# Multi-Language Support Implementation Summary

## Overview

Added comprehensive multi-language support to the PR/MR review system. The review engine now automatically detects languages from file extensions and provides language-specific standards, idioms, anti-patterns, and security concerns for 12 major programming languages.

## Changes Made

### 1. New File: `language_profiles.py`

**Location**: `src/mcp_vector_search/analysis/review/language_profiles.py`

**Purpose**: Define language profiles with language-specific standards

**Key Components**:
- `LanguageProfile` dataclass: Stores name, extensions, config files, idioms, anti-patterns, security patterns
- `LANGUAGE_PROFILES` dict: 12 language profiles (Python, TypeScript, JavaScript, Java, C#, Ruby, Go, Rust, PHP, Swift, Kotlin, Scala)
- `detect_languages()`: Detect languages from PR patches based on file extensions
- `get_profile()`: Get language profile from file path
- `get_languages_in_pr()`: Get unique language profiles present in a PR

**Language Profiles Include**:
- **Idioms**: 5-8 language-specific best practices (e.g., "Use type hints for Python", "Prefer const/let over var in JavaScript")
- **Anti-patterns**: 5-7 common mistakes to flag (e.g., "Mutable default arguments in Python", "Using any type in TypeScript")
- **Security patterns**: 4-6 language-specific vulnerabilities (e.g., "SQL injection via string formatting", "XSS via innerHTML")

### 2. Updated: `instructions.py`

**Location**: `src/mcp_vector_search/analysis/review/instructions.py`

**Changes**:
- Added `LANGUAGE_CONFIG_FILES` dict: Maps config files to descriptions (`.rubocop.yml`, `tsconfig.json`, `.eslintrc.json`, etc.)
- Added `_extract_from_language_configs()`: Extract standards from language-specific config files
- Added `_extract_tsconfig_rules()`: Parse TypeScript compiler options
- Added `_extract_rubocop_rules()`: Parse Ruby style rules
- Updated `discover_and_load()`: Include language config extraction in discovery pipeline

**Config Files Discovered**:
- Ruby: `.rubocop.yml`
- Java: `checkstyle.xml`, `pom.xml`
- JavaScript/TypeScript: `.eslintrc.js`, `.eslintrc.json`, `tsconfig.json`
- Go: `.golangci.yml`
- Rust: `Cargo.toml`
- PHP: `.php-cs-fixer.php`, `phpstan.neon`
- Swift: `.swiftlint.yml`
- Kotlin: `detekt.yml`
- Scala: `scalafmt.conf`, `.scalafmt.conf`

### 3. Updated: `pr_engine.py`

**Location**: `src/mcp_vector_search/analysis/review/pr_engine.py`

**Changes**:
- Import `get_languages_in_pr` from `language_profiles`
- Added `_build_language_context()` method: Build language-specific context block for LLM prompt
- Updated `review_pr()`: Call `_build_language_context()` and inject into prompt
- Updated `PR_REVIEW_PROMPT`: Add `{language_context}` placeholder before review instructions

**Language Context Format**:
```markdown
## Python Standards

**Idioms to enforce:**
- Use type hints for all function signatures (PEP 484)
- Follow PEP 8 style guide
...

**Anti-patterns to flag:**
- Mutable default arguments (def f(x=[]))
- Catching bare except: without specifying exception type
...

**Security concerns:**
- SQL injection via string formatting in queries
- Command injection via subprocess/os.system with user input
...
```

### 4. Updated: `prompts.py`

**Location**: `src/mcp_vector_search/analysis/review/prompts.py`

**Changes**:
- Updated module docstring to document multi-language support
- Listed all 12 supported languages

### 5. New Test: `test_language_profiles.py`

**Location**: `tests/unit/test_language_profiles.py`

**Coverage**:
- Test all profiles have required fields
- Test Python and TypeScript profiles are comprehensive
- Test language detection from file extensions
- Test multi-language PR detection
- Test deleted files are skipped
- Test all 12 documented languages are present
- Test config files are defined for each language
- Test security patterns cover OWASP vulnerabilities

**Test Results**: All 12 tests pass ✅

### 6. Documentation

**Location**: `docs/multi-language-pr-review-example.md`

**Contents**:
- Overview of multi-language support
- List of 12 supported languages with file extensions
- How language detection works
- Example of mixed-language PR review
- Example review comments for Python and TypeScript
- Usage examples (CLI and programmatic)
- Configuration guide
- Benefits and architecture

## Supported Languages

1. **Python** (.py, .pyw, .pyi)
   - Config: pyproject.toml, .flake8, mypy.ini, ruff.toml
   - Focus: PEP 8, type hints, context managers, f-strings

2. **TypeScript** (.ts, .tsx, .mts, .cts)
   - Config: tsconfig.json, .eslintrc.js
   - Focus: Strict mode, avoid any, optional chaining, readonly

3. **JavaScript** (.js, .jsx, .mjs, .cjs)
   - Config: .eslintrc.js, prettier.config.js
   - Focus: const/let over var, async/await, strict equality

4. **Java** (.java)
   - Config: checkstyle.xml, pmd.xml, pom.xml
   - Focus: Optional over null, immutability, try-with-resources

5. **C#** (.cs, .csx)
   - Config: .editorconfig, stylecop.json
   - Focus: async/await, LINQ, nullable references, IDisposable

6. **Ruby** (.rb, .rake, .gemspec)
   - Config: .rubocop.yml, Gemfile
   - Focus: Guard clauses, duck typing, blocks/procs

7. **Go** (.go)
   - Config: .golangci.yml, go.mod
   - Focus: Error handling, goroutines, interfaces, defer

8. **Rust** (.rs)
   - Config: Cargo.toml, clippy.toml
   - Focus: Result types, ownership, iterators, ? operator

9. **PHP** (.php, .phtml)
   - Config: .php-cs-fixer.php, phpstan.neon
   - Focus: Strict types, PSR-12, PDO with prepared statements

10. **Swift** (.swift)
    - Config: .swiftlint.yml, Package.swift
    - Focus: Guard, let over var, optional chaining

11. **Kotlin** (.kt, .kts)
    - Config: build.gradle.kts, detekt.yml
    - Focus: val over var, data classes, when expressions

12. **Scala** (.scala, .sc)
    - Config: build.sbt, scalafmt.conf
    - Focus: Immutable collections, case classes, Option over null

## Key Features

### 1. Automatic Language Detection
- Scans file extensions in PR patches
- No manual configuration needed
- Handles mixed-language PRs gracefully

### 2. Language-Specific Standards
- **Idioms**: Best practices and conventions
- **Anti-patterns**: Common mistakes to avoid
- **Security**: Language-specific vulnerabilities (OWASP-aligned)

### 3. Config File Discovery
- Auto-discovers language tool configs (`.rubocop.yml`, `tsconfig.json`, etc.)
- Extracts key settings (strict mode, line length, etc.)
- Merges with project standards

### 4. Additive Configuration
- Language context + custom instructions + discovered standards
- User overrides are preserved
- Language standards enhance, don't replace

## Testing

```bash
# Run language profile tests
uv run pytest tests/unit/test_language_profiles.py -v

# Run all tests
uv run pytest tests/ -x -q
```

**Results**:
- New tests: 12 tests, all passing ✅
- All existing tests: 1437 tests, all passing ✅
- No regressions introduced

## Code Quality

### Lines of Code (LOC) Delta

**New Files**:
- `language_profiles.py`: 508 lines (comprehensive profiles)
- `test_language_profiles.py`: 247 lines (full test coverage)
- Documentation: 450 lines

**Modified Files**:
- `instructions.py`: +147 lines (config extraction)
- `pr_engine.py`: +56 lines (language context injection)
- `prompts.py`: +12 lines (documentation)

**Net Change**: +1,420 lines

**Justification**: Comprehensive multi-language support for 12 languages with extensive standards, anti-patterns, and security patterns. Investment in architecture enables language-specific reviews across the entire codebase.

## Usage Example

```python
from mcp_vector_search.analysis.review import PRReviewEngine

# Review PR (language context automatically injected)
result = await engine.review_from_git(
    base_ref="main",
    head_ref="feature-branch"
)

# Language context is automatically injected:
# - Python: PEP 8, type hints, SQL injection patterns
# - TypeScript: Strict mode, XSS patterns
# - Java: SOLID principles, XXE patterns
```

## Benefits

1. **Language-Aware Reviews**: Python reviewed against PEP 8, TypeScript against strict typing
2. **Mixed-Language PRs**: Handle multi-language PRs gracefully
3. **Security**: Language-specific vulnerability detection (SQL injection patterns differ by language)
4. **Consistency**: Uniform review quality across languages
5. **Learning**: Developers learn language best practices through reviews
6. **Extensible**: Easy to add new languages or update existing profiles

## Architecture Decisions

### Why Language Profiles?
- Centralized definition of standards per language
- Easy to maintain and extend
- Clear separation from review logic

### Why Auto-Detection?
- Zero configuration overhead for users
- Works out of the box for all languages
- Mixed-language PRs handled automatically

### Why Additive Context?
- Custom instructions preserved
- Language standards enhance reviews
- Users can override or extend defaults

## Future Enhancements

- Add more languages (Perl, Elixir, Haskell, Clojure)
- Parse config files for actual rules (e.g., extract RuboCop cops)
- Framework-specific standards (Django, Rails, React, Angular)
- Language-specific complexity metrics
- Team-specific language profiles

## Files Changed

```
Modified:
  src/mcp_vector_search/analysis/review/instructions.py
  src/mcp_vector_search/analysis/review/pr_engine.py
  src/mcp_vector_search/analysis/review/prompts.py

New:
  src/mcp_vector_search/analysis/review/language_profiles.py
  tests/unit/test_language_profiles.py
  docs/multi-language-pr-review-example.md
  docs/multi-language-support-summary.md
```

## Verification

All tests pass:
```bash
uv run pytest tests/ -x -q
# 1437 passed, 108 skipped in 67.03s ✅
```

Language-specific review context is injected for all PRs with detected languages. No manual configuration required.
