name: validate-pr

# Default to 'contents: read', which grants actions to read commits.
#
# If any permission is set, any permission not included in the list is
# implicitly set to "none".
#
# see https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#permissions
permissions:
  contents: read

on:
  pull_request:
    types: [opened, edited, labeled, unlabeled]

jobs:
  check-area-label:
    runs-on: ubuntu-20.04
    steps:
      - name: Missing `area/` label
        if: contains(join(github.event.pull_request.labels.*.name, ','), 'impact/') && !contains(join(github.event.pull_request.labels.*.name, ','), 'area/')
        run: |
          echo "::error::Every PR with an 'impact/*' label should also have an 'area/*' label"
          exit 1
      - name: OK
        run: exit 0

  check-changelog:
    if: contains(join(github.event.pull_request.labels.*.name, ','), 'impact/')
    runs-on: ubuntu-20.04
    env:
      PR_BODY: |
        ${{ github.event.pull_request.body }}
    steps:
      - name: Check changelog description
        run: |
          # Extract the `markdown changelog` note code block
          block=$(echo -n "$PR_BODY" | tr -d '\r' | awk '/^```markdown changelog$/{flag=1;next}/^```$/{flag=0}flag')

          # Strip empty lines
          desc=$(echo "$block" |  awk NF)

          if [ -z "$desc" ]; then
            echo "::error::Changelog section is empty. Provide a description for the changelog."
            exit 1
          fi

          len=$(echo -n "$desc" | wc -c)
          if [[ $len -le 6 ]]; then
            echo "::error::Description looks too short: $desc"
            exit 1
          fi

          echo "This PR will be included in the release notes with the following note:"
          echo "$desc"

  check-pr-branch:
    runs-on: ubuntu-20.04
    env:
      PR_TITLE: ${{ github.event.pull_request.title }}
    steps:
      # Backports or PR that target a release branch directly should mention the target branch in the title, for example:
      # [X.Y backport] Some change that needs backporting to X.Y
      # [X.Y] Change directly targeting the X.Y branch
      - name: Check release branch
        id: title_branch
        run: |
          # get the intended major version prefix ("[27.1 backport]" -> "27.") from the PR title.
          [[ "$PR_TITLE" =~ ^\[([0-9]*\.)[^]]*\] ]] && branch="${BASH_REMATCH[1]}"

          # get major version prefix from the release branch ("27.x -> "27.")
          [[ "$GITHUB_BASE_REF" =~ ^([0-9]*\.) ]] && target_branch="${BASH_REMATCH[1]}" || target_branch="$GITHUB_BASE_REF"

          if [[ "$target_branch" != "$branch" ]] && ! [[ "$GITHUB_BASE_REF" == "master" && "$branch" == "" ]]; then
              echo "::error::PR is opened against the $GITHUB_BASE_REF branch, but its title suggests otherwise."
              exit 1
          fi