mpd/src/queue/PlaylistControl.cxx

/*
 * Copyright 2003-2021 The Music Player Daemon Project
 * http://www.musicpd.org
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/*
 * Functions for controlling playback on the playlist level.
 *
 */

#include "Playlist.hxx"
#include "PlaylistError.hxx"
#include "player/Control.hxx"
#include "song/DetachedSong.hxx"
#include "Log.hxx"

void
playlist::Stop(PlayerControl &pc) noexcept
{
	if (!playing)
		return;

	assert(current >= 0);

	LogDebug(playlist_domain, "stop");
	pc.LockStop();
	queued = -1;
	playing = false;

	if (queue.random) {
		/* shuffle the playlist, so the next playback will
		   result in a new random order */

		unsigned current_position = queue.OrderToPosition(current);

		queue.ShuffleOrder();

		/* make sure that "current" stays valid, and the next
		   "play" command plays the same song again */
		current = queue.PositionToOrder(current_position);
	}
}

unsigned
playlist::MoveOrderToCurrent(unsigned old_order) noexcept
{
	if (!queue.random)
		/* no-op because there is no order list */
		return old_order;

	if (playing) {
		/* already playing: move the specified song after the
		   current one (because the current one has already
		   been playing and shall not be played again) */
		return queue.MoveOrderAfter(old_order, current);
	} else if (current >= 0) {
		/* not playing: move the specified song before the
		   current one, so it will be played eventually */
		return queue.MoveOrderBefore(old_order, current);
	} else {
		/* not playing anything: move the specified song to
		   the front */
		return queue.MoveOrderBefore(old_order, 0);
	}
}

void
playlist::PlayPosition(PlayerControl &pc, int song)
{
	pc.LockClearError();

	unsigned i = song;
	if (song == -1) {
		/* play any song ("current" song, or the first song */

		if (queue.IsEmpty())
			return;

		if (playing) {
			/* already playing: unpause playback, just in
			   case it was paused, and return */
			pc.LockSetPause(false);
			return;
		}

		/* select a song: "current" song, or the first one */
		i = current >= 0
			? current
			: 0;
	} else if (!queue.IsValidPosition(song))
		throw PlaylistError::BadRange();

	if (queue.random) {
		if (song >= 0)
			/* "i" is currently the song position (which
			   would be equal to the order number in
			   no-random mode); convert it to a order
			   number, because random mode is enabled */
			i = queue.PositionToOrder(song);

		i = MoveOrderToCurrent(i);
	}

	stop_on_error = false;
	error_count = 0;

	PlayOrder(pc, i);
}

void
playlist::PlayId(PlayerControl &pc, int id)
{
	if (id == -1) {
		PlayPosition(pc, id);
		return;
	}

	int song = queue.IdToPosition(id);
	if (song < 0)
		throw PlaylistError::NoSuchSong();

	PlayPosition(pc, song);
}

void
playlist::PlayNext(PlayerControl &pc)
{
	if (!playing)
		throw PlaylistError::NotPlaying();

	assert(!queue.IsEmpty());
	assert(queue.IsValidOrder(current));

	const int old_current = current;
	stop_on_error = false;

	/* determine the next song from the queue's order list */

	const int next_order = queue.GetNextOrder(current);
	if (next_order < 0) {
		/* no song after this one: stop playback */
		Stop(pc);

		/* reset "current song" */
		current = -1;
	}
	else
	{
		if (next_order == 0 && queue.random) {
			/* The queue told us that the next song is the first
			   song.  This means we are in repeat mode.  Shuffle
			   the queue order, so this time, the user hears the
			   songs in a different than before */
			assert(queue.repeat);

			queue.ShuffleOrder();

			/* note that current and queued are
			   now invalid, but PlayOrder() will
			   discard them anyway */
		}

		PlayOrder(pc, next_order);
	}

	/* Consume mode removes each played songs. */
	if (queue.consume)
		DeleteOrder(pc, old_current);
}

void
playlist::PlayPrevious(PlayerControl &pc)
{
	if (!playing)
		throw PlaylistError::NotPlaying();

	assert(!queue.IsEmpty());

	int order;
	if (current > 0) {
		/* play the preceding song */
		order = current - 1;
	} else if (queue.repeat) {
		/* play the last song in "repeat" mode */
		order = queue.GetLength() - 1;
	} else {
		/* re-start playing the current song if it's
		   the first one */
		order = current;
	}

	PlayOrder(pc, order);
}

void
playlist::SeekSongOrder(PlayerControl &pc, unsigned i, SongTime seek_time)
{
	assert(queue.IsValidOrder(i));

	pc.LockClearError();
	stop_on_error = true;
	error_count = 0;

	if (!playing || (unsigned)current != i) {
		/* seeking is not within the current song - prepare
		   song change */

		i = MoveOrderToCurrent(i);

		playing = true;
		current = i;
	}

	queued = -1;

	try {
		pc.LockSeek(std::make_unique<DetachedSong>(queue.GetOrder(i)), seek_time);
	} catch (...) {
		UpdateQueuedSong(pc, nullptr);
		throw;
	}

	UpdateQueuedSong(pc, nullptr);
}

void
playlist::SeekSongPosition(PlayerControl &pc, unsigned song,
			   SongTime seek_time)
{
	if (!queue.IsValidPosition(song))
		throw PlaylistError::BadRange();

	unsigned i = queue.random
		? queue.PositionToOrder(song)
		: song;

	SeekSongOrder(pc, i, seek_time);
}

void
playlist::SeekSongId(PlayerControl &pc, unsigned id, SongTime seek_time)
{
	int song = queue.IdToPosition(id);
	if (song < 0)
		throw PlaylistError::NoSuchSong();

	SeekSongPosition(pc, song, seek_time);
}

void
playlist::SeekCurrent(PlayerControl &pc,
		      SignedSongTime seek_time, bool relative)
{
	if (!playing)
		throw PlaylistError::NotPlaying();

	if (relative) {
		const auto status = pc.LockGetStatus();

		if (status.state != PlayerState::PLAY &&
		    status.state != PlayerState::PAUSE)
			throw PlaylistError::NotPlaying();

		seek_time += status.elapsed_time;
	}

	if (seek_time.IsNegative())
		seek_time = SignedSongTime::zero();

	SeekSongOrder(pc, current, SongTime(seek_time));
}