from __future__ import annotations

import argparse
import hashlib
import os

import libtorrent as lt

from common import file_sha1, parse_size, write_manifest


def deterministic_bytes(offset: int, size: int) -> bytes:
    out = bytearray()
    counter = offset // 32
    while len(out) < size:
        out.extend(hashlib.sha256(f"torrent-peer-interop:{counter}".encode()).digest())
        counter += 1
    return bytes(out[:size])


def write_data(path: str, size: int) -> None:
    with open(path, "wb") as f:
        off = 0
        while off < size:
            n = min(1024 * 1024, size - off)
            f.write(deterministic_bytes(off, n))
            off += n


def make_torrent(root: str, size: int, piece_size: int) -> str:
    os.makedirs(root, exist_ok=True)
    data_path = os.path.join(root, "data.bin")
    torrent_path = os.path.join(root, "test.torrent")
    write_data(data_path, size)

    fs = lt.file_storage()
    lt.add_files(fs, data_path)
    t = lt.create_torrent(fs, piece_size=piece_size)
    t.set_priv(True)
    t.add_tracker("http://fixture:9/announce")
    lt.set_piece_hashes(t, root)
    with open(torrent_path, "wb") as f:
        f.write(lt.bencode(t.generate()))
    return torrent_path


def main() -> int:
    ap = argparse.ArgumentParser(description="Create the offline interop fixture.")
    ap.add_argument("--out", required=True)
    ap.add_argument("--size", default="32M")
    ap.add_argument("--piece-size", default="256K")
    args = ap.parse_args()

    size = parse_size(args.size)
    piece_size = parse_size(args.piece_size)
    torrent_path = make_torrent(args.out, size, piece_size)
    data_path = os.path.join(args.out, "data.bin")

    ti = lt.torrent_info(torrent_path)
    write_manifest(
        os.path.join(args.out, "manifest.json"),
        name=ti.name(),
        size=size,
        piece_size=piece_size,
        num_pieces=ti.num_pieces(),
        sha1=file_sha1(data_path),
        announce="http://fixture:9/announce",
        torrent=os.path.basename(torrent_path),
        data=os.path.basename(data_path),
    )
    print(f"fixture ready: {size} bytes, {ti.num_pieces()} pieces", flush=True)
    return 0


if __name__ == "__main__":
    raise SystemExit(main())