name: Check PR for changes that trigger CP/CPS review

on:
  pull_request:
    types: [ready_for_review, review_requested]
    paths:
      - 'features/features.go'

jobs:
  check-features:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
    steps:
      - name: Setup Go
        uses: actions/setup-go@v5
        with:
          go-version: "stable"

      - name: Checkout Upstream
        uses: actions/checkout@v4
        with:
          ref: ${{ github.event.pull_request.base.ref }}
      - name: Get Current Flags
        run: go run ./test/list-features/list-features.go | sort >| /tmp/currflags.txt

      - name: Checkout PR
        uses: actions/checkout@v4
      - name: Get PR Flags
        run: go run ./test/list-features/list-features.go | sort >| /tmp/prflags.txt

      - name: Identify New Flags
        id: newflags
        run: echo flagnames=$(comm -13 /tmp/currflags.txt /tmp/prflags.txt | paste -sd,) >> $GITHUB_OUTPUT

      - name: Comment PR
        if: ${{ steps.newflags.outputs.flagnames != '' }}
        uses: actions/github-script@v7
        with:
          script: |
            const { owner, repo, number: issue_number } = context.issue;

            // No need to comment if the PR description already has a CPS review.
            const reviewRegexp = /^CPS Compliance Review:/;
            if (reviewRegexp.test(context.payload.pull_request.body)) {
              return;
            }

            // No need to comment if this task has previously commented on this PR.
            const commentMarker = '<!-- cps_review_check -->';
            const comments = await github.rest.issues.listComments({
              owner,
              repo,
              issue_number
            });
            if (comments.data.find(c => c.body.includes(commentMarker))) {
              return;
            }

            // No existing review or comment found, post the comment.
            const prAuthor = context.payload.pull_request.user.login;
            const flagNames = '${{ steps.newflags.outputs.flagnames }}';
            const commentBody = `${commentMarker}\n@${prAuthor}, this PR adds one or more new feature flags: ${flagNames}. As such, this PR must be accompanied by a review of the Let's Encrypt CP/CPS to ensure that our behavior both before and after this flag is flipped is compliant with that document.\n\nPlease conduct such a review, then add your findings to the PR description in a paragraph beginning with "CPS Compliance Review:".`;
            await github.rest.issues.createComment({
              owner,
              repo,
              issue_number,
              body: commentBody
            });