name: Performance Regression Detection

on:
  pull_request:
    branches: [ main ]
  push:
    branches: [ main ]
  # Allow manual triggering
  workflow_dispatch:

env:
  CARGO_TERM_COLOR: always
  RUST_BACKTRACE: 1

jobs:
  benchmark:
    name: Run Performance Benchmarks
    runs-on: ubuntu-latest
    
    steps:
    - name: Checkout code
      uses: actions/checkout@v4
      with:
        fetch-depth: 0  # Need full history for comparison
    
    - name: Install Rust toolchain
      uses: dtolnay/rust-toolchain@stable
      with:
        components: rustfmt, clippy
    
    - name: Cache cargo registry
      uses: actions/cache@v4
      with:
        path: ~/.cargo/registry
        key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
        restore-keys: |
          ${{ runner.os }}-cargo-registry-
    
    - name: Cache cargo index
      uses: actions/cache@v4
      with:
        path: ~/.cargo/git
        key: ${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
        restore-keys: |
          ${{ runner.os }}-cargo-index-
    
    - name: Cache target directory
      uses: actions/cache@v4
      with:
        path: target
        key: ${{ runner.os }}-target-bench-${{ hashFiles('**/Cargo.lock') }}
        restore-keys: |
          ${{ runner.os }}-target-bench-
    
    - name: Install criterion dependencies
      run: |
        sudo apt-get update
        sudo apt-get install -y gnuplot
    
    - name: Run benchmarks
      run: |
        cargo bench --workspace --all-features -- --save-baseline current
    
    - name: Download previous baseline
      if: github.event_name == 'pull_request'
      continue-on-error: true
      uses: actions/download-artifact@v4
      with:
        name: benchmark-baseline
        path: target/criterion
    
    - name: Compare with baseline
      if: github.event_name == 'pull_request'
      run: |
        cargo bench --workspace --all-features -- --baseline main --load-baseline current
    
    - name: Upload benchmark results
      if: github.event_name == 'push' && github.ref == 'refs/heads/main'
      uses: actions/upload-artifact@v4
      with:
        name: benchmark-baseline
        path: target/criterion
        retention-days: 90
    
    - name: Generate performance report
      run: |
        echo "# Performance Benchmark Results" > benchmark_report.md
        echo "" >> benchmark_report.md
        echo "## Summary" >> benchmark_report.md
        echo "" >> benchmark_report.md
        
        # Trading Latency
        echo "### Trading Latency Benchmarks" >> benchmark_report.md
        echo "- Order creation: See criterion HTML reports" >> benchmark_report.md
        echo "- Market event processing: See criterion HTML reports" >> benchmark_report.md
        echo "- Position calculations: See criterion HTML reports" >> benchmark_report.md
        echo "" >> benchmark_report.md
        
        # Database Performance
        echo "### Database Performance Benchmarks" >> benchmark_report.md
        echo "- Connection acquisition: See criterion HTML reports" >> benchmark_report.md
        echo "- Query execution: See criterion HTML reports" >> benchmark_report.md
        echo "- Pool saturation: See criterion HTML reports" >> benchmark_report.md
        echo "" >> benchmark_report.md
        
        # Streaming Throughput
        echo "### Streaming Throughput Benchmarks" >> benchmark_report.md
        echo "- Message throughput: See criterion HTML reports" >> benchmark_report.md
        echo "- Stream latency: See criterion HTML reports" >> benchmark_report.md
        echo "- Backpressure handling: See criterion HTML reports" >> benchmark_report.md
        echo "" >> benchmark_report.md
        
        # Metrics Overhead
        echo "### Metrics Overhead Benchmarks" >> benchmark_report.md
        echo "- Observation overhead: See criterion HTML reports" >> benchmark_report.md
        echo "- Registry lookup: See criterion HTML reports" >> benchmark_report.md
        echo "- Label cardinality: See criterion HTML reports" >> benchmark_report.md
        echo "" >> benchmark_report.md
        
        # End-to-End
        echo "### End-to-End Pipeline Benchmarks" >> benchmark_report.md
        echo "- Full pipeline latency: See criterion HTML reports" >> benchmark_report.md
        echo "- Pipeline under load: See criterion HTML reports" >> benchmark_report.md
        echo "- Risk validation overhead: See criterion HTML reports" >> benchmark_report.md
        echo "" >> benchmark_report.md
        
        echo "## Performance Targets" >> benchmark_report.md
        echo "" >> benchmark_report.md
        echo "| Component | Target | Status |" >> benchmark_report.md
        echo "|-----------|--------|--------|" >> benchmark_report.md
        echo "| Order Processing | <50μs p99 | ⏳ See reports |" >> benchmark_report.md
        echo "| Risk Validation | <5μs p99 | ⏳ See reports |" >> benchmark_report.md
        echo "| Market Data Processing | <10μs p99 | ⏳ See reports |" >> benchmark_report.md
        echo "| Event Queue | <1μs p99 | ⏳ See reports |" >> benchmark_report.md
        echo "| DB Connection | <5ms p99 | ⏳ See reports |" >> benchmark_report.md
        echo "| gRPC Streaming | >10K msg/sec | ⏳ See reports |" >> benchmark_report.md
        echo "| Metrics Collection | <5μs | ⏳ See reports |" >> benchmark_report.md
        echo "| End-to-End Pipeline | <200μs p99 | ⏳ See reports |" >> benchmark_report.md
        echo "" >> benchmark_report.md
        
        echo "Detailed HTML reports available in CI artifacts under \`target/criterion\`" >> benchmark_report.md
    
    - name: Upload performance report
      uses: actions/upload-artifact@v4
      with:
        name: performance-report
        path: benchmark_report.md
        retention-days: 30
    
    - name: Comment PR with results
      if: github.event_name == 'pull_request'
      uses: actions/github-script@v7
      with:
        script: |
          const fs = require('fs');
          const report = fs.readFileSync('benchmark_report.md', 'utf8');
          
          github.rest.issues.createComment({
            issue_number: context.issue.number,
            owner: context.repo.owner,
            repo: context.repo.repo,
            body: report
          });

  regression-check:
    name: Check for Performance Regressions
    runs-on: ubuntu-latest
    needs: benchmark
    if: github.event_name == 'pull_request'
    
    steps:
    - name: Checkout code
      uses: actions/checkout@v4
    
    - name: Download benchmark results
      uses: actions/download-artifact@v4
      with:
        name: benchmark-baseline
        path: current-results
    
    - name: Analyze regressions
      run: |
        echo "Checking for performance regressions..."
        echo "⚠️  Manual review of criterion HTML reports required"
        echo "📊 Check for >10% performance degradation in critical paths"
        echo ""
        echo "Critical paths to review:"
        echo "- Order processing latency"
        echo "- Risk validation overhead"  
        echo "- Event queue operations"
        echo "- Database connection acquisition"
        echo "- gRPC message throughput"
        echo ""
        echo "If regressions found, investigate before merging!"