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CRUNCHYROLL DOWNLOADER - CHALLENGE 1 SOLUTION
Chapter 3: JWT Login & Authentication
Challenge: Implement Login
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THIS IS THE CORE OF JWT AUTHENTICATION!

PROBLEM:
Create login() function that authenticates with Crunchyroll and returns JWT token.

SOLUTION:
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File: crunchyroll_utils.py

import requests
import json
from pathlib import Path
from config import Config

def login(config: Config) -> str:
    """Login to Crunchyroll and get JWT token."""

    print("🔐 Authenticating with Crunchyroll...")

    # Crunchyroll login endpoint
    url = f"{config.api_base}/auth/v1/authenticate"

    # Prepare login payload
    payload = {
        "username": config.email,
        "password": config.password,
        "grant_type": "password"
    }

    try:
        # POST request with credentials
        response = requests.post(url, json=payload, timeout=10)

        # Check for errors
        if response.status_code != 200:
            print(f"❌ Login failed: {response.status_code}")
            print(f"   Response: {response.text}")
            return None

        # Extract JWT token from response
        data = response.json()
        token = data.get('access_token')

        if not token:
            print("❌ No token in response!")
            print(f"   Response: {data}")
            return None

        print("✅ Login successful!")
        print(f"   Token: {token[:50]}...")  # Show first 50 chars
        return token

    except requests.exceptions.Timeout:
        print("❌ Login timeout - server not responding")
        return None
    except requests.exceptions.ConnectionError:
        print("❌ Connection error - check internet")
        return None
    except Exception as e:
        print(f"❌ Unexpected error: {e}")
        return None


HOW JWT LOGIN WORKS
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Step 1: SEND CREDENTIALS
  POST /auth/v1/authenticate
  Body: {
    "username": "emubantam@gmail.com",
    "password": "mypassword123",
    "grant_type": "password"
  }

Step 2: SERVER VALIDATES
  - Checks if username exists
  - Checks if password matches
  - If valid, creates JWT token

Step 3: SERVER RESPONDS
  200 OK:
  {
    "access_token": "eyJhbGciOiJIUzI1NiIs...",
    "token_type": "Bearer",
    "expires_in": 3600
  }

Step 4: EXTRACT TOKEN
  token = data.get('access_token')
  Returns: "eyJhbGciOiJIUzI1NiIs..."

Step 5: USE TOKEN IN FUTURE REQUESTS
  Headers: {
    "Authorization": "Bearer eyJhbGciOiJIUzI1NiIs..."
  }


JWT TOKEN STRUCTURE
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A JWT token has 3 parts separated by dots:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.
eyJzdWIiOiIxMjM0NTY3ODkwIiwiZW1haWwiOiJqb2huQGV4YW1wbGUuY29tIn0.
TJVA95OrM7E2cBab30RMHrHDcEfxjoYZgeFONFh7HgQ

Part 1 (Header): {"alg":"HS256","typ":"JWT"}
Part 2 (Payload): {"sub":"1234567890","email":"john@example.com"}
Part 3 (Signature): Server's signature to verify it's legitimate


ERROR HANDLING
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Common errors and solutions:

401 Unauthorized:
  → Wrong username or password
  → Check .env file for typos

403 Forbidden:
  → Account suspended or locked
  → Try logging in on website first

400 Bad Request:
  → Missing or malformed payload
  → Check email/password format

Network Error:
  → Internet not connected
  → API server down

Timeout:
  → Server taking too long
  → Check internet speed


TESTING YOUR LOGIN
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Test script:

from config import Config
from crunchyroll_utils import login

config = Config()
if config.validate():
    token = login(config)
    if token:
        print(f"✅ Successfully logged in!")
        print(f"Token: {token[:50]}...")
    else:
        print("❌ Login failed")
else:
    print("❌ Config invalid")


SECURITY NOTE
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⚠️ IMPORTANT:
- token_cache.json will store your JWT token
- JWT tokens are like passwords - keep them secret!
- Never commit token_cache.json to Git
- If token is exposed, Crunchyroll can revoke it
- Tokens expire (usually in 1 hour)
- Can be refreshed without re-logging in

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