/**
 * Copyright (c) 2025 Dominic Masters
 * 
 * This software is released under the MIT License.
 * https://opensource.org/licenses/MIT
 */

#include "ecssystem.h"
#include "util/memory.h"
#include "assert/assert.h"

ecssystem_t ECS_SYSTEM;

void ecsSystemInit() {
  memoryZero(&ECS_SYSTEM, sizeof(ecssystem_t));

  // Fill ECS ids
  for(uint32_t i = 0; i < ECS_ENTITY_COUNT_MAX; i++) {
    ECS_SYSTEM.entities[i].id = i;
  }

  // Fill the available array.
  for(uint32_t i = 0; i < ECS_ENTITY_COUNT_MAX; i++) {
    ECS_SYSTEM.available[i] = &ECS_SYSTEM.entities[i];
  }
  ECS_SYSTEM.availableCount = ECS_ENTITY_COUNT_MAX;

  // Reserve root entity
  ECS_SYSTEM.root = ecsEntityAdd();
}

ecsid_t ecsEntityAdd() {
  assertTrue(ECS_SYSTEM.availableCount > 0, "No available entities to create");

  // Pop off the last available entity.
  ecsentity_t *entity = ECS_SYSTEM.available[--ECS_SYSTEM.availableCount];
  assertTrue((entity->flags & ECS_ENTITY_FLAG_USED) == 0, "Entity is used.");
  assertTrue(entity->id >= 0, "Entity is invalid.");
  assertTrue(entity->id < ECS_ENTITY_COUNT_MAX, "Entity ID out of bounds");

  entity->flags |= ECS_ENTITY_FLAG_USED;

  return entity->id;
}

void ecsEntityRemove(const ecsid_t id) {
  assertTrue(id < ECS_ENTITY_COUNT_MAX, "Invalid entity ID");

  ecsentity_t *entity = &ECS_SYSTEM.entities[id];
  assertTrue(entity->id >= 0, "Entity is invalid.");
  assertTrue((entity->flags & ECS_ENTITY_FLAG_USED) != 0, "Entity is not used.");

  // Mark the entity as available.
  ECS_SYSTEM.available[ECS_SYSTEM.availableCount++] = entity;
  assertTrue(
    ECS_SYSTEM.availableCount <= ECS_ENTITY_COUNT_MAX,
    "Available count exceeded maximum limit"
  );
}