import { IEntity, System, World } from "quick-ecs";

/**
 * Optionally define dependencies to be injected into Systems.
 * They will be accessible at runtime.
 *
 * Some usage examples include:
 * - Accessing information about current frame (delta time)
 * - Sharing information between Systems
 * - Getting information from your engine to improve performance (such as current camera frustrum)
 */

interface IExampleDependencies {
  timer: {
    getDeltaTime(): number;
  };
}

/**
 * Define example Component.
 *
 * In pure ECS this only contains data describing the Component.
 *
 * However, if you need to you can easily use this as wrapper for objects
 * which are used by engine of your choice and manipulate them - just pass them in constructor.
 */
class ExampleComponent {
  private _prop: number;

  constructor(initialValue: number) {
    this._prop = initialValue;
  }

  public get prop() {
    return this._prop;
  }

  public updateProp = (value: number) => {
    this._prop = value;
  };
}

/**
 * Define example System.
 *
 * Systems are intended to have single responsibility - they target single group of entities.
 */

/**
 * Define type for components that this system will handle.
 */
type TExampleSystemComponents = [typeof ExampleComponent]

export default class ExampleSystem extends System<
  TExampleSystemComponents,
  IExampleDependencies
> {
  constructor() {
    super();
    /**
     * Set component types for the system to use.
     *
     * This is type-safe - only component types specified for this system are allowed.
     */
    this.setComponents(ExampleComponent);
  }

  /**
   * Define your update function which will perform logic on Entities matching specified Components.
   *
   * This function is ran for each matching Entity.
   */
  public update(entity: IEntity<TExampleSystemComponents>, { timer }: IExampleDependencies) {
    const { prop, updateProp } = entity.getComponent(ExampleComponent);

    updateProp(prop * timer.getDeltaTime());
  }
}

// Create and run!

interface IExampleEngine {
  timer: {
    getDeltaTime: () => Math.random()
  };
  runRenderLoop(renderFunction: () => void): void
}

export const main = async ({timer, runRenderLoop}: IExampleEngine) => {
  // Create World and add ExampleSystem to it
  const world = new World<IExampleDependencies>({ timer });
  world.addSystem(ExampleSystem);

  /**
   * Create Entity and add Component to it.
   * Second argument of addComponent accepts array of constructor params, type safe!
   */
  const entity = world.createEntity<TExampleSystemComponents>();
  entity.addComponent(ExampleComponent, 0);

  // Initialize the World. This runs all init functions in added Systems.
  await world.init();

  /**
   * Following step runs the World and depends on engine you're using.
   * This is fully generic - you just need to run update in render loop!
   */
  runRenderLoop(() => world.update())
};