Implement new Artist refresh

model/album.go

@@ -1,6 +1,11 @@
 package model
 
-import "time"
+import (
+	"time"
+
+	"github.com/navidrome/navidrome/utils/slice"
+	"golang.org/x/exp/slices"
+)
 
 type Album struct {
 	Annotations `structs:"-"`
@@ -42,13 +47,35 @@ func (a Album) CoverArtID() ArtworkID {
 	return artworkIDFromAlbum(a)
 }
 
-type (
-	Albums []Album
-	DiscID struct {
-		AlbumID    string `json:"albumId"`
-		DiscNumber int    `json:"discNumber"`
+type DiscID struct {
+	AlbumID    string `json:"albumId"`
+	DiscNumber int    `json:"discNumber"`
+}
+
+type Albums []Album
+
+// ToAlbumArtist creates an Artist object based on the attributes of this Albums collection.
+// It assumes all albums have the same AlbumArtist, or else results are unpredictable.
+func (als Albums) ToAlbumArtist() Artist {
+	a := Artist{AlbumCount: len(als)}
+	var mbzArtistIds []string
+	for _, al := range als {
+		a.ID = al.AlbumArtistID
+		a.Name = al.AlbumArtist
+		a.SortArtistName = al.SortAlbumArtistName
+		a.OrderArtistName = al.OrderAlbumArtistName
+
+		a.SongCount += al.SongCount
+		a.Size += al.Size
+		a.Genres = append(a.Genres, al.Genres...)
+		mbzArtistIds = append(mbzArtistIds, al.MbzAlbumArtistID)
 	}
-)
+	slices.SortFunc(a.Genres, func(a, b Genre) bool { return a.ID < b.ID })
+	a.Genres = slices.Compact(a.Genres)
+	a.MbzArtistID = slice.MostFrequent(mbzArtistIds)
+
+	return a
+}
 
 type AlbumRepository interface {
 	CountAll(...QueryOptions) (int64, error)