/*
 * This software is licensed under the terms of the MIT-License
 * See COPYING for further information.
 * ---
 * Copyright (c) 2011-2018, Lukas Weber <laochailan@web.de>.
 * Copyright (c) 2012-2018, Andrei Alexeyev <akari@alienslab.net>.
 */

#include "taisei.h"

#include "entity.h"
#include "util.h"
#include "renderer/api.h"

static struct {
	EntityInterface **array;
	uint num;
	uint capacity;
	uint32_t total_spawns;
} entities;

#define FOR_EACH_ENT(ent) for(EntityInterface **_ent = entities.array, *ent = *entities.array; _ent < entities.array + entities.num; ent = *(++_ent))

void ent_init(void) {
	memset(&entities, 0, sizeof(entities));
	entities.capacity = 4096;
	entities.array = calloc(entities.capacity, sizeof(EntityInterface*));
}

void ent_shutdown(void) {
	if(entities.num) {
		log_warn("%u entities were not properly unregistered", entities.num);
	}

	FOR_EACH_ENT(ent) {
		ent_unregister(ent);
	}

	free(entities.array);
}

void ent_register(EntityInterface *ent, EntityType type) {
	assert(type > _ENT_TYPE_ENUM_BEGIN && type < _ENT_TYPE_ENUM_END);
	ent->type = type;
	ent->index = entities.num++;
	ent->spawn_id = ++entities.total_spawns;

	if(ent->spawn_id == 0) {
		// This is not really an error, but it may result in weird draw order
		// in some corner cases. If this overflow ever actually occurs, though,
		// then you've probably got much bigger problems.
		log_debug("spawn_id just overflowed. You might be spawning stuff waaaay too often");
	}

	if(entities.capacity < entities.num) {
		entities.capacity *= 2;
		entities.array = realloc(entities.array, entities.capacity * sizeof(EntityInterface*));
	}

	entities.array[ent->index] = ent;

	assert(ent->index < entities.num);
	assert(entities.array[ent->index] == ent);
}

void ent_unregister(EntityInterface *ent) {
	EntityInterface *sub = entities.array[--entities.num];
	assert(ent->index <= entities.num);
	assert(entities.array[ent->index] == ent);
	entities.array[sub->index = ent->index] = sub;
}

static int ent_cmp(const void *ptr1, const void *ptr2) {
	const EntityInterface *ent1 = *(const EntityInterface**)ptr1;
	const EntityInterface *ent2 = *(const EntityInterface**)ptr2;

	int r = (ent1->draw_layer > ent2->draw_layer) - (ent1->draw_layer < ent2->draw_layer);

	if(r == 0) {
		// Same layer? Put whatever spawned later on top, then.
		r = (ent1->spawn_id > ent2->spawn_id) - (ent1->spawn_id < ent2->spawn_id);
	}

	return r;
}

void ent_draw(EntityPredicate predicate) {
	qsort(entities.array, entities.num, sizeof(EntityInterface*), ent_cmp);

	if(predicate) {
		FOR_EACH_ENT(ent) {
			ent->index = _ent - entities.array;
			assert(entities.array[ent->index] == ent);

			if(ent->draw_func && predicate(ent)) {
				r_state_push();
				ent->draw_func(ent);
				r_state_pop();
			}
		}
	} else {
		FOR_EACH_ENT(ent) {
			ent->index = _ent - entities.array;
			assert(entities.array[ent->index] == ent);

			if(ent->draw_func) {
				r_state_push();
				ent->draw_func(ent);
				r_state_pop();
			}
		}
	}
}