#!/usr/bin/env python3
from __future__ import annotations

import json
import os
import pathlib
import re
import subprocess
import sys
from typing import Dict, List, Optional, Tuple


def _eprint(*args: object) -> None:
    print(*args, file=sys.stderr)


def _git(*args: str) -> str:
    return subprocess.check_output(["git", *args], text=True).strip()


def _repo_root() -> pathlib.Path:
    return pathlib.Path(_git("rev-parse", "--show-toplevel"))


def _find_commit_spec(root: pathlib.Path) -> pathlib.Path:
    candidates = [
        root / "docs" / "common" / "commit_message.md",
        root / "docs" / "standards" / "playbook" / "docs" / "common" / "commit_message.md",
    ]
    for path in candidates:
        if path.is_file():
            return path
    raise FileNotFoundError(
        "commit_message.md not found; expected one of:\n"
        + "\n".join(f"- {p}" for p in candidates)
    )


def _parse_type_emoji_mapping(md_text: str) -> Dict[str, str]:
    mapping: Dict[str, str] = {}
    for raw_line in md_text.splitlines():
        line = raw_line.strip()
        if not (line.startswith("|") and line.endswith("|")):
            continue
        if "type" in line and "emoji" in line:
            continue
        if re.fullmatch(r"\|\s*-+\s*(\|\s*-+\s*)+\|", line):
            continue

        cols = [c.strip() for c in line.strip("|").split("|")]
        if len(cols) < 2:
            continue

        m_type = re.search(r"`([^`]+)`", cols[0])
        m_emoji = re.search(r"`(:[^`]+:)`", cols[1])
        if not m_type or not m_emoji:
            continue

        type_name = m_type.group(1).strip()
        emoji_code = m_emoji.group(1).strip()
        mapping[type_name] = emoji_code

    if not mapping:
        raise ValueError("failed to parse type/emoji mapping from commit_message.md")
    return mapping


def _validate_subject_line(
    line: str,
    mapping: Dict[str, str],
    *,
    require_emoji: bool,
) -> Optional[str]:
    subject = line.strip()
    if not subject:
        return "empty subject"

    m = re.match(
        r"^(?:(?P<emoji>:[a-z0-9_+-]+:)\s+)?"
        r"(?P<type>[a-z]+)"
        r"(?P<scope>\([a-z0-9_]+\))?"
        r":\s+(?P<text>.+)$",
        subject,
    )
    if not m:
        return "does not match ':emoji: type(scope): subject' or 'type(scope): subject'"

    emoji = m.group("emoji")
    type_name = m.group("type")
    text = (m.group("text") or "").rstrip()

    if type_name not in mapping:
        return f"unknown type: {type_name}"

    if emoji:
        expected = mapping[type_name]
        if emoji != expected:
            return f"emoji/type mismatch: got {emoji} {type_name}, expected {expected} for type {type_name}"
    elif require_emoji:
        return "missing emoji (set COMMIT_LINT_REQUIRE_EMOJI=0 to allow)"

    if text.endswith((".", "。")):
        return "subject should not end with a period"

    return None


def _load_event_payload() -> Tuple[str, Optional[dict]]:
    event_name = os.getenv("GITHUB_EVENT_NAME") or os.getenv("GITEA_EVENT_NAME") or ""
    event_path = os.getenv("GITHUB_EVENT_PATH") or os.getenv("GITEA_EVENT_PATH") or ""
    if not event_path:
        return event_name, None

    path = pathlib.Path(event_path)
    if not path.is_file():
        return event_name, None

    try:
        return event_name, json.loads(path.read_text(encoding="utf-8"))
    except Exception as exc:
        _eprint(f"WARN: failed to parse event payload: {path} ({exc})")
        return event_name, None


def _gather_subjects(event_name: str, payload: Optional[dict]) -> List[Tuple[str, str]]:
    subjects: List[Tuple[str, str]] = []

    if isinstance(payload, dict):
        if event_name.startswith("pull_request"):
            pr = payload.get("pull_request")
            if isinstance(pr, dict):
                title = (pr.get("title") or "").strip()
                if title:
                    subjects.append(("pull_request.title", title.splitlines()[0].strip()))

        if event_name == "push":
            commits = payload.get("commits")
            if isinstance(commits, list):
                for commit in commits:
                    if not isinstance(commit, dict):
                        continue
                    msg = (commit.get("message") or "").strip()
                    if not msg:
                        continue
                    subject = msg.splitlines()[0].strip()
                    sha = commit.get("id") or commit.get("sha") or ""
                    label = f"push.commit {sha[:7]}" if sha else "push.commit"
                    subjects.append((label, subject))

    if subjects:
        return subjects

    try:
        subjects.append(("HEAD", _git("log", "-1", "--format=%s", "HEAD")))
    except Exception:
        pass
    return subjects


def main() -> int:
    try:
        root = _repo_root()
    except Exception as exc:
        _eprint(f"ERROR: not a git repository: {exc}")
        return 2

    os.chdir(root)

    require_emoji = os.getenv("COMMIT_LINT_REQUIRE_EMOJI", "1") not in ("0", "false", "False")

    try:
        spec_path = _find_commit_spec(root)
    except FileNotFoundError as exc:
        _eprint(f"ERROR: {exc}")
        return 2

    try:
        mapping = _parse_type_emoji_mapping(spec_path.read_text(encoding="utf-8"))
    except Exception as exc:
        _eprint(f"ERROR: failed to read/parse {spec_path}: {exc}")
        return 2

    event_name, payload = _load_event_payload()
    subjects = _gather_subjects(event_name, payload)

    print(f"commit spec: {spec_path}")
    if event_name:
        print(f"event: {event_name}")
    print(f"require emoji: {require_emoji}")
    print(f"checks: {len(subjects)} subject(s)")

    errors: List[str] = []
    for label, subject in subjects:
        err = _validate_subject_line(subject, mapping, require_emoji=require_emoji)
        if err:
            errors.append(f"- {label}: {err}\n  subject: {subject}")

    if errors:
        _eprint("ERROR: commit message lint failed:")
        for item in errors:
            _eprint(item)
        return 1

    print("OK")
    return 0


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