benchmarks.yml

name: Benchmarks

# Run on every push to main only — benchmarks are expensive and comparing
# against a moving baseline in PRs adds noise.  Regressions surface on the
# next main push and are reported as PR comments on the triggering merge.

on:
  push:
    branches: [main]

env:
  CARGO_TERM_COLOR: always
  TUITBOT_SKIP_DASHBOARD_BUILD: '1'
  # benchmark-action/github-action-benchmark still declares node20 upstream.
  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: 'true'

jobs:
  # ─────────────────────────────────────────────────────────────────────────
  # Rust benchmarks — cargo criterion (scoring + content hot paths)
  # ─────────────────────────────────────────────────────────────────────────
  rust-benchmarks:
    name: Rust benchmarks (criterion)
    runs-on: ubuntu-latest
    permissions:
      contents: write   # required by benchmark-action to push to gh-pages

    steps:
      - uses: actions/checkout@v6

      - name: Install Rust toolchain
        uses: dtolnay/rust-toolchain@stable

      - name: Cache cargo registry + build artifacts
        uses: actions/cache@v5
        with:
          path: |
            ~/.cargo/registry
            ~/.cargo/git
            target
          key: ${{ runner.os }}-cargo-bench-${{ hashFiles('**/Cargo.lock') }}
          restore-keys: ${{ runner.os }}-cargo-bench-

      - name: Run benchmarks
        run: |
          mkdir -p bench-output
          cargo bench -p tuitbot-core \
            2>&1 | tee bench-output/raw.txt

      - name: Convert criterion output to JSON
        # criterion 0.8 outputs: <name>  time:  [low median high]
        # Convert to customSmallerIsBetter JSON for benchmark-action.
        run: |
          grep 'time:' bench-output/raw.txt | awk '{
            name = $1
            # fields: $3=low $4=low_unit $5=median $6=med_unit $7=high $8=high_unit
            # strip trailing ] from high_unit
            gsub(/\]/, "", $8)
            med = $5; unit = $6
            printf "{\"name\": \"%s\", \"unit\": \"%s\", \"value\": %s}\n", name, unit, med
          }' | jq -s '.' > bench-output/rust.json

      - name: Upload criterion HTML report (artifact)
        uses: actions/upload-artifact@v7
        with:
          name: criterion-report
          path: target/criterion/
          retention-days: 30

      - name: Clean working tree before gh-pages push
        run: git checkout -- .

      - name: Store benchmark results + alert on regression
        uses: benchmark-action/github-action-benchmark@v1
        with:
          name: Rust Benchmarks
          tool: customSmallerIsBetter
          output-file-path: bench-output/rust.json
          # Alert when a benchmark regresses by more than 10% vs stored baseline.
          alert-threshold: '110%'
          comment-on-alert: true
          fail-on-alert: false          # Warn, don't hard-fail (flaky hardware)
          github-token: ${{ secrets.GITHUB_TOKEN }}
          # Persist results to gh-pages branch under benchmarks/rust/
          auto-push: true
          benchmark-data-dir-path: benchmarks/rust

  # ─────────────────────────────────────────────────────────────────────────
  # Frontend bundle size — track JS/CSS growth commit-to-commit
  # ─────────────────────────────────────────────────────────────────────────
  bundle-size:
    name: Frontend bundle size
    runs-on: ubuntu-latest
    permissions:
      contents: write

    steps:
      - uses: actions/checkout@v6

      - name: Setup Node.js
        uses: actions/setup-node@v6
        with:
          node-version: '20'
          cache: 'npm'
          cache-dependency-path: dashboard/package-lock.json

      - name: Install dependencies
        run: cd dashboard && npm ci

      - name: Build dashboard
        run: cd dashboard && npm run build

      - name: Measure bundle sizes
        id: sizes
        run: |
          set -euo pipefail

          js_bytes=$(find dashboard/build -name "*.js" -not -name "*.map" \
            | xargs wc -c 2>/dev/null | awk 'END {print $1+0}')
          css_bytes=$(find dashboard/build -name "*.css" -not -name "*.map" \
            | xargs wc -c 2>/dev/null | awk 'END {print $1+0}')
          total_bytes=$(du -sb dashboard/build | awk '{print $1}')

          echo "js_bytes=$js_bytes"
          echo "css_bytes=$css_bytes"
          echo "total_bytes=$total_bytes"

          # github-action-benchmark customSmallerIsBetter format
          cat > bundle-size.json <<EOF
          [
            { "name": "JS (minified)", "unit": "bytes", "value": $js_bytes },
            { "name": "CSS (minified)", "unit": "bytes", "value": $css_bytes },
            { "name": "Total build", "unit": "bytes", "value": $total_bytes }
          ]
          EOF

          echo "=== Bundle sizes ==="
          echo "  JS:    $(numfmt --to=iec $js_bytes)"
          echo "  CSS:   $(numfmt --to=iec $css_bytes)"
          echo "  Total: $(numfmt --to=iec $total_bytes)"

      - name: Upload bundle-size JSON (artifact)
        uses: actions/upload-artifact@v7
        with:
          name: bundle-size
          path: bundle-size.json
          retention-days: 90

      - name: Store bundle size + alert on growth > 5%
        uses: benchmark-action/github-action-benchmark@v1
        with:
          name: Frontend Bundle Size
          tool: customSmallerIsBetter
          output-file-path: bundle-size.json
          # Alert when any metric grows more than 5% vs stored baseline.
          alert-threshold: '105%'
          comment-on-alert: true
          fail-on-alert: false
          github-token: ${{ secrets.GITHUB_TOKEN }}
          auto-push: true
          benchmark-data-dir-path: benchmarks/bundle-size