name: Check PR Target Branch

on:
  pull_request_target:
    types: [opened, edited, reopened, synchronize]

concurrency:
  group: check-pr-target-${{ github.event.pull_request.number }}
  cancel-in-progress: true

permissions:
  pull-requests: write

jobs:
  check-target:
    runs-on: ubuntu-latest
    steps:
      - name: Reject PR targeting main
        uses: actions/github-script@f28e40c7f34bde8b3046d885e986cb6290c5673b # v7.1.0
        with:
          script: |
            const pull = context.payload.pull_request;
            const owner = context.repo.owner;
            const repo = context.repo.repo;
            const pullNumber = context.issue.number;
            const botLogin = 'github-actions[bot]';

            const { data: reviews } = await github.rest.pulls.listReviews({
              owner,
              repo,
              pull_number: pullNumber,
              per_page: 100
            });

            const latestBotReview = reviews
              .filter((review) => review.user?.login === botLogin)
              .sort((a, b) => new Date(a.submitted_at ?? a.created_at) - new Date(b.submitted_at ?? b.created_at))
              .at(-1);

            const latestBotState = latestBotReview?.state;

            if (pull.base.ref === 'main') {
              if (latestBotState !== 'CHANGES_REQUESTED') {
                const requestChangesBody = [
                  '⚠️ **This PR targets `main`, but PRs should target `staged`.**',
                  '',
                  'The `main` branch is auto-published from `staged` and should not receive direct PRs.',
                  'Please close this PR and re-open it against the `staged` branch.',
                  '',
                  'You can change the base branch using the **Edit** button at the top of this PR,',
                  'or run: `gh pr edit ${{ github.event.pull_request.number }} --base staged`'
                ].join('\n');

                await github.rest.pulls.createReview({
                  owner,
                  repo,
                  pull_number: pullNumber,
                  event: 'REQUEST_CHANGES',
                  body: requestChangesBody
                });
              }

              return;
            }

            if (latestBotState === 'CHANGES_REQUESTED') {
              const approveBody = [
                '✅ Base branch is now set correctly.',
                '',
                'Removing the prior block because this PR no longer targets `main`.'
              ].join('\n');

              await github.rest.pulls.createReview({
                owner,
                repo,
                pull_number: pullNumber,
                event: 'APPROVE',
                body: approveBody
              });
            }