Edmonds Commerce - Legacy Code Refactoring
Overview
Systematic refactoring to introduce modern patterns, improve testability, and reduce technical debt.
What We Do
Professional code refactoring for legacy applications. We systematically improve code quality, introduce modern patterns, and reduce technical debt whilst keeping the application running.
Refactoring Goals
Code Quality Improvement
Reduce complexity and improve maintainability.
Improvements:
- Reduce cyclomatic complexity
- Eliminate code duplication
- Improve naming clarity
- Break down large functions
- Extract classes from monoliths
- Simplify conditional logic
Modern Patterns
Introduce proven design patterns.
Patterns:
- Dependency injection
- Repository pattern
- Service layer
- Observer pattern
- Command pattern
- Factory pattern
SOLID Principles
Implement SOLID principles systematically.
Principles:
- Single Responsibility: Classes do one thing
- Open/Closed: Open for extension, closed for modification
- Liskov Substitution: Subtypes must be substitutable
- Interface Segregation: Specific interfaces vs. general
- Dependency Inversion: Depend on abstractions
Testability
Make code easier to test.
Testability Improvements:
- Dependency injection enables mocking
- Small, focused functions test easily
- Clear responsibilities enable unit testing
- Reduced tight coupling improves isolation
Performance
Improve algorithmic and runtime performance.
Improvements:
- Algorithm optimisation
- Database query optimisation
- Remove unnecessary computations
- Caching opportunities
- Collection efficiency
Refactoring Techniques
Extract Methods
Break large functions into smaller, focused functions.
Before:
function processOrder($order) {
// 200 lines of mixed logic
}
After:
function processOrder($order) {
$this->validateOrder($order);
$this->calculateTotals($order);
$this->applyDiscounts($order);
$this->saveOrder($order);
}
Extract Classes
Separate concerns into different classes.
Before:
class User {
// 1000+ lines with mixed responsibilities
}
After:
class User { }
class UserRepository { }
class UserValidator { }
class PasswordHasher { }
Introduce Interfaces
Define contracts for dependencies.
Before:
class Service {
public function __construct(Database $db) { }
}
After:
interface UserRepository { }
class Service {
public function __construct(UserRepository $repo) { }
}
Remove Duplication
Eliminate repeated code patterns.
Before:
$discount1 = $price1 * 0.1;
$discount2 = $price2 * 0.1;
$discount3 = $price3 * 0.1;
After:
function calculateDiscount($price) {
return $price * 0.1;
}
Simplify Conditionals
Reduce nested conditionals complexity.
Before:
if ($user) {
if ($user->isActive()) {
if ($user->hasPermission()) {
// do something
}
}
}
After:
if ($this->userCanAccess($user)) {
// do something
}
Refactoring Approach
1. Baseline Metrics
Establish code quality baseline.
Metrics:
- Cyclomatic complexity
- Code duplication %
- Test coverage %
- LOC distribution
- Dependency coupling
2. Test Coverage
Add tests before refactoring.
Testing Strategy:
- Characterisation tests for current behavior
- Unit test targets for refactored code
- Integration tests for workflows
- Regression test prevention
3. Incremental Refactoring
Refactor in small, validated batches.
Process:
- Refactor one piece at a time
- Run tests after each change
- Commit working changes
- Get code review
- Validate continuously
4. Validation
Measure improvements after refactoring.
Validation:
- Cyclomatic complexity reduced
- Test coverage improved
- Performance measured
- Manual testing
- User acceptance
5. Documentation
Update documentation with improvements.
Documentation:
- Architecture diagrams
- Class responsibilities
- Design pattern documentation
- API documentation
Refactoring Scope Options
Focused Refactoring
Target specific problematic areas.
Scope:
- High-complexity modules
- Frequently changed code
- Performance bottlenecks
- Security-sensitive code
Timeline: 4-12 weeks
Comprehensive Refactoring
Systematic improvement across codebase.
Scope:
- All modules touched
- Consistent patterns
- Full test coverage
- Complete architecture improvement
Timeline: 3-12 months
Selective Refactoring
Refactor as you build features.
Scope:
- Improve while adding features
- Gradual improvement
- Lower upfront cost
- Slower overall progress
Timeline: Ongoing
Technology & Tools
Refactoring Tools:
- Rector for automated refactoring
- PHP_CodeSniffer for standards
- PHPStan for type checking
- PHPMD for metrics
- IDE refactoring tools
Testing Tools:
- PHPUnit/Pest for unit tests
- Mockery for mocking
- Prophecy for test doubles
- Approval testing for legacy code
Target Audiences
Legacy System Teams: Improve code quality in large, complex systems.
Scaling Teams: Clean up codebase as you grow.
Acquisition Teams: Improve acquired codebases.
Quality-Focused Teams: Invest in technical debt reduction.
Performance After Refactoring
Refactoring often improves performance through:
- Better algorithms: Direct impact on speed
- Reduced complexity: Fewer CPU cycles
- Better caching: Clearer performance optimisation points
- Query optimisation: Cleaner database access
Common Refactoring Metrics
Before Refactoring:
- High cyclomatic complexity (>10)
- Low test coverage (<50%)
- High code duplication (>10%)
- Large classes (>500 LOC)
- Long methods (>20 LOC)
After Refactoring:
- Low cyclomatic complexity (<7)
- High test coverage (>80%)
- Low duplication (<5%)
- Small classes (<200 LOC)
- Short methods (<10 LOC)
Timeline & Cost
Typical Projects:
- Small module: 2-4 weeks
- Medium module: 4-8 weeks
- Large system: 8-16 weeks
- Ongoing program: 3-6 months
Related Services
Legacy Testing: Add tests before and during refactoring.
PHP 8 Migration: Refactor to modern PHP whilst upgrading versions.
Performance Optimisation: Improve algorithm and query efficiency.
Framework Upgrade: Refactor to new framework during upgrade.
Contact
Based in the UK, serving global clients. Discuss your refactoring goals, code quality concerns, or technical debt reduction strategy.