package playback

import "time"

type PlaylistTimingState struct {
	Revision  uint64
	Duration  time.Duration
	Ready     bool
	Started   bool
	Paused    bool
	Expired   bool
	Remaining time.Duration
	Deadline  time.Time
}

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

func StartPlaylistTiming(
	current PlaylistTimingState,
	revision uint64,
	now time.Time,
) (PlaylistTimingState, bool) {
	if revision != current.Revision ||
		current.Duration <= 0 ||
		current.Started ||
		current.Paused ||
		current.Expired {
		return current, false
	}
	next := current
	if next.Remaining <= 0 {
		next.Remaining = next.Duration
	}
	next.Ready = true
	next.Started = true
	next.Deadline = now.Add(next.Remaining)
	return next, true
}

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

	next := current
	if next.Started {
		next.Remaining = next.Deadline.Sub(now)
		if next.Remaining < 0 {
			next.Remaining = 0
		}
		if next.Remaining > next.Duration {
			next.Remaining = next.Duration
		}
		next.Started = false
		next.Deadline = time.Time{}
	}
	next.Paused = true
	return next, true
}

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

	next := current
	next.Paused = false
	if next.Ready {
		next.Started = true
		next.Deadline = now.Add(next.Remaining)
	}
	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.Paused = false
	next.Deadline = time.Time{}
	next.Expired = true
	next.Remaining = 0
	return next, true
}