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

import {Shader, ShaderProps, CompilerMessage, log} from '@luma.gl/core';
import {GL} from '@luma.gl/constants';
import {parseShaderCompilerLog} from '../helpers/parse-shader-compiler-log';
import {WebGLDevice} from '../webgl-device';

/**
 * An immutable compiled shader program that execute portions of the GPU Pipeline
 */
export class WEBGLShader extends Shader {
  readonly device: WebGLDevice;
  readonly handle: WebGLShader;

  constructor(device: WebGLDevice, props: ShaderProps) {
    super(device, props);
    this.device = device;
    switch (this.props.stage) {
      case 'vertex':
        this.handle = this.props.handle || this.device.gl.createShader(GL.VERTEX_SHADER);
        break;
      case 'fragment':
        this.handle = this.props.handle || this.device.gl.createShader(GL.FRAGMENT_SHADER);
        break;
      default:
        throw new Error(this.props.stage);
    }
    this._compile(this.source);
  }

  override destroy(): void {
    if (this.handle) {
      this.removeStats();
      this.device.gl.deleteShader(this.handle);
      // this.handle = null;
      this.destroyed = true;
    }
  }

  get asyncCompilationStatus(): Promise<'pending' | 'success' | 'error'> {
    return this._waitForCompilationComplete().then(() => this.compilationStatus);
  }

  override async getCompilationInfo(): Promise<readonly CompilerMessage[]> {
    await this._waitForCompilationComplete();
    return this.getCompilationInfoSync();
  }

  override getCompilationInfoSync(): readonly CompilerMessage[] {
    const shaderLog = this.device.gl.getShaderInfoLog(this.handle);
    return shaderLog ? parseShaderCompilerLog(shaderLog) : [];
  }

  override getTranslatedSource(): string | null {
    const extensions = this.device.getExtension('WEBGL_debug_shaders');
    const ext = extensions.WEBGL_debug_shaders;
    return ext?.getTranslatedShaderSource(this.handle) || null;
  }

  // PRIVATE METHODS

  /** Compile a shader and get compilation status */
  protected async _compile(source: string): Promise<void> {
    source = source.startsWith('#version ') ? source : `#version 300 es\n${source}`;

    const {gl} = this.device;
    gl.shaderSource(this.handle, source);
    gl.compileShader(this.handle);

    // For performance reasons, avoid checking shader compilation errors on production
    if (!this.device.props.debug) {
      this.compilationStatus = 'pending';
      return;
    }

    // Sync case - slower, but advantage is that it throws in the constructor, making break on error more useful
    if (!this.device.features.has('compilation-status-async-webgl')) {
      this._getCompilationStatus();
      // The `Shader` base class will determine if debug window should be opened based on this.compilationStatus
      this.debugShader();
      if (this.compilationStatus === 'error') {
        throw new Error(`GLSL compilation errors in ${this.props.stage} shader ${this.props.id}`);
      }
      return;
    }

    // async case
    log.once(1, 'Shader compilation is asynchronous')();
    await this._waitForCompilationComplete();
    log.info(2, `Shader ${this.id} - async compilation complete: ${this.compilationStatus}`)();
    this._getCompilationStatus();

    // The `Shader` base class will determine if debug window should be opened based on this.compilationStatus
    this.debugShader();
  }

  /** Use KHR_parallel_shader_compile extension if available */
  protected async _waitForCompilationComplete(): Promise<void> {
    const waitMs = async (ms: number) => await new Promise(resolve => setTimeout(resolve, ms));
    const DELAY_MS = 10; // Shader compilation is typically quite fast (with some exceptions)

    // If status polling is not available, we can't wait for completion. Just wait a little to minimize blocking
    if (!this.device.features.has('compilation-status-async-webgl')) {
      await waitMs(DELAY_MS);
      return;
    }

    const {gl} = this.device;
    for (;;) {
      const complete = gl.getShaderParameter(this.handle, GL.COMPLETION_STATUS_KHR);
      if (complete) {
        return;
      }
      await waitMs(DELAY_MS);
    }
  }

  /**
   * Get the shader compilation status
   * TODO - Load log even when no error reported, to catch warnings?
   * https://gamedev.stackexchange.com/questions/30429/how-to-detect-glsl-warnings
   */
  protected _getCompilationStatus() {
    this.compilationStatus = this.device.gl.getShaderParameter(this.handle, GL.COMPILE_STATUS)
      ? 'success'
      : 'error';
  }
}

// TODO - Original code from luma.gl v8 - keep until new debug functionality has matured
// if (!compilationSuccess) {
//   const parsedLog = shaderLog ? parseShaderCompilerLog(shaderLog) : [];
//   const messages = parsedLog.filter(message => message.type === 'error');
//   const formattedLog = formatCompilerLog(messages, source, {showSourceCode: 'all', html: true});
//   const shaderDescription = `${this.stage} shader ${shaderName}`;
//   log.error(`GLSL compilation errors in ${shaderDescription}\n${formattedLog}`)();
//   displayShaderLog(parsedLog, source, shaderName);
// }