"""Verify ADR language pair invariants.

Policy (see CLAUDE.md Part 2 -> ADR Translation Discipline):
  docs/adr/        : English canonical
  docs/adr-ko/     : Korean translation (1:1 mirror)
  docs/adr-history/: frozen, not checked (transitional)
  docs/adr-proposed/: language-free, not checked

Checks:
  - every docs/adr/<X>.md has a matching docs/adr-ko/<X>.md
  - every docs/adr-ko/<X>.md has a matching docs/adr/<X>.md (no orphans)
  - title line `# ADR-NNNN:` of each pair matches the filename's NNNN
  - `## Status` block content is byte-equal (after CRLF/LF normalization)
    between EN and KO

Exit code: 0 if all OK, 1 if any mismatch.
"""

from __future__ import annotations

import argparse
import re
import sys
from pathlib import Path

ADR_FILENAME_RE = re.compile(r"^ADR-(\d{4})-[a-z0-9_-]+\.md$")
TITLE_RE = re.compile(r"^# ADR-(\d{4}):")


def _normalize(text: str) -> str:
    return text.replace("\r\n", "\n").replace("\r", "\n")


def find_adr_files(adr_dir: Path) -> dict[str, Path]:
    if not adr_dir.is_dir():
        return {}
    return {
        p.name: p
        for p in sorted(adr_dir.iterdir())
        if p.is_file() and ADR_FILENAME_RE.match(p.name)
    }


def extract_title_id(text: str) -> str | None:
    lines = _normalize(text).splitlines()
    if not lines:
        return None
    m = TITLE_RE.match(lines[0])
    return m.group(1) if m else None


def extract_status_block(text: str) -> str | None:
    """Return content between `## Status` and the next `## ` heading, stripped.

    Returns None if no `## Status` heading exists.
    """
    lines = _normalize(text).splitlines()
    in_status = False
    collected: list[str] = []
    for line in lines:
        if line.strip() == "## Status":
            in_status = True
            continue
        if in_status and line.startswith("## "):
            break
        if in_status:
            collected.append(line)
    if not in_status:
        return None
    return "\n".join(collected).strip()


def verify(root: Path) -> list[str]:
    errors: list[str] = []
    en_dir = root / "docs" / "adr"
    ko_dir = root / "docs" / "adr-ko"

    en_files = find_adr_files(en_dir)
    ko_files = find_adr_files(ko_dir)

    for name in en_files:
        if name not in ko_files:
            errors.append(f"missing KO translation: docs/adr-ko/{name}")
    for name in ko_files:
        if name not in en_files:
            errors.append(f"orphan KO (no canonical EN): docs/adr-ko/{name}")

    for name in sorted(en_files.keys() & ko_files.keys()):
        m = ADR_FILENAME_RE.match(name)
        assert m is not None
        expected_id = m.group(1)

        en_text = en_files[name].read_text(encoding="utf-8")
        ko_text = ko_files[name].read_text(encoding="utf-8")

        en_id = extract_title_id(en_text)
        ko_id = extract_title_id(ko_text)
        if en_id != expected_id:
            errors.append(
                f"{name}: EN title ADR-ID {en_id!r} != filename {expected_id!r}"
            )
        if ko_id != expected_id:
            errors.append(
                f"{name}: KO title ADR-ID {ko_id!r} != filename {expected_id!r}"
            )

        en_status = extract_status_block(en_text)
        ko_status = extract_status_block(ko_text)
        if en_status is None:
            errors.append(f"{name}: EN missing `## Status` section")
        if ko_status is None:
            errors.append(f"{name}: KO missing `## Status` section")
        if en_status is not None and ko_status is not None and en_status != ko_status:
            errors.append(
                f"{name}: Status block mismatch\n"
                f"      EN: {en_status!r}\n"
                f"      KO: {ko_status!r}"
            )

    return errors


def main(argv: list[str] | None = None) -> int:
    p = argparse.ArgumentParser(description=__doc__)
    p.add_argument(
        "--root",
        type=Path,
        default=Path.cwd(),
        help="Repository root (default: cwd)",
    )
    args = p.parse_args(argv)

    errors = verify(args.root)
    if errors:
        print("ADR language pair verification FAILED:")
        for e in errors:
            print(f"  - {e}")
        return 1
    print("ADR language pair verification OK")
    return 0


if __name__ == "__main__":
    sys.exit(main())