feat(server): add index-based play queue endpoints to native API (#4210)

* Add migration converting playqueue current to index

* refactor

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(queue): ensure valid current index and improve test coverage

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

server/nativeapi/queue.go

@@ -0,0 +1,76 @@
+package nativeapi
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+
+	"github.com/navidrome/navidrome/log"
+	"github.com/navidrome/navidrome/model"
+	"github.com/navidrome/navidrome/model/request"
+	"github.com/navidrome/navidrome/utils/slice"
+)
+
+type queuePayload struct {
+	Ids      []string `json:"ids"`
+	Current  int      `json:"current"`
+	Position int64    `json:"position"`
+}
+
+func getQueue(ds model.DataStore) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+		user, _ := request.UserFrom(ctx)
+		repo := ds.PlayQueue(ctx)
+		pq, err := repo.Retrieve(user.ID)
+		if err != nil && !errors.Is(err, model.ErrNotFound) {
+			log.Error(ctx, "Error retrieving queue", err)
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		if pq == nil {
+			pq = &model.PlayQueue{}
+		}
+		resp, err := json.Marshal(pq)
+		if err != nil {
+			log.Error(ctx, "Error marshalling queue", err)
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write(resp)
+	}
+}
+
+func saveQueue(ds model.DataStore) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+		var payload queuePayload
+		if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		user, _ := request.UserFrom(ctx)
+		client, _ := request.ClientFrom(ctx)
+		items := slice.Map(payload.Ids, func(id string) model.MediaFile {
+			return model.MediaFile{ID: id}
+		})
+		if len(payload.Ids) > 0 && (payload.Current < 0 || payload.Current >= len(payload.Ids)) {
+			http.Error(w, "current index out of bounds", http.StatusBadRequest)
+			return
+		}
+		pq := &model.PlayQueue{
+			UserID:    user.ID,
+			Current:   payload.Current,
+			Position:  max(payload.Position, 0),
+			ChangedBy: client,
+			Items:     items,
+		}
+		if err := ds.PlayQueue(ctx).Store(pq); err != nil {
+			log.Error(ctx, "Error saving queue", err)
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		w.WriteHeader(http.StatusNoContent)
+	}
+}