package playback

import "time"

type PlaylistTimingState struct {
	Revision uint64
	Duration time.Duration
	Started  bool
	Deadline time.Time
}

func NewPlaylistTiming(
	revision uint64,
	duration time.Duration,
) PlaylistTimingState {
	return PlaylistTimingState{
		Revision: revision,
		Duration: duration,
	}
}

func StartPlaylistTiming(
	current PlaylistTimingState,
	revision uint64,
	now time.Time,
) (PlaylistTimingState, bool) {
	if revision != current.Revision || current.Duration <= 0 || current.Started {
		return current, false
	}

	next := current
	next.Started = true
	next.Deadline = now.Add(current.Duration)
	return next, true
}

func ExpirePlaylistTiming(
	current PlaylistTimingState,
	revision uint64,
	now time.Time,
) (PlaylistTimingState, bool) {
	if revision != current.Revision ||
		!current.Started ||
		now.Before(current.Deadline) {
		return current, false
	}

	next := current
	next.Started = false
	next.Deadline = time.Time{}
	return next, true
}