// luma.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

import {Fence, type FenceProps} from '@luma.gl/core';
import {WebGLDevice} from '../webgl-device';

/** WebGL fence implemented with gl.fenceSync */
export class WEBGLFence extends Fence {
  readonly device: WebGLDevice;
  readonly gl: WebGL2RenderingContext;
  readonly handle: WebGLSync;
  readonly signaled: Promise<void>;
  private _signaled = false;

  constructor(device: WebGLDevice, props: FenceProps = {}) {
    super(device, {});
    this.device = device;
    this.gl = device.gl;

    const sync = this.props.handle || this.gl.fenceSync(this.gl.SYNC_GPU_COMMANDS_COMPLETE, 0);
    if (!sync) {
      throw new Error('Failed to create WebGL fence');
    }
    this.handle = sync;

    this.signaled = new Promise(resolve => {
      const poll = () => {
        const status = this.gl.clientWaitSync(this.handle, 0, 0);
        if (status === this.gl.ALREADY_SIGNALED || status === this.gl.CONDITION_SATISFIED) {
          this._signaled = true;
          resolve();
        } else {
          setTimeout(poll, 1);
        }
      };
      poll();
    });
  }

  isSignaled(): boolean {
    if (this._signaled) {
      return true;
    }
    const status = this.gl.getSyncParameter(this.handle, this.gl.SYNC_STATUS);
    this._signaled = status === this.gl.SIGNALED;
    return this._signaled;
  }

  destroy(): void {
    if (!this.destroyed) {
      this.gl.deleteSync(this.handle);
    }
  }
}