import logging

from logging.handlers import SMTPHandler

from werkzeug.contrib.fixers import ProxyFix
from flask import Flask, render_template
from celery import Celery
from itsdangerous import URLSafeTimedSerializer

from snakeeyes.blueprints.admin import admin
from snakeeyes.blueprints.page import page
from snakeeyes.blueprints.contact import contact
from snakeeyes.blueprints.user import user
from snakeeyes.blueprints.user.models import User
from snakeeyes.extensions import (
    debug_toolbar,
    mail,
    csrf,
    db,
    login_manager
)

CELERY_TASK_LIST = [
    'snakeeyes.blueprints.contact.tasks',
    'snakeeyes.blueprints.user.tasks',
]


def create_celery_app(app=None):
    """
    Create a new Celery object and tie together the Celery config to the app's
    config. Wrap all tasks in the context of the application.

    :param app: Flask app
    :return: Celery app
    """
    app = app or create_app()

    celery = Celery(app.import_name, broker=app.config['CELERY_BROKER_URL'],
                    include=CELERY_TASK_LIST)
    celery.conf.update(app.config)
    TaskBase = celery.Task

    class ContextTask(TaskBase):
        abstract = True

        def __call__(self, *args, **kwargs):
            with app.app_context():
                return TaskBase.__call__(self, *args, **kwargs)

    celery.Task = ContextTask
    return celery


def create_app(settings_override=None):
    """
    Create a Flask application using the app factory pattern.

    :param settings_override: Override settings
    :return: Flask app
    """
    app = Flask(__name__, instance_relative_config=True)

    app.config.from_object('config.settings')
    app.config.from_pyfile('settings.py', silent=True)

    if settings_override:
        app.config.update(settings_override)

    app.logger.setLevel(app.config['LOG_LEVEL'])

    middleware(app)
    error_templates(app)
    exception_handler(app)
    app.register_blueprint(admin)
    app.register_blueprint(page)
    app.register_blueprint(contact)
    app.register_blueprint(user)
    extensions(app)
    authentication(app, User)

    return app


def extensions(app):
    """
    Register 0 or more extensions (mutates the app passed in).

    :param app: Flask application instance
    :return: None
    """
    debug_toolbar.init_app(app)
    mail.init_app(app)
    csrf.init_app(app)
    db.init_app(app)
    login_manager.init_app(app)

    return None


def authentication(app, user_model):
    """
    Initialize the Flask-Login extension (mutates the app passed in).

    :param app: Flask application instance
    :param user_model: Model that contains the authentication information
    :type user_model: SQLAlchemy model
    :return: None
    """
    login_manager.login_view = 'user.login'

    @login_manager.user_loader
    def load_user(uid):
        return user_model.query.get(uid)

    @login_manager.token_loader
    def load_token(token):
        duration = app.config['REMEMBER_COOKIE_DURATION'].total_seconds()
        serializer = URLSafeTimedSerializer(app.secret_key)

        data = serializer.loads(token, max_age=duration)
        user_uid = data[0]

        return user_model.query.get(user_uid)


def middleware(app):
    """
    Register 0 or more middleware (mutates the app passed in).

    :param app: Flask application instance
    :return: None
    """
    # Swap request.remote_addr with the real IP address even if behind a proxy.
    app.wsgi_app = ProxyFix(app.wsgi_app)

    return None


def error_templates(app):
    """
    Register 0 or more custom error pages (mutates the app passed in).

    :param app: Flask application instance
    :return: None
    """

    def render_status(status):
        """
         Render a custom template for a specific status.
           Source: http://stackoverflow.com/a/30108946

         :param status: Status as a written name
         :type status: str
         :return: None
         """
        # Get the status code from the status, default to a 500 so that we
        # catch all types of errors and treat them as a 500.
        code = getattr(status, 'code', 500)
        return render_template('errors/{0}.html'.format(code)), code

    for error in [404, 500]:
        app.errorhandler(error)(render_status)

    return None


def exception_handler(app):
    """
    Register 0 or more exception handlers (mutates the app passed in).

    :param app: Flask application instance
    :return: None
    """
    mail_handler = SMTPHandler((app.config.get('MAIL_SERVER'),
                                app.config.get('MAIL_PORT')),
                               app.config.get('MAIL_USERNAME'),
                               [app.config.get('MAIL_USERNAME')],
                               '[Exception handler] A 5xx was thrown',
                               (app.config.get('MAIL_USERNAME'),
                                app.config.get('MAIL_PASSWORD')),
                               secure=())

    mail_handler.setLevel(logging.ERROR)
    mail_handler.setFormatter(logging.Formatter("""
    Time:               %(asctime)s
    Message type:       %(levelname)s


    Message:

    %(message)s
    """))
    app.logger.addHandler(mail_handler)

    return None