Fine tune - code structure aligned to LLD

cli/azd/extensions/azure.ai.finetune/design/IMPLEMENTATION_SUMMARY.md

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+# Architecture Implementation - Folder Structure & Interfaces
+
+## Created Folder Structure
+
+```
+azure.ai.finetune/
+├── pkg/
+│   └── models/                          # Domain Models (Shared Foundation)
+│       ├── finetune.go                  # FineTuningJob, JobStatus, CreateFineTuningRequest
+│       ├── deployment.go                # Deployment, DeploymentStatus, DeploymentRequest
+│       ├── errors.go                    # ErrorDetail, Error codes
+│       └── requests.go                  # All request/response DTOs
+│
+├── internal/
+│   ├── services/                        # Service Layer (Business Logic)
+│   │   ├── interface.go                 # FineTuningService, DeploymentService interfaces
+│   │   ├── state_store.go              # StateStore, ErrorTransformer interfaces
+│   │   ├── finetune_service.go         # FineTuningService implementation (stub)
+│   │   └── deployment_service.go       # DeploymentService implementation (stub)
+│   │
+│   └── providers/                       # Provider Layer (SDK Adapters)
+│       ├── interface.go                 # FineTuningProvider, ModelDeploymentProvider interfaces
+│       ├── openai/
+│       │   └── provider.go             # OpenAI provider implementation (stub)
+│       └── azure/
+│           └── provider.go             # Azure provider implementation (stub)
+│
+├── design/
+│   └── architecture.md                  # Architecture documentation
+└── [existing files unchanged]
+```
+
+## Files Created
+
+### 1. Domain Models (pkg/models/)
+
+#### finetune.go
+- `JobStatus` enum: pending, queued, running, succeeded, failed, cancelled, paused
+- `FineTuningJob` - main domain model for jobs
+- `CreateFineTuningRequest` - request DTO
+- `Hyperparameters` - hyperparameter configuration
+- `ListFineTuningJobsRequest` - pagination request
+- `FineTuningJobDetail` - detailed job info
+- `JobEvent` - event information
+- `JobCheckpoint` - checkpoint data
+
+#### deployment.go
+- `DeploymentStatus` enum: pending, active, updating, failed, deleting
+- `Deployment` - main domain model for deployments
+- `DeploymentRequest` - request DTO
+- `DeploymentConfig` - configuration for deployments
+- `BaseModel` - base model information
+
+#### errors.go
+- `ErrorDetail` - standardized error structure
+- Error code constants: INVALID_REQUEST, NOT_FOUND, UNAUTHORIZED, RATE_LIMITED, etc.
+- Error method implementation
+
+#### requests.go
+- All request DTOs: PauseJobRequest, ResumeJobRequest, CancelJobRequest, etc.
+- ListDeploymentsRequest, GetDeploymentRequest, UpdateDeploymentRequest, etc.
+
+---
+
+### 2. Provider Layer (internal/providers/)
+
+#### interface.go
+Defines two main interfaces:
+
+**FineTuningProvider Interface**
+- `CreateFineTuningJob()`
+- `GetFineTuningStatus()`
+- `ListFineTuningJobs()`
+- `GetFineTuningJobDetails()`
+- `GetJobEvents()`
+- `GetJobCheckpoints()`
+- `PauseJob()`
+- `ResumeJob()`
+- `CancelJob()`
+- `UploadFile()`
+- `GetUploadedFile()`
+
+**ModelDeploymentProvider Interface**
+- `DeployModel()`
+- `GetDeploymentStatus()`
+- `ListDeployments()`
+- `UpdateDeployment()`
+- `DeleteDeployment()`
+
+#### openai/provider.go (Stub Implementation)
+- `OpenAIProvider` struct
+- Implements both `FineTuningProvider` and `ModelDeploymentProvider`
+- All methods have TODO comments (ready for implementation)
+- Constructor: `NewOpenAIProvider(apiKey, endpoint)`
+
+#### azure/provider.go (Stub Implementation)
+- `AzureProvider` struct
+- Implements both `FineTuningProvider` and `ModelDeploymentProvider`
+- All methods have TODO comments (ready for implementation)
+- Constructor: `NewAzureProvider(endpoint, apiKey)`
+
+---
+
+### 3. Service Layer (internal/services/)
+
+#### interface.go
+Defines two service interfaces:
+
+**FineTuningService Interface**
+- `CreateFineTuningJob()` - with business validation
+- `GetFineTuningStatus()`
+- `ListFineTuningJobs()`
+- `GetFineTuningJobDetails()`
+- `GetJobEvents()` - with filtering
+- `GetJobCheckpoints()` - with pagination
+- `PauseJob()` - with state validation
+- `ResumeJob()` - with state validation
+- `CancelJob()` - with proper validation
+- `UploadTrainingFile()` - with validation
+- `UploadValidationFile()` - with validation
+- `PollJobUntilCompletion()` - async polling
+
+**DeploymentService Interface**
+- `DeployModel()` - with validation
+- `GetDeploymentStatus()`
+- `ListDeployments()`
+- `UpdateDeployment()` - with validation
+- `DeleteDeployment()` - with validation
+- `WaitForDeployment()` - timeout support
+
+#### state_store.go
+Defines persistence interfaces:
+
+**StateStore Interface**
+- Job persistence: SaveJob, GetJob, ListJobs, UpdateJobStatus, DeleteJob
+- Deployment persistence: SaveDeployment, GetDeployment, ListDeployments, UpdateDeploymentStatus, DeleteDeployment
+
+**ErrorTransformer Interface**
+- `TransformError()` - converts vendor errors to standardized ErrorDetail
+
+#### finetune_service.go (Stub Implementation)
+- `fineTuningServiceImpl` struct
+- Implements `FineTuningService` interface
+- Constructor: `NewFineTuningService(provider, stateStore)`
+- All methods have TODO comments (ready for implementation)
+- Takes `FineTuningProvider` and `StateStore` as dependencies
+
+#### deployment_service.go (Stub Implementation)
+- `deploymentServiceImpl` struct
+- Implements `DeploymentService` interface
+- Constructor: `NewDeploymentService(provider, stateStore)`
+- All methods have TODO comments (ready for implementation)
+- Takes `ModelDeploymentProvider` and `StateStore` as dependencies
+
+---
+
+## Architecture Verification
+
+### Import Rules Enforced
+
+✅ **pkg/models/** - No imports from other layers
+- Pure data structures only
+
+✅ **internal/providers/interface.go** - Only imports models
+- Vendor-agnostic interface definitions
+
+✅ **internal/providers/openai/provider.go** - Can import:
+- `pkg/models` (domain models)
+- OpenAI SDK (when implemented)
+
+✅ **internal/providers/azure/provider.go** - Can import:
+- `pkg/models` (domain models)
+- Azure SDK (when implemented)
+
+✅ **internal/services/interface.go** - Only imports:
+- `pkg/models`
+- `context`
+
+✅ **internal/services/finetune_service.go** - Only imports:
+- `pkg/models`
+- `internal/providers` (interface, not concrete)
+- `internal/services` (own package for StateStore)
+
+✅ **internal/services/deployment_service.go** - Only imports:
+- `pkg/models`
+- `internal/providers` (interface, not concrete)
+- `internal/services` (own package for StateStore)
+
+---
+
+## Next Steps
+
+### To Implement Provider Layer:
+
+1. **OpenAI Provider** (`internal/providers/openai/provider.go`)
+   - Add OpenAI SDK imports
+   - Implement domain ↔ SDK conversions
+   - Fill in method bodies
+   - Add error transformation logic
+
+2. **Azure Provider** (`internal/providers/azure/provider.go`)
+   - Add Azure SDK imports
+   - Implement domain ↔ SDK conversions
+   - Fill in method bodies
+   - Add error transformation logic
+
+### To Implement Service Layer:
+
+1. **FineTuningService** (`internal/services/finetune_service.go`)
+   - Implement validation logic
+   - Add state persistence calls
+   - Error transformation
+   - Fill in method bodies
+
+2. **DeploymentService** (`internal/services/deployment_service.go`)
+   - Implement validation logic
+   - Add state persistence calls
+   - Error transformation
+   - Fill in method bodies
+
+3. **StateStore Implementation**
+   - File-based storage (JSON files)
+   - Or in-memory with persistence
+
+### To Refactor CLI Layer:
+
+1. Update `internal/cmd/operations.go`
+   - Remove direct SDK calls
+   - Use service layer instead
+   - Inject services via DI
+   - Format output only
+
+2. Create command factory
+   - Initialize providers
+   - Initialize services
+   - Pass to command constructors
+
+---
+
+## Key Benefits of This Structure
+
+✅ **No Existing Files Modified**
+- All new files
+- Extension to existing code without breaking changes
+
+✅ **Clear Separation of Concerns**
+- Models: Pure data
+- Providers: SDK integration
+- Services: Business logic
+- CLI: User interface
+
+✅ **Multi-Vendor Ready**
+- Add new vendor: Just implement provider interface
+- No CLI or service changes needed
+
+✅ **Testable**
+- Mock provider at interface level
+- Test services independently
+- Integration tests for providers
+
+✅ **Future Proof**
+- Easy to add Anthropic, Cohere, etc.
+- Easy to swap implementations
+- Easy to add new features
+
+---
+
+## File Summary
+
+| File | Lines | Purpose |
+|------|-------|---------|
+| pkg/models/finetune.go | ~100 | Fine-tuning domain models |
+| pkg/models/deployment.go | ~80 | Deployment domain models |
+| pkg/models/errors.go | ~40 | Error handling models |
+| pkg/models/requests.go | ~60 | Request DTOs |
+| internal/providers/interface.go | ~70 | Provider interfaces |
+| internal/providers/openai/provider.go | ~150 | OpenAI stub (TODO) |
+| internal/providers/azure/provider.go | ~150 | Azure stub (TODO) |
+| internal/services/interface.go | ~100 | Service interfaces |
+| internal/services/state_store.go | ~60 | Persistence interfaces |
+| internal/services/finetune_service.go | ~120 | Fine-tuning service stub |
+| internal/services/deployment_service.go | ~90 | Deployment service stub |
+| **Total** | **~920** | **Complete stub structure** |
+