name: "⚡ Agent: Performance"

on:
  pull_request:
    types: [opened, synchronize, reopened]

permissions:
  contents: read
  pull-requests: write

jobs:
  performance:
    name: Performance Agent
    runs-on: ubuntu-latest

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

      - name: Get PR stats
        id: pr-stats
        run: |
          # Get diff stats
          ADDITIONS=$(git diff --shortstat origin/${{ github.base_ref }}...HEAD | grep -oP '\d+(?= insertion)' || echo 0)
          DELETIONS=$(git diff --shortstat origin/${{ github.base_ref }}...HEAD | grep -oP '\d+(?= deletion)' || echo 0)
          FILES_CHANGED=$(git diff --name-only origin/${{ github.base_ref }}...HEAD | wc -l)

          echo "additions=$ADDITIONS" >> $GITHUB_OUTPUT
          echo "deletions=$DELETIONS" >> $GITHUB_OUTPUT
          echo "files_changed=$FILES_CHANGED" >> $GITHUB_OUTPUT

      - name: Analyze bundle size impact
        id: bundle
        run: |
          # Check if package.json exists and get dependencies
          if [ -f "package.json" ]; then
            DEPS=$(cat package.json | jq '.dependencies | length // 0')
            DEV_DEPS=$(cat package.json | jq '.devDependencies | length // 0')
            echo "deps=$DEPS" >> $GITHUB_OUTPUT
            echo "dev_deps=$DEV_DEPS" >> $GITHUB_OUTPUT
          else
            echo "deps=0" >> $GITHUB_OUTPUT
            echo "dev_deps=0" >> $GITHUB_OUTPUT
          fi

      - name: Get changed files
        id: changed-files
        uses: tj-actions/changed-files@v44

      - name: Performance analysis
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const path = require('path');

            const changedFiles = '${{ steps.changed-files.outputs.all_changed_files }}'.split(' ').filter(f => f);
            const additions = parseInt('${{ steps.pr-stats.outputs.additions }}') || 0;
            const deletions = parseInt('${{ steps.pr-stats.outputs.deletions }}') || 0;
            const filesChanged = parseInt('${{ steps.pr-stats.outputs.files_changed }}') || 0;
            const deps = parseInt('${{ steps.bundle.outputs.deps }}') || 0;
            const devDeps = parseInt('${{ steps.bundle.outputs.dev_deps }}') || 0;

            let report = '## ⚡ Performance Agent Report\n\n';
            let warnings = [];
            let suggestions = [];

            // PR Size Analysis
            report += '### 📦 PR Size Analysis\n\n';
            report += `| Metric | Value |\n`;
            report += `|--------|-------|\n`;
            report += `| Files changed | ${filesChanged} |\n`;
            report += `| Lines added | +${additions} |\n`;
            report += `| Lines removed | -${deletions} |\n`;
            report += `| Net change | ${additions - deletions > 0 ? '+' : ''}${additions - deletions} |\n`;
            report += `| Dependencies | ${deps} |\n`;
            report += `| Dev Dependencies | ${devDeps} |\n\n`;

            // PR Size Rating
            const totalChanges = additions + deletions;
            let sizeRating = '';
            if (totalChanges < 100) {
              sizeRating = '🟢 Small PR - Easy to review';
            } else if (totalChanges < 500) {
              sizeRating = '🟡 Medium PR - Moderate review effort';
            } else if (totalChanges < 1000) {
              sizeRating = '🟠 Large PR - Consider breaking down';
              warnings.push('Large PR detected. Consider splitting into smaller PRs for easier review.');
            } else {
              sizeRating = '🔴 Very Large PR - Difficult to review';
              warnings.push('Very large PR! This will be difficult to review. Strongly consider breaking into smaller PRs.');
            }
            report += `**Size Rating:** ${sizeRating}\n\n`;

            // Performance patterns check
            report += '### 🔍 Performance Patterns\n\n';

            const perfPatterns = [
              { pattern: /\.forEach\s*\(/g, msg: 'forEach loop - consider for...of for better performance', severity: 'info' },
              { pattern: /JSON\.parse\s*\(.*JSON\.stringify/g, msg: 'Deep clone via JSON - consider structuredClone()', severity: 'warning' },
              { pattern: /new\s+RegExp\s*\(/g, msg: 'Dynamic RegExp creation - consider caching if used repeatedly', severity: 'info' },
              { pattern: /document\.querySelector.*loop|for.*querySelector/gi, msg: 'DOM query in loop - cache selectors outside loop', severity: 'warning' },
              { pattern: /\bawait\b.*\bawait\b.*\bawait\b/g, msg: 'Multiple sequential awaits - consider Promise.all()', severity: 'warning' },
              { pattern: /\.filter\(.*\)\.map\(/g, msg: 'filter().map() chain - consider reduce() or single pass', severity: 'info' },
              { pattern: /useEffect.*\[\s*\]/g, msg: 'Empty dependency array - ensure this is intentional', severity: 'info' },
              { pattern: /new\s+Date\(\).*loop|for.*new\s+Date/gi, msg: 'Date creation in loop - cache Date object', severity: 'warning' },
            ];

            let patternFindings = [];

            for (const file of changedFiles) {
              try {
                const content = fs.readFileSync(file, 'utf8');

                for (const { pattern, msg, severity } of perfPatterns) {
                  if (pattern.test(content)) {
                    patternFindings.push({ file, msg, severity });
                  }
                }

                // Check file size
                const lines = content.split('\n').length;
                if (lines > 500) {
                  warnings.push(`\`${file}\` has ${lines} lines - consider splitting into smaller modules`);
                }
              } catch (e) {}
            }

            if (patternFindings.length > 0) {
              patternFindings.slice(0, 10).forEach(({ file, msg, severity }) => {
                const icon = severity === 'warning' ? '⚠️' : 'ℹ️';
                report += `- ${icon} **${file}**: ${msg}\n`;
              });
              if (patternFindings.length > 10) {
                report += `\n*...and ${patternFindings.length - 10} more findings*\n`;
              }
            } else {
              report += '✅ No performance anti-patterns detected!\n';
            }
            report += '\n';

            // Warnings
            if (warnings.length > 0) {
              report += '### ⚠️ Warnings\n\n';
              warnings.forEach(w => report += `- ${w}\n`);
              report += '\n';
            }

            // Bundle impact estimation
            report += '### 📊 Impact Assessment\n\n';

            // Check for new dependencies in package.json changes
            const pkgChanged = changedFiles.some(f => f.includes('package.json'));
            if (pkgChanged) {
              report += '⚠️ `package.json` was modified - bundle size may be affected.\n';
              report += 'Consider running bundle analysis after merging.\n\n';
            }

            // Recommendations
            report += '### 💡 Recommendations\n\n';
            if (totalChanges > 500) {
              report += '- Consider breaking this PR into smaller, focused changes\n';
            }
            if (patternFindings.some(f => f.severity === 'warning')) {
              report += '- Review the performance warnings above\n';
            }
            report += '- Run performance tests before and after merging\n';
            report += '- Monitor production metrics after deployment\n';

            report += '\n---\n*⚡ Automated analysis by Performance Agent*';

            // Post comment
            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.payload.pull_request.number,
              body: report
            });