mutation.yml

name: "Pull Request Mutation"

run-name: "Pull Request Mutation: ${{ github.event.workflow_run.head_branch }}"

on:
  workflow_run:
    workflows:
      - Build
    types:
      - completed

concurrency:
  group: "mutation-${{ github.event.workflow_run.head_branch }}"
  cancel-in-progress: true

permissions:
  contents: read
  packages: read
  statuses: write

jobs:
  mutate:
    runs-on: ubuntu-latest
    if: github.event.workflow_run.event == 'pull_request' && github.event.workflow_run.conclusion == 'failure' && (!contains(fromJSON('["main", "dev"]'), github.event.workflow_run.head_branch) || github.event.workflow_run.head_repository.fork)
    steps:
      - name: Download artifacts
        id: download-artifacts
        uses: dawidd6/action-download-artifact@v2
        with:
          github_token: ${{secrets.GITHUB_TOKEN}}
          run_id: ${{ github.event.workflow_run.id }}
          name: .+\.diff$
          name_is_regexp: true
          if_no_artifact_found: ignore
          path: patches

      - uses: marocchino/action-workflow_run-status@54b6e87d6cb552fc5f36dbe9a722a6048725917a
        if: steps.download-artifacts.outputs.found_artifact == 'true'
        with:
          github_token: ${{secrets.GITHUB_TOKEN}}

      - name: Token check
        if: steps.download-artifacts.outputs.found_artifact == 'true'
        run: |
          if ${{ secrets.MUTATION_TOKEN && 'true' || 'false' }}; then
            echo "Token available, enabling self mutation"
            exit 0
          else
            echo "Add a MUTATION_TOKEN repository secret with a personal access token to enable self mutation.
            It requires private repo read/write permissions." >> $GITHUB_STEP_SUMMARY
            exit 1
          fi

      - name: Disable Git Hooks
        if: steps.download-artifacts.outputs.found_artifact == 'true'
        run: |
          git config --global core.hooksPath /dev/null

      - name: Update PR Branch
        uses: actions/github-script@v6
        if: github.event.workflow_run.event == 'pull_request' && steps.download-artifacts.outputs.found_artifact == 'true'
        with:
          github-token: ${{ secrets.MUTATION_TOKEN }}
          script: |
            // use API to get the PR data since we can't rely on the context across forks
            const pulls = await github.rest.pulls.list({
              per_page: 1,
              owner: context.repo.owner,
              repo: context.repo.repo,
              head: `${context.payload.workflow_run.head_repository.full_name}:${context.payload.workflow_run.head_branch}`
            });

            const prContextData = pulls.data[0];
            const prNumber = prContextData.number;
            const originalSha = prContextData.head.sha;

            try {
              console.log("Updating PR branch");
              await github.rest.pulls.updateBranch({
                owner: context.repo.owner,
                repo: context.repo.repo,
                pull_number: prNumber
              });
              console.log("PR branch updated");

              let updatedSha = originalSha;
              let retries = 0;
              const MAX_RETRIES = 10;
              while (updatedSha == originalSha && retries++ < MAX_RETRIES) {
                console.log(`Waiting for PR branch to update (attempt ${retries}/${MAX_RETRIES})`);
                
                await new Promise(r => setTimeout(r, 500));
                const updatedPR = await github.rest.pulls.get({
                  owner: context.repo.owner,
                  repo: context.repo.repo,
                  pull_number: prNumber
                });
                updatedSha = updatedPR.data.head.sha;
              }
            } catch (error) {
              // The branch is already up to date or can't otherwise be updated
              // That's fine, we tried our best
              console.warn(error);
            }

      - name: Checkout Workflow Branch
        if: steps.download-artifacts.outputs.found_artifact == 'true'
        uses: actions/checkout@v3
        with:
          token: ${{ secrets.MUTATION_TOKEN }}
          ref: ${{ github.event.workflow_run.head_branch }}
          repository: ${{ github.event.workflow_run.head_repository.full_name }}
          path: repo

      - id: self_mutation
        if: steps.download-artifacts.outputs.found_artifact == 'true'
        name: Apply downloaded patches
        working-directory: repo
        env:
          HEAD_REF: ${{ github.event.workflow_run.head_branch }}
        run: |
          git config user.name "monada-bot[bot]"
          git config user.email "monabot@monada.co"

          for f in $(find ../patches/*.diff/*.diff); do
            echo "Applying $f"
            git apply --binary $f
            if [ $? -eq 0 ]; then
              git add --all
              git commit -s -m "chore: self mutation ($(basename $f))"
              echo "Patch applied successfully"
              rm $f
            else
              echo "Patch failed to apply"
              cat $f
              exit 1
            fi
          done

          git push origin HEAD:$HEAD_REF

      - name: Add label to block auto merge
        uses: actions/github-script@v6
        if: github.event.workflow_run.event == 'pull_request' && steps.download-artifacts.outputs.found_artifact == 'true'
        with:
          github-token: ${{ secrets.MUTATION_TOKEN }}
          script: |
            // use API to get the PR number since we can't rely on the context across forks
            const pulls = await github.rest.pulls.list({
              per_page: 1,
              owner: context.repo.owner,
              repo: context.repo.repo,
              head: `${context.payload.workflow_run.head_repository.full_name}:${context.payload.workflow_run.head_branch}`
            });
            const prNumber = pulls.data[0].number;
            const labels = ["⚠️ pr/review-mutation"];

            await github.rest.issues.addLabels({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: prNumber,
              labels: labels
            });