        if let Some(index) = self.state.list.selected() {
-            self.album.reset(&artists[index].albums);
-        }
-    }
-
-    fn reset_track(&mut self, artists: &[Artist]) {
-        if let Some(index) = self.state.list.selected() {
-            self.album.reset_track(&artists[index].albums);
-        }
-    }
-
-    fn increment_by(&mut self, artists: &[Artist], by: usize) {
-        if let Some(index) = self.state.list.selected() {
-            let result = index.saturating_add(by);
-            self.select_to(artists, result);
-        }
-    }
-
-    fn increment(&mut self, artists: &[Artist], delta: Delta) {
-        self.increment_by(artists, delta.as_usize(&self.state));
-    }
-
-    fn increment_album(&mut self, artists: &[Artist], delta: Delta) {
-        if let Some(index) = self.state.list.selected() {
-            self.album.increment(&artists[index].albums, delta);
-        }
-    }
-
-    fn increment_track(&mut self, artists: &[Artist], delta: Delta) {
-        if let Some(index) = self.state.list.selected() {
-            self.album.increment_track(&artists[index].albums, delta);
-        }
-    }
-
-    fn decrement_by(&mut self, artists: &[Artist], by: usize) {
-        if let Some(index) = self.state.list.selected() {
-            let result = index.saturating_sub(by);
-            if self.state.list.selected() != Some(result) {
-                self.state.list.select(Some(result));
-                self.album = AlbumSelection::initialise(&artists[result].albums);
-            }
-        }
-    }
-
-    fn decrement(&mut self, artists: &[Artist], delta: Delta) {
-        self.decrement_by(artists, delta.as_usize(&self.state));
-    }
-
-    fn decrement_album(&mut self, artists: &[Artist], delta: Delta) {
-        if let Some(index) = self.state.list.selected() {
-            self.album.decrement(&artists[index].albums, delta);
-        }
-    }
-
-    fn decrement_track(&mut self, artists: &[Artist], delta: Delta) {
-        if let Some(index) = self.state.list.selected() {
-            self.album.decrement_track(&artists[index].albums, delta);
-        }
-    }
-}
-
-impl AlbumSelection {
-    fn initialise(albums: &[Album]) -> Self {
-        let mut selection = AlbumSelection {
-            state: WidgetState::default(),
-            track: TrackSelection::initialise(&[]),
-        };
-        selection.reinitialise(albums, None);
-        selection
-    }
-
-    fn reinitialise(&mut self, albums: &[Album], album: Option<IdSelectAlbum>) {
-        if let Some(album) = album {
-            let result = albums.binary_search_by(|a| a.get_sort_key().cmp(&album.album_id));
-            match result {
-                Ok(index) => self.reinitialise_with_index(albums, index, album.track),
-                Err(index) => self.reinitialise_with_index(albums, index, None),
-            }
-        } else {
-            self.reinitialise_with_index(albums, 0, None)
-        }
-    }
-
-    fn reinitialise_with_index(
-        &mut self,
-        albums: &[Album],
-        index: usize,
-        active_track: Option<IdSelectTrack>,
-    ) {
-        if albums.is_empty() {
-            self.state.list.select(None);
-            self.track = TrackSelection::initialise(&[]);
-        } else if index >= albums.len() {
-            let end = albums.len() - 1;
-            self.state.list.select(Some(end));
-            self.track = TrackSelection::initialise(&albums[end].tracks);
-        } else {
-            self.state.list.select(Some(index));
-            self.track.reinitialise(&albums[index].tracks, active_track);
-        }
-    }
-
-    fn selected(&self) -> Option<usize> {
-        self.state.list.selected()
-    }
-
-    fn selected_track(&self) -> Option<usize> {
-        self.track.selected()
-    }
-
-    fn select(&mut self, albums: &[Album], to: Option<usize>) {
-        match to {
-            Some(to) => self.select_to(albums, to),
-            None => self.state.list.select(None),
-        }
-    }
-
-    fn select_track(&mut self, albums: &[Album], to: Option<usize>) {
-        if let Some(index) = self.state.list.selected() {
-            self.track.select(&albums[index].tracks, to);
-        }
-    }
-
-    fn select_to(&mut self, albums: &[Album], mut to: usize) {
-        to = cmp::min(to, albums.len() - 1);
-        if self.state.list.selected() != Some(to) {
-            self.state.list.select(Some(to));
-            self.track = TrackSelection::initialise(&albums[to].tracks);
-        }
-    }
-
-    fn selection_state<'a>(&self, list: &'a [Album]) -> Option<SelectionState<'a, Album>> {
-        let selected = self.state.list.selected();
-        selected.map(|index| SelectionState { list, index })
-    }
-
-    fn state_tracks<'a>(&self, albums: &'a [Album]) -> Option<SelectionState<'a, Track>> {
-        let selected = self.state.list.selected();
-        selected.and_then(|index| self.track.selection_state(&albums[index].tracks))
-    }
-
-    fn reset(&mut self, albums: &[Album]) {
-        if self.state.list.selected() != Some(0) {
-            self.reinitialise(albums, None);
-        }
-    }
-
-    fn reset_track(&mut self, albums: &[Album]) {
-        if let Some(index) = self.state.list.selected() {
-            self.track.reset(&albums[index].tracks);
-        }
-    }
-
-    fn increment_by(&mut self, albums: &[Album], by: usize) {
-        if let Some(index) = self.state.list.selected() {
-            let mut result = index.saturating_add(by);
-            if result >= albums.len() {
-                result = albums.len() - 1;
-            }
-            if self.state.list.selected() != Some(result) {
-                self.state.list.select(Some(result));
-                self.track = TrackSelection::initialise(&albums[result].tracks);
-            }
-        }
-    }
-
-    fn increment(&mut self, albums: &[Album], delta: Delta) {
-        self.increment_by(albums, delta.as_usize(&self.state));
-    }
-
-    fn increment_track(&mut self, albums: &[Album], delta: Delta) {
-        if let Some(index) = self.state.list.selected() {
-            self.track.increment(&albums[index].tracks, delta);
-        }
-    }
-
-    fn decrement_by(&mut self, albums: &[Album], by: usize) {
-        if let Some(index) = self.state.list.selected() {
-            let result = index.saturating_sub(by);
-            if self.state.list.selected() != Some(result) {
-                self.state.list.select(Some(result));
-                self.track = TrackSelection::initialise(&albums[result].tracks);
-            }
-        }
-    }
-
-    fn decrement(&mut self, albums: &[Album], delta: Delta) {
-        self.decrement_by(albums, delta.as_usize(&self.state));
-    }
-
-    fn decrement_track(&mut self, albums: &[Album], delta: Delta) {
-        if let Some(index) = self.state.list.selected() {
-            self.track.decrement(&albums[index].tracks, delta);
-        }
-    }
-}
-
-impl TrackSelection {
-    fn initialise(tracks: &[Track]) -> Self {
-        let mut selection = TrackSelection {
-            state: WidgetState::default(),
-        };
-        selection.reinitialise(tracks, None);
-        selection
-    }
-
-    fn reinitialise(&mut self, tracks: &[Track], track: Option<IdSelectTrack>) {
-        if let Some(track) = track {
-            let result = tracks.binary_search_by(|t| t.get_sort_key().cmp(&track.track_id));
-            match result {
-                Ok(index) | Err(index) => self.reinitialise_with_index(tracks, index),
-            }
-        } else {
-            self.reinitialise_with_index(tracks, 0)
-        }
-    }
-
-    fn reinitialise_with_index(&mut self, tracks: &[Track], index: usize) {
-        if tracks.is_empty() {
-            self.state.list.select(None);
-        } else if index >= tracks.len() {
-            self.state.list.select(Some(tracks.len() - 1));
-        } else {
-            self.state.list.select(Some(index));
-        }
-    }
-
-    fn selected(&self) -> Option<usize> {
-        self.state.list.selected()
-    }
-
-    fn select(&mut self, tracks: &[Track], to: Option<usize>) {
-        match to {
-            Some(to) => self.select_to(tracks, to),
-            None => self.state.list.select(None),
-        }
-    }
-
-    fn select_to(&mut self, tracks: &[Track], mut to: usize) {
-        to = cmp::min(to, tracks.len() - 1);
-        self.state.list.select(Some(to));
-    }
-
-    fn selection_state<'a>(&self, list: &'a [Track]) -> Option<SelectionState<'a, Track>> {
-        let selected = self.state.list.selected();
-        selected.map(|index| SelectionState { list, index })
-    }
-
-    fn reset(&mut self, tracks: &[Track]) {
-        if self.state.list.selected() != Some(0) {
-            self.reinitialise(tracks, None);
-        }
-    }
-
-    fn increment_by(&mut self, tracks: &[Track], by: usize) {
-        if let Some(index) = self.state.list.selected() {
-            let mut result = index.saturating_add(by);
-            if result >= tracks.len() {
-                result = tracks.len() - 1;
-            }
-            if self.state.list.selected() != Some(result) {
-                self.state.list.select(Some(result));
-            }
-        }
-    }
-
-    fn increment(&mut self, tracks: &[Track], delta: Delta) {
-        self.increment_by(tracks, delta.as_usize(&self.state));
-    }
-
-    fn decrement_by(&mut self, _tracks: &[Track], by: usize) {
-        if let Some(index) = self.state.list.selected() {
-            let result = index.saturating_sub(by);
-            if self.state.list.selected() != Some(result) {
-                self.state.list.select(Some(result));
-            }
-        }
-    }
-
-    fn decrement(&mut self, tracks: &[Track], delta: Delta) {
-        self.decrement_by(tracks, delta.as_usize(&self.state));
-    }
-}
-
 pub struct ListSelection {
     pub artist: ListState,
     pub album: ListState,
@@ -621,20 +217,6 @@ pub struct IdSelection {
     artist: Option<IdSelectArtist>,
 }
 
-struct IdSelectArtist {
-    artist_id: ArtistId,
-    album: Option<IdSelectAlbum>,
-}
-
-struct IdSelectAlbum {
-    album_id: AlbumId,
-    track: Option<IdSelectTrack>,
-}
-
-struct IdSelectTrack {
-    track_id: TrackId,
-}
-
 impl IdSelection {
     pub fn get(collection: &Collection, selection: &Selection) -> Self {
         IdSelection {
@@ -643,398 +225,12 @@ impl IdSelection {
     }
 }
 
-impl IdSelectArtist {
-    fn get(artists: &[Artist], selection: &ArtistSelection) -> Option<Self> {
-        selection.state.list.selected().map(|index| {
-            let artist = &artists[index];
-            IdSelectArtist {
-                artist_id: artist.get_sort_key().clone(),
-                album: IdSelectAlbum::get(&artist.albums, &selection.album),
-            }
-        })
-    }
-}
-
-impl IdSelectAlbum {
-    fn get(albums: &[Album], selection: &AlbumSelection) -> Option<Self> {
-        selection.state.list.selected().map(|index| {
-            let album = &albums[index];
-            IdSelectAlbum {
-                album_id: album.get_sort_key().clone(),
-                track: IdSelectTrack::get(&album.tracks, &selection.track),
-            }
-        })
-    }
-}
-
-impl IdSelectTrack {
-    fn get(tracks: &[Track], selection: &TrackSelection) -> Option<Self> {
-        selection.state.list.selected().map(|index| {
-            let track = &tracks[index];
-            IdSelectTrack {
-                track_id: track.get_sort_key().clone(),
-            }
-        })
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use crate::tui::testmod::COLLECTION;
 
     use super::*;
 
-    #[test]
-    fn track_selection() {
-        let tracks = &COLLECTION[0].albums[0].tracks;
-        assert!(tracks.len() > 1);
-
-        let mut empty = TrackSelection::initialise(&[]);
-        assert_eq!(empty.state.list.selected(), None);
-
-        empty.increment(tracks, Delta::Line);
-        assert_eq!(empty.state.list.selected(), None);
-
-        empty.decrement(tracks, Delta::Line);
-        assert_eq!(empty.state.list.selected(), None);
-
-        let mut sel = TrackSelection::initialise(tracks);
-        assert_eq!(sel.state.list.selected(), Some(0));
-
-        sel.decrement(tracks, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-
-        sel.increment(tracks, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(1));
-
-        sel.decrement(tracks, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-
-        for _ in 0..(tracks.len() + 5) {
-            sel.increment(tracks, Delta::Line);
-        }
-        assert_eq!(sel.state.list.selected(), Some(tracks.len() - 1));
-    }
-
-    #[test]
-    fn track_delta_page() {
-        let tracks = &COLLECTION[0].albums[0].tracks;
-        assert!(tracks.len() > 1);
-
-        let empty = TrackSelection::initialise(&[]);
-        assert_eq!(empty.state.list.selected(), None);
-
-        let mut sel = TrackSelection::initialise(tracks);
-        assert_eq!(sel.state.list.selected(), Some(0));
-
-        assert!(tracks.len() >= 4);
-        sel.state.height = 3;
-
-        sel.decrement(tracks, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(0));
-
-        sel.increment(tracks, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(2));
-
-        sel.decrement(tracks, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(0));
-
-        for _ in 0..(tracks.len() + 5) {
-            sel.increment(tracks, Delta::Page);
-        }
-        assert_eq!(sel.state.list.selected(), Some(tracks.len() - 1));
-    }
-
-    #[test]
-    fn track_reinitialise() {
-        let tracks = &COLLECTION[0].albums[0].tracks;
-        assert!(tracks.len() > 1);
-
-        let mut sel = TrackSelection::initialise(tracks);
-        sel.state.list.select(Some(tracks.len() - 1));
-
-        // Re-initialise.
-        let expected = sel.clone();
-        let active_track = IdSelectTrack::get(tracks, &sel);
-        sel.reinitialise(tracks, active_track);
-        assert_eq!(sel, expected);
-
-        // Re-initialise out-of-bounds.
-        let mut expected = sel.clone();
-        expected.decrement(tracks, Delta::Line);
-        let active_track = IdSelectTrack::get(tracks, &sel);
-        sel.reinitialise(&tracks[..(tracks.len() - 1)], active_track);
-        assert_eq!(sel, expected);
-
-        // Re-initialise empty.
-        let expected = TrackSelection::initialise(&[]);
-        let active_track = IdSelectTrack::get(tracks, &sel);
-        sel.reinitialise(&[], active_track);
-        assert_eq!(sel, expected);
-    }
-
-    #[test]
-    fn album_selection() {
-        let albums = &COLLECTION[0].albums;
-        assert!(albums.len() > 1);
-
-        let mut empty = AlbumSelection::initialise(&[]);
-        assert_eq!(empty.state.list.selected(), None);
-        assert_eq!(empty.track.state.list.selected(), None);
-
-        empty.increment(albums, Delta::Line);
-        assert_eq!(empty.state.list.selected(), None);
-        assert_eq!(empty.track.state.list.selected(), None);
-
-        empty.decrement(albums, Delta::Line);
-        assert_eq!(empty.state.list.selected(), None);
-        assert_eq!(empty.track.state.list.selected(), None);
-
-        let mut sel = AlbumSelection::initialise(albums);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.track.state.list.selected(), Some(0));
-
-        sel.increment_track(albums, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.track.state.list.selected(), Some(1));
-
-        // Verify that decrement that doesn't change index does not reset track.
-        sel.decrement(albums, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.track.state.list.selected(), Some(1));
-
-        sel.increment(albums, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(1));
-        assert_eq!(sel.track.state.list.selected(), Some(0));
-
-        sel.decrement(albums, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.track.state.list.selected(), Some(0));
-
-        for _ in 0..(albums.len() + 5) {
-            sel.increment(albums, Delta::Line);
-        }
-        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
-        assert_eq!(sel.track.state.list.selected(), Some(0));
-
-        sel.increment_track(albums, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
-        assert_eq!(sel.track.state.list.selected(), Some(1));
-
-        // Verify that increment that doesn't change index does not reset track.
-        sel.increment(albums, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
-        assert_eq!(sel.track.state.list.selected(), Some(1));
-    }
-
-    #[test]
-    fn album_delta_page() {
-        let albums = &COLLECTION[1].albums;
-        assert!(albums.len() > 1);
-
-        let empty = AlbumSelection::initialise(&[]);
-        assert_eq!(empty.state.list.selected(), None);
-
-        let mut sel = AlbumSelection::initialise(albums);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.track.state.list.selected(), Some(0));
-
-        assert!(albums.len() >= 4);
-        sel.state.height = 3;
-
-        sel.increment_track(albums, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.track.state.list.selected(), Some(1));
-
-        // Verify that decrement that doesn't change index does not reset track.
-        sel.decrement(albums, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.track.state.list.selected(), Some(1));
-
-        sel.increment(albums, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(2));
-        assert_eq!(sel.track.state.list.selected(), Some(0));
-
-        sel.decrement(albums, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.track.state.list.selected(), Some(0));
-
-        for _ in 0..(albums.len() + 5) {
-            sel.increment(albums, Delta::Page);
-        }
-        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
-        assert_eq!(sel.track.state.list.selected(), Some(0));
-
-        sel.increment_track(albums, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
-        assert_eq!(sel.track.state.list.selected(), Some(1));
-
-        // Verify that increment that doesn't change index does not reset track.
-        sel.increment(albums, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(albums.len() - 1));
-        assert_eq!(sel.track.state.list.selected(), Some(1));
-    }
-
-    #[test]
-    fn album_reinitialise() {
-        let albums = &COLLECTION[0].albums;
-        assert!(albums.len() > 1);
-
-        let mut sel = AlbumSelection::initialise(albums);
-        sel.state.list.select(Some(albums.len() - 1));
-        sel.track.state.list.select(Some(1));
-
-        // Re-initialise.
-        let expected = sel.clone();
-        let active_album = IdSelectAlbum::get(albums, &sel);
-        sel.reinitialise(albums, active_album);
-        assert_eq!(sel, expected);
-
-        // Re-initialise out-of-bounds.
-        let mut expected = sel.clone();
-        expected.decrement(albums, Delta::Line);
-        let active_album = IdSelectAlbum::get(albums, &sel);
-        sel.reinitialise(&albums[..(albums.len() - 1)], active_album);
-        assert_eq!(sel, expected);
-
-        // Re-initialise empty.
-        let expected = AlbumSelection::initialise(&[]);
-        let active_album = IdSelectAlbum::get(albums, &sel);
-        sel.reinitialise(&[], active_album);
-        assert_eq!(sel, expected);
-    }
-
-    #[test]
-    fn artist_selection() {
-        let artists = &COLLECTION;
-        assert!(artists.len() > 1);
-
-        let mut empty = ArtistSelection::initialise(&[]);
-        assert_eq!(empty.state.list.selected(), None);
-        assert_eq!(empty.album.state.list.selected(), None);
-
-        empty.increment(artists, Delta::Line);
-        assert_eq!(empty.state.list.selected(), None);
-        assert_eq!(empty.album.state.list.selected(), None);
-
-        empty.decrement(artists, Delta::Line);
-        assert_eq!(empty.state.list.selected(), None);
-        assert_eq!(empty.album.state.list.selected(), None);
-
-        let mut sel = ArtistSelection::initialise(artists);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.album.state.list.selected(), Some(0));
-
-        sel.increment_album(artists, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.album.state.list.selected(), Some(1));
-
-        // Verify that decrement that doesn't change index does not reset album.
-        sel.decrement(artists, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.album.state.list.selected(), Some(1));
-
-        sel.increment(artists, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(1));
-        assert_eq!(sel.album.state.list.selected(), Some(0));
-
-        sel.decrement(artists, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.album.state.list.selected(), Some(0));
-
-        for _ in 0..(artists.len() + 5) {
-            sel.increment(artists, Delta::Line);
-        }
-        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
-        assert_eq!(sel.album.state.list.selected(), Some(0));
-
-        sel.increment_album(artists, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
-        assert_eq!(sel.album.state.list.selected(), Some(1));
-
-        // Verify that increment that doesn't change index does not reset album.
-        sel.increment(artists, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
-        assert_eq!(sel.album.state.list.selected(), Some(1));
-    }
-
-    #[test]
-    fn artist_delta_page() {
-        let artists = &COLLECTION;
-        assert!(artists.len() > 1);
-
-        let empty = ArtistSelection::initialise(&[]);
-        assert_eq!(empty.state.list.selected(), None);
-
-        let mut sel = ArtistSelection::initialise(artists);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.album.state.list.selected(), Some(0));
-
-        assert!(artists.len() >= 4);
-        sel.state.height = 3;
-
-        sel.increment_album(artists, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.album.state.list.selected(), Some(1));
-
-        // Verify that decrement that doesn't change index does not reset album.
-        sel.decrement(artists, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.album.state.list.selected(), Some(1));
-
-        sel.increment(artists, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(2));
-        assert_eq!(sel.album.state.list.selected(), Some(0));
-
-        sel.decrement(artists, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(0));
-        assert_eq!(sel.album.state.list.selected(), Some(0));
-
-        for _ in 0..(artists.len() + 5) {
-            sel.increment(artists, Delta::Page);
-        }
-        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
-        assert_eq!(sel.album.state.list.selected(), Some(0));
-
-        sel.increment_album(artists, Delta::Line);
-        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
-        assert_eq!(sel.album.state.list.selected(), Some(1));
-
-        // Verify that increment that doesn't change index does not reset album.
-        sel.increment(artists, Delta::Page);
-        assert_eq!(sel.state.list.selected(), Some(artists.len() - 1));
-        assert_eq!(sel.album.state.list.selected(), Some(1));
-    }
-
-    #[test]
-    fn artist_reinitialise() {
-        let artists = &COLLECTION;
-        assert!(artists.len() > 1);
-
-        let mut sel = ArtistSelection::initialise(artists);
-        sel.state.list.select(Some(artists.len() - 1));
-        sel.album.state.list.select(Some(1));
-
-        // Re-initialise.
-        let expected = sel.clone();
-        let active_artist = IdSelectArtist::get(artists, &sel);
-        sel.reinitialise(artists, active_artist);
-        assert_eq!(sel, expected);
-
-        // Re-initialise out-of-bounds.
-        let mut expected = sel.clone();
-        expected.decrement(artists, Delta::Line);
-        let active_artist = IdSelectArtist::get(artists, &sel);
-        sel.reinitialise(&artists[..(artists.len() - 1)], active_artist);
-        assert_eq!(sel, expected);
-
-        // Re-initialise empty.
-        let expected = ArtistSelection::initialise(&[]);
-        let active_artist = IdSelectArtist::get(artists, &sel);
-        sel.reinitialise(&[], active_artist);
-        assert_eq!(sel, expected);
-    }
-
     #[test]
     fn selection() {
         let mut selection = Selection::new(&COLLECTION);

src/tui/app/selection/track.rs

@@ -0,0 +1,208 @@
+use std::cmp;
+
+use musichoard::collection::track::{Track, TrackId};
+
+use crate::tui::app::selection::{Delta, SelectionState, WidgetState};
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct TrackSelection {
+    pub state: WidgetState,
+}
+
+impl TrackSelection {
+    pub fn initialise(tracks: &[Track]) -> Self {
+        let mut selection = TrackSelection {
+            state: WidgetState::default(),
+        };
+        selection.reinitialise(tracks, None);
+        selection
+    }
+
+    pub fn reinitialise(&mut self, tracks: &[Track], track: Option<IdSelectTrack>) {
+        if let Some(track) = track {
+            let result = tracks.binary_search_by(|t| t.get_sort_key().cmp(&track.track_id));
+            match result {
+                Ok(index) | Err(index) => self.reinitialise_with_index(tracks, index),
+            }
+        } else {
+            self.reinitialise_with_index(tracks, 0)
+        }
+    }
+
+    fn reinitialise_with_index(&mut self, tracks: &[Track], index: usize) {
+        if tracks.is_empty() {
+            self.state.list.select(None);
+        } else if index >= tracks.len() {
+            self.state.list.select(Some(tracks.len() - 1));
+        } else {
+            self.state.list.select(Some(index));
+        }
+    }
+
+    pub fn selected(&self) -> Option<usize> {
+        self.state.list.selected()
+    }
+
+    pub fn select(&mut self, tracks: &[Track], to: Option<usize>) {
+        match to {
+            Some(to) => self.select_to(tracks, to),
+            None => self.state.list.select(None),
+        }
+    }
+
+    fn select_to(&mut self, tracks: &[Track], mut to: usize) {
+        to = cmp::min(to, tracks.len() - 1);
+        self.state.list.select(Some(to));
+    }
+
+    pub fn selection_state<'a>(&self, list: &'a [Track]) -> Option<SelectionState<'a, Track>> {
+        let selected = self.state.list.selected();
+        selected.map(|index| SelectionState { list, index })
+    }
+
+    pub fn reset(&mut self, tracks: &[Track]) {
+        if self.state.list.selected() != Some(0) {
+            self.reinitialise(tracks, None);
+        }
+    }
+
+    pub fn increment(&mut self, tracks: &[Track], delta: Delta) {
+        self.increment_by(tracks, delta.as_usize(&self.state));
+    }
+
+    fn increment_by(&mut self, tracks: &[Track], by: usize) {
+        if let Some(index) = self.state.list.selected() {
+            let mut result = index.saturating_add(by);
+            if result >= tracks.len() {
+                result = tracks.len() - 1;
+            }
+            if self.state.list.selected() != Some(result) {
+                self.state.list.select(Some(result));
+            }
+        }
+    }
+
+    pub fn decrement(&mut self, tracks: &[Track], delta: Delta) {
+        self.decrement_by(tracks, delta.as_usize(&self.state));
+    }
+
+    fn decrement_by(&mut self, _tracks: &[Track], by: usize) {
+        if let Some(index) = self.state.list.selected() {
+            let result = index.saturating_sub(by);
+            if self.state.list.selected() != Some(result) {
+                self.state.list.select(Some(result));
+            }
+        }
+    }
+}
+
+pub struct IdSelectTrack {
+    track_id: TrackId,
+}
+
+impl IdSelectTrack {
+    pub fn get(tracks: &[Track], selection: &TrackSelection) -> Option<Self> {
+        selection.state.list.selected().map(|index| {
+            let track = &tracks[index];
+            IdSelectTrack {
+                track_id: track.get_sort_key().clone(),
+            }
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tui::testmod::COLLECTION;
+
+    use super::*;
+
+    #[test]
+    fn track_selection() {
+        let tracks = &COLLECTION[0].albums[0].tracks;
+        assert!(tracks.len() > 1);
+
+        let mut empty = TrackSelection::initialise(&[]);
+        assert_eq!(empty.state.list.selected(), None);
+
+        empty.increment(tracks, Delta::Line);
+        assert_eq!(empty.state.list.selected(), None);
+
+        empty.decrement(tracks, Delta::Line);
+        assert_eq!(empty.state.list.selected(), None);
+
+        let mut sel = TrackSelection::initialise(tracks);
+        assert_eq!(sel.state.list.selected(), Some(0));
+
+        sel.decrement(tracks, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+
+        sel.increment(tracks, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(1));
+
+        sel.decrement(tracks, Delta::Line);
+        assert_eq!(sel.state.list.selected(), Some(0));
+
+        for _ in 0..(tracks.len() + 5) {
+            sel.increment(tracks, Delta::Line);
+        }
+        assert_eq!(sel.state.list.selected(), Some(tracks.len() - 1));
+    }
+
+    #[test]
+    fn track_delta_page() {
+        let tracks = &COLLECTION[0].albums[0].tracks;
+        assert!(tracks.len() > 1);
+
+        let empty = TrackSelection::initialise(&[]);
+        assert_eq!(empty.state.list.selected(), None);
+
+        let mut sel = TrackSelection::initialise(tracks);
+        assert_eq!(sel.state.list.selected(), Some(0));
+
+        assert!(tracks.len() >= 4);
+        sel.state.height = 3;
+
+        sel.decrement(tracks, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(0));
+
+        sel.increment(tracks, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(2));
+
+        sel.decrement(tracks, Delta::Page);
+        assert_eq!(sel.state.list.selected(), Some(0));
+
+        for _ in 0..(tracks.len() + 5) {
+            sel.increment(tracks, Delta::Page);
+        }
+        assert_eq!(sel.state.list.selected(), Some(tracks.len() - 1));
+    }
+
+    #[test]
+    fn track_reinitialise() {
+        let tracks = &COLLECTION[0].albums[0].tracks;
+        assert!(tracks.len() > 1);
+
+        let mut sel = TrackSelection::initialise(tracks);
+        sel.state.list.select(Some(tracks.len() - 1));
+
+        // Re-initialise.
+        let expected = sel.clone();
+        let active_track = IdSelectTrack::get(tracks, &sel);
+        sel.reinitialise(tracks, active_track);
+        assert_eq!(sel, expected);
+
+        // Re-initialise out-of-bounds.
+        let mut expected = sel.clone();
+        expected.decrement(tracks, Delta::Line);
+        let active_track = IdSelectTrack::get(tracks, &sel);
+        sel.reinitialise(&tracks[..(tracks.len() - 1)], active_track);
+        assert_eq!(sel, expected);
+
+        // Re-initialise empty.
+        let expected = TrackSelection::initialise(&[]);
+        let active_track = IdSelectTrack::get(tracks, &sel);
+        sel.reinitialise(&[], active_track);
+        assert_eq!(sel, expected);
+    }
+}