Greenfield vs Maintenance: Navigeren van Development op Nieuwe en Bestaande Projecten

// Greenfield vs Maintenance comparison
interface DevelopmentComparison {
  greenfield: {
    velocity: 100;        // baseline
    complexity: 20;       // low
    satisfaction: 90;     // high
    risk: 30;            // medium
  };
  maintenance: {
    velocity: 30;        // 3x slower
    complexity: 80;      // high
    satisfaction: 40;    // low
    risk: 70;           // high
  };
}

// Codebase assessment framework
interface CodebaseAssessment {
  health: CodebaseHealth;
  architecture: ArchitectureAnalysis;
  technicalDebt: TechnicalDebtAnalysis;
  teamKnowledge: TeamKnowledgeAnalysis;
  improvementStrategy: ImprovementStrategy;
}

interface CodebaseHealth {
  maintainability: number;    // 0-100
  testability: number;        // 0-100
  performance: number;        // 0-100
  security: number;          // 0-100
  documentation: number;     // 0-100
}

interface ImprovementStrategy {
  approach: 'strangler_fig' | 'modular_refactor' | 'facade_pattern' | 'complete_rewrite';
  timeline: string;
  risk: 'low' | 'medium' | 'high';
  effort: number;            // story points
  benefits: string[];
}

class CodebaseAssessor {
  async assessCodebase(codebase: Codebase): Promise<CodebaseAssessment> {
    // Assess codebase health
    const health = await this.assessHealth(codebase);
    
    // Analyze architecture
    const architecture = await this.analyzeArchitecture(codebase);
    
    // Analyze technical debt
    const technicalDebt = await this.analyzeTechnicalDebt(codebase);
    
    // Assess team knowledge
    const teamKnowledge = await this.assessTeamKnowledge(codebase);
    
    // Determine improvement strategy
    const improvementStrategy = await this.determineStrategy(health, architecture, technicalDebt, teamKnowledge);
    
    return {
      health,
      architecture,
      technicalDebt,
      teamKnowledge,
      improvementStrategy
    };
  }

  private async assessHealth(codebase: Codebase): Promise<CodebaseHealth> {
    return {
      maintainability: await this.calculateMaintainability(codebase),
      testability: await this.calculateTestability(codebase),
      performance: await this.calculatePerformance(codebase),
      security: await this.calculateSecurity(codebase),
      documentation: await this.calculateDocumentation(codebase)
    };
  }

  private async determineStrategy(
    health: CodebaseHealth,
    architecture: ArchitectureAnalysis,
    technicalDebt: TechnicalDebtAnalysis,
    teamKnowledge: TeamKnowledgeAnalysis
  ): Promise<ImprovementStrategy> {
    const healthScore = (health.maintainability + health.testability + health.performance + health.security + health.documentation) / 5;
    
    if (healthScore < 30) {
      return {
        approach: 'complete_rewrite',
        timeline: '6-12 months',
        risk: 'high',
        effort: 200,
        benefits: ['Clean architecture', 'Modern patterns', 'High performance', 'Maintainable code']
      };
    } else if (healthScore < 60) {
      return {
        approach: 'strangler_fig',
        timeline: '3-6 months',
        risk: 'medium',
        effort: 100,
        benefits: ['Gradual improvement', 'Reduced risk', 'Continuous delivery', 'Team learning']
      };
    } else {
      return {
        approach: 'modular_refactor',
        timeline: '2-4 months',
        risk: 'low',
        effort: 50,
        benefits: ['Incremental improvement', 'Low risk', 'Quick wins', 'Team confidence']
      };
    }
  }
}

// Strangler fig pattern implementatie
interface StranglerFigStrategy {
  newSystem: NewSystemArchitecture;
  legacySystem: LegacySystemIntegration;
  migration: MigrationPlan;
  cohabitation: CohabitationStrategy;
}

interface NewSystemArchitecture {
  technology: string;
  patterns: string[];
  interfaces: SystemInterface[];
  dataFlow: DataFlowStrategy;
}

interface MigrationPlan {
  phases: MigrationPhase[];
  timeline: string;
  rollback: RollbackStrategy;
  testing: TestingStrategy;
}

class StranglerFigImplementer {
  private strategy: StranglerFigStrategy;

  constructor() {
    this.strategy = {
      newSystem: {
        technology: 'Modern Stack',
        patterns: ['Microservices', 'Event-Driven', 'CQRS'],
        interfaces: [
          {
            name: 'API Gateway',
            purpose: 'Unified entry point',
            implementation: 'Kong/AWS API Gateway'
          },
          {
            name: 'Event Bus',
            purpose: 'System communication',
            implementation: 'Apache Kafka/RabbitMQ'
          }
        ],
        dataFlow: {
          strategy: 'event-sourcing',
          consistency: 'eventual',
          backup: 'dual-write'
        }
      },
      legacySystem: {
        integration: {
          approach: 'adapter-pattern',
          interfaces: ['REST API', 'Database', 'File System'],
          monitoring: 'health-checks'
        },
        maintenance: {
          approach: 'minimal-changes',
          focus: 'stability',
          timeline: 'gradual-phaseout'
        }
      },
      migration: {
        phases: [
          {
            name: 'Phase 1: New Features',
            description: 'All new features in new system',
            duration: '2 months',
            risk: 'low'
          },
          {
            name: 'Phase 2: Core Migration',
            description: 'Migrate core business logic',
            duration: '3 months',
            risk: 'medium'
          },
          {
            name: 'Phase 3: Legacy Decommission',
            description: 'Remove legacy system',
            duration: '1 month',
            risk: 'high'
          }
        ],
        timeline: '6 months total',
        rollback: {
          strategy: 'feature-flags',
          triggers: ['performance-degradation', 'critical-bugs'],
          process: 'automated-rollback'
        },
        testing: {
          strategy: 'parallel-testing',
          coverage: 'comprehensive',
          automation: 'ci-cd-integrated'
        }
      },
      cohabitation: {
        strategy: 'gradual-replacement',
        communication: 'event-driven',
        data: 'eventual-consistency',
        monitoring: 'dual-system'
      }
    };
  }

  async implementStranglerFig(): Promise<void> {
    // Setup new system architecture
    await this.setupNewSystem();
    
    // Implement legacy integration
    await this.implementLegacyIntegration();
    
    // Execute migration plan
    await this.executeMigration();
    
    // Monitor cohabitation
    await this.monitorCohabitation();
  }

  private async setupNewSystem(): Promise<void> {
    console.log('Setting up new system architecture...');
    
    const newSystemConfig = {
      apiGateway: {
        provider: 'Kong',
        features: ['Rate Limiting', 'Authentication', 'Load Balancing'],
        monitoring: 'Prometheus + Grafana'
      },
      eventBus: {
        provider: 'Apache Kafka',
        topics: ['user-events', 'order-events', 'payment-events'],
        partitions: 3,
        replication: 2
      },
      microservices: [
        {
          name: 'user-service',
          technology: 'Node.js + TypeScript',
          database: 'PostgreSQL',
          cache: 'Redis'
        },
        {
          name: 'order-service',
          technology: 'Node.js + TypeScript',
          database: 'PostgreSQL',
          cache: 'Redis'
        }
      ]
    };

    console.log('New system configured:', newSystemConfig);
  }
}

// Knowledge transfer systeem
interface KnowledgeTransfer {
  documentation: DocumentationStrategy;
  training: TrainingProgram;
  mentoring: MentoringProgram;
  tools: KnowledgeTools;
}

interface DocumentationStrategy {
  types: DocumentationType[];
  format: 'markdown' | 'confluence' | 'notion';
  maintenance: 'automated' | 'manual';
  access: 'team' | 'public';
}

interface TrainingProgram {
  modules: TrainingModule[];
  assessment: AssessmentStrategy;
  certification: CertificationProgram;
  continuous: ContinuousLearning;
}

class KnowledgeTransferManager {
  private transfer: KnowledgeTransfer;

  constructor() {
    this.transfer = {
      documentation: {
        types: [
          {
            name: 'Architecture Documentation',
            content: 'System overview, components, data flow',
            audience: 'all-developers',
            frequency: 'monthly-updates'
          },
          {
            name: 'API Documentation',
            content: 'Endpoints, schemas, examples',
            audience: 'api-consumers',
            frequency: 'per-release'
          },
          {
            name: 'Runbook Documentation',
            content: 'Deployment, monitoring, troubleshooting',
            audience: 'devops-team',
            frequency: 'per-change'
          }
        ],
        format: 'notion',
        maintenance: 'automated',
        access: 'team'
      },
      training: {
        modules: [
          {
            name: 'Legacy System Overview',
            duration: 120, // minutes
            content: 'System history, architecture, business logic',
            exercises: ['Code walkthrough', 'Bug investigation', 'Feature analysis']
          },
          {
            name: 'New System Architecture',
            duration: 180,
            content: 'Microservices, event-driven patterns, modern practices',
            exercises: ['Service development', 'Event handling', 'Testing strategies']
          },
          {
            name: 'Migration Strategies',
            duration: 90,
            content: 'Strangler fig, data migration, testing approaches',
            exercises: ['Migration planning', 'Risk assessment', 'Rollback procedures']
          }
        ],
        assessment: {
          type: 'practical-exercises',
          passingScore: 80,
          retakePolicy: 'unlimited',
          certification: 'required'
        },
        certification: {
          name: 'Legacy System Expert',
          requirements: ['Complete training', 'Pass assessment', 'Practical project'],
          validity: '1 year',
          renewal: 'continuous-learning'
        },
        continuous: {
          frequency: 'monthly',
          content: 'New patterns, tools, best practices',
          format: 'workshop + documentation',
          participation: 'mandatory'
        }
      },
      mentoring: {
        pairs: 'senior-junior',
        duration: '3 months',
        focus: ['Legacy knowledge', 'New patterns', 'Migration strategies'],
        evaluation: 'monthly-reviews'
      },
      tools: {
        knowledgeBase: 'Notion',
        codeExploration: 'Sourcegraph',
        documentation: 'Swagger/OpenAPI',
        monitoring: 'Grafana + Prometheus'
      }
    };
  }

  async executeKnowledgeTransfer(): Promise<void> {
    // Setup documentation
    await this.setupDocumentation();
    
    // Execute training program
    await this.executeTraining();
    
    // Setup mentoring
    await this.setupMentoring();
    
    // Configure tools
    await this.configureTools();
  }

  private async setupDocumentation(): Promise<void> {
    const documentationConfig = {
      platform: 'Notion',
      structure: {
        'System Overview': {
          'Architecture': 'High-level system design',
          'Components': 'Individual service descriptions',
          'Data Flow': 'How data moves through the system'
        },
        'Development': {
          'Setup Guide': 'How to set up development environment',
          'Coding Standards': 'Team coding conventions',
          'Testing Guide': 'How to write and run tests'
        },
        'Operations': {
          'Deployment': 'How to deploy to different environments',
          'Monitoring': 'How to monitor system health',
          'Troubleshooting': 'Common issues and solutions'
        }
      },
      automation: {
        'API Docs': 'Auto-generated from OpenAPI specs',
        'Code Coverage': 'Auto-updated from CI/CD',
        'Performance Metrics': 'Auto-updated from monitoring'
      }
    };

    console.log('Documentation configured:', documentationConfig);
  }
}

// Probleem: Legacy system limitations
interface LegacySystemLimitations {
  noCI: boolean;
  noMonitoring: boolean;
  noAutomatedTesting: boolean;
  noCodeQuality: boolean;
}

// Modern tooling integratie
interface ModernTooling {
  ci: CIConfiguration;
  monitoring: MonitoringConfiguration;
  testing: TestingConfiguration;
  quality: QualityConfiguration;
}

interface CIConfiguration {
  platform: 'GitHub Actions' | 'Jenkins' | 'GitLab CI';
  stages: CIStage[];
  automation: AutomationFeatures;
}

interface MonitoringConfiguration {
  metrics: MetricsCollection;
  logging: LoggingStrategy;
  alerting: AlertingConfiguration;
  dashboards: DashboardConfiguration;
}

class ModernToolingIntegrator {
  private tooling: ModernTooling;

  constructor() {
    this.tooling = {
      ci: {
        platform: 'GitHub Actions',
        stages: [
          {
            name: 'Build',
            commands: ['npm install', 'npm run build'],
            artifacts: ['dist/']
          },
          {
            name: 'Test',
            commands: ['npm run test', 'npm run test:coverage'],
            coverage: 80
          },
          {
            name: 'Quality',
            commands: ['npm run lint', 'npm run security-audit'],
            gates: ['no-critical-vulnerabilities', 'lint-score > 8']
          },
          {
            name: 'Deploy',
            commands: ['npm run deploy:staging'],
            environment: 'staging'
          }
        ],
        automation: {
          triggers: ['push', 'pull-request'],
          notifications: ['slack', 'email'],
          rollback: 'automatic-on-failure'
        }
      },
      monitoring: {
        metrics: {
          collection: 'Prometheus',
          targets: ['application', 'database', 'infrastructure'],
          frequency: '15s',
          retention: '30d'
        },
        logging: {
          platform: 'ELK Stack',
          levels: ['error', 'warn', 'info', 'debug'],
          format: 'structured-json',
          retention: '90d'
        },
        alerting: {
          platform: 'AlertManager',
          channels: ['slack', 'email', 'pagerduty'],
          rules: [
            {
              name: 'High Error Rate',
              condition: 'error_rate > 5%',
              severity: 'critical',
              duration: '5m'
            },
            {
              name: 'Slow Response Time',
              condition: 'response_time > 2s',
              severity: 'warning',
              duration: '10m'
            }
          ]
        },
        dashboards: {
          platform: 'Grafana',
          panels: [
            'System Overview',
            'Application Performance',
            'Error Analysis',
            'User Experience'
          ],
          refresh: '30s',
          sharing: 'team-access'
        }
      },
      testing: {
        unit: {
          framework: 'Jest',
          coverage: 80,
          automation: 'ci-integrated'
        },
        integration: {
          framework: 'Supertest',
          database: 'test-db',
          automation: 'ci-integrated'
        },
        e2e: {
          framework: 'Playwright',
          browsers: ['Chrome', 'Firefox', 'Safari'],
          automation: 'nightly-runs'
        },
        performance: {
          tool: 'Artillery',
          scenarios: ['load-testing', 'stress-testing'],
          automation: 'weekly-runs'
        }
      },
      quality: {
        linting: {
          tool: 'ESLint',
          rules: 'airbnb-base',
          automation: 'pre-commit-hook'
        },
        security: {
          tool: 'Snyk',
          scanning: 'dependencies + code',
          automation: 'daily-scans'
        },
        complexity: {
          tool: 'SonarQube',
          metrics: ['cyclomatic-complexity', 'cognitive-complexity'],
          gates: 'quality-gates'
        },
        documentation: {
          tool: 'JSDoc',
          generation: 'automated',
          hosting: 'GitHub Pages'
        }
      }
    };
  }

  async integrateModernTooling(): Promise<void> {
    // Setup CI/CD
    await this.setupCI();
    
    // Setup monitoring
    await this.setupMonitoring();
    
    // Setup testing
    await this.setupTesting();
    
    // Setup quality tools
    await this.setupQualityTools();
  }

  private async setupCI(): Promise<void> {
    const ciConfig = {
      workflow: {
        name: 'Legacy System CI/CD',
        triggers: ['push', 'pull_request'],
        jobs: {
          'build-and-test': {
            runsOn: 'ubuntu-latest',
            steps: [
              'Checkout code',
              'Setup Node.js',
              'Install dependencies',
              'Run linting',
              'Run tests',
              'Generate coverage report',
              'Upload artifacts'
            ]
          },
          'security-scan': {
            runsOn: 'ubuntu-latest',
            steps: [
              'Security audit',
              'Dependency check',
              'Code vulnerability scan'
            ]
          },
          'deploy-staging': {
            runsOn: 'ubuntu-latest',
            needs: ['build-and-test', 'security-scan'],
            steps: [
              'Deploy to staging',
              'Run smoke tests',
              'Notify team'
            ]
          }
        }
      }
    };

    console.log('CI/CD configured:', ciConfig);
  }
}

// Probleem: Knowledge silos
interface KnowledgeSilos {
  legacyExperts: string[];
  newSystemExperts: string[];
  knowledgeGaps: string[];
  burnoutRisk: number;
}

// Team rotation en knowledge sharing
interface TeamRotation {
  strategy: RotationStrategy;
  schedule: RotationSchedule;
  knowledgeSharing: KnowledgeSharingProgram;
  burnoutPrevention: BurnoutPrevention;
}

interface RotationStrategy {
  approach: 'pair-rotation' | 'project-rotation' | 'skill-rotation';
  frequency: 'monthly' | 'quarterly' | 'project-based';
  duration: number; // weeks
  overlap: number;  // weeks
}

class TeamRotationManager {
  private rotation: TeamRotation;

  constructor() {
    this.rotation = {
      strategy: {
        approach: 'pair-rotation',
        frequency: 'monthly',
        duration: 4, // weeks
        overlap: 1   // week
      },
      schedule: {
        rotations: [
          {
            month: 'January',
            pairs: [
              { senior: 'Alice', junior: 'Bob', focus: 'Legacy System' },
              { senior: 'Charlie', junior: 'Diana', focus: 'New System' }
            ]
          },
          {
            month: 'February',
            pairs: [
              { senior: 'Bob', junior: 'Alice', focus: 'New System' },
              { senior: 'Diana', junior: 'Charlie', focus: 'Legacy System' }
            ]
          }
        ]
      },
      knowledgeSharing: {
        sessions: [
          {
            name: 'Weekly Tech Talk',
            frequency: 'weekly',
            duration: 30,
            format: 'presentation + q&a',
            topics: ['New patterns', 'Legacy insights', 'Tool updates']
          },
          {
            name: 'Monthly Deep Dive',
            frequency: 'monthly',
            duration: 120,
            format: 'workshop',
            topics: ['Architecture decisions', 'Migration strategies', 'Performance optimization']
          }
        ],
        documentation: {
          platform: 'Notion',
          structure: 'wiki-style',
          maintenance: 'rotating-responsibility',
          review: 'monthly'
        }
      },
      burnoutPrevention: {
        strategies: [
          {
            name: 'Workload Balancing',
            description: 'Distribute challenging and routine tasks',
            implementation: 'sprint-planning-integration'
          },
          {
            name: 'Skill Development',
            description: 'Regular learning opportunities',
            implementation: '20%-time-for-learning'
          },
          {
            name: 'Recognition Program',
            description: 'Regular recognition of contributions',
            implementation: 'monthly-team-recognition'
          }
        ],
        monitoring: {
          metrics: ['satisfaction-surveys', 'workload-assessment', 'burnout-indicators'],
          frequency: 'monthly',
          action: 'immediate-intervention'
        }
      }
    };
  }

  async implementTeamRotation(): Promise<void> {
    // Execute rotation schedule
    await this.executeRotation();
    
    // Setup knowledge sharing
    await this.setupKnowledgeSharing();
    
    // Implement burnout prevention
    await this.implementBurnoutPrevention();
    
    // Monitor effectiveness
    await this.monitorEffectiveness();
  }

  private async executeRotation(): Promise<void> {
    console.log('Executing team rotation...');
    
    const currentRotation = this.rotation.schedule.rotations[0];
    
    for (const pair of currentRotation.pairs) {
      console.log(`Pairing ${pair.senior} with ${pair.junior} for ${pair.focus}`);
      
      // Setup pair programming sessions
      await this.setupPairProgramming(pair);
      
      // Schedule knowledge transfer sessions
      await this.scheduleKnowledgeTransfer(pair);
      
      // Setup mentoring relationship
      await this.setupMentoring(pair);
    }
  }

  private async setupKnowledgeSharing(): Promise<void> {
    const knowledgeSharingConfig = {
      sessions: {
        'Weekly Tech Talk': {
          schedule: 'Fridays 3-3:30 PM',
          format: 'Presentation + Q&A',
          topics: [
            'This week\'s learnings',
            'Challenges faced',
            'Solutions discovered',
            'Tools and techniques'
          ],
          rotation: 'speaker-rotation'
        },
        'Monthly Deep Dive': {
          schedule: 'First Friday of month 2-4 PM',
          format: 'Workshop + Hands-on',
          topics: [
            'Architecture deep dive',
            'Migration strategies',
            'Performance optimization',
            'Security best practices'
          ],
          preparation: 'pre-session-research'
        }
      },
      documentation: {
        platform: 'Notion',
        structure: {
          'Team Knowledge Base': {
            'Legacy System': 'Documentation, patterns, gotchas',
            'New System': 'Architecture, patterns, best practices',
            'Migration Guide': 'Step-by-step migration strategies',
            'Tooling Guide': 'Setup and usage of development tools'
          }
        },
        maintenance: {
          responsibility: 'rotating-monthly',
          review: 'monthly-team-review',
          updates: 'continuous-improvement'
        }
      }
    };

    console.log('Knowledge sharing configured:', knowledgeSharingConfig);
  }
}