⚙️ [Day 1 - Hour 4] Core Services Foundation Implementation

[uozopio]

📋 Task Overview

Sprint Day: Day 1 - Morning Session
Time Slot: 12:00 - 13:00 (1 hour)
Task Type: Collaborative Service Implementation (All Team Members)
Estimated Duration: 1 hour
Dependencies: Project Structure (Issue #4)

🎯 Objectives

Implement the foundation of core services including basic EscrowService class, PaymentService skeleton, database service methods, and a basic state machine for escrow transaction management. This establishes the business logic foundation before afternoon's parallel development.

📝 Detailed Requirements

1. EscrowService Class Implementation

• Create services/escrow/EscrowService.ts with:
  • Class structure with dependency injection setup
  • Methods for transaction lifecycle:
    • createTransaction() - Initialize new escrow
    • updateStatus() - State transitions
    • getTransaction() - Retrieve transaction details
    • listTransactions() - Query transactions with filters
    • validateTransition() - Validate state changes
  • Integration with Prisma client
  • Error handling with custom error classes
• Create services/escrow/types.ts with:
  • CreateEscrowInput interface
  • UpdateEscrowInput interface
  • EscrowStatus enum
  • TransactionResponse type
• Implement basic validation logic
• Add activity logging for all operations

2. PaymentService Skeleton

• Create services/payment/PaymentService.ts with:
  • Jetcheckout API integration structure
  • Payment method interfaces:
    • createPayment() - Initialize payment
    • verifyPayment() - Check payment status
    • processRefund() - Handle refunds
    • handleWebhook() - Process gateway webhooks
  • Hash generation utilities for security
  • Mock responses for development
• Create services/payment/types.ts with:
  • PaymentRequest interface
  • PaymentResponse interface
  • WebhookPayload type
  • PaymentStatus enum
• Set up payment gateway configuration
• Prepare webhook signature verification

3. Database Service Methods

• Create services/database/DatabaseService.ts with:
  • Prisma client singleton pattern
  • Transaction management utilities
  • Common query builders:
    • findWithPagination()
    • upsertRecord()
    • softDelete()
    • bulkUpdate()
  • Connection health check
  • Query performance logging
• Implement repository pattern for each model:
  • UserRepository
  • EscrowRepository
  • PaymentRepository
  • DocumentRepository
• Add database transaction support
• Create query optimization helpers

4. State Machine Implementation

• Create services/escrow/StateMachine.ts with:
  • State transition definitions:
    • DRAFT → PENDING_PAYMENT
    • PENDING_PAYMENT → PAYMENT_RECEIVED
    • PAYMENT_RECEIVED → PENDING_DELIVERY
    • PENDING_DELIVERY → DELIVERED
    • DELIVERED → COMPLETED
    • Any state → DISPUTED
    • Certain states → CANCELLED
  • Transition validation rules
  • Guard conditions for each transition
  • Event emission for state changes
  • Rollback capabilities
• Create state machine tests structure
• Document state transition diagram
• Implement transition history tracking

🔧 Technical Context

Service Architecture Principles

• Dependency Injection: Services should be loosely coupled
• Single Responsibility: Each service handles one domain
• Error Handling: Consistent error types and messages
• Logging: Comprehensive logging for debugging
• Testing: Services designed for easy unit testing

State Machine Design

The state machine ensures transaction integrity by:

• Enforcing valid transitions only
• Preventing race conditions with locks
• Maintaining audit trail of all changes
• Supporting rollback for failed operations
• Emitting events for external integrations

Database Patterns

• Repository Pattern: Abstraction over Prisma
• Unit of Work: Transaction management
• Query Builder: Flexible query construction
• Connection Pooling: Optimal performance
• Read Replicas: Future scalability consideration

Integration Considerations

• API Contracts: Well-defined interfaces
• Error Recovery: Graceful failure handling
• Idempotency: Safe retry mechanisms
• Monitoring: Health checks and metrics
• Documentation: Inline JSDoc comments

✅ Acceptance Criteria

• All services compile without TypeScript errors
• Basic CRUD operations work for escrow transactions
• State machine validates transitions correctly
• Payment service can mock payment creation
• Database service handles connections properly
• Services are properly exported and importable
• Basic unit test structure is in place
• Services follow SOLID principles

👥 Team Assignments

All Team Members:

• @uozopio (Umut) - Lead service architecture and state machine
• @mbyzopio (Burak) - Review service interfaces for frontend needs
• @teczopio (Enes) - Ensure services support UI requirements

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This task is part of the 2-day MVP sprint for the Paylox Escrow System