name: Detect Non-RE2 Regex
on:
  pull_request:
    types: [opened, synchronize]

jobs:
  check-non-re2-regex:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Get diff of backend/*
        run: |
          git diff --unified=0 "origin/${{ github.base_ref }}"...HEAD -- backend/ > diff.txt

      - name: Scan backend diff for non-RE2 regex
        run: |
          # Extract only added lines (excluding file headers)
          grep '^+' diff.txt | grep -v '^+++' | sed 's/^\+//' > added_lines.txt

          if [ ! -s added_lines.txt ]; then
            echo "✅ No added lines in backend/ to check for regex usage."
            exit 0
          fi

          regex_usage_pattern='(^|[^A-Za-z0-9_"'"'"'`\.\/\\])(\/(?:\\.|[^\/\n\\])+\/[gimsuyv]*(?=\s*[\.\(;,)\]}:]|$)|new RegExp\()'

          # Find all added lines that contain regex patterns
          if grep -E "$regex_usage_pattern" added_lines.txt > potential_violations.txt 2>/dev/null; then
            # Filter out lines that contain 'new RE2' (allowing for whitespace variations)
            if grep -v -E 'new\s+RE2\s*\(' potential_violations.txt > actual_violations.txt 2>/dev/null && [ -s actual_violations.txt ]; then
              echo "🚨 ERROR: Found forbidden regex pattern in added/modified backend code."
              echo ""
              echo "The following lines use raw regex literals (/.../) or new RegExp(...):"
              echo "Please replace with 'new RE2(...)' for RE2 compatibility."
              echo ""
              echo "Offending lines:"
              cat actual_violations.txt
              exit 1
            else
              echo "✅ All identified regex usages are correctly using 'new RE2(...)'."
            fi
          else
            echo "✅ No regex patterns found in added/modified backend lines."
          fi

      - name: Cleanup temporary files
        if: always()
        run: |
          rm -f diff.txt added_lines.txt potential_violations.txt actual_violations.txt