#!/usr/bin/env python
import argparse
import os
import glob

"""
Usage:
command line
python aria2_to_magnet.py -e .aria2 .
"""


def main():
    # codes from gist
    # https://gist.github.com/89465127/5273149
    parser = argparse.ArgumentParser(
        description='Read in a file or set of files, and return the result.',
        formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument('path',
                        nargs='+',
                        help='Path of a file or a folder of files.')
    parser.add_argument('-e',
                        '--extension',
                        default='',
                        help='File extension to filter by.')
    args = parser.parse_args()

    # Parse paths
    full_paths = [os.path.join(os.getcwd(), path) for path in args.path]
    files = set()
    for path in full_paths:
        if os.path.isfile(path):
            files.add(path)
        else:
            files |= set(glob.glob(path + '/*' + args.extension))

    for f in files:
        magnet = parse_aria_control_file(f)
        print(f'file name: {os.path.basename(f)}, {magnet}')

# ================================================================
#  0                   1                   2                   3
#  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
# +---+-------+-------+-------------------------------------------+
# |VER|  EXT  |INFO   |INFO HASH ...                              |
# |(2)|  (4)  |HASH   | (INFO HASH LENGTH)                        |
# |   |       |LENGTH |                                           |
# |   |       |  (4)  |                                           |
# +---+---+---+-------+---+---------------+-------+---------------+
# |PIECE  |TOTAL LENGTH   |UPLOAD LENGTH  |BIT-   |BITFIELD ...   |
# |LENGTH |     (8)       |     (8)       |FIELD  | (BITFIELD     |
# |  (4)  |               |               |LENGTH |  LENGTH)      |
# |       |               |               |  (4)  |               |
# +-------+-------+-------+-------+-------+-------+---------------+
# |NUM    |INDEX  |LENGTH |PIECE  |PIECE BITFIELD ...             |
# |IN-    |  (4)  |  (4)  |BIT-   | (PIECE BITFIELD LENGTH)       |
# |FLIGHT |       |       |FIELD  |                               |
# |PIECE  |       |       |LENGTH |                               |
# |  (4)  |       |       |  (4)  |                               |
# +-------+-------+-------+-------+-------------------------------+
#
#         ^                                                       ^
#         |                                                       |
#         +-------------------------------------------------------+
#                 Repeated in (NUM IN-FLIGHT) PIECE times

# more detail
# https://aria2.github.io/manual/en/html/technical-notes.html
# ================================================================


def parse_aria_control_file(file_name):
    with open(file_name, "rb") as f:
        try:

            f.seek(0)  # Go to beginning, read VER
            version = f.read(2)

            i = int.from_bytes(version, 'big')
            # print("version is " + str(i))

            # skip  EXT, find info  hash_binary length
            f.seek(6)

            length = f.read(4)
            hash_length = int.from_bytes(length, 'big')
            # print "hash length is " + str(hash_length)

            # read next hash_length
            f.seek(10)  # Go to info hash
            hash_binary = f.read(hash_length)
            info_hash = hash_binary.hex().upper()

            magnet_link = "magnet:?xt=urn:btih:" + info_hash
            return magnet_link
        except:
            pass
        finally:
            f.close()


if __name__ == '__main__':
    # file_list = args.file
    # for file_name in file_list:
    #     parse_aria_control_file(file_name)
    # version is 1
    # hash length is 20
    # magnet:?xt=urn:btih:959E2ECEB954313D38690EFF7924CA7CD80DE739
    main()