#!/usr/bin/env python3
"""demo_ids.py -- real-data demo: 128-bit human-transcribable IDs with check symbols.

Takes a real file's SHA-256, folds it to a 128-bit integer, and emits a hyphenated
Crockford Base32 ID with a check symbol (transcription-safe: O/0 and I/L/1 confusions
are folded, hyphens ignored, one bad symbol caught). Verifies and decodes it back,
then proves the check symbol catches every single-symbol typo in the printed ID.

Run:  python3 demo_ids.py [FILE ...]
"""

from __future__ import annotations

import hashlib
import os
import sys

HERE = os.path.dirname(os.path.abspath(__file__))
if HERE not in sys.path:
    sys.path.insert(0, HERE)

import base32c  # noqa: E402

DEFAULT_TARGETS = ["/usr/share/common-licenses/GPL-3", os.path.join(HERE, "base32c.py")]


def make_id(path: str) -> dict:
    digest = hashlib.sha256(open(path, "rb").read()).digest()
    value = int.from_bytes(digest[:16], "big")  # 128-bit id space
    ident = base32c.encode_checked(value, min_length=26, hyphenate=4)
    decoded = base32c.decode_checked(ident)
    typos = tested = caught = 0
    body = ident.replace("-", "")
    for pos in range(len(body)):
        alternatives = base32c.CHECK_ALPHABET if pos == len(body) - 1 else base32c.ALPHABET
        for alt in alternatives:
            if alt == body[pos]:
                continue
            mutated = body[:pos] + alt + body[pos + 1 :]
            tested += 1
            if not base32c.verify(mutated):
                caught += 1
    return {
        "path": path,
        "sha256": digest.hex(),
        "value": value,
        "id": ident,
        "roundtrip_ok": decoded == value,
        "typos_tested": tested,
        "typos_caught": caught,
    }


def main(argv: list[str]) -> int:
    targets = argv or DEFAULT_TARGETS
    all_ok = True
    for path in targets:
        if not os.path.isfile(path):
            print(f"SKIP {path}: not a file")
            continue
        row = make_id(path)
        print(f"file       {row['path']}")
        print(f"sha256     {row['sha256']}")
        print(f"id value   {row['value']}")
        print(f"public id  {row['id']}")
        print(f"round-trip {'OK' if row['roundtrip_ok'] else 'BROKEN'} (decode_checked == value)")
        print(
            f"typo sweep {row['typos_caught']}/{row['typos_tested']} single-symbol typos rejected"
            f" ({row['typos_caught'] / row['typos_tested']:.1%})"
        )
        print()
        all_ok &= row["roundtrip_ok"] and row["typos_caught"] == row["typos_tested"]
    print("DEMO OK" if all_ok else "DEMO FAILED")
    return 0 if all_ok else 1


if __name__ == "__main__":
    raise SystemExit(main(sys.argv[1:]))