name: Benchmark

on:
  push:
    branches:
      - master
    paths:
      - 'internal/**/*.go'
      - 'go.mod'
      - 'go.sum'
  pull_request:
    branches:
      - master
    paths:
      - 'internal/**/*.go'
      - 'go.mod'
      - 'go.sum'
  workflow_dispatch:

permissions:
  contents: write

jobs:
  benchmark:
    name: Run Benchmarks
    runs-on: ubuntu-latest
    timeout-minutes: 30

    steps:
      - name: Checkout code
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Setup Go
        uses: actions/setup-go@v5
        with:
          go-version-file: 'go.mod'
          cache: true

      - name: Install benchstat
        run: go install golang.org/x/perf/cmd/benchstat@latest

      - name: Download dependencies
        run: go mod download

      - name: Fetch baseline benchmark
        run: |
          if git show origin/master:benchmark-baseline.txt >/dev/null 2>&1; then
            git show origin/master:benchmark-baseline.txt > benchmark-baseline.txt
            echo "baseline_found=true" >> $GITHUB_ENV
          else
            echo "baseline_found=false" >> $GITHUB_ENV
          fi

      - name: Run benchmarks
        run: |
          go test -bench=. -benchmem -count=10 ./... 2>&1 | tee benchmark-current.txt

      - name: Compare benchmarks
        if: env.baseline_found == 'true'
        run: |
          benchstat benchmark-baseline.txt benchmark-current.txt > benchmark-comparison.txt
          cat benchmark-comparison.txt

      - name: Check for regressions
        if: env.baseline_found == 'true'
        run: |
          if command -v python3 >/dev/null 2>&1; then
            benchstat benchmark-baseline.txt benchmark-current.txt | \
              python3 scripts/check_regression.py - \
              --config .benchmark-thresholds.yaml \
              --environment ci \
              || echo "regression_detected=$?" >> $GITHUB_OUTPUT
          else
            echo "Python3 not available, skipping regression check"
          fi
        id: regression_check

      - name: Save current benchmark as baseline
        if: github.ref == 'refs/heads/master'
        run: |
          cp benchmark-current.txt benchmark-baseline.txt
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"
          git add benchmark-baseline.txt || true
          git commit -m "chore(bench): update benchmark baseline" || true
          git push || true

      - name: Upload benchmark results
        uses: actions/upload-artifact@v4
        with:
          name: benchmark-results
          path: |
            benchmark-current.txt
            benchmark-baseline.txt
            benchmark-comparison.txt
          retention-days: 30

      - name: Fail on regression
        if: steps.regression_check.outputs.regression_detected == '2'
        run: |
          echo "::error::BLOCK level performance regression detected"
          exit 2