name: Run benchmarks
on:
  pull_request:
    branches: [master]

permissions:
  contents: read

jobs:
  benchmark:
    runs-on: ubuntu-latest
    steps:
    # Base for comparison is master branch.
    - name: Checkout code
      uses: actions/checkout@v4.2.2
      with:
        ref: master
    - name: Install Go
      uses: actions/setup-go@v5.2.0
      with:
        go-version-file: 'go.mod'

    # 30 runs with 100ms benchtime seems to result in acceptable p-values
    # When I tried with count=10, it would be unreliable because of the actions
    # runner is in a shared environment and CPU and mem would be affected by others. (or so I think)
    - run: go test -run=none -bench=. -count=30 -benchtime=100ms -timeout=20m > /tmp/prev
    - name: Checkout code
      uses: actions/checkout@v4.2.2
    - run: go test -run=none -bench=. -count=30 -benchtime=100ms -timeout=20m > /tmp/curr

    - run: go install golang.org/x/perf/cmd/benchstat@latest
    - run: benchstat /tmp/prev /tmp/curr