/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 */

//
// Sprite caching system.
//
// SpriteFile handles sprite serialization and streaming.
// SpriteCache provides bitmaps by demand; it uses SpriteFile to load sprites
// and does MRU (most-recent-use) caching.
//
// TODO: store sprite data in a specialized container type that is optimized
// for having most keys allocated in large continious sequences by default.
//
// Only for the reference: one of the ideas is for container to have a table
// of arrays of fixed size internally. When getting an item the hash would be
// first divided on array size to find the array the item resides in, then the
// item is taken from item from slot index = (hash - arrsize * arrindex).
// TODO: find out if there is already a hash table kind that follows similar
// principle.
//
//=============================================================================

#ifndef AGS_SHARED_AC_SPRITE_CACHE_H
#define AGS_SHARED_AC_SPRITE_CACHE_H

#include "ags/lib/std/memory.h"
#include "ags/lib/std/vector.h"
#include "ags/lib/std/list.h"
#include "ags/shared/ac/sprite_file.h"
#include "ags/shared/core/platform.h"
#include "ags/shared/util/error.h"
#include "ags/shared/util/geometry.h"

namespace AGS3 {

namespace AGS {
namespace Shared {
class String;
class Stream;
class Bitmap;
} // namespace AGS3
} // namespace AGS

using namespace AGS; // FIXME later
typedef AGS::Shared::HError HAGSError;

struct SpriteInfo;

// Tells that the sprite is found in the game resources.
#define SPRCACHEFLAG_ISASSET        0x01
// Tells that the sprite index was remapped to another existing sprite.
#define SPRCACHEFLAG_REMAPPED       0x02
// Locked sprites are ones that should not be freed when out of cache space.
#define SPRCACHEFLAG_LOCKED         0x04

// Max size of the sprite cache, in bytes
#if AGS_PLATFORM_OS_ANDROID || AGS_PLATFORM_OS_IOS
#define DEFAULTCACHESIZE_KB (32 * 1024)
#else
#define DEFAULTCACHESIZE_KB (128 * 1024)
#endif

struct SpriteInfo;

namespace AGS {
namespace Shared {

class SpriteCache {
public:
	static const sprkey_t MIN_SPRITE_INDEX = 1; // 0 is reserved for "empty sprite"
	static const sprkey_t MAX_SPRITE_INDEX = INT32_MAX - 1;
	static const size_t   MAX_SPRITE_SLOTS = INT32_MAX;

	SpriteCache(std::vector<SpriteInfo> &sprInfos);
	~SpriteCache();

	// Loads sprite reference information and inits sprite stream
	HError      InitFile(const Shared::String &filename, const Shared::String &sprindex_filename);
	// Saves current cache contents to the file
	int         SaveToFile(const Shared::String &filename, int store_flags, SpriteCompression compress, SpriteFileIndex &index);
	// Closes an active sprite file stream
	void        DetachFile();

	inline int GetStoreFlags() const {
		return _file.GetStoreFlags();
	}
	inline SpriteCompression GetSpriteCompression() const {
		return _file.GetSpriteCompression();
	}

	// Tells if there is a sprite registered for the given index;
	// this includes sprites that were explicitly assigned but failed to init and were remapped
	bool        DoesSpriteExist(sprkey_t index) const;
	// Makes sure sprite cache has allocated slots for all sprites up to the given inclusive limit;
	// returns requested index on success, or -1 on failure.
	sprkey_t    EnlargeTo(sprkey_t topmost);
	// Finds a free slot index, if all slots are occupied enlarges sprite bank; returns index
	sprkey_t    GetFreeIndex();
	// Returns current size of the cache, in bytes; this includes locked size too!
	size_t      GetCacheSize() const;
	// Gets the total size of the locked sprites, in bytes
	size_t      GetLockedSize() const;
	// Returns maximal size limit of the cache, in bytes; this includes locked size too!
	size_t      GetMaxCacheSize() const;
	// Returns number of sprite slots in the bank (this includes both actual sprites and free slots)
	size_t      GetSpriteSlotCount() const;
	// Loads sprite and and locks in memory (so it cannot get removed implicitly)
	void        Precache(sprkey_t index);
	// Remap the given index to the sprite 0
	void        RemapSpriteToSprite0(sprkey_t index);
	// Unregisters sprite from the bank and optionally deletes bitmap
	void        RemoveSprite(sprkey_t index, bool freeMemory);
	// Deletes all loaded (non-locked, non-external) images from the cache;
	// this keeps all the auxiliary sprite information intact
	void        DisposeAll();
	// Deletes all data and resets cache to the clear state
	void        Reset();
	// Assigns new sprite for the given index; this sprite won't be auto disposed
	// flags are SPF_* constants that define sprite's behavior in game.
	bool        SetSprite(sprkey_t index, Shared::Bitmap *, int flags = 0);
	// Assigns new sprite for the given index, remapping it to sprite 0;
	// optionally marks it as an asset placeholder
	void        SetEmptySprite(sprkey_t index, bool as_asset);
	// Assigns new bitmap for the *registered* sprite without changing its properties
	void        SubstituteBitmap(sprkey_t index, Shared::Bitmap *);
	// Sets max cache size in bytes
	void        SetMaxCacheSize(size_t size);

	// Loads (if it's not in cache yet) and returns bitmap by the sprite index
	Shared::Bitmap *operator[](sprkey_t index);

private:
	// Load sprite from game resource
	size_t      LoadSprite(sprkey_t index);
	// Gets the index of a sprite which data is used for the given slot;
	// in case of remapped sprite this will return the one given sprite is remapped to
	sprkey_t    GetDataIndex(sprkey_t index);
	// Delete the oldest (least recently used) image in cache
	void        DisposeOldest();
	// Keep disposing oldest elements until cache has at least the given free space
	void        FreeMem(size_t space);

	// Information required for the sprite streaming
	struct SpriteData {
		size_t          Size = 0; // to track cache size
		uint32_t        Flags = 0;
		// TODO: investigate if we may safely use unique_ptr here
		// (some of these bitmaps may be assigned from outside of the cache)
		Shared::Bitmap *Image = nullptr; // actual bitmap
		// MRU list reference
		std::list<sprkey_t>::iterator MruIt;

		// Tells if there actually is a registered sprite in this slot
		bool DoesSpriteExist() const;
		// Tells if there's a game resource corresponding to this slot
		bool IsAssetSprite() const;
		// Tells if sprite was added externally, not loaded from game resources
		bool IsExternalSprite() const;
		// Tells if sprite is locked and should not be disposed by cache logic
		bool IsLocked() const;
	};

	// Provided map of sprite infos, to fill in loaded sprite properties
	std::vector<SpriteInfo> &_sprInfos;
	// Array of sprite references
	std::vector<SpriteData> _spriteData;

	SpriteFile _file;

	size_t _maxCacheSize;  // cache size limit
	size_t _lockedSize;    // size in bytes of currently locked images
	size_t _cacheSize;     // size in bytes of currently cached images

	// MRU list: the way to track which sprites were used recently.
	// When clearing up space for new sprites, cache first deletes the sprites
	// that were last time used long ago.
	std::list<sprkey_t> _mru;

	// Initialize the empty sprite slot
	void        InitNullSpriteParams(sprkey_t index);
};

} // namespace Shared
} // namespace AGS
} // namespace AGS3

#endif