Add Grab System (#9)

[rbdr/sumo] / lib / systems / dash.js

import { System } from '@serpentity/serpentity';

const internals = {
  kForce: 20
};

import DasherNode from '../nodes/dasher';

/**
 * Applies a dash as a force on an entity. Locks it until the button is released
 * and a cooldown period has passed
 *
 * @extends {external:Serpentity.System}
 * @class DashSystem
 * @param {object} config a configuration object to extend.
 */
export default class DashSystem extends System {

  constructor(config = {}) {

    super();

    /**
     * The node collection of dashers
     *
     * @property {external:Serpentity.NodeCollection} dashers
     * @instance
     * @memberof DashSystem
     */
    this.dashers = null;
  }

  /**
   * Initializes system when added. Requests dasher nodes
   *
   * @function added
   * @memberof DashSystem
   * @instance
   * @param {external:Serpentity.Engine} engine the serpentity engine to
   * which we are getting added
   */
  added(engine) {

    this.dashers = engine.getNodes(DasherNode);
  }

  /**
   * Clears system resources when removed.
   *
   * @function removed
   * @instance
   * @memberof DashSystem
   */
  removed() {

    this.dashers = null;
  }

  /**
   * Runs on every update of the loop. Triggers dash and manages cooldown
   *
   * @function update
   * @instance
   * @param {Number} currentFrameDuration the duration of the current
   * frame
   * @memberof DashSystem
   */
  update(currentFrameDuration) {

    for (const dasher of this.dashers) {

      const dash = dasher.dash;

      if (dash.dashing && !dash.locked) {
        this._dash(dasher);
      }

      if (!dash.dashing && dash.locked && dash.currentCooldown >= dash.cooldown) {
        this._unlock(dasher);
      }

      if (dash.locked) {
        dash.currentCooldown += currentFrameDuration;
      }

      dash.dashing = 0;
    }
  }

  // Executes the dash action

  _dash(dasher) {

    const dash = dasher.dash;
    const force = dasher.force;

    const angle = force.lastAngle || 0;
    dash.locked = true;
    dash.currentCooldown = 0;

    const xComponent = internals.kForce * Math.cos(angle);
    const yComponent = internals.kForce * Math.sin(angle);

    force.x += xComponent;
    force.y += yComponent;
  }

  // Executes the unlock action

  _unlock(dasher) {

    dasher.dash.locked = false;
  }
};