/**
 * @file game.c
 * @brief Implements the game subsystem.
 */

#include <SDL3/SDL.h>
#include <SDL3_image/SDL_image.h>
#include <SDL3_mixer/SDL_mixer.h>
#include <SDL3_ttf/SDL_ttf.h>
#include <stdio.h>
#include <akerror.h>
#include <semver.h>

#include <akstdlib.h>
#include <akgl/game.h>
#include <akgl/controller.h>
#include <akgl/tilemap.h>
#include <akgl/sprite.h>
#include <akgl/heap.h>
#include <akgl/registry.h>
#include <akgl/staticstring.h>
#include <akgl/iterator.h>
#include <akgl/physics.h>
#include <akgl/error.h>
#include <akgl/SDL_GameControllerDB.h>

SDL_Window *window = NULL;

// Currently active objects
akgl_RenderBackend *renderer;
akgl_PhysicsBackend *physics;
SDL_FRect *camera;
akgl_Tilemap *gamemap;

// Default objects
akgl_RenderBackend _akgl_renderer;
akgl_PhysicsBackend _akgl_physics;
SDL_FRect _akgl_camera;
akgl_Tilemap _akgl_gamemap;

MIX_Audio *bgm = NULL;
MIX_Mixer *akgl_mixer = NULL;
MIX_Track *akgl_tracks[AKGL_GAME_AUDIO_MAX_TRACKS];
akgl_Game game;

void akgl_game_lowfps(void)
{
    SDL_Log("Low FPS! %d", game.fps);
    return;
}

akerr_ErrorContext AKERR_NOIGNORE *akgl_game_init()
{
    int screenwidth = 0;
    int screenheight = 0;

    int i = 0;
    PREPARE_ERROR(e);
    // First, before anything that can raise: everything below reports through
    // AKGL_ERR_* codes, and a code raised before its name is registered prints
    // as "Unknown Error" in the stack trace the caller is left holding.
    PASS(e, akgl_error_init());
    strncpy((char *)&game.libversion, AKGL_VERSION, 32);
    game.gameStartTime = SDL_GetTicksNS();
    game.lastIterTime = game.gameStartTime;
    game.lastFPSTime = game.gameStartTime;
    game.lowfpsfunc = &akgl_game_lowfps;
    game.statelock = SDL_CreateMutex();
    FAIL_ZERO_RETURN(e, game.statelock, AKGL_ERR_SDL, "%s", SDL_GetError());
    PASS(e, akgl_game_state_lock());
    FAIL_ZERO_RETURN(e, strlen((char *)&game.name), AKERR_NULLPOINTER, "Must provide game name");
    FAIL_ZERO_RETURN(e, strlen((char *)&game.version), AKERR_NULLPOINTER, "Must provide game version");
    FAIL_ZERO_RETURN(e, strlen((char *)&game.uri), AKERR_NULLPOINTER, "Must provide game uri");
    PASS(e, akgl_heap_init());
    PASS(e, akgl_registry_init_actor());
    PASS(e, akgl_registry_init_sprite());
    PASS(e, akgl_registry_init_spritesheet());
    PASS(e, akgl_registry_init_character());
    PASS(e, akgl_registry_init_font());
    PASS(e, akgl_registry_init_music());
    PASS(e, akgl_registry_init_properties());
    PASS(e, akgl_registry_init_actor_state_strings());

    SDL_SetAppMetadata(game.name, game.version, game.uri);

    for ( i = 0 ; i < AKGL_MAX_CONTROL_MAPS; i++ ) {
	memset(&GAME_ControlMaps[i], 0x00, sizeof(akgl_ControlMap));
    }

    FAIL_ZERO_RETURN(
	e,
	SDL_Init(SDL_INIT_VIDEO | SDL_INIT_GAMEPAD | SDL_INIT_AUDIO),
	AKGL_ERR_SDL,
	"Couldn't initialize SDL: %s",
	SDL_GetError());

    // Load the Game Controller DB

    for ( i = 0; i < AKGL_SDL_GAMECONTROLLER_DB_LEN ; i++ ) {
	if ( SDL_AddGamepadMapping(SDL_GAMECONTROLLER_DB[i]) == -1 ) {
	    FAIL_ZERO_RETURN(e, 0, AKGL_ERR_SDL, "%s", SDL_GetError());
	}
    }
    PASS(e, akgl_controller_open_gamepads());

    FAIL_ZERO_RETURN(
	e,
	MIX_Init(),
	AKGL_ERR_SDL,
	"Couldn't initialize audio: %s",
	SDL_GetError());
    akgl_mixer = MIX_CreateMixerDevice(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, 0);
    FAIL_ZERO_RETURN(
	e,
	akgl_mixer,
	AKGL_ERR_SDL,
	"Unable to create mixer device: %s",
	SDL_GetError());

    FAIL_ZERO_RETURN(
	e,
	TTF_Init(),
	AKGL_ERR_SDL,
	"Couldn't initialize front engine: %s",
	SDL_GetError());

    camera = &_akgl_camera;
    renderer = &_akgl_renderer;
    physics = &_akgl_physics;
    gamemap = &_akgl_gamemap;

    PASS(e, akgl_game_state_unlock());
    SUCCEED_RETURN(e);
}

akerr_ErrorContext AKERR_NOIGNORE *akgl_game_state_lock(void)
{
    PREPARE_ERROR(e);
    SDL_Time totaltime = 0;

    while ( totaltime < AKGL_TIME_ONESEC_MS ) {
	if ( SDL_TryLockMutex(game.statelock) == true ) {
	    SUCCEED_RETURN(e);
	}
	totaltime += 100;
	SDL_Delay(100);
    }
    FAIL_RETURN(e, AKGL_ERR_SDL, "%s", SDL_GetError());
}

akerr_ErrorContext AKERR_NOIGNORE *akgl_game_state_unlock(void)
{
    PREPARE_ERROR(e);
    SDL_UnlockMutex(game.statelock);
    SUCCEED_RETURN(e);
}

void akgl_game_updateFPS()
{
    SDL_Time curTime;
    curTime = SDL_GetTicksNS();
    if ( (curTime - game.lastFPSTime) > AKGL_TIME_ONESEC_NS ) {
	game.fps = game.framesSinceUpdate;
	game.framesSinceUpdate = 0;
	game.lastFPSTime = curTime;
    }
    if ( game.fps < 30 ) {
	game.lowfpsfunc();
    }
    game.framesSinceUpdate += 1;
    game.lastIterTime = curTime;
}

/*
 * entity name -> pointer map tables
 */

/**
 * @brief Serializes an actor name-to-pointer entry.
 * @param userdata Open output stream supplied by the caller.
 * @param props Actor registry being iterated.
 * @param name Actor registry key to serialize.
 */
void akgl_game_save_actorname_iterator(void *userdata, SDL_PropertiesID props, const char *name)
{
    FILE *fp = (FILE *)userdata;
    akgl_Actor *actor = NULL;
    PREPARE_ERROR(e);
    ATTEMPT {
	FAIL_ZERO_BREAK(e, fp, AKERR_NULLPOINTER, "NULL file pointer");
	CATCH(e, aksl_fwrite((char *)name, 1, AKGL_ACTOR_MAX_NAME_LENGTH, fp));
	actor = SDL_GetPointerProperty(props, name, NULL);
	CATCH(e, aksl_fwrite(&actor, 1, sizeof(akgl_Actor *), fp));
    } CLEANUP {
    } PROCESS(e) {
    } FINISH_NORETURN(e);
}

/**
 * @brief Game save spritename iterator.
 * @param userdata Caller data supplied to the SDL property iterator.
 * @param props SDL property collection being iterated.
 * @param name Registry key or human-readable object name.
 */
void akgl_game_save_spritename_iterator(void *userdata, SDL_PropertiesID props, const char *name)
{
    FILE *fp = (FILE *)userdata;
    akgl_Sprite *sprite = NULL;
    PREPARE_ERROR(e);
    ATTEMPT {
	FAIL_ZERO_BREAK(e, fp, AKERR_NULLPOINTER, "NULL file pointer");
	sprite = SDL_GetPointerProperty(props, name, NULL);
	CATCH(e, aksl_fwrite((char *)name, 1, AKGL_SPRITE_MAX_NAME_LENGTH, fp));
	CATCH(e, aksl_fwrite(&sprite, 1, sizeof(akgl_Sprite *), fp));
    } CLEANUP {
    } PROCESS(e) {
    } FINISH_NORETURN(e);
}

/**
 * @brief Game save spritesheetname iterator.
 * @param userdata Caller data supplied to the SDL property iterator.
 * @param props SDL property collection being iterated.
 * @param name Registry key or human-readable object name.
 */
void akgl_game_save_spritesheetname_iterator(void *userdata, SDL_PropertiesID props, const char *name)
{
    FILE *fp = (FILE *)userdata;
    akgl_SpriteSheet *spritesheet = NULL;
    PREPARE_ERROR(e);
    ATTEMPT {
	FAIL_ZERO_BREAK(e, fp, AKERR_NULLPOINTER, "NULL file pointer");
	spritesheet = SDL_GetPointerProperty(props, name, NULL);
	CATCH(e, aksl_fwrite((char *)name, 1, AKGL_SPRITE_SHEET_MAX_FILENAME_LENGTH, fp));
	CATCH(e, aksl_fwrite(&spritesheet, 1, sizeof(akgl_SpriteSheet *), fp));
    } CLEANUP {
    } PROCESS(e) {
    } FINISH_NORETURN(e);
}

/**
 * @brief Game save charactername iterator.
 * @param userdata Caller data supplied to the SDL property iterator.
 * @param props SDL property collection being iterated.
 * @param name Registry key or human-readable object name.
 */
void akgl_game_save_charactername_iterator(void *userdata, SDL_PropertiesID props, const char *name)
{
    FILE *fp = (FILE *)userdata;
    PREPARE_ERROR(e);
    akgl_Character *character = NULL;
    ATTEMPT {
	FAIL_ZERO_BREAK(e, fp, AKERR_NULLPOINTER, "NULL file pointer");
	character = SDL_GetPointerProperty(props, name, NULL);
	CATCH(e, aksl_fwrite((char *)name, 1, AKGL_SPRITE_MAX_CHARACTER_NAME_LENGTH, fp));
	CATCH(e, aksl_fwrite(&character, 1, sizeof(akgl_Character *), fp));
    } CLEANUP {
    } PROCESS(e) {
    } FINISH_NORETURN(e);
}

/**
 * @brief Game save actors.
 * @param fp Open save-game stream.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_NULLPOINTER When the corresponding validation or operation fails.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_game_save_actors(FILE *fp)
{
    PREPARE_ERROR(e);
    // Each name table ends with a zeroed name field and a zeroed pointer, which
    // is what akgl_game_load_objectnamemap() looks for to stop reading. The
    // terminator has to come from a buffer at least as long as the longest name
    // field: writing N bytes from the address of a single char would emit N-1
    // bytes of whatever happened to follow it on the stack, which both leaks
    // stack contents into the save file and produces a sentinel the loader
    // cannot recognize.
    char nullbuf[AKGL_SPRITE_SHEET_MAX_FILENAME_LENGTH];

    memset((void *)&nullbuf, 0x00, sizeof(nullbuf));

    ATTEMPT {
	FAIL_ZERO_BREAK(e, fp, AKERR_NULLPOINTER, "NULL file pointer");
	// write the actor name pointer table
	SDL_EnumerateProperties(
	    AKGL_REGISTRY_ACTOR,
	    &akgl_game_save_actorname_iterator,
	    (void *)fp);
	CATCH(e, aksl_fwrite((void *)&nullbuf, 1, AKGL_ACTOR_MAX_NAME_LENGTH, fp));
	CATCH(e, aksl_fwrite((void *)&nullbuf, 1, sizeof(akgl_Actor *), fp));
	// write the sprite name pointer table
	SDL_EnumerateProperties(
	    AKGL_REGISTRY_SPRITE,
	    &akgl_game_save_spritename_iterator,
	    (void *)fp);
	CATCH(e, aksl_fwrite((void *)&nullbuf, 1, AKGL_SPRITE_MAX_NAME_LENGTH, fp));
	CATCH(e, aksl_fwrite((void *)&nullbuf, 1, sizeof(akgl_Sprite *), fp));
	// write the spritesheet name pointer table
	SDL_EnumerateProperties(
	    AKGL_REGISTRY_SPRITESHEET,
	    &akgl_game_save_spritesheetname_iterator,
	    (void *)fp);
	CATCH(e, aksl_fwrite((void *)&nullbuf, 1, AKGL_SPRITE_SHEET_MAX_FILENAME_LENGTH, fp));
	CATCH(e, aksl_fwrite((void *)&nullbuf, 1, sizeof(akgl_SpriteSheet *), fp));
	// write the character name pointer table
	SDL_EnumerateProperties(
	    AKGL_REGISTRY_CHARACTER,
	    &akgl_game_save_charactername_iterator,
	    (void *)fp);
	CATCH(e, aksl_fwrite((void *)&nullbuf, 1, AKGL_SPRITE_MAX_CHARACTER_NAME_LENGTH, fp));
	CATCH(e, aksl_fwrite((void *)&nullbuf, 1, sizeof(akgl_Character *), fp));
    } CLEANUP {
    } PROCESS(e) {
    } FINISH(e, true);
    SUCCEED_RETURN(e);
}

akerr_ErrorContext AKERR_NOIGNORE *akgl_game_save(char *fpath)
{
    FILE *fp = NULL;
    PREPARE_ERROR(e);

    ATTEMPT {
	FAIL_ZERO_BREAK(e, fpath, AKERR_NULLPOINTER, "NULL file path");
	CATCH(e, aksl_fopen(fpath, "wb", &fp));
	CATCH(e, aksl_fwrite(&game, 1, sizeof(akgl_Game), fp));
	CATCH(e, akgl_game_save_actors(fp));
    } CLEANUP {
	// CLEANUP must precede PROCESS: with the two transposed, the fclose
	// lands inside the PROCESS switch and only runs when an error context
	// exists and reports success, so an ordinary save never flushed or
	// closed its stream.
	if ( fp != NULL )
	    fclose(fp);
    } PROCESS(e) {
    } FINISH(e, true);
    SUCCEED_RETURN(e); // SUCCEED_NORETURN if in main().
}

/**
 * @brief Game load objectnamemap.
 * @param fp Open save-game stream.
 * @param map Tilemap to inspect, draw, or modify.
 * @param namelength Fixed serialized name-field length.
 * @param ptrlength Serialized pointer-field length.
 * @param registry SDL property registry being queried.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_* Propagates an error reported by a delegated operation.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_game_load_objectnamemap(FILE *fp, SDL_PropertiesID map, int namelength, int ptrlength, SDL_PropertiesID registry)
{
    void *ptr = NULL;
    char ptrstring[32];
    char objname[namelength];
    int retval = 0;
    bool done = false;

    PREPARE_ERROR(e);
    // The ATTEMPT block sits inside the loop on purpose. CATCH reports a
    // failure by breaking, and a break binds to the innermost enclosing switch
    // or loop, so a CATCH written directly inside `while` would leave the loop
    // and then fall through to SUCCEED_RETURN -- reporting a truncated or
    // corrupt name table as a successful load.
    while ( done == false ) {
	ATTEMPT {
	    CATCH(e, aksl_fread((void *)&objname, 1, namelength, fp));
	    CATCH(e, aksl_fread((void *)&ptr, 1, ptrlength, fp));
	    // End of the map
	    if ( ptr == 0x00 && objname[0] == 0x00 ) {
		done = true;
		break;
	    }
	    // The map allows us to say "Object X has a reference to object Y at
	    // address Z. The object they had at address Z was named A. Our current
	    // instance of object named A is at address B. So we map address Z to
	    // address B, so that we can reconnect function pointers on objects loaded
	    // from the save game state."

	    // SDL_Properties objects can only use string keys, so we can't use the
	    // old pointer as a key without first converting it to a string.
	    CATCH(e, aksl_memset((void *)&ptrstring, 0x00, 32));
	    snprintf((char *)&ptrstring, 32, "%p", ptr);
	    SDL_SetPointerProperty(
		map,
		ptrstring,
		SDL_GetPointerProperty(registry, objname, NULL));
	} CLEANUP {
	} PROCESS(e) {
	} FINISH(e, true);
    };
    SUCCEED_RETURN(e);
}

/**
 * @brief Game load versioncmp.
 * @param versiontype Description of the version being compared.
 * @param newversion Version read from the save data.
 * @param curversion Version supported by the running library.
 * @return `NULL` on success, otherwise an error context owned by the caller.
 * @throws AKERR_API When the corresponding validation or operation fails.
 * @throws AKERR_NULLPOINTER When the corresponding validation or operation fails.
 * @throws AKERR_VALUE When the corresponding validation or operation fails.
 */
akerr_ErrorContext AKERR_NOIGNORE *akgl_game_load_versioncmp(char *versiontype, char *newversion, char *curversion)
{
    semver_t current_version = {};
    semver_t compare_version = {};
    PREPARE_ERROR(e);
    FAIL_ZERO_RETURN(e, versiontype, AKERR_NULLPOINTER, "NULL argument");
    FAIL_ZERO_RETURN(e, curversion, AKERR_NULLPOINTER, "NULL argument");
    FAIL_ZERO_RETURN(e, newversion, AKERR_NULLPOINTER, "NULL argument");

    ATTEMPT {
	// Check save game library version
	FAIL_NONZERO_BREAK(
	    e,
	    semver_parse((const char *)curversion, &current_version),
	    AKERR_VALUE,
	    "Invalid semantic %s version in current game: %s",
	    versiontype,
	    (char *)curversion);
	FAIL_NONZERO_BREAK(
	    e,
	    semver_parse((const char *)newversion, &compare_version),
	    AKERR_VALUE,
	    "Invalid semantic %s version in save game: %s",
	    versiontype,
	    (char *)&newversion);
	FAIL_ZERO_BREAK(
	    e,
	    semver_satisfies(compare_version, current_version, "="),
	    AKERR_API,
	    "Incompatible save game %s version (%s != %s)",
	    versiontype,
	    curversion,
	    (char *)&newversion);
    } CLEANUP {
	semver_free(&current_version);
	semver_free(&compare_version);
    } PROCESS(e) {
    } FINISH(e, true);
    SUCCEED_RETURN(e);
}

akerr_ErrorContext AKERR_NOIGNORE *akgl_game_load(char *fpath)
{
    akgl_Game savegame;
    SDL_PropertiesID actormap;
    SDL_PropertiesID spritemap;
    SDL_PropertiesID spritesheetmap;
    SDL_PropertiesID charactermap;
    FILE *fp = NULL;

    PREPARE_ERROR(e);
    FAIL_ZERO_RETURN(e, fpath, AKERR_NULLPOINTER, "NULL file path");

    ATTEMPT {
	CATCH(e, aksl_fopen(fpath, "rb", &fp));
	CATCH(e, aksl_fread((void *)&savegame, 1, sizeof(akgl_Game), fp));
	CATCH(e, akgl_game_load_versioncmp("library", (char *)&savegame.libversion, (char *)AKGL_VERSION));
	CATCH(e, akgl_game_load_versioncmp("game", (char *)&savegame.version, (char *)&game.version));
	FAIL_NONZERO_RETURN(
	    e,
	    strncmp((char *)&savegame.name, (char *)&game.name, 256),
	    AKERR_API,
	    "Savegame is not compatible with this game");
	FAIL_NONZERO_RETURN(
	    e,
	    strncmp((char *)&savegame.uri, (char *)&game.uri, 256),
	    AKERR_API,
	    "Savegame is not compatible with this game");

	memcpy((void *)&game, (void *)&savegame, sizeof(akgl_Game));
	// Load actor name map
	actormap = SDL_CreateProperties();
	CATCH(e, akgl_game_load_objectnamemap(fp, actormap, AKGL_ACTOR_MAX_NAME_LENGTH, sizeof(akgl_Actor *), AKGL_REGISTRY_ACTOR));
	// Load sprite name map
	spritemap = SDL_CreateProperties();
	CATCH(e, akgl_game_load_objectnamemap(fp, spritemap, AKGL_ACTOR_MAX_NAME_LENGTH, sizeof(akgl_Sprite *), AKGL_REGISTRY_SPRITE));
	// Load spritesheet name map
	spritesheetmap = SDL_CreateProperties();
	CATCH(e, akgl_game_load_objectnamemap(fp, spritesheetmap, AKGL_ACTOR_MAX_NAME_LENGTH, sizeof(akgl_SpriteSheet *), AKGL_REGISTRY_SPRITESHEET));
	// Load character name map
	charactermap = SDL_CreateProperties();
	CATCH(e, akgl_game_load_objectnamemap(fp, charactermap, AKGL_ACTOR_MAX_NAME_LENGTH, sizeof(akgl_Character *), AKGL_REGISTRY_CHARACTER));
	// Now that we have all of our pointer maps built, we can load the actual binary objects and reset their pointers
    } CLEANUP {
	if ( fp != NULL ) {
	    fclose(fp);
	}
    } PROCESS(e) {
    } FINISH(e, true);

    SUCCEED_RETURN(e);
}

akerr_ErrorContext AKERR_NOIGNORE *akgl_game_update(akgl_Iterator *opflags)
{
    PREPARE_ERROR(e);
    akgl_Iterator defflags = {
	.flags = (AKGL_ITERATOR_OP_LAYERMASK | AKGL_ITERATOR_OP_LAYERMASK),
	.layerid = 0
    };
    SDL_Time curTime = SDL_GetTicksNS();
    akgl_Actor *actor = NULL;

    if ( opflags == NULL ) {
	opflags = &defflags;
    }

    PASS(e, akgl_game_state_lock());

    akgl_game_updateFPS();

    for ( int i = 0; i < AKGL_TILEMAP_MAX_LAYERS; i++ ) {
	if ( opflags == &defflags ) {
	    opflags->layerid = i;
	}
	for ( int j = 0; j < AKGL_MAX_HEAP_ACTOR; j++ ) {
	    actor = &HEAP_ACTOR[j];
	    if ( actor->refcount == 0 ) {
		continue;
	    }
	    if ( AKGL_BITMASK_HAS(opflags->flags, AKGL_ITERATOR_OP_TILEMAPSCALE) ) {
		PASS(e, akgl_tilemap_scale_actor(gamemap, actor));
	    } else {
		actor->scale = 1.0;
	    }
	    PASS(e, actor->updatefunc(actor));
	}
    }
    PASS(e, physics->simulate(physics, NULL));
    PASS(e, renderer->draw_world(renderer, NULL));
    PASS(e, akgl_game_state_unlock());
    SUCCEED_RETURN(e);
}