/*
 * libmedia mp4 schm box parser
 *
 * 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 type { Atom, IsobmffContext, IsobmffStreamContext } from '../type'
import { logger } from '@libmedia/common'
import { type IOReader } from '@libmedia/common/io'
import { type AVStream } from '@libmedia/avutil'

export default async function read(ioReader: IOReader, stream: AVStream, atom: Atom, isobmffContext: IsobmffContext) {

  const now = ioReader.getPos()

  // version and flags
  await ioReader.skip(4)

  const streamContext = stream.privData as IsobmffStreamContext

  let cenc = isobmffContext.cencs ? isobmffContext.cencs[streamContext.trackId] : null
  if (!cenc) {
    cenc = {
      schemeType: 0,
      schemeVersion: 0,
      isProtected: 0,
      defaultPerSampleIVSize: 0,
      defaultKeyId: null,
      defaultConstantIV: null,
      cryptByteBlock: 0,
      skipByteBlock: 0,
      pattern: false
    }
  }

  cenc.schemeType = await ioReader.readUint32()
  cenc.schemeVersion = await ioReader.readUint32()

  if (!isobmffContext.cencs) {
    isobmffContext.cencs = {
      [streamContext.trackId]: cenc
    }
  }
  else {
    isobmffContext.cencs[streamContext.trackId] = cenc
  }

  const remainingLength = atom.size - Number(ioReader.getPos() - now)
  if (remainingLength > 0) {
    await ioReader.skip(remainingLength)
  }
  else if (remainingLength < 0) {
    logger.error(`read schm error, size: ${atom.size}, read: ${atom.size - remainingLength}`)
  }
}