mpd/src/playlist/plugins/SoundCloudPlaylistPlugin.cxx

/*
 * Copyright 2003-2019 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.
 */

#include "SoundCloudPlaylistPlugin.hxx"
#include "../PlaylistPlugin.hxx"
#include "../MemorySongEnumerator.hxx"
#include "lib/yajl/Handle.hxx"
#include "lib/yajl/Callbacks.hxx"
#include "lib/yajl/ParseInputStream.hxx"
#include "config/Block.hxx"
#include "input/InputStream.hxx"
#include "tag/Builder.hxx"
#include "util/ASCII.hxx"
#include "util/StringCompare.hxx"
#include "util/Alloc.hxx"
#include "util/Domain.hxx"
#include "util/ScopeExit.hxx"
#include "Log.hxx"

#include <string>

#include <string.h>
#include <stdlib.h>

static struct {
	std::string apikey;
} soundcloud_config;

static constexpr Domain soundcloud_domain("soundcloud");

static bool
soundcloud_init(const ConfigBlock &block)
{
	// APIKEY for MPD application, registered under DarkFox' account.
	soundcloud_config.apikey = block.GetBlockValue("apikey", "a25e51780f7f86af0afa91f241d091f8");
	if (soundcloud_config.apikey.empty()) {
		LogDebug(soundcloud_domain,
			 "disabling the soundcloud playlist plugin "
			 "because API key is not set");
		return false;
	}

	return true;
}

/**
 * Construct a full soundcloud resolver URL from the given fragment.
 * @param uri uri of a soundcloud page (or just the path)
 * @return Constructed URL. Must be freed with free().
 */
static char *
soundcloud_resolve(const char* uri)
{
	char *u, *ru;

	if (StringStartsWithCaseASCII(uri, "https://")) {
		u = xstrdup(uri);
	} else if (StringStartsWith(uri, "soundcloud.com")) {
		u = xstrcatdup("https://", uri);
	} else {
		/* assume it's just a path on soundcloud.com */
		u = xstrcatdup("https://soundcloud.com/", uri);
	}

	ru = xstrcatdup("https://api.soundcloud.com/resolve.json?url=",
			u, "&client_id=",
			soundcloud_config.apikey.c_str());
	free(u);

	return ru;
}

/* YAJL parser for track data from both /tracks/ and /playlists/ JSON */

static const char *const key_str[] = {
	"duration",
	"title",
	"stream_url",
	nullptr,
};

struct SoundCloudJsonData {
	enum class Key {
		DURATION,
		TITLE,
		STREAM_URL,
		OTHER,
	};

	Key key;
	std::string stream_url;
	long duration;
	std::string title;
	int got_url = 0; /* nesting level of last stream_url */

	std::forward_list<DetachedSong> songs;

	bool Integer(long long value) noexcept;
	bool String(StringView value) noexcept;
	bool StartMap() noexcept;
	bool MapKey(StringView value) noexcept;
	bool EndMap() noexcept;
};

inline bool
SoundCloudJsonData::Integer(long long intval) noexcept
{
	switch (key) {
	case SoundCloudJsonData::Key::DURATION:
		duration = intval;
		break;
	default:
		break;
	}

	return true;
}

inline bool
SoundCloudJsonData::String(StringView value) noexcept
{
	switch (key) {
	case SoundCloudJsonData::Key::TITLE:
		title.assign(value.data, value.size);
		break;

	case SoundCloudJsonData::Key::STREAM_URL:
		stream_url.assign(value.data, value.size);
		got_url = 1;
		break;

	default:
		break;
	}

	return true;
}

inline bool
SoundCloudJsonData::MapKey(StringView value) noexcept
{
	const auto *i = key_str;
	while (*i != nullptr && !StringStartsWith(*i, value))
		++i;

	key = SoundCloudJsonData::Key(i - key_str);
	return true;
}

inline bool
SoundCloudJsonData::StartMap() noexcept
{
	if (got_url > 0)
		got_url++;

	return true;
}

inline bool
SoundCloudJsonData::EndMap() noexcept
{
	if (got_url > 1) {
		got_url--;
		return 1;
	}

	if (got_url == 0)
		return 1;

	/* got_url == 1, track finished, make it into a song */
	got_url = 0;

	const std::string u = stream_url + "?client_id=" +
		soundcloud_config.apikey;

	TagBuilder tag;
	tag.SetDuration(SignedSongTime::FromMS(duration));
	if (!title.empty())
		tag.AddItem(TAG_NAME, title.c_str());

	songs.emplace_front(u.c_str(), tag.Commit());

	return true;
}

using Wrapper = Yajl::CallbacksWrapper<SoundCloudJsonData>;
static constexpr yajl_callbacks parse_callbacks = {
	nullptr,
	nullptr,
	Wrapper::Integer,
	nullptr,
	nullptr,
	Wrapper::String,
	Wrapper::StartMap,
	Wrapper::MapKey,
	Wrapper::EndMap,
	nullptr,
	nullptr,
};

/**
 * Read JSON data and parse it using the given YAJL parser.
 * @param url URL of the JSON data.
 * @param handle YAJL parser handle.
 */
static void
soundcloud_parse_json(const char *url, Yajl::Handle &handle,
		      Mutex &mutex)
{
	auto input_stream = InputStream::OpenReady(url, mutex);
	Yajl::ParseInputStream(handle, *input_stream);
}

/**
 * Parse a soundcloud:// URL and create a playlist.
 * @param uri A soundcloud URL. Accepted forms:
 *	soundcloud://track/<track-id>
 *	soundcloud://playlist/<playlist-id>
 *	soundcloud://url/<url or path of soundcloud page>
 */
static std::unique_ptr<SongEnumerator>
soundcloud_open_uri(const char *uri, Mutex &mutex)
{
	assert(StringEqualsCaseASCII(uri, "soundcloud://", 13));
	uri += 13;

	char *u = nullptr;
	if (strncmp(uri, "track/", 6) == 0) {
		const char *rest = uri + 6;
		u = xstrcatdup("https://api.soundcloud.com/tracks/",
			       rest, ".json?client_id=",
			       soundcloud_config.apikey.c_str());
	} else if (strncmp(uri, "playlist/", 9) == 0) {
		const char *rest = uri + 9;
		u = xstrcatdup("https://api.soundcloud.com/playlists/",
			       rest, ".json?client_id=",
			       soundcloud_config.apikey.c_str());
	} else if (strncmp(uri, "user/", 5) == 0) {
		const char *rest = uri + 5;
		u = xstrcatdup("https://api.soundcloud.com/users/",
			       rest, "/tracks.json?client_id=",
			       soundcloud_config.apikey.c_str());
	} else if (strncmp(uri, "search/", 7) == 0) {
		const char *rest = uri + 7;
		u = xstrcatdup("https://api.soundcloud.com/tracks.json?q=",
			       rest, "&client_id=",
			       soundcloud_config.apikey.c_str());
	} else if (strncmp(uri, "url/", 4) == 0) {
		const char *rest = uri + 4;
		/* Translate to soundcloud resolver call. libcurl will automatically
		   follow the redirect to the right resource. */
		u = soundcloud_resolve(rest);
	}

	AtScopeExit(u) { free(u); };

	if (u == nullptr) {
		LogWarning(soundcloud_domain, "unknown soundcloud URI");
		return nullptr;
	}

	SoundCloudJsonData data;
	Yajl::Handle handle(&parse_callbacks, nullptr, &data);
	soundcloud_parse_json(u, handle, mutex);

	data.songs.reverse();
	return std::make_unique<MemorySongEnumerator>(std::move(data.songs));
}

static const char *const soundcloud_schemes[] = {
	"soundcloud",
	nullptr
};

const PlaylistPlugin soundcloud_playlist_plugin =
	PlaylistPlugin("soundcloud", soundcloud_open_uri)
	.WithInit(soundcloud_init)
	.WithSchemes(soundcloud_schemes);