name: PR Closes-Issue Check

# Require every PR targeting main to reference at least one issue via
# the GitHub auto-close keywords. Aligns 99 PR / 43 issue asymmetry —
# every change should be traceable to a stated problem.
#
# Accepted keywords (case-insensitive, must use #N format):
#   Closes #N, Close #N, Closed #N
#   Fixes #N, Fix #N, Fixed #N
#   Resolves #N, Resolve #N, Resolved #N
#
# Per feedback_github_pr_close_issue_keywords: keyword must be
# immediately followed by #N (no intervening words), otherwise GitHub
# auto-close does not fire.
#
# Override: include [skip-closes-check] in PR body with justification.

on:
  pull_request:
    types: [opened, edited, synchronize, reopened, ready_for_review]
    branches: [main]

concurrency:
  group: pr-closes-issue-${{ github.event.pull_request.number }}-${{ github.event_name }}
  cancel-in-progress: true

permissions:
  contents: read
  pull-requests: read

jobs:
  closes-check:
    runs-on: ubuntu-latest
    steps:
      - name: Validate PR body
        env:
          PR_BODY: ${{ github.event.pull_request.body }}
        run: |
          set -euo pipefail

          if [ -z "${PR_BODY:-}" ]; then
            echo "::error::PR body is empty. Add a 'Closes #N' reference (or [skip-closes-check] with justification)."
            exit 1
          fi

          if echo "$PR_BODY" | grep -qF '[skip-closes-check]'; then
            echo "Override [skip-closes-check] present — skipping."
            exit 0
          fi

          # Strict GitHub auto-close pattern: keyword + space + #N (no intervening tokens)
          PATTERN='(^|[^a-zA-Z])(Clos(e|es|ed)|Fix(es|ed)?|Resolv(e|es|ed))[[:space:]]+#[0-9]+'
          if echo "$PR_BODY" | grep -qiE "$PATTERN"; then
            echo "Found valid closes-issue reference."
            echo "$PR_BODY" | grep -iE "$PATTERN" | head -5
            exit 0
          fi

          echo "::error::PR body must contain a GitHub auto-close keyword followed by #N."
          echo "::error::Examples: 'Closes #134', 'Fixes #138', 'Resolves #102'"
          echo "::error::Bypass: add [skip-closes-check] + justification to the PR body."
          exit 1