#!/usr/bin/env python3
# usage (after "chmod a+x ./thisscript.py"):
# "./thisscript.py piece_size_in_bytes filename.torrent"
import sys
import bencodepy
import math

piecesize = int(sys.argv[1])
torrent = sys.argv[2]
data = open(torrent, "rb").read()
struct = bencodepy.decode(data)
num_bytes = sum(entry[b'length'] for entry in struct[b"info"][b"files"])
offset = 0
piece1 = 0
piece2 = 1

print("version of this script: 2023.03.25.05.07.18.Z")
print("filename:", torrent)
print("torrent total size:", num_bytes, "bytes")
print("torrent piece size:", piecesize, "bytes")
print("first_chunk_number first_chunk_offset file_offset length path")

for entry in struct[b"info"][b"files"]:
    print(piece2, piece1, offset, entry[b'length'], entry[b'path'])
    offset += entry[b'length']
    piece1 = math.floor(offset / piecesize) * piecesize
    piece2 = math.floor(offset / piecesize) + 1