JSON playlist loader

cmd/mxl-player/playlist_file.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"mxl-player/internal/playback"
+)
+
+type playlistFile struct {
+	Entries []playlistFileEntry `json:"entries"`
+	Loop    bool                `json:"loop"`
+}
+
+type playlistFileEntry struct {
+	Name     string            `json:"name"`
+	Video    *playlistFileFeed `json:"video"`
+	Audio    *playlistFileFeed `json:"audio"`
+	Sync     bool              `json:"sync"`
+	Duration string            `json:"duration"`
+}
+
+type playlistFileFeed struct {
+	Domain string `json:"domain"`
+	UUID   string `json:"uuid"`
+}
+
+func loadPlaylistFile(path string) (playback.Playlist, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return playback.Playlist{}, fmt.Errorf("open playlist %q: %w", path, err)
+	}
+	defer file.Close()
+
+	playlist, err := decodePlaylistFile(file)
+	if err != nil {
+		return playback.Playlist{}, fmt.Errorf("decode playlist %q: %w", path, err)
+	}
+	return playlist, nil
+}
+
+func decodePlaylistFile(reader io.Reader) (playback.Playlist, error) {
+	decoder := json.NewDecoder(reader)
+	decoder.DisallowUnknownFields()
+
+	var file playlistFile
+	if err := decoder.Decode(&file); err != nil {
+		return playback.Playlist{}, fmt.Errorf("decode JSON: %w", err)
+	}
+	var extra any
+	if err := decoder.Decode(&extra); err != io.EOF {
+		if err == nil {
+			return playback.Playlist{}, fmt.Errorf("decode JSON: multiple root values")
+		}
+		return playback.Playlist{}, fmt.Errorf("decode trailing JSON: %w", err)
+	}
+
+	playlist := playback.Playlist{
+		Entries: make([]playback.PlaylistEntry, len(file.Entries)),
+		Loop:    file.Loop,
+	}
+	for index, entry := range file.Entries {
+		duration := time.Duration(0)
+		if entry.Duration != "" {
+			parsed, err := time.ParseDuration(entry.Duration)
+			if err != nil {
+				return playback.Playlist{}, fmt.Errorf(
+					"playlist entry %d duration %q: %w",
+					index,
+					entry.Duration,
+					err,
+				)
+			}
+			duration = parsed
+		}
+
+		playlist.Entries[index] = playback.PlaylistEntry{
+			Name:          entry.Name,
+			Video:         playlistFileFeedToPlayback(entry.Video),
+			Audio:         playlistFileFeedToPlayback(entry.Audio),
+			SyncRequested: entry.Sync,
+			Duration:      duration,
+		}
+	}
+
+	if err := playlist.Validate(); err != nil {
+		return playback.Playlist{}, fmt.Errorf("validate playlist: %w", err)
+	}
+	return playlist, nil
+}
+
+func playlistFileFeedToPlayback(feed *playlistFileFeed) playback.PlaylistFeed {
+	if feed == nil {
+		return playback.PlaylistFeed{}
+	}
+	return playback.PlaylistFeed{Domain: feed.Domain, UUID: feed.UUID}
+}