downloader

type Client struct {
	// contains filtered or unexported fields
}

type Events interface {
	// Info fires once metadata is resolved and formats are chosen.
	Info(video *youtube.Video, sel *Selection)
	// StreamStart fires before each stream download. label is "video" or
	// "audio"; size is the expected byte count (0 if unknown).
	StreamStart(label string, size int64)
	// StreamProgress reports newly downloaded bytes for the active stream.
	StreamProgress(label string, delta int64)
	// StreamDone fires when a stream finishes.
	StreamDone(label string)
	// MuxStart fires before ffmpeg combines video and audio.
	MuxStart()
	// ConvertStart fires before ffmpeg re-encodes audio (e.g. to mp3).
	ConvertStart(format string)
	// ClipStart fires before ffmpeg extracts a clip segment.
	ClipStart(from, to time.Duration)
	// SubsStart fires before subtitles are fetched (only when requested).
	SubsStart(lang string)
	// SubsDone fires after the subtitle attempt: path on success, err on
	// failure. Subtitle failures never fail the download itself.
	SubsDone(path string, err error)
}

type Options struct {
	URL       string
	Quality   string
	OutputDir string
	Filename  string
	AudioOnly bool
	// AudioFormat converts audio downloads: "" or "m4a" keeps the native
	// stream, "mp3" re-encodes with ffmpeg.
	AudioFormat string
	SubsLang    string // e.g. "en": also download subtitles as .srt
	EmbedSubs   bool   // mux subtitles into the mp4 (needs ffmpeg)
	// ClipFrom/ClipTo select a segment instead of the whole video (ClipTo
	// zero means "until the end"). Requires ffmpeg.
	ClipFrom time.Duration
	ClipTo   time.Duration
}

type PlaylistEvents interface {
	Events
	// PlaylistInfo fires once the playlist is resolved. items is the queue
	// after applying Limit/Reverse; dest is the folder files land in.
	PlaylistInfo(pl *youtube.Playlist, items []*youtube.PlaylistEntry, dest string)
	// ItemStart fires before each queue item is fetched.
	ItemStart(index int, entry *youtube.PlaylistEntry)
	// ItemDone fires after each queue item: path on success, err on failure.
	// One bad video does not stop the queue.
	ItemDone(index int, path string, err error)
}

type PlaylistOptions struct {
	Limit   int  // 0 = every video
	Reverse bool // download oldest-first on playlists sorted newest-first
}

type Selection struct {
	Video *youtube.Format // nil for audio-only downloads
	Audio *youtube.Format // set when muxing or audio-only; nil when Video is already muxed
	// NeedsMux is true when Video and Audio are separate streams that must
	// be combined with ffmpeg.
	NeedsMux bool
	// FellBack is a human-readable note set when the requested quality was
	// unavailable and a lower one was chosen instead.
	FellBack string
}