name: Unstick auto-merge pull requests

on:
  schedule:
    # Poll while the PRs from the other scheduled workflows that write to master are opening and merging.
    - cron: '45 18-23 * * 1-4'
  workflow_dispatch:

concurrency:
  group: pull-request-unstick

jobs:
  unstick:
    # Prevent this workflow from running elsewhere.
    if: github.repository_owner == 'php-curl-class'

    runs-on: ubuntu-latest
    steps:
      - name: Update oldest pull request held back only by being behind master
        run: |
          set -eo pipefail

          # List the PRs opened by the scheduled update workflows.
          pull_requests="$(
              gh pr list \
                  --author="php-curl-class-helper" \
                  --json="autoMergeRequest,createdAt,mergeStateStatus,number,reviewDecision,statusCheckRollup" \
                  --repo="${GITHUB_REPOSITORY}" \
                  --state="open"
          )"

          # Count a PR with no checks yet as running. Checks take a few seconds to register after a push.
          running="$(
              echo "${pull_requests}" |
                  jq --compact-output '[
                      .[] |
                      select(.autoMergeRequest != null) |
                      select(
                          (.statusCheckRollup | length) == 0 or
                          any(
                              .statusCheckRollup[];
                              if .__typename == "CheckRun" then
                                  .status != "COMPLETED"
                              else
                                  .state == "PENDING" or .state == "EXPECTED"
                              end
                          )
                      ) |
                      .number
                  ]'
          )"
          echo "Pull requests with checks running: ${running}"

          # Update one PR at a time so a second one isn't left behind when the first merges.
          if [[ "${running}" != "[]" ]]; then
              exit 0
          fi

          pick="$(
              echo "${pull_requests}" |
                  jq '[
                      .[] |
                      select(.autoMergeRequest != null) |
                      select(.reviewDecision == "APPROVED") |
                      # TODO: Confirm GitHub reports BEHIND, not BLOCKED, for a green, approved PR behind master.
                      select(.mergeStateStatus == "BEHIND") |
                      select(
                          all(
                              .statusCheckRollup[];
                              if .__typename == "CheckRun" then
                                  .conclusion == "SUCCESS" or .conclusion == "SKIPPED" or .conclusion == "NEUTRAL"
                              else
                                  .state == "SUCCESS"
                              end
                          )
                      )
                  ] |
                  sort_by(.createdAt) |
                  first |
                  .number // empty'
          )"
          echo "Pull request to update: ${pick:-none}"

          if [[ -n "${pick}" ]]; then
              # Use the bot token so the new merge commit starts CI. GITHUB_TOKEN pushes don't trigger workflows.
              # TODO: Confirm the bot token can update branches on the php-curl-class-helper fork.
              GH_TOKEN="${BOT_TOKEN}" \
              gh pr update-branch \
                  --repo="${GITHUB_REPOSITORY}" \
                  "${pick}"
          fi
        env:
          BOT_TOKEN: ${{ secrets.PHP_CURL_CLASS_BOT_TOKEN }}
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}