# Audit Service Implementation Summary

## Overview

The Audit Service has been successfully implemented as an independent microservice. It provides audit logging functionality with gRPC API, database persistence, and service registry integration.

## Completed Components

### 1. Service Implementation (`services/audit/internal/service/audit_service.go`)
- **AuditService**: Core business logic for audit logging
- **Record**: Records audit log entries to database
- **Query**: Queries audit logs with filters (user_id, action, resource, time range, pagination)
- Uses Ent ORM for database operations
- Supports metadata as JSON

### 2. gRPC Server Implementation (`cmd/audit-service/audit_service_fx.go`)
- **auditServerImpl**: Implements `AuditService` gRPC interface
- **Record RPC**: Records audit log entries
- **Query RPC**: Queries audit logs with filters
- Converts between proto types and service types
- Error handling with proper gRPC status codes

### 3. Service Entry Point (`cmd/audit-service/main.go`)
- Independent service entry point
- Dependency injection using uber-go/fx
- Database connection with schema isolation (`audit` schema)
- Automatic migrations on startup
- Health check registry with database checker
- gRPC server lifecycle management
- Service registry registration (Consul)
- Graceful shutdown handling

### 4. Database Schema (`internal/ent/schema/audit_log.go`)
- **AuditLog** entity with fields:
  - `id`: Unique identifier
  - `user_id`: ID of the user/actor
  - `action`: Action performed (e.g., "user.create")
  - `resource`: Resource type (e.g., "user", "role")
  - `resource_id`: ID of the target resource
  - `ip_address`: Client IP address
  - `user_agent`: Client user agent
  - `metadata`: Additional metadata as JSON
  - `timestamp`: When the action occurred
- Indexes on: user_id, resource_id, timestamp, action, resource

### 5. Configuration (`config/default.yaml`)
- Added service configuration:
  ```yaml
  services:
    audit:
      port: 8084
      host: "localhost"
  ```

## Architecture

The Audit Service follows the microservices architecture pattern:

- **Independent Deployment**: Has its own entry point (`cmd/audit-service/main.go`)
- **Schema Isolation**: Uses `audit` database schema
- **Service Discovery**: Registers with Consul service registry
- **gRPC API**: Exposes gRPC server on port 8084 (configurable)
- **Health Checks**: Implements gRPC health check protocol
- **Reflection**: Enabled for grpcurl testing

## Files Created

1. `services/audit/internal/service/audit_service.go` - Service business logic
2. `services/audit/internal/api/server.go` - gRPC server implementation (for reference, actual implementation in cmd)
3. `services/audit/internal/api/grpc_server.go` - gRPC server wrapper (for reference)
4. `cmd/audit-service/main.go` - Service entry point
5. `cmd/audit-service/audit_service_fx.go` - FX providers for service creation
6. `services/audit/service.go` - Public API package (placeholder)

## Testing the Audit Service

### Prerequisites

1. **PostgreSQL** running and accessible
2. **Consul** running (optional, for service discovery)
3. **Configuration** set up in `config/default.yaml`

### Start the Service

```bash
# Using nix-shell (recommended)
nix-shell
go run ./cmd/audit-service/main.go

# Or build and run
go build -o bin/audit-service ./cmd/audit-service
./bin/audit-service
```

### Verify Service Startup

The service should:
1. Connect to database
2. Create `audit` schema if it doesn't exist
3. Run migrations (create `audit_logs` table)
4. Start gRPC server on port 8084
5. Register with Consul (if available)

Check logs for:
- "Database migrations completed for audit service"
- "Starting Audit Service gRPC server"
- "Audit Service gRPC server started successfully"
- "Registered Audit Service with service registry"

### Test with grpcurl

```bash
# List available services
grpcurl -plaintext localhost:8084 list

# Check health
grpcurl -plaintext localhost:8084 grpc.health.v1.Health/Check

# Record an audit log entry
grpcurl -plaintext -d '{
  "entry": {
    "user_id": "user-123",
    "action": "user.login",
    "resource": "user",
    "resource_id": "user-123",
    "ip_address": "192.168.1.1",
    "user_agent": "Mozilla/5.0",
    "metadata": {
      "method": "POST",
      "endpoint": "/api/v1/auth/login"
    },
    "timestamp": 1699123456
  }
}' localhost:8084 audit.v1.AuditService/Record

# Query audit logs
grpcurl -plaintext -d '{
  "user_id": "user-123",
  "limit": 10,
  "offset": 0
}' localhost:8084 audit.v1.AuditService/Query
```

### Verify Database

```bash
# Connect to database
docker exec -it goplt-postgres psql -U goplt -d goplt

# Switch to audit schema
SET search_path TO audit;

# Check table exists
\dt

# Query audit logs
SELECT * FROM audit_logs ORDER BY timestamp DESC LIMIT 10;
```

## Next Steps

The Audit Service is complete and ready for use. Other services (Auth, Identity, Authz) can use the Audit Service via the `AuditServiceClient` interface to record audit events.

## Notes

- The service uses inline implementation in `cmd/audit-service/audit_service_fx.go` to avoid importing internal packages from cmd
- The internal service implementation in `services/audit/internal/service/` exists for reference and can be used by other internal packages
- Service registry registration happens on startup; deregistration on shutdown (service ID stored for proper cleanup)
- Health checks are available via gRPC health protocol

