"""Bitmapper

Usage:
  bitmapper.py <input> <output> [<width>]

Options:
  -h --help     Show this screen.
  <input>       The input binary file.
  <output>      The output bitmap.
  <width>       The width of the bitmap in pixels. Optional.
"""

import docopt
import struct

DEFAULT_WIDTH = 1000

HEADER = ("42 4D 36 E0 2E 00 00 00 00 00 36 00 00 00 28 00"
          "00 00 E8 03 00 00 00 04 00 00 01 00 20 00 00 00"
          "00 00 00 E0 2E 00 00 00 00 00 00 00 00 00 00 00"
          "00 00 00 00 00 00").decode("hex-bytes")


def make_bitmap(data, width=1000):
    size = len(data)
    height = len(data) / 4 / width
    header = (HEADER[:2] +
              struct.pack("<I", size) +
              HEADER[6:0x12] +
              struct.pack("<I", width) +
              struct.pack("<I", height) +
              HEADER[0x1A:0x22] +
              struct.pack("<I", size - 54) +
              HEADER[0x26:])

    return header + data


if __name__ == '__main__':
    arguments = docopt.docopt(__doc__)

    input_path = arguments["<input>"]
    output_path = arguments["<output>"]

    try:
        width = int(arguments["<width>"])
    except (ValueError, TypeError):
        width = DEFAULT_WIDTH

    with open(input_path, "rb") as f:
        data = f.read()

    bitmap = make_bitmap(data, width)

    with open(output_path, "wb") as f:
        f.write(bitmap)