#!/usr/bin/env python3
"""CI guard: validate CHANGELOG.md versioning and the in-package copy.

Run on pull requests. Two checks:

1. If CHANGELOG.md changed in the PR, its top version must be a clean
   single-step SemVer bump above the latest ``v*`` tag. (Non-changing PRs —
   dependabot bumps, docs — are not version-checked, so they don't release.)
2. ``src/slack-bot/CHANGELOG.md`` (the copy that ships with the bot and feeds the
   App Home "What's New" tab) must match the canonical root CHANGELOG.md.

The workflow passes context via env: ``PREV_TAG`` (latest tag) and
``CHANGELOG_CHANGED`` ("true"/"false"). Run locally it assumes the changelog
changed so the bump is validated.
"""

import os
import pathlib
import sys

sys.path.insert(0, str(pathlib.Path(__file__).resolve().parents[1] / "src" / "shared"))

from shared.changelog import bump_kind, top_version  # noqa: E402

ROOT = pathlib.Path(__file__).resolve().parents[1]
PKG_COPY = ROOT / "src" / "slack-bot" / "CHANGELOG.md"


def evaluate(
    top: str | None, prev_tag: str, changelog_changed: bool, copies_match: bool
) -> list[str]:
    """Return a list of problems (empty == pass). Pure, for unit testing."""
    problems = []
    if not copies_match:
        problems.append(
            "src/slack-bot/CHANGELOG.md is out of sync with CHANGELOG.md — "
            "run scripts/sync_changelog.py"
        )
    if changelog_changed:
        if top is None:
            problems.append("CHANGELOG.md changed but has no version entry at the top")
        else:
            prev = (prev_tag or "v0.0.0").lstrip("v")
            if bump_kind(top, prev) is None:
                problems.append(
                    f"top version v{top} is not a clean single-step SemVer bump "
                    f"above the latest tag v{prev} (expected one of "
                    f"inc-major / inc-minor / inc-patch)"
                )
    return problems


def main() -> int:
    root_text = (ROOT / "CHANGELOG.md").read_text()
    copies_match = PKG_COPY.exists() and PKG_COPY.read_text() == root_text

    problems = evaluate(
        top=top_version(root_text),
        prev_tag=os.environ.get("PREV_TAG", ""),
        changelog_changed=os.environ.get("CHANGELOG_CHANGED", "true") == "true",
        copies_match=copies_match,
    )
    if problems:
        for problem in problems:
            print(f"::error::{problem}")
        return 1
    print("CHANGELOG guard passed.")
    return 0


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