import { Engine } from "@nova-engine/ecs";
const engine = new Engine();

import { Component } from "@nova-engine/ecs";

// Components can have custom constructors, but they must be able to be initialized
// with no arguments, because entities creates the instances for you.
// Try not to save complex data types in yout components
class PositionComponent implements Component {
  x = 0;
  y = 0;
}

class VelocityComponent implements Component {
  x = 0;
  y = 0;
}

// If you are making a component library, and want to avoid collitions
// You can add a tag to your component implementations

class MyLibraryComponent implements Component {
  // This will ensure your component won't collide with other "MyLibraryComponent"
  static readonly tag = "my-library/MyLibraryComponent";
}

import { Component, Family, System, FamilyBuilder } from "@nova-engine/ecs";
class GravitySystem extends System {
  static readonly DEFAULT_ACCELERATION = 0.98;
  family?: Family;
  acceleration: number;

  // Constructors are free for your own implementation
  constructor(acceleration = GravitySystem.DEFAULT_ACCELERATION) {
    super();
    this.acceleration = acceleration;
    // higher priorities means the system runs before others with lower priority
    this.priority = 300;
  }
  // This is called when a system is added to an engine, you may want to
  // startup your families here.
  onAttach(engine: Engine) {
    // Needed to work properly
    super.onAttach(engine);
    // Families are an easy way to have groups of entities with some criteria.
    this.family = new FamilyBuilder(engine).include(VelocityComponent).build();
  }

  // This, in reality is the only method your system must implement
  // but using onAttach to prepare your families is useful.
  update(engine: Engine, delta: number) {
    for (let entity of this.family.entities) {
      // Easy to get a component by class
      // Be warned, if the entity lacks this component, an error *will* be thrown.
      // But families ensures than we will always have the required components.
      const velocity = entity.getComponent(VelocityComponent);
      velocity.y += this.acceleration;
      // if the family doesn't require that component
      // you can always check for it
      if (entity.hasComponent(PositionComponent)) {
        const position = entity.getComponent(PositionComponent);
      } else {
        // You can create components on an entity easily.
        const position = entity.putComponent(PositionComponent);
      }
    }
  }
}

entity.id = myGeneratedId();