"""Conventional-commit + ISSUES CLOSED footer linter.

Extracted from :mod:`_review_validate_helpers` in Phase 0 so the
implementer pipeline can reuse the same lint without depending on
reviewer-specific helpers. The implementer's own self-validation
CLI (:mod:`implementer_validate`) and the reviewer's CLI
(:mod:`review_validate`) both call :func:`lint_commit_message` —
keeping the lint here gives them a single source of truth and
matches the project's CONTRIBUTING.md / worker-prompt contract.

What's here:

- :data:`CONVENTIONAL_TYPES` -- whitelist of conventional-commit
  type prefixes (``feat`` / ``fix`` / ``refactor`` / ...).
- :func:`lint_commit_message` -- subject-prefix + ISSUES CLOSED
  footer + bot-author exemption check. Returns a structured dict
  matching the CLI output contract; never raises.
- :func:`_bot_committer_email` -- resolves the bot identity from
  ``REVIEW_BOT_COMMITTER_EMAIL`` (default
  ``forgejo@cleverthis.com``). Bot-authored merge commits bypass
  every check.

The lint is INTENTIONALLY identical between dispatchers: a draft
that passes the reviewer's lint must also pass the implementer's
lint by construction, so a worker can self-validate against either
CLI and trust the verdict.
"""

from __future__ import annotations

import os
import re
from typing import Any


CONVENTIONAL_TYPES: tuple[str, ...] = (
    "feat",
    "fix",
    "refactor",
    "perf",
    "docs",
    "test",
    "build",
    "ci",
    "chore",
    "style",
    "revert",
)
_CONVENTIONAL_SUBJECT_RE = re.compile(
    r"^(?P<type>" + "|".join(CONVENTIONAL_TYPES) + r")"
    r"(?:\([^)]+\))?"  # optional scope
    r"(?P<bang>!?)"  # optional breaking-change marker
    r": (?P<rest>.+)$"
)
_ISSUES_CLOSED_RE = re.compile(
    r"(?im)^ISSUES CLOSED:\s*#(?P<n>\d+)(?:\s*,\s*#\d+)*\s*$"
)


def _bot_committer_email() -> str:
    """Resolve the bot committer email used for the lint-commit
    exemption. Defaults to ``forgejo@cleverthis.com``, overridable
    via ``REVIEW_BOT_COMMITTER_EMAIL`` so forks / test deployments
    don't have to monkey-patch a private constant. Always
    lowercased so the callers' comparison is case-insensitive."""
    return os.environ.get(
        "REVIEW_BOT_COMMITTER_EMAIL", "forgejo@cleverthis.com"
    ).lower()


# Module-level constant for back-compat with older tests / callers
# that patch this directly. New code should call
# :func:`_bot_committer_email` at use site so a per-test
# ``monkeypatch.setenv`` flows through without re-importing.
BOT_COMMITTER_EMAIL = _bot_committer_email()


def lint_commit_message(
    message: str, committer_email: str, *, is_head: bool
) -> dict[str, Any]:
    """Lint one commit's message + committer.

    Returns the same shape the CLIs ultimately serialise to stdout::

        {"ok": bool, "exempt_bot": bool, "violations": [{"rule": ..., "details": ...}, ...]}

    Bot-authored merge commits (committer email matches
    :func:`_bot_committer_email` verbatim) bypass every check —
    they are mechanical merge artifacts (umbrella PR titles,
    train-merge sub-merges) and were never produced by an
    implementer. Per CONTRIBUTING.md / the worker prompt's
    Review Checklist category 10 exemption. The bot identity is
    overridable via ``REVIEW_BOT_COMMITTER_EMAIL`` for forks /
    test deployments.

    The ``is_head`` flag activates the ``ISSUES CLOSED: #N`` footer
    check; only the head commit is required to carry it (the merge
    driver checks the merge commit, the linter must run on HEAD
    here because the dispatcher does not produce a merge commit
    until the merge supervisor runs much later).
    """
    # Resolve at use site so a test's ``monkeypatch.setenv`` (set
    # AFTER module import) is honoured without requiring a fresh
    # re-import. Both sides are lowercased to make the comparison
    # case-insensitive even if a future operator overrides the env
    # var to mixed case.
    exempt_bot = committer_email.lower() == _bot_committer_email()
    violations: list[dict[str, str]] = []
    if not exempt_bot:
        subject = (message.splitlines() or [""])[0].strip()
        if not _CONVENTIONAL_SUBJECT_RE.match(subject):
            violations.append(
                {
                    "rule": "subject-prefix",
                    "details": (
                        f"subject {subject!r} does not match conventional-commit "
                        f"format <type>[(scope)][!]: <description>; allowed "
                        f"types: {', '.join(CONVENTIONAL_TYPES)}"
                    ),
                }
            )
        if is_head and not _ISSUES_CLOSED_RE.search(message):
            violations.append(
                {
                    "rule": "issues-closed-footer",
                    "details": (
                        "head commit body is missing the required "
                        "'ISSUES CLOSED: #N' footer (case-insensitive, "
                        "must be on its own line)"
                    ),
                }
            )
    return {
        "ok": not violations,
        "exempt_bot": exempt_bot,
        "violations": violations,
    }


__all__ = (
    "BOT_COMMITTER_EMAIL",
    "CONVENTIONAL_TYPES",
    "_bot_committer_email",
    "lint_commit_message",
)