name: Enable auto-merge

on:
  pull_request:
    types: [opened, ready_for_review, reopened, synchronize]
    branches: [main]
  pull_request_review:
    types: [submitted]

permissions:
  contents: read

jobs:
  enable:
    if: >-
      github.event.pull_request.draft == false
      && github.event.pull_request.base.ref == 'main'
      && github.event.pull_request.head.repo.full_name == github.repository
      && github.event.pull_request.user.login != 'dependabot[bot]'
      && github.event.pull_request.user.login != 'renovate[bot]'
      && (github.event_name != 'pull_request_review' || github.event.review.state == 'approved')
    runs-on: ubuntu-latest
    concurrency:
      group: enable-auto-merge-${{ github.event.pull_request.number }}
      cancel-in-progress: true
    steps:
      - name: Mint seahaven-bot token
        id: app-token
        uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
        with:
          app-id: ${{ secrets.SEAHAVEN_BOT_APP_ID }}
          private-key: ${{ secrets.SEAHAVEN_BOT_PRIVATE_KEY }}
          owner: Sea-Haven-Industries
          repositories: ${{ github.event.repository.name }}

      - name: Enqueue or arm auto-merge
        env:
          GH_TOKEN: ${{ steps.app-token.outputs.token }}
          PR: ${{ github.event.pull_request.number }}
          REPO: ${{ github.repository }}
          PR_NODE_ID: ${{ github.event.pull_request.node_id }}
        run: |
          set -euo pipefail
          BOT_LOGIN='seahaven-bot[bot]'
          GQL_STATE="query(\$id:ID!) { node(id:\$id) { ... on PullRequest { isInMergeQueue autoMergeRequest { mergeMethod enabledBy { login } } } } }"

          pr_json() {
            gh api graphql -f query="$GQL_STATE" -f id="$PR_NODE_ID" "$@"
          }

          in_queue() {
            pr_json --jq '.data.node.isInMergeQueue'
          }

          enabled_by() {
            pr_json --jq '.data.node.autoMergeRequest.enabledBy.login // ""'
          }

          armed_as_bot() {
            by="$(enabled_by)"
            [ "$by" = "$BOT_LOGIN" ] || [ "$by" = "seahaven-bot" ]
          }

          if [ "$(in_queue)" = "true" ]; then
            echo "already in merge queue"
            exit 0
          fi

          set +e
          out="$(gh api graphql -f query="mutation(\$id:ID!) { enqueuePullRequest(input:{pullRequestId:\$id}) { mergeQueueEntry { state } } }" -f id="$PR_NODE_ID" 2>&1)"
          status=$?
          set -e
          if [ "$status" -eq 0 ]; then
            printf '%s\n' "$out"
            exit 0
          fi
          echo "$out"

          if [ "$(in_queue)" = "true" ]; then
            echo "in merge queue"
            exit 0
          fi
          if armed_as_bot; then
            echo "auto-merge already armed as seahaven-bot"
            exit 0
          fi

          # Re-arm as seahaven-bot. A leftover GITHUB_TOKEN auto-merge would
          # enqueue without starting merge_group. Do not treat an unknown
          # autoMergeRequest as success.
          by="$(enabled_by)"
          if [ -n "$by" ]; then
            set +e
            disable_out="$(gh pr merge "$PR" --repo "$REPO" --disable-auto 2>&1)"
            set -e
            echo "$disable_out"
            by="$(enabled_by)"
            if [ -n "$by" ]; then
              echo "failed to disable auto-merge (enabledBy=$by)"
              exit 1
            fi
          fi

          set +e
          arm_out="$(gh pr merge "$PR" --repo "$REPO" --auto 2>&1)"
          arm_status=$?
          set -e
          printf '%s\n' "$arm_out"

          if [ "$(in_queue)" = "true" ]; then
            echo "in merge queue"
            exit 0
          fi
          if armed_as_bot; then
            echo "auto-merge armed as seahaven-bot"
            exit 0
          fi
          by="$(enabled_by)"
          echo "auto-merge not armed as seahaven-bot (enabledBy=${by:-none} arm_status=$arm_status)"
          exit 1