Source code for topchef.wsgi_app

"""
Contains the factories for making the WSGI application that handles HTTP
requests.

The `web server gateway interface (WSGI) <https://goo.gl/s8T9V7>`_ is an API
for web application servers like Apache to call Python programs in order to
execute HTTP methods. It accomplishes an equivalent role as Java's servlet
API, enabling multiple web frameworks to use the same web server.

`Flask <http://flask.pocoo.org/>`_ is a web framework built on top of WSGI
for making dynamic web applications. At its core is an application object of
type ``Flask`` that maps WSGI to plain Python functions. This module takes
care of generating this flask application.
"""
import abc
from flask import Flask
from .api import APIMetadata, ServicesList, ServiceDetail
from .api import JobsList, JobsForService, JobQueueForService
from .api import NextJob as NextJobEndpoint, JobDetail
from .api import JSONSchemaValidator
from .method_override_middleware import HTTPMethodOverrideMiddleware
from sqlalchemy import create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.orm import scoped_session
from .config import config


class WSGIAppFactory(object, metaclass=abc.ABCMeta):
    """
    Defines a factory for making the Flask application
    """
    @property
    @abc.abstractmethod
    def app(self) -> Flask:
        """

        :return: The flask app
        """
        raise NotImplementedError()


class DatabaseEngineFactory(object, metaclass=abc.ABCMeta):
    @property
    @abc.abstractmethod
    def engine(self) -> Engine:
        raise NotImplementedError()


class ProductionWSGIAppFactory(
    WSGIAppFactory, DatabaseEngineFactory
):
    """
    Factory for making the app
    """
    def __init__(self):
        self._app = Flask(__name__)
        self._app.wsgi_app = HTTPMethodOverrideMiddleware(self._app.wsgi_app)

        self._engine = create_engine(config.DATABASE_URI)

        self._app.add_url_rule(
            '/', view_func=APIMetadata.as_view(
                APIMetadata.__name__, self._session_factory()
            )
        )
        self._app.add_url_rule(
            '/services',
            view_func=ServicesList.as_view(
                ServicesList.__name__, self._session_factory()
            )
        )
        self._app.add_url_rule(
            '/services/<service_id>',
            view_func=ServiceDetail.as_view(
                ServiceDetail.__name__, self._session_factory()
            )
        )
        self._app.add_url_rule(
            '/services/<service_id>/queue',
            view_func=JobQueueForService.as_view(
                JobQueueForService.__name__, self._session_factory()
            )
        )
        self._app.add_url_rule(
            '/jobs',
            view_func=JobsList.as_view(
                JobsList.__name__, self._session_factory()
            )
        )
        self._app.add_url_rule(
            '/jobs/<job_id>',
            view_func=JobDetail.as_view(
                JobDetail.__name__, self._session_factory()
            )
        )
        self._app.add_url_rule(
            '/services/<service_id>/jobs',
            view_func=JobsForService.as_view(
                JobsForService.__name__, self._session_factory()
            )
        )
        self._app.add_url_rule(
            '/services/<service_id>/jobs/next',
            view_func=NextJobEndpoint.as_view(
                NextJobEndpoint.__name__, self._session_factory()
            )
        )
        self._app.add_url_rule(
            '/validator',
            view_func=JSONSchemaValidator.as_view(
                JSONSchemaValidator.__name__, self._session_factory()
            )
        )

    @property
    def app(self) -> Flask:
        return self._app

    @property
    def engine(self) -> Engine:
        return self._engine

    @property
    def _session_factory(self) -> sessionmaker:
        return scoped_session(sessionmaker(bind=self._engine))


class TestingWSGIAPPFactory(
    ProductionWSGIAppFactory, WSGIAppFactory, DatabaseEngineFactory
):
    pass

APP_FACTORY = ProductionWSGIAppFactory()