reflex/pynecone/app.py

"""The main Pynecone app."""

from typing import Any, Callable, Coroutine, Dict, List, Optional, Type, Union

from fastapi import FastAPI
from socketio import ASGIApp, AsyncNamespace, AsyncServer

from pynecone import constants, utils
from pynecone.base import Base
from pynecone.compiler import compiler
from pynecone.compiler import utils as compiler_utils
from pynecone.components.component import Component, ComponentStyle
from pynecone.event import Event, EventHandler
from pynecone.middleware import HydrateMiddleware, Middleware
from pynecone.model import Model
from pynecone.state import DefaultState, Delta, State, StateManager, StateUpdate

# Define custom types.
ComponentCallable = Callable[[], Component]
Reducer = Callable[[Event], Coroutine[Any, Any, StateUpdate]]


class App(Base):
    """A Pynecone application."""

    # A map from a page route to the component to render.
    pages: Dict[str, Component] = {}

    # A list of URLs to stylesheets to include in the app.
    stylesheets: List[str] = []

    # The backend API object.
    api: FastAPI = None  # type: ignore

    # The Socket.IO AsyncServer.
    sio: Optional[AsyncServer] = None

    # The state class to use for the app.
    state: Type[State] = DefaultState

    # Class to manage many client states.
    state_manager: StateManager = StateManager()

    # The styling to apply to each component.
    style: ComponentStyle = {}

    # Middleware to add to the app.
    middleware: List[Middleware] = []

    # events handlers to trigger when a page load
    load_events: Dict[str, EventHandler] = {}

    def __init__(self, *args, **kwargs):
        """Initialize the app.

        Args:
            *args: Args to initialize the app with.
            **kwargs: Kwargs to initialize the app with.
        """
        super().__init__(*args, **kwargs)

        # Add middleware.
        self.middleware.append(HydrateMiddleware())

        # Set up the state manager.
        self.state_manager.setup(state=self.state)

        # Set up the API.
        self.api = FastAPI()

        # Set up the Socket.IO AsyncServer.
        self.sio = AsyncServer(async_mode="asgi", cors_allowed_origins="*")

        # Create the socket app. Note event endpoint constant replaces the default 'socket.io' path.
        socket_app = ASGIApp(self.sio, socketio_path=str(constants.Endpoint.EVENT))

        # Create the event namespace and attach the main app. Not related to the path above.
        event_namespace = EventNamespace("/event")
        event_namespace.app = self

        # Register the event namespace with the socket.
        self.sio.register_namespace(event_namespace)

        # Mount the socket app with the API.
        self.api.mount("/", socket_app)

    def __repr__(self) -> str:
        """Get the string representation of the app.

        Returns:
            The string representation of the app.
        """
        return f"<App state={self.state.__name__}>"

    def __call__(self) -> FastAPI:
        """Run the backend api instance.

        Returns:
            The backend api.
        """
        return self.api

    def preprocess(self, state: State, event: Event) -> Optional[Delta]:
        """Preprocess the event.

        This is where middleware can modify the event before it is processed.
        Each middleware is called in the order it was added to the app.

        If a middleware returns a delta, the event is not processed and the
        delta is returned.

        Args:
            state: The state to preprocess.
            event: The event to preprocess.

        Returns:
            An optional state to return.
        """
        for middleware in self.middleware:
            out = middleware.preprocess(app=self, state=state, event=event)
            if out is not None:
                return out

    def postprocess(self, state: State, event: Event, delta: Delta) -> Optional[Delta]:
        """Postprocess the event.

        This is where middleware can modify the delta after it is processed.
        Each middleware is called in the order it was added to the app.

        If a middleware returns a delta, the delta is not processed and the
        delta is returned.

        Args:
            state: The state to postprocess.
            event: The event to postprocess.
            delta: The delta to postprocess.

        Returns:
            An optional state to return.
        """
        for middleware in self.middleware:
            out = middleware.postprocess(
                app=self, state=state, event=event, delta=delta
            )
            if out is not None:
                return out

    def add_middleware(self, middleware: Middleware, index: Optional[int] = None):
        """Add middleware to the app.

        Args:
            middleware: The middleware to add.
            index: The index to add the middleware at.
        """
        if index is None:
            self.middleware.append(middleware)
        else:
            self.middleware.insert(index, middleware)

    def add_page(
        self,
        component: Union[Component, ComponentCallable],
        route: Optional[str] = None,
        title: str = constants.DEFAULT_TITLE,
        description: str = constants.DEFAULT_DESCRIPTION,
        image=constants.DEFAULT_IMAGE,
        on_load: Optional[EventHandler] = None,
        path: Optional[str] = None,
    ):
        """Add a page to the app.

        If the component is a callable, by default the route is the name of the
        function. Otherwise, a route must be provided.

        Args:
            component: The component to display at the page.
            path: (deprecated) The path to the component.
            route: The route to display the component at.
            title: The title of the page.
            description: The description of the page.
            image: The image to display on the page.
            on_load: The event handler that will be called each time the page load.
        """
        if path is not None:
            utils.deprecate(
                "The `path` argument is deprecated for `add_page`. Use `route` instead."
            )
            route = path

        # If the route is not set, get it from the callable.
        if route is None:
            assert isinstance(
                component, Callable
            ), "Route must be set if component is not a callable."
            route = component.__name__

        # Check if the route given is valid
        utils.verify_route_validity(route)

        # Apply dynamic args to the route.
        self.state.setup_dynamic_args(utils.get_route_args(route))

        # Generate the component if it is a callable.
        component = component if isinstance(component, Component) else component()

        # Add meta information to the component.
        compiler_utils.add_meta(
            component, title=title, image=image, description=description
        )

        # Format the route.
        route = utils.format_route(route)

        # Add the page.
        self._check_routes_conflict(route)
        self.pages[route] = component

        if on_load:
            self.load_events[route] = on_load

    def _check_routes_conflict(self, new_route: str):
        """Verify if there is any conflict between the new route and any existing route.

        Based on conflicts that NextJS would throw if not intercepted.

        Raises:
            ValueError: exception showing which conflict exist with the route to be added

        Args:
            new_route: the route being newly added.
        """
        newroute_catchall = utils.catchall_in_route(new_route)
        if not newroute_catchall:
            return

        for route in self.pages:
            route = "" if route == "index" else route

            if new_route.startswith(f"{route}/[[..."):
                raise ValueError(
                    f"You cannot define a route with the same specificity as a optional catch-all route ('{route}' and '{new_route}')"
                )

            route_catchall = utils.catchall_in_route(route)
            if (
                route_catchall
                and newroute_catchall
                and utils.catchall_prefix(route) == utils.catchall_prefix(new_route)
            ):
                raise ValueError(
                    f"You cannot use multiple catchall for the same dynamic route ({route} !== {new_route})"
                )

    def add_custom_404_page(self, component, title=None, image=None, description=None):
        """Define a custom 404 page for any url having no match.

        If there is no page defined on 'index' route, add the 404 page to it.
        If there is no global catchall defined, add the 404 page with a catchall

        Args:
            component: The component to display at the page.
            title: The title of the page.
            description: The description of the page.
            image: The image to display on the page.
        """
        title = title or constants.TITLE_404
        image = image or constants.FAVICON_404
        description = description or constants.DESCRIPTION_404

        component = component if isinstance(component, Component) else component()

        compiler_utils.add_meta(
            component, title=title, image=image, description=description
        )

        froute = utils.format_route
        if (froute(constants.ROOT_404) not in self.pages) and (
            not any(page.startswith("[[...") for page in self.pages)
        ):
            self.pages[froute(constants.ROOT_404)] = component
        if not any(
            page.startswith("[...") or page.startswith("[[...") for page in self.pages
        ):
            self.pages[froute(constants.SLUG_404)] = component

    def compile(self, force_compile: bool = False):
        """Compile the app and output it to the pages folder.

        If the config environment is set to production, the app will
        not be compiled.

        Args:
            force_compile: Whether to force the app to compile.
        """
        # Get the env mode.
        config = utils.get_config()
        if config.env != constants.Env.DEV and not force_compile:
            print("Skipping compilation in non-dev mode.")
            return

        # Create the database models.
        if config.db_url is not None:
            Model.create_all()

        # Empty the .web pages directory
        compiler.purge_web_pages_dir()

        # Compile the root document with base styles and fonts.
        compiler.compile_document_root(self.stylesheets)

        # Compile the theme.
        compiler.compile_theme(self.style)

        # Compile the pages.
        custom_components = set()
        for route, component in self.pages.items():
            component.add_style(self.style)
            compiler.compile_page(route, component, self.state)

            # Add the custom components from the page to the set.
            custom_components |= component.get_custom_components()

        # Compile the custom components.
        compiler.compile_components(custom_components)


async def process(app: App, event: Event) -> StateUpdate:
    """Process an event.

    Args:
        app: The app to process the event for.
        event: The event to process.

    Returns:
        The state update after processing the event.
    """
    # Get the state for the session.
    state = app.state_manager.get_state(event.token)

    # pass router_data to the state of the App
    state.router_data = event.router_data
    # also pass router_data to all substates
    for _, substate in state.substates.items():
        substate.router_data = event.router_data
    state.router_data[constants.RouteVar.CLIENT_TOKEN] = event.token

    # Preprocess the event.
    pre = app.preprocess(state, event)
    if pre is not None:
        return StateUpdate(delta=pre)

    # Apply the event to the state.
    update = await state.process(event)
    app.state_manager.set_state(event.token, state)

    # Postprocess the event.
    post = app.postprocess(state, event, update.delta)
    if post is not None:
        return StateUpdate(delta=post)

    # Return the update.
    return update


class EventNamespace(AsyncNamespace):
    """The event namespace."""

    # The backend API object.
    app: App

    def on_connect(self, sid, environ):
        """Event for when the websocket disconnects.

        Args:
            sid: The Socket.IO session id.
            environ: The request information, including HTTP headers.
        """
        pass

    def on_disconnect(self, sid):
        """Event for when the websocket disconnects.

        Args:
            sid: The Socket.IO session id.
        """
        pass

    async def on_event(self, sid, data):
        """Event for receiving front-end websocket events.

        Args:
            sid: The Socket.IO session id.
            data: The event data.
        """
        # Get the event.
        event = Event.parse_raw(data)

        # Process the event.
        update = await process(self.app, event)

        # Emit the event.
        await self.emit(str(constants.SocketEvent.EVENT), update.json(), to=sid)

    async def on_ping(self, sid):
        """Event for testing the API endpoint.

        Args:
            sid: The Socket.IO session id.
        """
        # Emit the test event.
        await self.emit(str(constants.SocketEvent.PING), "pong", to=sid)