#! /usr/bin/env nix-shell
#! nix-shell -p typst dmtx-utils -i python

import subprocess
import argparse
import shlex
import tempfile
from pathlib import Path
from math import ceil


def sub(cmd: str, *args, **kwargs):
    return subprocess.check_output(shlex.split(cmd), *args, **kwargs)


def typst_file_tmpl(files):
    local_paths = [f.relative_to(Path.cwd()) for f in files]
    return "\n".join(f'#image("{f}")' for f in local_paths)


def chunk_key(key):
    """
    split byte string into even chunks
    chunks will be <= 1555 bytes in length since
    1555 is the maxiumum byte size for datamatrix
    """
    n = ceil(len(key) / ceil(len(key) / 1555))
    return [key[i : i + n] for i in range(0, len(key), n)]


def generate_pdf(byte_chunks, svgpath, outpath):
    for f, data in zip(
        files := [svgpath / f"dmtx-{i}.svg" for i, _ in enumerate(byte_chunks)],
        byte_chunks,
    ):
        sub(f"dmtxwrite -e 8 -o {f}", input=data)
    sub(f"typst compile - {outpath}", input=typst_file_tmpl(files), text=True)


def get_key_data(key):
    suffix = key if key else ""
    return chunk_key(
        sub(f"gpg --export-secret-key --export-options export-minimal {suffix}")
    )


def main():
    p = argparse.ArgumentParser()
    p.add_argument("--key", help="key id")
    p.add_argument(
        "--output", help="pdf to write matrices to", default=Path.cwd() / "key.pdf"
    )

    args = p.parse_args()
    byte_chunks = get_key_data(args.key)

    with tempfile.TemporaryDirectory(dir=Path.cwd()) as tmpdirname:
        tmpdir = Path(tmpdirname)
        generate_pdf(byte_chunks, tmpdir, args.output)


if __name__ == "__main__":
    main()