Flask Google Login

app.py

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from Flask import Flask, redirect, request, url_for
from flask_sqlalchemy import SQLAlchemy
from flask_login import LoginManager, current_user, login_user, logout_user, login_required
import json
import os
from oauthlib.oauth2 import WebApplicationClient
import requests

# Configuration
GOOGLE_CLIENT_ID = os.environ.get("GOOGLE_CLIENT_ID", None)
GOOGLE_CLIENT_SECRET = os.environ.get("GOOGLE_CLIENT_SECRET", None)
GOOGLE_DISCOVERY_URL = (
    "https://accounts.google.com/.well-known/openid-configuration"
)

app = Flask(__name__)

app.secret_key = "i-am-very-secret"
app.config['SQLALCHEMY_DATABASE_URI'] = "sqlite:///iread.db"
db = SQLAlchemy(app)

# User session management setup
# https://flask-login.readthedocs.io/en/latest
login_manager = LoginManager()
login_manager.init_app(app)

class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50), nullable=False)
    email = db.Column(db.String(50), nullable=False)
    profile_image = db.Column(db.String(500), nullable=True)

@app.route('/')
def index():
    if current_user.is_authenticated:
        return (
            "<p>Hello, {}! You're logged in! Email: {}</p>"
            "<div><p>Google Profile Picture:</p>"
            '<img src="{}" alt="Google profile pic"></img></div>'
            '<a class="button" href="/logout">Logout</a>'.format(
                current_user.name, current_user.email, current_user.profile_pic
            )
        )
    else:
        return '<a class="button" href="/login">Google Login</a>'

def get_google_provider_cfg():
    return requests.get(GOOGLE_DISCOVERY_URL).json()

@app.route('/login')
def login():
    # Find out what URL to hit for Google login
    google_provider_cfg = get_google_provider_cfg()
    authorization_endpoint = google_provider_cfg["authorization_endpoint"]

    # Use library to construct the request for Google login and provide
    # scopes that let you retrieve user's profile from Google
    request_uri = client.prepare_request_uri(
        authorization_endpoint,
        redirect_uri=request.base_url + "/callback",
        scope=["openid", "email", "profile"],
    )
    return redirect(request_uri)

@app.route("/login/callback")
def callback():
    # Get authorization code Google sent back to you
    code = request.args.get("code")
    # Find out what URL to hit to get tokens that allow you to ask for
    # things on behalf of a user
    google_provider_cfg = get_google_provider_cfg()
    token_endpoint = google_provider_cfg["token_endpoint"]
    
    # Prepare and send a request to get tokens! Yay tokens!
    token_url, headers, body = client.prepare_token_request(
        token_endpoint,
        authorization_response=request.url,
        redirect_url=request.base_url,
        code=code
    )
    token_response = requests.post(
        token_url,
        headers=headers,
        data=body,
        auth=(GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET),
    )

    # Parse the tokens!
    client.parse_request_body_response(json.dumps(token_response.json()))
    
    # Now that you have tokens (yay) let's find and hit the URL
    # from Google that gives you the user's profile information,
    # including their Google profile image and email
    userinfo_endpoint = google_provider_cfg["userinfo_endpoint"]
    uri, headers, body = client.add_token(userinfo_endpoint)
    userinfo_response = requests.get(uri, headers=headers, data=body)
    
    # You want to make sure their email is verified.
    # The user authenticated with Google, authorized your
    # app, and now you've verified their email through Google!
    if userinfo_response.json().get("email_verified"):
        users_email = userinfo_response.json()["email"]
        picture = userinfo_response.json()["picture"]
        users_name = userinfo_response.json()["given_name"]
    else:
        return "User email not available or not verified by Google.", 400
    
    # Create a user in your db with the information provided
    # by Google


    # Doesn't exist? Add it to the database.
    if not User.query.filter_by(email=username).first():
        new_user = User(name=users_name, email=users_email, profile_image=picture)
        db.session.add(new_user)
        db.session.commit()


    # Begin user session by logging the user in
    user = User.query.filter_by(email=users_email).first()
    login_user(user)

    # Send user back to homepage
    return redirect(url_for("index"))
    
@app.route("/logout")
@login_required
def logout():
    logout_user()
    return redirect(url_for("index"))
    
if __name__ == '__main__':
    app.run(port=5000, debug=True)