/*
 * libmedia Shader
 *
 * 版权所有 (C) 2024 赵高兴
 * Copyright (C) 2024 Gaoxing Zhao
 *
 * 此文件是 libmedia 的一部分
 * This file is part of libmedia.
 * 
 * libmedia 是自由软件；您可以根据 GNU Lesser General Public License（GNU LGPL）3.1
 * 或任何其更新的版本条款重新分发或修改它
 * libmedia is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3.1 of the License, or (at your option) any later version.
 * 
 * libmedia 希望能够为您提供帮助，但不提供任何明示或暗示的担保，包括但不限于适销性或特定用途的保证
 * 您应自行承担使用 libmedia 的风险，并且需要遵守 GNU Lesser General Public License 中的条款和条件。
 * libmedia is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 */

import { logger } from '@libmedia/common'

export const enum ShaderType {
  VERTEX,
  FRAGMENT
}

export default abstract class Shader {

  public readonly type: ShaderType

  private _shader: WebGLShader

  private _source: string

  private compiled: boolean

  constructor(type: ShaderType, source: string) {
    this.type = type
    this._shader = null
    this._source = source
    this.compiled = false
  }

  compile(gl: WebGLRenderingContext) {
    if (this.compiled) {
      return
    }
    this._shader = gl.createShader(this.type === ShaderType.VERTEX ? gl.VERTEX_SHADER : gl.FRAGMENT_SHADER)
    gl.shaderSource(this._shader, this._source)
    gl.compileShader(this._shader)

    if (process.env.NODE_ENV === 'development') {
      if (!gl.getShaderParameter(this._shader, gl.COMPILE_STATUS)) {
        logger.fatal(gl.getShaderInfoLog(this._shader))
      }
    }
    this.compiled = true
  }

  stop(gl: WebGLRenderingContext) {
    gl.deleteShader(this._shader)
    this._shader = null
  }

  get shader(): WebGLShader {
    return this._shader
  }
}