# Architecture Design Document

## Technology Stack

### Languages and Runtimes

| Technology | Version |
|------|-----------|
| Node.js | v24.11.0 |
| TypeScript | 5.x |
| npm | 11.x |

### Frameworks and Libraries

| Technology | Version | Purpose | Rationale |
|------|-----------|------|----------|
| [name] | [version] | [purpose] | [rationale] |
| [name] | [version] | [purpose] | [rationale] |

### Development Tools

| Technology | Version | Purpose | Rationale |
|------|-----------|------|----------|
| [name] | [version] | [purpose] | [rationale] |
| [name] | [version] | [purpose] | [rationale] |

## Architecture Pattern

### Layered Architecture

```
┌─────────────────────────┐
│   UI layer              │ ← Accepts and displays user input
├─────────────────────────┤
│   Service layer          │ ← Business logic
├─────────────────────────┤
│   Data layer             │ ← Data persistence
└─────────────────────────┘
```

#### UI Layer
- **Responsibility**: Accepting user input, validation, displaying results
- **Permitted operations**: Calling the service layer
- **Prohibited operations**: Direct access to the data layer

#### Service Layer
- **Responsibility**: Implementing business logic, data transformation
- **Permitted operations**: Calling the data layer
- **Prohibited operations**: Depending on the UI layer

#### Data Layer
- **Responsibility**: Data persistence and retrieval
- **Permitted operations**: Access to the file system and databases
- **Prohibited operations**: Implementing business logic

## Data Persistence Strategy

### Storage Method

| Data type | Storage | Format | Rationale |
|-----------|----------|-------------|------|
| [data 1] | [method] | [format] | [rationale] |
| [data 2] | [method] | [format] | [rationale] |

### Backup Strategy

- **Frequency**: [e.g., every hour]
- **Destination**: [e.g., `.backup/` directory]
- **Generation management**: [e.g., retain the latest 5 generations]
- **Restoration method**: [procedure]

## Performance Requirements

### Response Time

| Operation | Target time | Measurement environment |
|------|---------|---------|
| [operation 1] | [time] | [environment] |
| [operation 2] | [time] | [environment] |

### Resource Usage

| Resource | Limit | Rationale |
|---------|------|------|
| Memory | [MB] | [rationale] |
| CPU | [%] | [rationale] |
| Disk | [MB] | [rationale] |

## Security Architecture

### Data Protection

- **Encryption**: [target data and method]
- **Access control**: [file permissions, etc.]
- **Sensitive information management**: [environment variables, config files, etc.]

### Input Validation

- **Validation**: [validation items]
- **Sanitization**: [target and method]
- **Error handling**: [secure error display]

## Scalability Design

### Handling Data Growth

- **Expected data volume**: [e.g., 10,000 tasks]
- **Performance degradation countermeasures**: [method]
- **Archive strategy**: [handling of old data]

### Extensibility

- **Plugin system**: [presence/absence and design]
- **Configuration customization**: [scope of what is possible]
- **API extensibility**: [methods for future extension]

## Test Strategy

### Unit Tests
- **Framework**: [framework name]
- **Target**: [description of test target]
- **Coverage target**: [%]

### Integration Tests
- **Method**: [test method]
- **Target**: [description of test target]

### E2E Tests
- **Tool**: [tool name]
- **Scenarios**: [test scenarios]

## Technical Constraints

### Environment Requirements
- **OS**: [supported OS]
- **Minimum memory**: [MB]
- **Required disk space**: [MB]
- **Required external dependencies**: [list]

### Performance Constraints
- [constraint 1]
- [constraint 2]

### Security Constraints
- [constraint 1]
- [constraint 2]

## Dependency Management

| Library | Purpose | Version management policy |
|-----------|------|-------------------|
| [name] | [purpose] | [pinned/range] |
| [name] | [purpose] | [pinned/range] |
