misc: Decouple Grid view from Albums

The Grid view and related components were highly coupled to Albums,
including the filter button that is currently used only for album
filtering.

As part of the migration of Artists to Grid view, this is the smallest
possible change to convert many of the existing code to
generics/interfaces that will allow different media to be displayed and
filtered by using Grid views.

The main changes in this diff are:

* Introduction of generics for Media types (`M`) and Filter options
  (`F`), which can be later extended to other entities besides Albums.
* Complete decoupling of `GridViewPage` and related components from
  Albums (making these pages also generic).
* Refactoring of Subsonic/Jellyfin specific code to understand these new
  generics when dealing with filtering logic.

ui/widgets/albumfilterbutton.go

@@ -30,11 +30,11 @@ type AlbumFilterButton struct {
 
 	genreListChan chan []string
 
-	filter *mediaprovider.AlbumFilter
+	filter mediaprovider.AlbumFilter
 	dialog *widget.PopUp
 }
 
-func NewAlbumFilterButton(filter *mediaprovider.AlbumFilter, fetchGenresFunc func() ([]*mediaprovider.Genre, error)) *AlbumFilterButton {
+func NewAlbumFilterButton(filter mediaprovider.AlbumFilter, fetchGenresFunc func() ([]*mediaprovider.Genre, error)) *AlbumFilterButton {
 	a := &AlbumFilterButton{
 		filter: filter,
 		Button: widget.Button{
@@ -66,10 +66,19 @@ func (a *AlbumFilterButton) Refresh() {
 	a.Button.Refresh()
 }
 
+func (a *AlbumFilterButton) Filter() mediaprovider.AlbumFilter {
+	return a.filter
+}
+
+func (a *AlbumFilterButton) SetOnChanged(fn func()) {
+	a.OnChanged = fn
+}
+
 func (a *AlbumFilterButton) filterEmpty() bool {
-	return a.filter.MinYear == 0 && a.filter.MaxYear == 0 &&
-		(a.FavoriteDisabled || !a.filter.ExcludeFavorited && !a.filter.ExcludeUnfavorited) &&
-		(a.GenreDisabled || len(a.filter.Genres) == 0)
+	filterOptions := a.filter.Options()
+	return filterOptions.MinYear == 0 && filterOptions.MaxYear == 0 &&
+		(a.FavoriteDisabled || !filterOptions.ExcludeFavorited && !filterOptions.ExcludeUnfavorited) &&
+		(a.GenreDisabled || len(filterOptions.Genres) == 0)
 }
 
 func (a *AlbumFilterButton) onFilterChanged() {
@@ -115,53 +124,64 @@ func NewAlbumFilterPopup(filter *AlbumFilterButton) *AlbumFilterPopup {
 	minYear := NewTextRestrictedEntry(yearValidator)
 	minYear.SetMinCharWidth(4)
 	minYear.OnChanged = func(yearStr string) {
+		filterOptions := a.filterBtn.filter.Options()
 		if yearStr == "" {
-			a.filterBtn.filter.MinYear = 0
+			filterOptions.MinYear = 0
 		} else if i, err := strconv.Atoi(yearStr); err == nil {
-			a.filterBtn.filter.MinYear = i
+			filterOptions.MinYear = i
 		}
+		a.filterBtn.filter.SetOptions(filterOptions)
 		debounceOnChanged()
 	}
-	if a.filterBtn.filter.MinYear > 0 {
-		minYear.Text = strconv.Itoa(a.filterBtn.filter.MinYear)
+	filterOptions := a.filterBtn.filter.Options()
+	if filterOptions.MinYear > 0 {
+		minYear.Text = strconv.Itoa(filterOptions.MinYear)
 	}
 	maxYear := NewTextRestrictedEntry(yearValidator)
 	maxYear.SetMinCharWidth(4)
 	maxYear.OnChanged = func(yearStr string) {
+		filterOptions := a.filterBtn.filter.Options()
 		if yearStr == "" {
-			a.filterBtn.filter.MaxYear = 0
+			filterOptions.MaxYear = 0
 		} else if i, err := strconv.Atoi(yearStr); err == nil {
-			a.filterBtn.filter.MaxYear = i
+			filterOptions.MaxYear = i
 		}
+		a.filterBtn.filter.SetOptions(filterOptions)
 		debounceOnChanged()
 	}
-	if a.filterBtn.filter.MaxYear > 0 {
-		maxYear.Text = strconv.Itoa(a.filterBtn.filter.MaxYear)
+	if filterOptions.MaxYear > 0 {
+		maxYear.Text = strconv.Itoa(filterOptions.MaxYear)
 	}
 
 	// setup is favorite/not favorite filters
 	a.isFavorite = widget.NewCheck("Is favorite", func(fav bool) {
+		filterOptions := a.filterBtn.filter.Options()
 		if fav {
 			a.isNotFavorite.SetChecked(false)
 		}
-		a.filterBtn.filter.ExcludeUnfavorited = fav
+		filterOptions.ExcludeUnfavorited = fav
+		a.filterBtn.filter.SetOptions(filterOptions)
 		debounceOnChanged()
 	})
 	a.isFavorite.Hidden = a.filterBtn.FavoriteDisabled
 	a.isNotFavorite = widget.NewCheck("Is not favorite", func(fav bool) {
+		filterOptions := a.filterBtn.filter.Options()
 		if fav {
 			a.isFavorite.SetChecked(false)
 		}
-		a.filterBtn.filter.ExcludeFavorited = fav
+		filterOptions.ExcludeFavorited = fav
+		a.filterBtn.filter.SetOptions(filterOptions)
 		debounceOnChanged()
 	})
 	a.isNotFavorite.Hidden = a.filterBtn.FavoriteDisabled
 
 	// create genre filter subsection
 	a.genreFilter = NewGenreFilterSubsection(func(selectedGenres []string) {
-		a.filterBtn.filter.Genres = selectedGenres
+		filterOptions := a.filterBtn.filter.Options()
+		filterOptions.Genres = selectedGenres
+		a.filterBtn.filter.SetOptions(filterOptions)
 		debounceOnChanged()
-	}, a.filterBtn.filter.Genres)
+	}, filterOptions.Genres)
 	a.genreFilter.Hidden = a.filterBtn.GenreDisabled
 
 	// setup container

ui/widgets/filterbutton.go

@@ -0,0 +1,13 @@
+package widgets
+
+import (
+	"fyne.io/fyne/v2"
+	"github.com/dweymouth/supersonic/backend/mediaprovider"
+)
+
+type FilterButton[M, F any] interface {
+	fyne.CanvasObject
+
+	Filter() mediaprovider.MediaFilter[M, F]
+	SetOnChanged(func())
+}

ui/widgets/gridview.go

@@ -18,23 +18,23 @@ import (
 
 const batchFetchSize = 6
 
-type BatchingIterator struct {
-	iter mediaprovider.AlbumIterator
+type BatchingIterator[M any] struct {
+	iter mediaprovider.MediaIterator[M]
 }
 
-func NewBatchingIterator(iter mediaprovider.AlbumIterator) BatchingIterator {
-	return BatchingIterator{iter}
+func NewBatchingIterator[M any](iter mediaprovider.MediaIterator[M]) BatchingIterator[M] {
+	return BatchingIterator[M]{iter}
 }
 
-func (b *BatchingIterator) NextN(n int) []*mediaprovider.Album {
-	results := make([]*mediaprovider.Album, 0, n)
+func (b *BatchingIterator[M]) NextN(n int) []*M {
+	results := make([]*M, 0, n)
 	i := 0
 	for i < n {
-		album := b.iter.Next()
-		if album == nil {
+		value := b.iter.Next()
+		if value == nil {
 			break
 		}
-		results = append(results, album)
+		results = append(results, value)
 		i++
 	}
 	return results
@@ -45,7 +45,7 @@ type GridViewIterator interface {
 }
 
 type gridViewAlbumIterator struct {
-	iter BatchingIterator
+	iter BatchingIterator[mediaprovider.Album]
 }
 
 func (g gridViewAlbumIterator) NextN(n int) []GridViewItemModel {