session command

internal/playback/session_command.go

@@ -0,0 +1,110 @@
+package playback
+
+import (
+	"errors"
+	"fmt"
+)
+
+type SessionCommandKind uint8
+
+const (
+	CommandSetVideo SessionCommandKind = iota + 1
+	CommandSetAudio
+	CommandStopVideo
+	CommandStopAudio
+	CommandStopAll
+	CommandResumeVideo
+	CommandResumeAudio
+	CommandResumeAll
+	CommandRemoveVideo
+	CommandRemoveAudio
+	CommandEnableSync
+	CommandDisableSync
+)
+
+type SessionCommand struct {
+	Kind   SessionCommandKind
+	Config FeedConfig // Used only by SetVideo and SetAudio.
+}
+
+var (
+	ErrUnknownSessionCommand = errors.New("unknown session command")
+	ErrVideoNotConfigured    = errors.New("video feed is not configured")
+	ErrAudioNotConfigured    = errors.New("audio feed is not configured")
+)
+
+func ApplySessionCommand(
+	current SessionConfig,
+	command SessionCommand,
+) (SessionConfig, error) {
+	next := current
+	switch command.Kind {
+	case CommandSetVideo:
+		if !command.Config.IsConfigured() {
+			return current, ErrVideoNotConfigured
+		}
+		if err := command.Config.Validate(); err != nil {
+			return current, fmt.Errorf("validate video command: %w", err)
+		}
+		next.Video = command.Config
+
+	case CommandSetAudio:
+		if !command.Config.IsConfigured() {
+			return current, ErrAudioNotConfigured
+		}
+		if err := command.Config.Validate(); err != nil {
+			return current, fmt.Errorf("validate audio command: %w", err)
+		}
+		next.Audio = command.Config
+
+	case CommandStopVideo:
+		next.Video.Active = false
+		next.SyncRequested = false
+
+	case CommandStopAudio:
+		next.Audio.Active = false
+		next.SyncRequested = false
+
+	case CommandStopAll:
+		next.Video.Active = false
+		next.Audio.Active = false
+
+	case CommandResumeVideo:
+		if !next.Video.IsConfigured() {
+			return current, ErrVideoNotConfigured
+		}
+		next.Video.Active = true
+
+	case CommandResumeAudio:
+		if !next.Audio.IsConfigured() {
+			return current, ErrAudioNotConfigured
+		}
+		next.Audio.Active = true
+
+	case CommandResumeAll:
+		next.Video.Active = next.Video.IsConfigured()
+		next.Audio.Active = next.Audio.IsConfigured()
+
+	case CommandRemoveVideo:
+		next.Video = FeedConfig{}
+		next.SyncRequested = false
+
+	case CommandRemoveAudio:
+		next.Audio = FeedConfig{}
+		next.SyncRequested = false
+
+	case CommandEnableSync:
+		next.SyncRequested = true
+
+	case CommandDisableSync:
+		next.SyncRequested = false
+
+	default:
+		return current, ErrUnknownSessionCommand
+	}
+
+	if err := next.Validate(); err != nil {
+		return current, fmt.Errorf("validate desired session: %w", err)
+	}
+	return next, nil
+}