feat: Implement MongoProcessRepository (Issue #19)

[artcava]

📋 Description

Implementation of MongoProcessRepository following Clean Architecture principles and MongoDB best practices.

✅ Implemented Components

1. MongoProcessRepository (MongoProcessRepository.cs)

• ✅ Full implementation of IProcessRepository interface
• ✅ All CRUD operations with comprehensive error handling
• ✅ Duplicate key detection with specific error messages
• ✅ Detailed logging (Debug/Info/Error levels)
• ✅ Argument validation with meaningful exceptions

2. MongoDB Indexes (MongoDbIndexes.cs)

• ✅ 6 optimized indexes for performance:
  • idx_processId (unique) - Primary key
  • idx_clientId_clientProcessId (unique) - Idempotency
  • idx_status - Status queries
  • idx_createdAt - Temporal ordering
  • idx_idempotencyKey (unique) - Duplicate prevention
  • idx_clientId_processType_status - Concurrency limits
• ✅ Idempotent index creation (safe to run multiple times)
• ✅ Error handling for existing indexes

3. Configuration (MongoDbOptions.cs)

• ✅ Options pattern for appsettings.json binding
• ✅ Connection string, database name, timeouts
• ✅ Configurable index creation on startup

4. Dependency Injection (DependencyInjection.cs)

• ✅ IMongoClient as Singleton (connection pooling)
• ✅ IMongoDatabase as Singleton
• ✅ IProcessRepository as Scoped
• ✅ MongoDB health check registration
• ✅ Hosted service for index creation

5. Health Check (MongoDbHealthCheck.cs)

• ✅ IHealthCheck implementation
• ✅ Connection verification with ping command
• ✅ Detailed diagnostics in health response
• ✅ Kubernetes readiness probe support

6. Hosted Service (MongoDbIndexCreationService.cs)

• ✅ Background index creation on startup
• ✅ Non-blocking application initialization
• ✅ Error logging without startup failure

7. Documentation

• ✅ Comprehensive README in Persistence/ folder
• ✅ Configuration example in docs/examples/
• ✅ Architecture decisions documented
• ✅ Troubleshooting guide included

🎯 Acceptance Criteria (from Issue #19)

• ✅ MongoProcessRepository implements IProcessRepository
• ✅ All 7 interface methods implemented
• ✅ 6 MongoDB indexes created automatically
• ✅ Unique constraint violations handled with specific errors
• ✅ Comprehensive logging at Debug/Info/Error levels
• ✅ Connection pooling with singleton IMongoClient
• ✅ Health check returns MongoDB status
• ✅ Configuration via appsettings.json
• ✅ NuGet packages: MongoDB.Driver
• ✅ Code follows CODING-CONVENTIONS.md
• ✅ Clean Architecture principles respected
• ✅ Documentation complete

🧪 Testing

Manual Testing

# Start MongoDB
docker run -d -p 27017:27017 --name mongodb mongo:7.0

# Run application
dotnet run --project src/StarGate.Api

# Verify indexes
mongosh stargate --eval "db.processes.getIndexes()"

# Check health
curl http://localhost:5000/health

Automated Tests

• Unit tests: Issue Phase 2.1: Write Unit Tests for Repositories #22 (next)
• Integration tests: Issue Phase 2.1: Integration Tests with MongoDB Container #23 (next)

📦 Dependencies

• ✅ Issue Phase 2.1: Create MongoDB Documents and Mapping Logic #21: ProcessDocument and mapping (COMPLETED)
• ✅ MongoDB.Driver NuGet package
• ✅ Microsoft.Extensions.Diagnostics.HealthChecks

🔗 Related Issues

• Closes Phase 2.1: Implement MongoProcessRepository #19
• Prerequisite for Phase 2.1: Implement MongoPolicyRepository #20 (MongoPolicyRepository)
• Prerequisite for Phase 2.1: Write Unit Tests for Repositories #22 (Unit Tests)
• Prerequisite for Phase 2.1: Integration Tests with MongoDB Container #23 (Integration Tests)

📋 Checklist

• ✅ Code follows project coding conventions
• ✅ Clean Architecture principles applied
• ✅ Comprehensive error handling
• ✅ Detailed logging implemented
• ✅ Health checks configured
• ✅ Documentation complete
• ✅ Configuration examples provided
• ✅ Commit messages follow conventional commits
• ✅ No compilation errors

🏗️ Architecture

Core (Interfaces)          Infrastructure (Implementation)
┌──────────────────┐       ┌──────────────────────────────┐
│ IProcessRepository│◄──────│ MongoProcessRepository       │
└──────────────────┘       │  - CRUD operations           │
                           │  - Error handling            │
                           │  - Logging                   │
                           ├──────────────────────────────┤
                           │ MongoDbIndexes               │
                           │  - 6 optimized indexes       │
                           ├──────────────────────────────┤
                           │ MongoDbHealthCheck           │
                           │  - Connection monitoring     │
                           └──────────────────────────────┘

📝 Notes

• Connection pooling is handled automatically by MongoDB.Driver
• Indexes are created asynchronously on startup
• Health check endpoint: /health
• All configuration via appsettings.json
• Repository follows fail-fast principle with specific exceptions

🚀 Next Steps

1. Issue Phase 2.1: Implement MongoPolicyRepository #20: Implement MongoPolicyRepository
2. Issue Phase 2.1: Write Unit Tests for Repositories #22: Write unit tests with mocks
3. Issue Phase 2.1: Integration Tests with MongoDB Container #23: Write integration tests with Testcontainers

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Reviewer Notes:

• Please verify index creation logic
• Check error messages are user-friendly
• Confirm logging levels are appropriate
• Review dependency injection lifetime scopes