# Documentation Standards

## Overview

Consistent documentation standards improve readability, maintainability, and usability. Well-documented code is easier to understand, modify, and extend.

## Documentation Types

### Code Documentation
- **Docstrings**: Function/class documentation
- **Comments**: Inline explanations
- **Type Hints**: Type annotations
- **Examples**: Usage examples

### API Documentation
- **Endpoints**: Route definitions
- **Parameters**: Request/response schemas
- **Examples**: Request/response examples
- **Error Codes**: Error handling

### Architecture Documentation
- **System Design**: Overall architecture
- **Data Flow**: Information flow
- **Component Diagrams**: System components
- **Decision Records**: Architecture decisions

### User Documentation
- **Getting Started**: Quick start guides
- **Tutorials**: Step-by-step guides
- **Reference**: Complete API reference
- **FAQ**: Common questions

## Code Documentation Standards

### Docstring Formats

**Google Style:**
```python
def calculate_total(items, tax_rate=0.1):
    """Calculate total price including tax.
    
    Args:
        items: List of items with 'price' attribute
        tax_rate: Tax rate as decimal (default: 0.1)
        
    Returns:
        Total price including tax
        
    Raises:
        ValueError: If tax_rate is negative
        
    Example:
        >>> items = [{'price': 10}, {'price': 20}]
        >>> calculate_total(items, 0.1)
        33.0
    """
    pass
```

**NumPy Style:**
```python
def calculate_total(items, tax_rate=0.1):
    """Calculate total price including tax.
    
    Parameters
    ----------
    items : list of dict
        List of items with 'price' attribute
    tax_rate : float, optional
        Tax rate as decimal (default: 0.1)
        
    Returns
    -------
    float
        Total price including tax
        
    Raises
    ------
    ValueError
        If tax_rate is negative
    """
    pass
```

### Inline Comments

**Good Comments:**
```python
# Calculate compound interest using formula: A = P(1 + r/n)^(nt)
principal = 1000
rate = 0.05
years = 10
# Compounded monthly
compounds_per_year = 12
amount = principal * (1 + rate / compounds_per_year) ** (compounds_per_year * years)
```

**Bad Comments:**
```python
# Increment counter
counter += 1  # This is obvious
```

## API Documentation

### OpenAPI/Swagger
```yaml
paths:
  /users/{id}:
    get:
      summary: Get user by ID
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: integer
      responses:
        200:
          description: User found
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/User'
```

### Endpoint Documentation
- **Method**: GET, POST, PUT, DELETE
- **Path**: URL endpoint
- **Parameters**: Query, path, body parameters
- **Responses**: Status codes and schemas
- **Authentication**: Required auth
- **Examples**: Request/response examples

## Documentation Best Practices

### Writing Guidelines

1. **Be Clear**: Use simple, direct language
2. **Be Concise**: Don't be verbose
3. **Be Accurate**: Keep docs current
4. **Be Complete**: Cover all important aspects
5. **Be Examples**: Include working examples

### Structure

1. **Overview**: High-level description
2. **Details**: In-depth explanation
3. **Examples**: Practical examples
4. **References**: Related documentation

### Maintenance

1. **Keep Current**: Update with code changes
2. **Review Regularly**: Quarterly reviews
3. **Remove Outdated**: Delete obsolete docs
4. **Version Control**: Track doc changes

## Documentation Tools

### Code Documentation
- **Sphinx**: Python documentation generator
- **JSDoc**: JavaScript documentation
- **Doxygen**: Multi-language documentation
- **Godoc**: Go documentation

### API Documentation
- **Swagger/OpenAPI**: API documentation standard
- **Postman**: API documentation and testing
- **Redoc**: OpenAPI documentation
- **Insomnia**: API documentation

### Documentation Platforms
- **Read the Docs**: Documentation hosting
- **GitBook**: Modern documentation platform
- **MkDocs**: Markdown documentation
- **Docusaurus**: Documentation website

## Documentation Metrics

### Quality Metrics
- **Coverage**: % of code documented
- **Freshness**: Last update date
- **Readability**: Readability scores
- **Completeness**: Required sections present

### Usage Metrics
- **Page Views**: Documentation visits
- **Search Queries**: What users search for
- **Feedback**: User comments/suggestions
- **Time on Page**: Engagement metrics
