import { IS_SAFARI_ON_DESKTOP } from "../utils/browser";

class WebGLAnimator {
  private _callback: ((...args: any[]) => any) | null;
  private _context: any;
  private _rafId: number;
  private _rafTimer: number;

  public constructor() {
    this._callback = null;
    this._context = window;
    this._rafId = -1;
    this._rafTimer = -1;
  }

  public setCallback(callback: (...args: any[]) => any) {
    this._callback = callback;
  }

  public setContext(context: any) {
    this._context = context;
  }

  public start() {
    const context = this._context;
    const callback = this._callback;

    // No context / callback set
    if (!context || !callback) return;
    // Animation already started
    if (this._rafId >= 0 || this._rafTimer >= 0) return;

    if (IS_SAFARI_ON_DESKTOP) {
      this._rafId = context.requestAnimationFrame(this._onLoopNextTick);
    } else {
      this._rafId = context.requestAnimationFrame(this._onLoop);
    }
  }

  public stop() {
    if (this._rafId >= 0) {
      this._context.cancelAnimationFrame(this._rafId);
    }

    if (this._rafTimer >= 0) {
      clearTimeout(this._rafTimer);
    }

    this._rafId = -1;
    this._rafTimer = -1;
  }

  /**
   * There can be more than 1 argument when we use XRSession's raf
   */
  private _onLoop = (...args: any[]) => {
    this._callback!(...args);
    this._rafId = this._context.requestAnimationFrame(this._onLoop);
  };

  /**
   * MacOS X Safari Bug Fix
   * This code guarantees that rendering should be occurred.
   *
   * In MacOS X(10.14.2), Safari (12.0.2)
   * The requestAnimationFrame(RAF) callback is called just after previous RAF callback without term
   * only if requestAnimationFrame is called for next frame while updating frame is delayed (~over 2ms)
   * So browser cannot render the frame and may be freezing.
   */
  private _onLoopNextTick = (...args: any[]) => {
    const before = performance.now();

    this._callback!(...args);

    const diff = performance.now() - before;

    if (this._rafTimer >= 0) {
      clearTimeout(this._rafTimer);
      this._rafTimer = -1;
    }

    /* Use requestAnimationFrame only if current rendering could be possible over 60fps (1000/60) */
    if (diff < 16) {
      this._rafId = this._context.requestAnimationFrame(this._onLoop);
    } else {
      /* Otherwise, Call setTimeout instead of requestAnimationFrame to gaurantee renering should be occurred */
      this._rafTimer = window.setTimeout(this._onLoop, 0);
    }
  };
}

export default WebGLAnimator;