/*
 * libmedia linear oetf
 *
 * 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 colorTransformPerChannelTransferFn from './colorTransformPerChannelTransferFn'
import type { ColorTransformOptions } from '../options'
import { GLType } from '../options'
import { AVColorTransferCharacteristic } from '@libmedia/avutil'

export default function fromLinear(transferId: AVColorTransferCharacteristic, options: ColorTransformOptions) {
  function fn() {
    switch (transferId) {
      case AVColorTransferCharacteristic.AVCOL_TRC_LOG:
        return `
          if (v < 0.0) {
            v = 0.0;
          }
          else {
            v =  1.0 + log(v) / log(10.0) / 2.0;
          }
        `
      case AVColorTransferCharacteristic.AVCOL_TRC_LOG_SQRT:
        return `
          if (v < sqrt(10.0) / 1000.0)
            v = 0.0;
          }
          else {
            v = 1.0 + log(v) / log(10.0) / 2.5;
          }
        `
      case AVColorTransferCharacteristic.AVCOL_TRC_IEC61966_2_4:
        return `
          ${options.type === GLType.kWebGPU ? 'let a: f32' : 'float a'} = 1.099296826809442;
          ${options.type === GLType.kWebGPU ? 'let b: f32' : 'float b'}= 0.018053968510807;
          if (v < -b) {
            v = -a * pow(-v, 0.45) + (a - 1.0);
          }
          else if (v <= b) {
            v = 4.5 * v;
          }
          else {
            v = a * pow(v, 0.45) - (a - 1.0);
          }
        `
      case AVColorTransferCharacteristic.AVCOL_TRC_BT1361_ECG:
        return `
          ${options.type === GLType.kWebGPU ? 'let a: f32' : 'float a'} = 1.099;
          ${options.type === GLType.kWebGPU ? 'let b: f32' : 'float b'} = 0.018;
          ${options.type === GLType.kWebGPU ? 'let l: f32' : 'float l'} = 0.0045;

          if (v < -l) {
            v = -(a * pow(-4.0 * v, 0.45) + (a - 1.0)) / 4.0;
          }
          else if (v <= b) {
            v = 4.5 * v;
          }
          else {
            v = a * pow(v, 0.45) - (a - 1.0);
          }
        `
      default:
        return ''
    }
  }
  return colorTransformPerChannelTransferFn(fn, false, options)
}