// We define a Component, just a regular class with some data, no functions!
class PositionComponent {
  constructor(canMove, pos = {}){
    this.canMove = canMove;
    this.pos = {
      x: pos.x,
      y: pos.y
    };
    this.dest = {
      x: pos.x,
      y: pos.y
    };
  }
}

// An entity is just an object with Components
let entity = {
  'POS_COMP': new PositionComponent(true, {x: 10, y: 20})
};

// An array of entities which we can easily extend
let entities = [entity];


// A move system
function moveSystem(entities){
  entities.forEach((entity) => {

    // only if a POS_COMP exists, else we do nothing
    if (entity.POS_COMP) {
      let distX = entity.POS_COMP.dest.x - entity.POS_COMP.pos.x;
      let distY = entity.POS_COMP.dest.y - entity.POS_COMP.pos.y;

      if (distX > 0) {
        entity.POS_COMP.pos.x = Math.min(entity.POS_COMP.dest.x, entity.POS_COMP.pos.x + 1);
      } else {
        entity.POS_COMP.pos.x = Math.max(entity.POS_COMP.dest.x, entity.POS_COMP.pos.x - 1);
      }

      if (distY > 0) {
        entity.POS_COMP.pos.y = Math.min(entity.POS_COMP.dest.y, entity.POS_COMP.pos.y + 1);
      } else {
        entity.POS_COMP.pos.y = Math.max(entity.POS_COMP.dest.y, entity.POS_COMP.pos.y - 1);
      }
    }
  });
}

// We loop over the system every second, trying to perform some logic
setInterval(() => {
  moveSystem(entities);
}, 1000);