name: PR build gate

on:
  workflow_call:
    outputs:
      run:
        description: Whether the push-triggered build should run
        value: ${{ jobs.gate.outputs.run }}

jobs:
  # Skip push builds for branches whose open PR (base master/release/*) already builds
  # them via the pull_request trigger. Pushes to master/release/* always build (they
  # may publish packages, and no PR of theirs may suppress that).
  gate:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: read
    outputs:
      run: ${{ steps.check.outputs.run }}
    steps:
    - id: check
      env:
        GH_TOKEN: ${{ github.token }}
      run: |
        prs=0
        case "$GITHUB_EVENT_NAME/$GITHUB_REF_NAME" in
          push/master|push/release/*) ;;
          push/*) prs=$(gh api -X GET "repos/$GITHUB_REPOSITORY/pulls" -f state=open \
            -f head="$GITHUB_REPOSITORY_OWNER:$GITHUB_REF_NAME" \
            --jq 'map(select(.base.ref == "master" or (.base.ref | startswith("release/")))) | length') ;;
        esac
        echo "run=$([ "$prs" = 0 ] && echo true || echo false)" >> "$GITHUB_OUTPUT"