/*
This file is part of Telegram Desktop,
the official desktop application for the Telegram messaging service.

For license and copyright information please follow this link:
https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
*/
#pragma once

#include "base/observer.h"
#include "base/timer.h"
#include "base/binary_guard.h"
#include "data/data_file_origin.h"
#include "mtproto/facade.h"

#include <QtNetwork/QNetworkReply>

class ApiWrap;

namespace Main {
class Session;
} // namespace Main

namespace Storage {
namespace Cache {
struct Key;
} // namespace Cache

// This value is used in local cache database settings!
constexpr auto kMaxFileInMemory = 10 * 1024 * 1024; // 10 MB max file could be hold in memory

constexpr auto kMaxVoiceInMemory = 2 * 1024 * 1024; // 2 MB audio is hold in memory and auto loaded
constexpr auto kMaxStickerInMemory = 2 * 1024 * 1024; // 2 MB stickers hold in memory, auto loaded and displayed inline
constexpr auto kMaxWallPaperInMemory = kMaxFileInMemory;
constexpr auto kMaxAnimationInMemory = kMaxFileInMemory; // 10 MB gif and mp4 animations held in memory while playing
constexpr auto kMaxWallPaperDimension = 4096; // 4096x4096 is max area.

// Different part sizes are not supported for now :(
// Because we start downloading with some part size
// and then we get a cdn-redirect where we support only
// fixed part size download for hash checking.
constexpr auto kDownloadPartSize = 128 * 1024;

class Downloader {
public:
	virtual ~Downloader() = default;

	[[nodiscard]] virtual MTP::DcId dcId() const = 0;
	[[nodiscard]] virtual bool readyToRequest() const = 0;
	virtual void loadPart(int dcIndex) = 0;

};

class DownloadManager final : public base::has_weak_ptr {
public:
	explicit DownloadManager(not_null<ApiWrap*> api);
	~DownloadManager();

	[[nodiscard]] ApiWrap &api() const {
		return *_api;
	}

	void enqueue(not_null<Downloader*> loader);
	void remove(not_null<Downloader*> loader);

	[[nodiscard]] base::Observable<void> &taskFinished() {
		return _taskFinishedObservable;
	}

	// dcId == 0 is for web requests.
	void requestedAmountIncrement(MTP::DcId dcId, int index, int amount);
	[[nodiscard]] int chooseDcIndexForRequest(MTP::DcId dcId);

private:
	class Queue final {
	public:
		void enqueue(not_null<Downloader*> loader);
		void remove(not_null<Downloader*> loader);
		void resetGeneration();
		[[nodiscard]] bool empty() const;
		[[nodiscard]] Downloader *nextLoader() const;

	private:
		std::vector<not_null<Downloader*>> _loaders;
		std::vector<not_null<Downloader*>> _previousGeneration;

	};

	void checkSendNext();

	void killDownloadSessionsStart(MTP::DcId dcId);
	void killDownloadSessionsStop(MTP::DcId dcId);
	void killDownloadSessions();

	void resetGeneration();

	const not_null<ApiWrap*> _api;

	base::Observable<void> _taskFinishedObservable;

	base::flat_map<MTP::DcId, std::vector<int>> _requestedBytesAmount;
	base::Timer _resetGenerationTimer;

	base::flat_map<MTP::DcId, crl::time> _killDownloadSessionTimes;
	base::Timer _killDownloadSessionsTimer;

	base::flat_map<MTP::DcId, Queue> _mtprotoLoaders;
	Queue _webLoaders;

};

} // namespace Storage

struct StorageImageSaved {
	StorageImageSaved() = default;
	explicit StorageImageSaved(const QByteArray &data) : data(data) {
	}

	QByteArray data;

};

class FileLoader : public QObject {
	Q_OBJECT

public:
	FileLoader(
		const QString &toFile,
		int32 size,
		LocationType locationType,
		LoadToCacheSetting toCache,
		LoadFromCloudSetting fromCloud,
		bool autoLoading,
		uint8 cacheTag);

	Main::Session &session() const;

	bool finished() const {
		return _finished;
	}
	void finishWithBytes(const QByteArray &data);
	bool cancelled() const {
		return _cancelled;
	}
	const QByteArray &bytes() const {
		return _data;
	}
	virtual uint64 objId() const {
		return 0;
	}
	QByteArray imageFormat(const QSize &shrinkBox = QSize()) const;
	QImage imageData(const QSize &shrinkBox = QSize()) const;
	QString fileName() const {
		return _filename;
	}
	virtual Data::FileOrigin fileOrigin() const;
	float64 currentProgress() const;
	virtual int currentOffset() const;
	int fullSize() const;

	bool setFileName(const QString &filename); // set filename for loaders to cache
	void permitLoadFromCloud();

	void start();
	void cancel();

	bool loadingLocal() const {
		return (_localStatus == LocalStatus::Loading);
	}
	bool autoLoading() const {
		return _autoLoading;
	}

	virtual void stop() {
	}
	virtual ~FileLoader();

	void localLoaded(
		const StorageImageSaved &result,
		const QByteArray &imageFormat,
		const QImage &imageData);

signals:
	void progress(FileLoader *loader);
	void failed(FileLoader *loader, bool started);

protected:
	enum class LocalStatus {
		NotTried,
		NotFound,
		Loading,
		Loaded,
	};

	void readImage(const QSize &shrinkBox) const;

	bool tryLoadLocal();
	void loadLocal(const Storage::Cache::Key &key);
	virtual Storage::Cache::Key cacheKey() const = 0;
	virtual std::optional<MediaKey> fileLocationKey() const = 0;
	virtual void cancelRequests() = 0;
	virtual void startLoading() = 0;

	void cancel(bool failed);

	void notifyAboutProgress();

	bool writeResultPart(int offset, bytes::const_span buffer);
	bool finalizeResult();
	[[nodiscard]] QByteArray readLoadedPartBack(int offset, int size);

	const not_null<Main::Session*> _session;

	bool _autoLoading = false;
	uint8 _cacheTag = 0;
	bool _finished = false;
	bool _cancelled = false;
	mutable LocalStatus _localStatus = LocalStatus::NotTried;

	QString _filename;
	QFile _file;
	bool _fileIsOpen = false;

	LoadToCacheSetting _toCache;
	LoadFromCloudSetting _fromCloud;

	QByteArray _data;

	int _size = 0;
	int _skippedBytes = 0;
	LocationType _locationType = LocationType();

	base::binary_guard _localLoading;
	mutable QByteArray _imageFormat;
	mutable QImage _imageData;

};