# Code Style Guide - Quick Reference

## Language: ENGLISH ONLY

All code, comments, docstrings, and variable names **MUST** be in English.

---

## Formatting

### Line Length
- **Maximum: 100 characters**
- Configure editor ruler: `View → Toggle Rulers`

### Indentation
- **4 spaces** (no tabs)
- Auto-enforced by Black

### Blank Lines
- **2 blank lines** between module-level definitions
- **1 blank line** between class methods
- **1 blank line** inside functions for logical grouping

---

## Imports

### Order
```python
# 1. Standard library
import sys
import os
from pathlib import Path
from typing import Optional, Dict, List, TypeVar, Type

# 2. Third-party
import requests
from pydantic import BaseModel, Field, ValidationError
from dotenv import load_dotenv

# 3. Local/relative
from .exceptions import ElytraAPIError
from .models import ProductResponse
```

### Rules
- ✅ Use absolute imports
- ✅ Group by: stdlib → third-party → local
- ✅ Alphabetical within groups
- ❌ No `from module import *` (use explicit imports)
- ❌ No unused imports (checked by flake8)

---

## Type Hints

### Functions
```python
# Good
def get_product(
    product_id: str,
    lang: str = "en"
) -> ProductResponse:
    """Get a product."""
    pass

# Good - with Optional
def find_product(
    name: Optional[str] = None
) -> Optional[ProductResponse]:
    """Find product by name."""
    pass

# Good - with Union (Python 3.10+)
def process(data: dict | list) -> str:
    """Process data."""
    pass

# Bad - missing type hints
def get_products(product_id):
    return response
```

### Variables
```python
# At module level
API_TIMEOUT: int = 30
DEFAULT_LANG: str = "en"
ALLOWED_LANGS: List[str] = ["en", "de", "fr"]

# In functions
active_products: List[Product] = []
product_map: Dict[str, Product] = {}
result: Optional[ProductResponse] = None
```

### Generic Types
```python
from typing import TypeVar, Generic, List

T = TypeVar('T', bound=BaseModel)

def validate_response(
    data: dict,
    model: Type[T]
) -> T:
    """Generic response validator."""
    return model.model_validate(data)
```

---

## Docstrings (Google Style)

### Module Level
```python
"""Module description.

Longer explanation if needed.

This module handles product management operations including
creating, updating, and retrieving products from the API.
"""
```

### Classes
```python
class ElytraClient:
    """A Pythonic client for the Elytra PIM API.

    This client provides convenient methods for interacting with
    the Elytra PIM API, including authentication and product management.

    Args:
        base_url: The base URL of the Elytra PIM API
        api_key: The API key for authentication
        timeout: Request timeout in seconds (default: 30)

    Attributes:
        session: Requests.Session instance for connection pooling
    """
    pass
```

### Functions/Methods
```python
def create_product(
    self,
    name: str,
    description: str,
    lang: str = "en"
) -> SingleProductResponse:
    """Create a new product.

    Creates a new product in the Elytra PIM system with the provided
    information.

    Args:
        name: Product name (required, max 255 chars)
        description: Product description
        lang: Language code (default: "en")

    Returns:
        SingleProductResponse: The newly created product with ID

    Raises:
        ElytraValidationError: If validation fails
        ElytraAuthenticationError: If authentication fails
        ElytraAPIError: For other API errors

    Example:
        >>> client = ElytraClient(base_url="...", api_key="...")
        >>> product = client.create_product("Widget", "A useful widget")
        >>> print(product.id)
    """
    pass
```

---

## Naming Conventions

### Constants
```python
# UPPER_CASE_WITH_UNDERSCORES
API_TIMEOUT = 30
MAX_RETRIES = 3
DEFAULT_LANGUAGE = "en"
```

### Classes
```python
# PascalCase
class ElytraClient:
    pass

class ProductResponse:
    pass

class InvalidProductError:
    pass
```

### Functions & Methods
```python
# snake_case
def get_products():
    pass

def create_new_product():
    pass

def validate_input():
    pass
```

### Variables
```python
# snake_case
product_id = "123"
api_key = "secret"
response_data = {}
is_valid = True
```

### Private Methods/Attributes
```python
# Leading underscore for private
def _make_request(self):
    pass

def _validate_response(self, response):
    pass

_cache = {}
_internal_state = None
```

### Constants vs Variables
```python
# Constants (module-level, unchanging)
DEFAULT_TIMEOUT = 30
API_VERSION = "v1"

# Variables (local, changeable)
timeout = config.get("timeout", DEFAULT_TIMEOUT)
request_id = str(uuid4())
```

---

## Strings

### Formatting
```python
# f-strings (Python 3.6+) - PREFERRED
name = "Product"
print(f"Created product: {name}")

# Format method
print("Created product: {}".format(name))

# % formatting - AVOID
print("Created product: %s" % name)
```

### Quotes
```python
# Use double quotes as default
message = "This is a message"
docstring = """Multi-line docstring used with three
double quotes."""

# Use single quotes when string contains double quote
message = 'He said "Hello"'
```

---

## Exceptions

### Handling
```python
# Good - specific exception, with context
try:
    response = self.session.request(method, url)
    response.raise_for_status()
except requests.HTTPError as e:
    if e.response.status_code == 404:
        raise ElytraNotFoundError("Resource not found") from e
    raise ElytraAPIError(f"HTTP Error: {e}") from e
except requests.RequestException as e:
    raise ElytraAPIError(f"Network error: {str(e)}") from e

# Bad - too broad, no context
try:
    response = requests.get(url)
except:
    print("Error")

# Bad - bare raise without context
except Exception:
    return None
```

### Raising
```python
# Good - with meaningful message
raise ElytraValidationError(f"Invalid product ID: {product_id}")

# Good - with cause chain
try:
    data = pydantic_model.model_validate(response)
except ValidationError as e:
    raise ElytraValidationError(f"Response validation failed") from e

# Bad - generic message
raise ElytraAPIError("Error")
```

---

## Pydantic Models

```python
from pydantic import BaseModel, Field, ConfigDict

class ProductResponse(BaseModel):
    """Response model for a single product.

    Validates and represents a product object from the API.
    """
    # Required field with description
    id: str = Field(..., description="Unique product identifier")
    name: str = Field(..., description="Product name", min_length=1, max_length=255)

    # Optional field with default
    description: Optional[str] = Field(None, description="Product description")

    # Field with default value
    language: str = Field("en", description="Language code")

    # List field with default factory
    tags: List[str] = Field(default_factory=list, description="Product tags")

    # Configuration
    model_config = ConfigDict(
        str_strip_whitespace=True,  # Automatically strip whitespace from strings
        validate_default=True,       # Validate default values
    )
```

---

## Comments

### Good Comments
```python
# Good - explains WHY, not WHAT
# We need to retry failed requests as the API has rate limiting
for retry in range(MAX_RETRIES):
    try:
        return self._make_request(...)
    except RequestException:
        if retry == MAX_RETRIES - 1:
            raise

# Good - documents non-obvious code
# Using session instead of individual requests for connection pooling
self.session = requests.Session()

# Good - TODO comments
# TODO: implement pagination for large datasets (issue #123)
def get_all_products(self):
    pass
```

### Bad Comments
```python
# Bad - obvious, doesn't add value
# Increment counter
counter += 1

# Bad - outdated/wrong info
# This will be removed next release (said in 2020)
def deprecated_method(self):
    pass

# BAD - NEVER DO THIS
# código de prueba
# 这个是测试代码
# Ceci est un test
```

---

## Control Flow

### If Statements
```python
# Good - clear and readable
if user_is_authenticated and not is_rate_limited:
    return process_request(data)

# Bad - too complex
if x and y or z and not w:
    pass

# Good - use `in` for membership
if method in ("GET", "POST", "PUT"):
    pass

# Good - use `is` for None, True, False
if result is None:
    pass

if is_valid is True:  # or just: if is_valid:
    pass
```

### Loops
```python
# Good - enumerate for index and value
for idx, item in enumerate(items):
    print(f"{idx}: {item}")

# Good - dict iteration
for key, value in config.items():
    print(f"{key} = {value}")

# Avoid - unnecessary else clause
for item in items:
    if match(item):
        break
else:
    # Only executes if loop completed without break
    # Often confusing - better to use explicit flag
    handle_not_found()
```

---

## Context Managers

```python
# Good - automatic cleanup
with session.get(url) as response:
    data = response.json()

# For custom classes
class ElytraClient:
    def __enter__(self):
        """Enter context."""
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        """Exit context and cleanup."""
        self.session.close()
        return False  # Don't suppress exceptions

# Usage
with ElytraClient(base_url, api_key) as client:
    products = client.get_products()
```

---

## Whitespace and Blank Lines

### Module Structure
```python
"""Module docstring."""

# Imports (with blank line after)
import os
from typing import List

# Module constants (with blank line before and after)
DEFAULT_TIMEOUT = 30
API_VERSION = "v1"

# Classes (with 2 blank lines before)


class FirstClass:
    """Class docstring."""

    def method_one(self):
        """First method."""
        pass

    def method_two(self):
        """Second method."""
        pass


class SecondClass:
    """Another class."""
    pass


# Module-level functions (with 2 blank lines before)


def module_function():
    """A module-level function."""
    pass
```

---

## Line Breaking

```python
# Good - break long imports
from pydantic import (
    BaseModel,
    Field,
    ValidationError,
    ConfigDict,
)

# Good - break long function signatures
def create_product(
    self,
    name: str,
    description: Optional[str] = None,
    lang: str = "en",
) -> SingleProductResponse:
    pass

# Good - break long lines with backslash (function calls)
result = self._make_request(
    method="POST",
    endpoint="/products",
    json_data=product_data,
    response_model=ProductResponse,
)

# Good - break long conditionals
if (
    user_is_authenticated and
    not is_rate_limited and
    has_valid_request_data
):
    process_request()
```

---

## Linting and Formatting Commands

```bash
# Format with Black
black elytra_client tests

# Sort imports with isort
isort elytra_client tests

# Lint with Flake8
flake8 elytra_client tests

# Type check with mypy
mypy elytra_client

# Run all (recommended before commit)
black elytra_client tests && \
isort elytra_client tests && \
flake8 elytra_client tests && \
mypy elytra_client && \
pytest tests/ -v
```

---

## Summary Checklist

Before committing code:

- [ ] All code is in **English**
- [ ] **No lines exceed 100 characters** (Black will enforce)
- [ ] **Type hints** on all functions
- [ ] **Docstrings** on all public APIs (Google style)
- [ ] **No unused imports** (Flake8 checks)
- [ ] **Proper exception handling** with meaningful messages
- [ ] **Tests** for new code
- [ ] Run Black and isort
- [ ] Run Flake8
- [ ] Run mypy
- [ ] Run pytest