name: Benchmark

on:
  pull_request:
    branches: [master]
  push:
    branches: [master]
  workflow_dispatch:

# Cancel in-flight benchmark runs for the same PR/branch so only the latest commit is benchmarked.
concurrency:
  group: benchmark-${{ github.ref }}
  cancel-in-progress: true

jobs:
  benchmark:
    name: Run CIBenchmark
    runs-on: ubuntu-latest

    permissions:
      contents: read

    steps:
      - uses: actions/checkout@v4

      - name: Set up JDK 21
        uses: actions/setup-java@v4
        with:
          java-version: "21"
          distribution: temurin

      - name: Set up Gradle
        uses: gradle/actions/setup-gradle@v4

      - name: Run CIBenchmark
        run: >
          ./gradlew :opendc-experiments:opendc-experiments-base:jmh
          -PjmhIncludes=.*CIBenchmark.*

      - name: Upload benchmark results
        uses: actions/upload-artifact@v4
        with:
          name: benchmark-results
          path: opendc-experiments/opendc-experiments-base/build/results/jmh/results.json
          retention-days: 7

      # Store the PR number so the comment workflow (which runs with write permissions)
      # knows which PR to comment on. Only needed for pull_request runs.
      - name: Save PR number
        if: github.event_name == 'pull_request'
        run: echo "${{ github.event.pull_request.number }}" > pr-number.txt

      - name: Upload PR number
        if: github.event_name == 'pull_request'
        uses: actions/upload-artifact@v4
        with:
          name: pr-number
          path: pr-number.txt
          retention-days: 1

  # ── Master push: store results on the benchmark-data branch ──────────────────
  store-results:
    name: Store benchmark results
    if: github.event_name == 'push'
    needs: benchmark
    runs-on: ubuntu-latest

    permissions:
      contents: write

    steps:
      - uses: actions/checkout@v4

      - name: Download current results
        uses: actions/download-artifact@v4
        with:
          name: benchmark-results
          path: current-results

      - name: Check out or create benchmark-data branch
        run: |
          git fetch origin benchmark-data 2>/dev/null || true
          if git rev-parse --verify origin/benchmark-data 2>/dev/null; then
            git worktree add benchmark-data-dir origin/benchmark-data
          else
            git worktree add --orphan -b benchmark-data benchmark-data-dir
          fi

      - name: Update history
        run: |
          python .github/scripts/update_history.py \
            current-results/results.json \
            benchmark-data-dir \
            "${{ github.sha }}"

      - name: Commit and push
        run: |
          git -C benchmark-data-dir config user.name  "github-actions[bot]"
          git -C benchmark-data-dir config user.email "github-actions[bot]@users.noreply.github.com"
          git -C benchmark-data-dir add benchmark-history.json
          git -C benchmark-data-dir commit \
            -m "chore: benchmark results for ${{ github.sha }}"
          git -C benchmark-data-dir push origin HEAD:benchmark-data