name: "Cancel runs of closed PRs"

# Merging or closing a PR leaves its pull_request runs going: concurrency
# groups cancel a run only when a newer push arrives. pull_request_target gives
# this job a token that can cancel runs, fork PRs included. It checks out and
# runs no PR code.
on:
  pull_request_target:
    types: [closed]

permissions:
  actions: write
  pull-requests: read

jobs:
  cancel:
    runs-on: ubuntu-latest
    timeout-minutes: 5
    steps:
      - name: Cancel the PR's queued and running pull_request runs
        env:
          GH_TOKEN: ${{ github.token }}
          GH_REPO: ${{ github.repository }}
          PR: ${{ github.event.pull_request.number }}
          HEAD_REF: ${{ github.event.pull_request.head.ref }}
        run: |
          set -euo pipefail
          # Match the PR's own commits: forks reuse branch names such as master.
          shas=$(gh api --paginate "repos/$GH_REPO/pulls/$PR/commits" --jq '.[].sha')
          for status in queued in_progress waiting pending requested; do
            gh run list --branch "$HEAD_REF" --event pull_request --status "$status" \
              --limit 200 --json databaseId,headSha --jq '.[] | "\(.databaseId) \(.headSha)"'
          done | while read -r id sha; do
            grep -qx "$sha" <<<"$shas" || continue
            echo "cancel run $id at $sha"
            gh run cancel "$id" || true
          done