Legacy Code Summarizer

# Legacy Codebase Summary: [Project Name]

## Executive Summary

[2-3 sentence overview of what the codebase does]

**Key Metrics:**
- Lines of Code: [X]
- Number of Files: [Y]
- Primary Language: [Language]
- Test Coverage: [Z%]
- Last Major Update: [Date]

## Architecture Overview

### High-Level Structure

[Include architecture diagram from Step 3]

### Key Components

1. **[Component Name]** (`path/to/component/`)
   - **Purpose:** [What it does]
   - **Entry Point:** [Main file/class]
   - **Dependencies:** [Key dependencies]
   - **Lines of Code:** [X]

2. **[Component Name]** (`path/to/component/`)
   - **Purpose:** [What it does]
   - **Entry Point:** [Main file/class]
   - **Dependencies:** [Key dependencies]
   - **Lines of Code:** [X]

[Repeat for 5-10 key components]

### Technology Stack

**Core Technologies:**
- [Language] [Version]
- [Framework] [Version]
- [Database] [Version]

**Key Dependencies:**
- [Library 1] - [Purpose]
- [Library 2] - [Purpose]
- [Library 3] - [Purpose]

## Entry Points and Workflows

### Main Entry Points

1. **[Entry Point Name]** - `path/to/file.py:function()`
   - **Purpose:** [What it does]
   - **Triggered by:** [User action, cron, API call, etc.]

2. **[Entry Point Name]** - `path/to/file.java:main()`
   - **Purpose:** [What it does]
   - **Triggered by:** [How it's invoked]

### Critical Workflows

**Workflow 1: [Name]** (e.g., User Registration)

**Workflow 2: [Name]** (e.g., Payment Processing)

## Dependency Analysis

### External Dependencies

**Total Dependencies:** [X]

**Outdated Dependencies (require updates):**
- [Library Name] [Current Version] → [Latest Version]
- [Library Name] [Current Version] → [Latest Version]

**Deprecated Dependencies (require replacement):**
- [Library Name] - Deprecated since [Date]
  - **Suggested Replacement:** [New Library]

### Internal Dependencies

**Highly Coupled Modules (>5 dependencies):**
- `module_a` - depends on [X] modules
- `module_b` - depends on [Y] modules

**Circular Dependencies:**
- ⚠️ `auth` → `user` → `auth`
- ⚠️ `order` → `payment` → `order`

## Code Quality Assessment

### Metrics Summary

- **Average File Size:** [X] lines
- **Largest File:** `path/to/file.py` ([X] lines) ⚠️
- **TODO/FIXME Comments:** [X] occurrences
- **Code Duplication:** [Low/Medium/High]

### Quality Issues

**Critical Issues (Fix Immediately):**
1. **Security Vulnerability:** SQL injection in `path/to/file.py:45`
2. **Large File:** `god_class.java` (2,500 lines) - violates SRP
3. **Circular Dependency:** [Details]

**High Priority (Address Soon):**
1. **No Error Handling:** Missing try/catch in payment module
2. **Hardcoded Credentials:** Found in `config/settings.py`
3. **Deprecated API:** Using old authentication library

**Medium Priority (Technical Debt):**
1. **Code Duplication:** Copy-pasted validation logic in 5 files
2. **Missing Documentation:** 60% of functions lack docstrings
3. **Long Methods:** 15 methods exceed 100 lines

**Low Priority (Improvements):**
1. **Outdated Naming:** Inconsistent variable names
2. **Missing Type Hints:** (Python) or generics (Java)
3. **Verbose Code:** Could be simplified with modern patterns

### Code Smells Detected

- **God Objects:** [List large classes/modules]
- **Feature Envy:** [Methods accessing other objects' data frequently]
- **Dead Code:** [Unused functions/classes]
- **Magic Numbers:** [Hardcoded values without constants]

## Test Coverage Analysis

### Coverage Summary

- **Overall Coverage:** [X%]
- **Critical Modules Coverage:**
  - auth module: [Y%]
  - payment module: [Z%]
  - user management: [W%]

### Testing Gaps

**Untested Critical Code:**
1. `payment/processor.py` - 0% coverage ⚠️
2. `auth/security.py` - 30% coverage
3. `api/routes.py` - 45% coverage

**Missing Test Types:**
- [ ] No integration tests for payment flow
- [ ] No end-to-end tests for user journey
- [ ] No performance/load tests

### Test Quality Issues

- **Slow Tests:** 20 tests take >5 seconds each
- **Flaky Tests:** `test_async_operation` fails intermittently
- **Coupled Tests:** Tests depend on database state

## Recommendations

### Immediate Actions (This Sprint)

1. **Fix Security Issues**
   - Patch SQL injection vulnerability in `auth/login.py`
   - Remove hardcoded credentials, use environment variables

2. **Add Critical Tests**
   - Write integration tests for payment processor
   - Add unit tests for authentication logic

3. **Break Circular Dependencies**
   - Refactor `auth` ↔ `user` circular dependency
   - Extract shared code to new `common` module

### Short-Term Improvements (This Quarter)

1. **Reduce Technical Debt**
   - Refactor `god_class.java` into 3-4 focused classes
   - Eliminate code duplication in validation logic
   - Update deprecated dependencies

2. **Improve Documentation**
   - Add docstrings to all public functions
   - Create architecture diagram
   - Document deployment process

3. **Enhance Test Coverage**
   - Achieve 70% coverage for core modules
   - Add integration tests for critical workflows
   - Set up CI/CD with automated testing

### Long-Term Improvements (This Year)

1. **Architectural Refactoring**
   - Extract microservices for payment and notification
   - Implement proper layering (separate business logic from data access)
   - Introduce dependency injection for better testability

2. **Modernization**
   - Upgrade to [Language] [Latest Version]
   - Adopt modern patterns (async/await, type hints, etc.)
   - Migrate from [Old Framework] to [New Framework]

3. **Quality Infrastructure**
   - Set up automated code quality checks (linting, complexity analysis)
   - Implement pre-commit hooks
   - Add performance monitoring

## Quick Reference

### Key Files to Understand First

1. `path/to/main.py` - Application entry point
2. `path/to/config.py` - Configuration
3. `path/to/models/user.py` - Core data model
4. `path/to/api/routes.py` - API endpoints
5. `path/to/services/auth_service.py` - Authentication logic

### Common Commands

```bash
# Start application
[command]

# Run tests
[command]

# Build for production
[command]

# Deploy
[command]

## Summary Output Examples

### Example 1: Small Python Flask App

```markdown
# Legacy Codebase Summary: Internal Dashboard

## Executive Summary

Internal dashboard for monitoring application metrics, built with Flask.
Provides real-time data visualization and alerting for operations team.

**Key Metrics:**
- Lines of Code: 3,500
- Number of Files: 42
- Primary Language: Python 3.7
- Test Coverage: 45%
- Last Major Update: 18 months ago

## Architecture Overview

Simple Flask application with SQLAlchemy ORM and PostgreSQL database.

### Key Components

1. **Metrics Dashboard** (`app/routes/dashboard.py`)
   - Purpose: Display real-time metrics
   - Entry Point: `dashboard_view()`
   - Dependencies: metrics_service, chart_generator
   - Lines of Code: 250

2. **Data Collection** (`app/services/collector.py`)
   - Purpose: Fetch metrics from external APIs
   - Entry Point: `collect_metrics()` (cron job)
   - Dependencies: requests, database models
   - Lines of Code: 180

3. **Alert System** (`app/services/alerts.py`)
   - Purpose: Send notifications when thresholds exceeded
   - Entry Point: `check_alerts()` (background task)
   - Dependencies: email_service, metrics_service
   - Lines of Code: 150

## Recommendations

### Immediate Actions
1. Update Flask to latest version (security patches)
2. Add tests for alert system (currently 0% coverage)
3. Fix hardcoded database credentials

### Short-Term
1. Increase test coverage to 70%
2. Add API documentation
3. Refactor large dashboard route (300+ lines)

# Legacy Codebase Summary: E-Commerce Platform

## Executive Summary

Full-featured e-commerce platform handling product catalog, orders, payments,
and customer management. Serves 100K+ daily active users.

**Key Metrics:**
- Lines of Code: 185,000
- Number of Files: 1,240
- Primary Language: Java 8
- Test Coverage: 62%
- Last Major Update: 6 months ago

## Architecture Overview

Layered Spring Boot application with microservice patterns emerging.

[Detailed architecture diagram showing layers]

### Critical Issues Identified

**High Priority:**
1. **Memory Leak:** Order processing service shows increasing heap usage
2. **N+1 Query Problem:** Product listing generates 500+ DB queries
3. **No Monitoring:** Missing APM tools for production

**Modernization Opportunities:**
1. Migrate to Java 17 (LTS)
2. Extract payment service as microservice
3. Implement caching layer (Redis)

## Recommendations

[Detailed phased approach to refactoring]