const decoder = new TextDecoder()
export class BmpDecoder {
  pos: number
  buffer: ArrayBuffer
  is_with_alpha: boolean
  bottom_up: boolean
  flag: string
  constructor(buffer: ArrayBuffer, is_with_alpha: boolean) {
    this.pos = 0
    this.buffer = buffer
    this.is_with_alpha = !!is_with_alpha
    this.bottom_up = true

    this.flag = decoder.decode(this.buffer.slice(0, (this.pos += 2)))

    if (this.flag != 'BM')
      throw new Error('Invalid BMP File')
    // this.parseHeader();
    // this.parseRGBA();
  }

  parseHeader() {}
  parseRGBA() {}
}

export function createBmpFile(
  imgData: ImageData,
  paramDic: { [key: string]: string } = {},
) {
  let dpi = 300
  let bitPP = paramDic.bpp ? Number(paramDic.bpp) : 24
  let printResolution = Math.round(dpi * 39.3701)

  if ([1, 24, 32].includes(bitPP) == false) {
    throw new Error(`不支持的${bitPP}bpp BMP`)
  }

  let data = imgData.data

  let width = imgData.width
  let height = imgData.height
  let extraBytes = width % 4
  let rgbSize = data.length
  switch (bitPP) {
    case 1:
      {
        let rowSize = width / 8 + (width % 8 > 0 ? 1 : 0)
        extraBytes = rowSize % 4
        rgbSize = height * (rowSize + extraBytes)
      }
      break
    case 24:
      {
        let rowSize = 3 * width
        extraBytes = rowSize % 4
        rgbSize = height * (rowSize + extraBytes)
      }
      break
  }
  let headerInfoSize = 40

  /** ****************header */
  let flag = 'BM'
  let reserved = 0
  let offset = 54
  let fileSize = rgbSize + offset
  let planes = 1

  let compress = 0
  let hr = printResolution
  let vr = printResolution
  let colors = 0
  let importantColors = 0
  let colorPaletteSize = 0
  if (bitPP == 1) {
    colorPaletteSize = 2 * 4
  }
  let buffer = new ArrayBuffer(offset + colorPaletteSize + rgbSize)
  let tempBuffer = new DataView(buffer)
  let pos = 0

  // BMP Header
  // ID
  tempBuffer.setUint8(pos, flag.charCodeAt(0))
  pos += 1
  tempBuffer.setUint8(pos, flag.charCodeAt(1))
  pos += 1
  // size
  tempBuffer.setUint32(pos, fileSize, true)
  pos += 4

  // Application specific
  tempBuffer.setUint32(pos, reserved, true)
  pos += 4
  // Offset
  tempBuffer.setUint32(pos, offset, true)
  pos += 4

  // DIB Header
  // Number of bytes in the DIB header (from this point)
  tempBuffer.setUint32(pos, headerInfoSize, true)
  pos += 4

  tempBuffer.setUint32(pos, width, true)
  pos += 4
  tempBuffer.setUint32(pos, height, true)
  pos += 4

  tempBuffer.setUint16(pos, planes, true)
  pos += 2
  tempBuffer.setUint16(pos, bitPP, true)
  pos += 2

  tempBuffer.setUint16(pos, compress, true)
  pos += 4

  tempBuffer.setUint16(pos, rgbSize, true)
  pos += 4

  tempBuffer.setUint16(pos, hr, true)
  pos += 4
  tempBuffer.setUint16(pos, vr, true)
  pos += 4

  tempBuffer.setUint16(pos, colors, true)
  pos += 4
  tempBuffer.setUint16(pos, importantColors, true)
  pos += 4

  if (bitPP == 1) {
    tempBuffer.setUint8(pos++, 0) // b
    tempBuffer.setUint8(pos++, 0) // g
    tempBuffer.setUint8(pos++, 0) // r
    tempBuffer.setUint8(pos++, 0) // a

    tempBuffer.setUint8(pos++, 255) // b
    tempBuffer.setUint8(pos++, 255) // g
    tempBuffer.setUint8(pos++, 255) // r
    tempBuffer.setUint8(pos++, 0) // a
  }

  let pixData = ''
  let writeBinData = () => {
    tempBuffer.setUint8(pos++, Number.parseInt(pixData.padEnd(8, '0'), 2))
    pixData = ''
  }
  for (let y = height - 1; y >= 0; y--) {
    let rowIndex = y * width * 4
    for (let x = 0; x < width; x++) {
      let p = rowIndex + x * 4

      if (bitPP == 1) {
        if (pixData.length == 8) {
          writeBinData()
        }
        let rgb = [data[p + 0], data[p + 1], data[p + 2]]
        pixData += rgb.filter((v, i) => v > 170).length == 3 ? '1' : '0' // 170 以下小板缩略图条会断
      } else {
        tempBuffer.setUint8(pos++, data[p + 2]) // b
        tempBuffer.setUint8(pos++, data[p + 1]) // g
        tempBuffer.setUint8(pos++, data[p + 0]) // r
        if (bitPP == 32) {
          tempBuffer.setUint8(pos++, data[p + 3]) // a
        }
      }
    }
    if (bitPP == 1 && pixData.length > 0) {
      writeBinData()
    }
    for (let index = 0; index < extraBytes; index++) {
      tempBuffer.setUint8(pos++, 0)
    }
  }

  return tempBuffer.buffer
}