/*
 * libmedia analyze ts packet length
 *
 * 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 * as mpegts from '../mpegts'

export default function analyzeTSLength(buffer: Uint8Array, packetSize: number, probe: boolean) {
  const stat = new Uint8Array(mpegts.TS_MAX_PACKET_SIZE)
  let statAll = 0
  let bestScore = 0

  for (let i = 0; i < buffer.length - 3; i++) {
    if (buffer[i] === 0x47) {
      const pid = ((buffer[i + 1] << 8) | buffer[i + 2]) & 0x1FFF
      let asc = buffer[i + 3] & 0x30
      if (!probe || pid === 0x1FFF || asc) {
        const x = i % packetSize
        stat[x]++
        statAll++
        if (stat[x] > bestScore) {
          bestScore = stat[x]
        }
      }
    }
  }

  return bestScore - Math.max(statAll - 10 * bestScore, 0) / 10
}