/*
 * Strawberry Music Player
 * This file was part of Clementine.
 * Copyright 2010, David Sansome <me@davidsansome.com>
 *
 * Strawberry 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 3 of the License, or
 * (at your option) any later version.
 *
 * Strawberry 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 Strawberry.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */

#ifndef ALBUMCOVERFETCHER_H
#define ALBUMCOVERFETCHER_H

#include "config.h"

#include "coversearchstatistics.h"

#include <QHash>
#include <QImage>
#include <QList>
#include <QMetaType>
#include <QNetworkAccessManager>
#include <QObject>
#include <QQueue>
#include <QUrl>

class QNetworkReply;
class QString;

class AlbumCoverFetcherSearch;
class CoverProviders;

// This class represents a single search-for-cover request. It identifies
// and describes the request.
struct CoverSearchRequest {
  // an unique (for one AlbumCoverFetcher) request identifier
  quint64 id;

  // a search query
  QString artist;
  QString album;

  // is this only a search request or should we also fetch the first
  // cover that's found?
  bool search;
};

// This structure represents a single result of some album's cover search request.
// It contains an URL that leads to a found cover plus its description (usually
// the "artist - album" string).
struct CoverSearchResult {
  // used for grouping in the user interface.  This is set automatically - don't
  // set it manually in your cover provider.
  QString provider;

  // description of this result (we suggest using the "artist - album" format)
  QString description;

  // an URL of a cover image described by this CoverSearchResult
  QUrl image_url;
};
Q_DECLARE_METATYPE(CoverSearchResult);

// This is a complete result of a single search request (a list of results, each
// describing one image, actually).
typedef QList<CoverSearchResult> CoverSearchResults;
Q_DECLARE_METATYPE(QList<CoverSearchResult>);

// This class searches for album covers for a given query or artist/album and
// returns URLs. It's NOT thread-safe.
class AlbumCoverFetcher : public QObject {
  Q_OBJECT

 public:
  AlbumCoverFetcher(CoverProviders *cover_providers, QObject *parent = nullptr, QNetworkAccessManager *network = 0);
  virtual ~AlbumCoverFetcher() {}

  static const int kMaxConcurrentRequests;

  quint64 SearchForCovers(const QString &artist, const QString &album);
  quint64 FetchAlbumCover(const QString &artist, const QString &album);

  void Clear();

signals:
  void AlbumCoverFetched(quint64, const QImage &cover, const CoverSearchStatistics &statistics);
  void SearchFinished(quint64, const CoverSearchResults &results, const CoverSearchStatistics &statistics);

 private slots:
  void SingleSearchFinished(quint64, CoverSearchResults results);
  void SingleCoverFetched(quint64, const QImage &cover);
  void StartRequests();

 private:
  void AddRequest(const CoverSearchRequest &req);

  CoverProviders *cover_providers_;
  QNetworkAccessManager *network_;
  quint64 next_id_;

  QQueue<CoverSearchRequest> queued_requests_;
  QHash<quint64, AlbumCoverFetcherSearch*> active_requests_;

  QTimer *request_starter_;
};

#endif  // ALBUMCOVERFETCHER_H