import { normalize } from 'node:path'

const CRC_TABLE = Array.from({ length: 256 }, (_, value) => {
  let crc = value
  for (let bit = 0; bit < 8; bit++) crc = (crc & 1) ? 0xedb88320 ^ (crc >>> 1) : crc >>> 1
  return crc >>> 0
})

function crc32(data) {
  let crc = 0xffffffff
  for (const byte of data) crc = CRC_TABLE[(crc ^ byte) & 0xff] ^ (crc >>> 8)
  return (crc ^ 0xffffffff) >>> 0
}

function archivePath(value) {
  const path = normalize(String(value || '').replace(/\\/g, '/')).replace(/\\/g, '/').replace(/^\.\//, '')
  if (!path || path.startsWith('/') || path === '..' || path.startsWith('../')) throw new Error('ZIP 文件路径无效')
  return path
}

function dosDateTime(date = new Date()) {
  const year = Math.max(1980, date.getFullYear())
  return {
    time: (date.getHours() << 11) | (date.getMinutes() << 5) | Math.floor(date.getSeconds() / 2),
    date: ((year - 1980) << 9) | ((date.getMonth() + 1) << 5) | date.getDate(),
  }
}

/** 创建无额外依赖的 ZIP（Store 模式）；PNG 和 .spine 本身已压缩，无需重复压缩。 */
export function createZipArchive(files) {
  const localParts = []
  const centralParts = []
  let offset = 0
  const timestamp = dosDateTime()

  for (const file of files) {
    const name = Buffer.from(archivePath(file.name), 'utf8')
    const data = Buffer.isBuffer(file.data) ? file.data : Buffer.from(file.data)
    const crc = crc32(data)
    const local = Buffer.alloc(30)
    local.writeUInt32LE(0x04034b50, 0)
    local.writeUInt16LE(20, 4)
    local.writeUInt16LE(0x0800, 6)
    local.writeUInt16LE(0, 8)
    local.writeUInt16LE(timestamp.time, 10)
    local.writeUInt16LE(timestamp.date, 12)
    local.writeUInt32LE(crc, 14)
    local.writeUInt32LE(data.length, 18)
    local.writeUInt32LE(data.length, 22)
    local.writeUInt16LE(name.length, 26)
    localParts.push(local, name, data)

    const central = Buffer.alloc(46)
    central.writeUInt32LE(0x02014b50, 0)
    central.writeUInt16LE(20, 4)
    central.writeUInt16LE(20, 6)
    central.writeUInt16LE(0x0800, 8)
    central.writeUInt16LE(0, 10)
    central.writeUInt16LE(timestamp.time, 12)
    central.writeUInt16LE(timestamp.date, 14)
    central.writeUInt32LE(crc, 16)
    central.writeUInt32LE(data.length, 20)
    central.writeUInt32LE(data.length, 24)
    central.writeUInt16LE(name.length, 28)
    central.writeUInt32LE(offset, 42)
    centralParts.push(central, name)
    offset += local.length + name.length + data.length
  }

  const centralDirectory = Buffer.concat(centralParts)
  const end = Buffer.alloc(22)
  end.writeUInt32LE(0x06054b50, 0)
  end.writeUInt16LE(files.length, 8)
  end.writeUInt16LE(files.length, 10)
  end.writeUInt32LE(centralDirectory.length, 12)
  end.writeUInt32LE(offset, 16)
  return Buffer.concat([...localParts, centralDirectory, end])
}