# Copyright 2015 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import json
import logging

from flask import current_app, Flask, redirect, request, session, url_for
import httplib2
from oauth2client.contrib.flask_util import UserOAuth2


oauth2 = UserOAuth2()


def create_app(config, debug=False, testing=False, config_overrides=None):
    app = Flask(__name__)
    app.config.from_object(config)

    app.debug = debug
    app.testing = testing

    if config_overrides:
        app.config.update(config_overrides)

    # Configure logging
    if not app.testing:
        logging.basicConfig(level=logging.INFO)

    # Setup the data model.
    with app.app_context():
        model = get_model()
        model.init_app(app)

    # Create a health check handler. Health checks are used when running on
    # Google Compute Engine by the load balancer to determine which instances
    # can serve traffic. Google App Engine also uses health checking, but
    # accepts any non-500 response as healthy.
    @app.route('/_ah/health')
    def health_check():
        return 'ok', 200

    # Initalize the OAuth2 helper.
    oauth2.init_app(
        app,
        scopes=['email', 'profile'],
        authorize_callback=_request_user_info)

    # Add a logout handler.
    @app.route('/logout')
    def logout():
        # Delete the user's profile and the credentials stored by oauth2.
        del session['profile']
        session.modified = True
        oauth2.storage.delete()
        return redirect(request.referrer or '/')

    # Register the Bookshelf CRUD blueprint.
    from .crud import crud
    app.register_blueprint(crud, url_prefix='/books')

    # Add a default root route.
    @app.route("/")
    def index():
        return redirect(url_for('crud.list'))

    # Add an error handler. This is useful for debugging the live application,
    # however, you should disable the output of the exception for production
    # applications.
    @app.errorhandler(500)
    def server_error(e):
        return """
        An internal error occurred: <pre>{}</pre>
        See logs for full stacktrace.
        """.format(e), 500

    return app


def get_model():
    model_backend = current_app.config['DATA_BACKEND']
    if model_backend == 'cloudsql':
        from . import model_cloudsql
        model = model_cloudsql
    elif model_backend == 'datastore':
        from . import model_datastore
        model = model_datastore
    elif model_backend == 'mongodb':
        from . import model_mongodb
        model = model_mongodb
    else:
        raise ValueError(
            "No appropriate databackend configured. "
            "Please specify datastore, cloudsql, or mongodb")

    return model


def _request_user_info(credentials):
    """
    Makes an HTTP request to the Google OAuth2 API to retrieve the user's basic
    profile information, including full name and photo, and stores it in the
    Flask session.
    """
    http = httplib2.Http()
    credentials.authorize(http)
    resp, content = http.request(
        'https://www.googleapis.com/oauth2/v3/userinfo')

    if resp.status != 200:
        current_app.logger.error(
            "Error while obtaining user profile: \n%s: %s", resp, content)
        return None

    session['profile'] = json.loads(content.decode('utf-8'))