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How does the authentication system work in FastAPI with OAuth2?

FastAPI implements OAuth2 with Password flow and Bearer tokens. Here's how it works:

auth.py
python
from fastapi import Depends, FastAPI, HTTPException, status
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from jose import JWTError, jwt
from passlib.context import CryptContext
from datetime import datetime, timedelta

# Password hashing
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

# Token setup
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

# Verify user function
def authenticate_user(username: str, password: str):
    user = get_user(username)
    if not user or not pwd_context.verify(password, user.hashed_password):
        return False
    return user

# Create access token
def create_access_token(data: dict, expires_delta: timedelta):
    to_encode = data.copy()
    expire = datetime.utcnow() + expires_delta
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt

Would you like me to explain how to implement the token endpoint or how to protect your routes?

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How do I implement a custom authentication middleware in Django?

To implement a custom authentication middleware in Django, you need to create a middleware class that processes requests and responses. Here's how:

middleware.py
python
# In your app directory, create middleware.py
from django.http import HttpResponseForbidden
from django.conf import settings
from django.contrib.auth.models import AnonymousUser
import jwt

class JWTAuthMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        # Check for token in headers
        auth_header = request.META.get('HTTP_AUTHORIZATION', '')
        if auth_header.startswith('Bearer '):
            token = auth_header.split(' ')[1]
            try:
                # Decode and verify the token
                payload = jwt.decode(
                    token, 
                    settings.JWT_SECRET_KEY,
                    algorithms=['HS256']
                )
                # Set user on request
                request.user_id = payload.get('user_id')
            except jwt.PyJWTError:
                # Invalid token
                return HttpResponseForbidden('Invalid authentication token')
        
        # Continue processing the request
        response = self.get_response(request)
        return response

Then register your middleware in settings.py:

settings.py
python
# In settings.py
MIDDLEWARE = [
    # Django middleware
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    
    # Your custom middleware
    'yourapp.middleware.JWTAuthMiddleware',
]

How can I implement a custom hook for managing form state in React?

Here's how to create a custom React hook for managing form state with validation:

useForm.ts
typescript
import { useState, ChangeEvent, FormEvent } from 'react';

type ValidationRules<T> = {
  [K in keyof T]?: (value: T[K]) => string | null;
};

type FormErrors<T> = {
  [K in keyof T]?: string;
};

export function useForm<T extends Record<string, any>>(
  initialValues: T,
  validationRules?: ValidationRules<T>,
  onSubmit?: (values: T) => void | Promise<void>
) {
  const [values, setValues] = useState<T>(initialValues);
  const [errors, setErrors] = useState<FormErrors<T>>({});
  const [isSubmitting, setIsSubmitting] = useState(false);

  const handleChange = (
    e: ChangeEvent<HTMLInputElement | HTMLSelectElement | HTMLTextAreaElement>
  ) => {
    const { name, value } = e.target;
    setValues({ ...values, [name]: value });
    
    // Clear error when field is edited
    if (errors[name as keyof T]) {
      setErrors({ ...errors, [name]: undefined });
    }
  };

  const validateField = (name: keyof T, value: any): string | null => {
    if (!validationRules || !validationRules[name]) return null;
    return validationRules[name]!(value);
  };

  const validateForm = (): boolean => {
    if (!validationRules) return true;
    
    const newErrors: FormErrors<T> = {};
    let isValid = true;
    
    Object.keys(values).forEach((key) => {
      const fieldKey = key as keyof T;
      const error = validateField(fieldKey, values[fieldKey]);
      if (error) {
        newErrors[fieldKey] = error;
        isValid = false;
      }
    });
    
    setErrors(newErrors);
    return isValid;
  };

  const handleSubmit = async (e: FormEvent) => {
    e.preventDefault();
    
    if (!validateForm()) return;
    
    setIsSubmitting(true);
    
    try {
      if (onSubmit) {
        await onSubmit(values);
      }
    } finally {
      setIsSubmitting(false);
    }
  };

  const resetForm = () => {
    setValues(initialValues);
    setErrors({});
  };

  return {
    values,
    errors,
    isSubmitting,
    handleChange,
    handleSubmit,
    resetForm,
    setValues
  };
}

This custom hook provides a complete form management solution with:

  • Type-safe form state management
  • Field-level validation
  • Submission handling with loading state
  • Form reset functionality

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