# AtlasOS - Calypso Backend Foundation (Phase B Complete)

## Summary

The backend foundation for AtlasOS - Calypso has been successfully implemented according to the SRS specifications. This document summarizes what has been delivered.

## Deliverables

### 1. Repository Structure ✅
```
/development/calypso/
├── backend/
│   ├── cmd/calypso-api/          # Main application entry point
│   ├── internal/
│   │   ├── auth/                 # Authentication handlers
│   │   ├── iam/                  # Identity and access management
│   │   ├── audit/                 # Audit logging middleware
│   │   ├── tasks/                 # Async task engine
│   │   ├── system/                # System management (placeholder)
│   │   ├── monitoring/            # Monitoring (placeholder)
│   │   └── common/                # Shared utilities
│   │       ├── config/            # Configuration management
│   │       ├── database/          # Database connection and migrations
│   │       ├── logger/            # Structured logging
│   │       └── router/            # HTTP router setup
│   ├── db/migrations/             # Database migration files
│   ├── config.yaml.example        # Example configuration
│   ├── go.mod                     # Go module definition
│   ├── Makefile                   # Build automation
│   └── README.md                  # Backend documentation
├── deploy/
│   └── systemd/
│       └── calypso-api.service    # Systemd service file
└── scripts/
    └── install-requirements.sh   # System requirements installer
```

### 2. System Requirements Installation Script ✅
- **Location**: `/development/calypso/scripts/install-requirements.sh`
- **Features**:
  - Installs Go 1.22.0
  - Installs Node.js 20.x LTS and pnpm
  - Installs PostgreSQL
  - Installs disk storage tools (LVM2, XFS, etc.)
  - Installs physical tape tools (lsscsi, sg3-utils, mt-st, mtx)
  - Installs iSCSI initiator tools
  - Installs SCST prerequisites
  - Includes verification section

### 3. Database Schema ✅
- **Location**: `/development/calypso/backend/internal/common/database/migrations/001_initial_schema.sql`
- **Tables Created**:
  - `users` - User accounts
  - `roles` - System roles (admin, operator, readonly)
  - `permissions` - Fine-grained permissions
  - `user_roles` - User-role assignments
  - `role_permissions` - Role-permission assignments
  - `sessions` - Active user sessions
  - `audit_log` - Audit trail for all mutating operations
  - `tasks` - Async task state
  - `alerts` - System alerts
  - `system_config` - System configuration key-value store
  - `schema_migrations` - Migration tracking

### 4. API Endpoints ✅

#### Health Check
- `GET /api/v1/health` - System health status (no auth required)

#### Authentication
- `POST /api/v1/auth/login` - User login (returns JWT token)
- `POST /api/v1/auth/logout` - User logout
- `GET /api/v1/auth/me` - Get current user info (requires auth)

#### Tasks
- `GET /api/v1/tasks/{id}` - Get task status by ID (requires auth)

#### IAM (Admin only)
- `GET /api/v1/iam/users` - List all users
- `GET /api/v1/iam/users/{id}` - Get user details
- `POST /api/v1/iam/users` - Create new user
- `PUT /api/v1/iam/users/{id}` - Update user
- `DELETE /api/v1/iam/users/{id}` - Delete user

### 5. Security Features ✅

#### Authentication
- JWT-based authentication
- Session management
- Password hashing (Argon2id - stub implementation, needs completion)
- Token expiration

#### Authorization (RBAC)
- Role-based access control middleware
- Three default roles:
  - **admin**: Full system access
  - **operator**: Day-to-day operations
  - **readonly**: Read-only access
- Permission-based access control (scaffold ready)

#### Audit Logging
- Automatic audit logging for all mutating HTTP methods (POST, PUT, DELETE, PATCH)
- Logs user, action, resource, IP address, user agent, request body, response status
- Immutable audit trail in PostgreSQL

### 6. Task Engine ✅
- **Location**: `/development/calypso/backend/internal/tasks/`
- **Features**:
  - Task state machine (pending → running → completed/failed/cancelled)
  - Progress reporting (0-100%)
  - Task persistence in database
  - Task metadata support (JSON)
  - Task types: inventory, load_unload, rescan, apply_scst, support_bundle

### 7. Configuration Management ✅
- YAML-based configuration with environment variable overrides
- Sensible defaults
- Example configuration file provided
- Supports:
  - Server settings (port, timeouts)
  - Database connection
  - JWT authentication
  - Logging configuration

### 8. Structured Logging ✅
- JSON-formatted logs (production)
- Text-formatted logs (development)
- Log levels: debug, info, warn, error
- Contextual logging with structured fields

### 9. Systemd Integration ✅
- Systemd service file provided
- Runs as non-root user (`calypso`)
- Security hardening (NoNewPrivileges, PrivateTmp, ProtectSystem)
- Automatic restart on failure
- Journald integration

## Architecture Highlights

### Clean Architecture
- Clear separation of concerns
- Domain boundaries respected
- No business logic in handlers
- Dependency injection pattern

### Error Handling
- Explicit error types
- Meaningful error messages
- Proper HTTP status codes

### Context Propagation
- Context used throughout for cancellation and timeouts
- Database operations respect context

### Database Migrations
- Automatic migration on startup
- Versioned migrations
- Migration tracking table

## Next Steps (Phase C - Backend Core Domains)

The following domains need to be implemented in Phase C:

1. **Storage Component** (SRS-01)
   - LVM management
   - Disk repository provisioning
   - iSCSI target creation

2. **Physical Tape Bridge** (SRS-02)
   - Tape library discovery
   - Changer and drive operations
   - Inventory management

3. **Virtual Tape Library** (SRS-02)
   - MHVTL integration
   - Virtual tape management
   - Tape image storage

4. **SCST Integration** (SRS-01, SRS-02)
   - SCST target configuration
   - iSCSI target management
   - LUN mapping

5. **System Management** (SRS-03)
   - Service management
   - Log viewing
   - Support bundle generation

6. **Monitoring** (SRS-05)
   - Health checks
   - Alerting
   - Metrics collection

## Running the Backend

### Prerequisites
1. Run the installation script:
   ```bash
   sudo ./scripts/install-requirements.sh
   ```

2. Create PostgreSQL database:
   ```bash
   sudo -u postgres createdb calypso
   sudo -u postgres createuser calypso
   sudo -u postgres psql -c "ALTER USER calypso WITH PASSWORD 'your_password';"
   ```

3. Set environment variables:
   ```bash
   export CALYPSO_DB_PASSWORD="your_password"
   export CALYPSO_JWT_SECRET="your_jwt_secret_min_32_chars"
   ```

### Build and Run
```bash
cd backend
go mod download
go run ./cmd/calypso-api -config config.yaml.example
```

The API will be available at `http://localhost:8080`

### Testing Endpoints

1. **Health Check**:
   ```bash
   curl http://localhost:8080/api/v1/health
   ```

2. **Login** (create a user first via IAM API):
   ```bash
   curl -X POST http://localhost:8080/api/v1/auth/login \
     -H "Content-Type: application/json" \
     -d '{"username":"admin","password":"password"}'
   ```

3. **Get Current User** (requires JWT token):
   ```bash
   curl http://localhost:8080/api/v1/auth/me \
     -H "Authorization: Bearer YOUR_JWT_TOKEN"
   ```

## Known Limitations / TODOs

1. **Password Hashing**: Argon2id implementation is stubbed - needs proper implementation
2. **Token Hashing**: Session token hashing is simplified - needs cryptographic hash
3. **Path Parsing**: Audit log path parsing is simplified - can be enhanced
4. **Error Messages**: Some error messages could be more specific
5. **Input Validation**: Additional validation needed for user inputs
6. **Rate Limiting**: Not yet implemented
7. **CORS**: Currently allows all origins - should be configurable

## Compliance with SRS

✅ **Section 0**: All authoritative specifications read and followed  
✅ **Section 1**: Platform assumptions respected (Ubuntu 24.04, single-node)  
✅ **Section 2**: Development order followed (Phase A & B complete)  
✅ **Section 3**: Environment & requirements installed  
✅ **Section 4**: Backend foundation created  
✅ **Section 5**: Minimum deliverables implemented  
✅ **Section 6**: Hard system rules respected (no shell execution, audit on mutating ops)  
✅ **Section 7**: Enterprise standards applied (structured logging, error handling)  
✅ **Section 8**: Workflow requirements followed  

## Files Created

### Core Application
- `backend/cmd/calypso-api/main.go`
- `backend/internal/common/config/config.go`
- `backend/internal/common/logger/logger.go`
- `backend/internal/common/database/database.go`
- `backend/internal/common/database/migrations.go`
- `backend/internal/common/router/router.go`
- `backend/internal/common/router/middleware.go`

### Domain Modules
- `backend/internal/auth/handler.go`
- `backend/internal/iam/user.go`
- `backend/internal/iam/handler.go`
- `backend/internal/audit/middleware.go`
- `backend/internal/tasks/handler.go`
- `backend/internal/tasks/engine.go`

### Database
- `backend/internal/common/database/migrations/001_initial_schema.sql`

### Configuration & Deployment
- `backend/config.yaml.example`
- `backend/go.mod`
- `backend/Makefile`
- `backend/README.md`
- `deploy/systemd/calypso-api.service`
- `scripts/install-requirements.sh`

---

**Status**: Phase B (Backend Foundation) - ✅ COMPLETE  
**Ready for**: Phase C (Backend Core Domains)

