"""Implements a FastAPI server to run the gradio interface. Note that some types in this
module use the Optional/Union notation so that they work correctly with pydantic."""

from __future__ import annotations

import asyncio
import inspect
import json
import mimetypes
import os
import posixpath
import secrets
import tempfile
import traceback
from asyncio import TimeoutError as AsyncTimeOutError
from collections import defaultdict
from copy import deepcopy
from pathlib import Path
from typing import Any, Dict, List, Optional, Type
from urllib.parse import urlparse

import fastapi
import httpx
import markupsafe
import orjson
import pkg_resources
from fastapi import Depends, FastAPI, File, HTTPException, UploadFile, WebSocket, status
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import (
    FileResponse,
    HTMLResponse,
    JSONResponse,
    PlainTextResponse,
)
from fastapi.security import OAuth2PasswordRequestForm
from fastapi.templating import Jinja2Templates
from gradio_client.documentation import document, set_documentation_group
from jinja2.exceptions import TemplateNotFound
from starlette.background import BackgroundTask
from starlette.responses import RedirectResponse, StreamingResponse
from starlette.websockets import WebSocketState

import gradio
import gradio.ranged_response as ranged_response
from gradio import utils, wasm_utils
from gradio.context import Context
from gradio.data_classes import PredictBody, ResetBody
from gradio.exceptions import Error
from gradio.helpers import EventData
from gradio.queueing import Estimation, Event
from gradio.utils import cancel_tasks, run_coro_in_background, set_task_name

mimetypes.init()

STATIC_TEMPLATE_LIB = pkg_resources.resource_filename("gradio", "templates/")
STATIC_PATH_LIB = pkg_resources.resource_filename("gradio", "templates/frontend/static")
BUILD_PATH_LIB = pkg_resources.resource_filename("gradio", "templates/frontend/assets")
VERSION_FILE = pkg_resources.resource_filename("gradio", "version.txt")
with open(VERSION_FILE) as version_file:
    VERSION = version_file.read()


class ORJSONResponse(JSONResponse):
    media_type = "application/json"

    @staticmethod
    def _render(content: Any) -> bytes:
        return orjson.dumps(
            content,
            option=orjson.OPT_SERIALIZE_NUMPY | orjson.OPT_PASSTHROUGH_DATETIME,
            default=str,
        )

    def render(self, content: Any) -> bytes:
        return ORJSONResponse._render(content)

    @staticmethod
    def _render_str(content: Any) -> str:
        return ORJSONResponse._render(content).decode("utf-8")


def toorjson(value):
    return markupsafe.Markup(
        ORJSONResponse._render_str(value)
        .replace("<", "\\u003c")
        .replace(">", "\\u003e")
        .replace("&", "\\u0026")
        .replace("'", "\\u0027")
    )


templates = Jinja2Templates(directory=STATIC_TEMPLATE_LIB)
templates.env.filters["toorjson"] = toorjson

client = httpx.AsyncClient()

###########
# Auth
###########


class App(FastAPI):
    """
    FastAPI App Wrapper
    """

    def __init__(self, **kwargs):
        self.tokens = {}
        self.auth = None
        self.blocks: gradio.Blocks | None = None
        self.state_holder = {}
        self.iterators = defaultdict(dict)
        self.lock = asyncio.Lock()
        self.queue_token = secrets.token_urlsafe(32)
        self.startup_events_triggered = False
        self.uploaded_file_dir = os.environ.get("GRADIO_TEMP_DIR") or str(
            Path(tempfile.gettempdir()) / "gradio"
        )
        # Allow user to manually set `docs_url` and `redoc_url`
        # when instantiating an App; when they're not set, disable docs and redoc.
        kwargs.setdefault("docs_url", None)
        kwargs.setdefault("redoc_url", None)
        super().__init__(**kwargs)

    def configure_app(self, blocks: gradio.Blocks) -> None:
        auth = blocks.auth
        if auth is not None:
            if not callable(auth):
                self.auth = {account[0]: account[1] for account in auth}
            else:
                self.auth = auth
        else:
            self.auth = None

        self.blocks = blocks
        if hasattr(self.blocks, "_queue"):
            self.blocks._queue.set_access_token(self.queue_token)
        self.cwd = os.getcwd()
        self.favicon_path = blocks.favicon_path
        self.tokens = {}
        self.root_path = blocks.root_path

    def get_blocks(self) -> gradio.Blocks:
        if self.blocks is None:
            raise ValueError("No Blocks has been configured for this app.")
        return self.blocks

    def build_proxy_request(self, url_path):
        url = httpx.URL(url_path)
        assert self.blocks
        # Don't proxy a URL unless it's a URL specifically loaded by the user using
        # gr.load() to prevent SSRF or harvesting of HF tokens by malicious Spaces.
        is_safe_url = any(
            url.host == httpx.URL(root).host for root in self.blocks.root_urls
        )
        if not is_safe_url:
            raise PermissionError("This URL cannot be proxied.")
        is_hf_url = url.host.endswith(".hf.space")
        headers = {}
        if Context.hf_token is not None and is_hf_url:
            headers["Authorization"] = f"Bearer {Context.hf_token}"
        rp_req = client.build_request("GET", url, headers=headers)
        return rp_req

    @staticmethod
    def create_app(
        blocks: gradio.Blocks, app_kwargs: Dict[str, Any] | None = None
    ) -> App:
        app_kwargs = app_kwargs or {}
        if not wasm_utils.IS_WASM:
            app_kwargs.setdefault("default_response_class", ORJSONResponse)
        app = App(**app_kwargs)
        app.configure_app(blocks)

        if not wasm_utils.IS_WASM:
            app.add_middleware(
                CORSMiddleware,
                allow_origins=["*"],
                allow_methods=["*"],
                allow_headers=["*"],
            )

        @app.get("/user")
        @app.get("/user/")
        def get_current_user(request: fastapi.Request) -> Optional[str]:
            token = request.cookies.get("access-token") or request.cookies.get(
                "access-token-unsecure"
            )
            return app.tokens.get(token)

        @app.get("/login_check")
        @app.get("/login_check/")
        def login_check(user: str = Depends(get_current_user)):
            if app.auth is None or user is not None:
                return
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED, detail="Not authenticated"
            )

        async def ws_login_check(websocket: WebSocket) -> Optional[str]:
            token = websocket.cookies.get("access-token") or websocket.cookies.get(
                "access-token-unsecure"
            )
            return token  # token is returned to allow request in queue

        @app.get("/token")
        @app.get("/token/")
        def get_token(request: fastapi.Request) -> dict:
            token = request.cookies.get("access-token")
            return {"token": token, "user": app.tokens.get(token)}

        @app.get("/app_id")
        @app.get("/app_id/")
        def app_id(request: fastapi.Request) -> dict:
            return {"app_id": app.get_blocks().app_id}

        @app.post("/login")
        @app.post("/login/")
        def login(form_data: OAuth2PasswordRequestForm = Depends()):
            username, password = form_data.username, form_data.password
            if app.auth is None:
                return RedirectResponse(url="/", status_code=status.HTTP_302_FOUND)
            if (
                not callable(app.auth)
                and username in app.auth
                and app.auth[username] == password
            ) or (callable(app.auth) and app.auth.__call__(username, password)):
                token = secrets.token_urlsafe(16)
                app.tokens[token] = username
                response = JSONResponse(content={"success": True})
                response.set_cookie(
                    key="access-token",
                    value=token,
                    httponly=True,
                    samesite="none",
                    secure=True,
                )
                response.set_cookie(
                    key="access-token-unsecure", value=token, httponly=True
                )
                return response
            else:
                raise HTTPException(status_code=400, detail="Incorrect credentials.")

        ###############
        # Main Routes
        ###############

        @app.head("/", response_class=HTMLResponse)
        @app.get("/", response_class=HTMLResponse)
        def main(request: fastapi.Request, user: str = Depends(get_current_user)):
            mimetypes.add_type("application/javascript", ".js")
            blocks = app.get_blocks()
            root_path = request.scope.get("root_path", "")

            if app.auth is None or user is not None:
                config = app.get_blocks().config
                config["root"] = root_path
            else:
                config = {
                    "auth_required": True,
                    "auth_message": blocks.auth_message,
                    "space_id": app.get_blocks().space_id,
                    "root": root_path,
                }

            try:
                template = (
                    "frontend/share.html" if blocks.share else "frontend/index.html"
                )
                return templates.TemplateResponse(
                    template,
                    {"request": request, "config": config},
                )
            except TemplateNotFound as err:
                if blocks.share:
                    raise ValueError(
                        "Did you install Gradio from source files? Share mode only "
                        "works when Gradio is installed through the pip package."
                    ) from err
                else:
                    raise ValueError(
                        "Did you install Gradio from source files? You need to build "
                        "the frontend by running /scripts/build_frontend.sh"
                    ) from err

        @app.get("/info/", dependencies=[Depends(login_check)])
        @app.get("/info", dependencies=[Depends(login_check)])
        def api_info(serialize: bool = True):
            config = app.get_blocks().config
            return gradio.blocks.get_api_info(config, serialize)  # type: ignore

        @app.get("/config/", dependencies=[Depends(login_check)])
        @app.get("/config", dependencies=[Depends(login_check)])
        def get_config(request: fastapi.Request):
            root_path = request.scope.get("root_path", "")
            config = app.get_blocks().config
            config["root"] = root_path
            return config

        @app.get("/static/{path:path}")
        def static_resource(path: str):
            static_file = safe_join(STATIC_PATH_LIB, path)
            return FileResponse(static_file)

        @app.get("/assets/{path:path}")
        def build_resource(path: str):
            build_file = safe_join(BUILD_PATH_LIB, path)
            return FileResponse(build_file)

        @app.get("/favicon.ico")
        async def favicon():
            blocks = app.get_blocks()
            if blocks.favicon_path is None:
                return static_resource("img/logo.svg")
            else:
                return FileResponse(blocks.favicon_path)

        @app.head("/proxy={url_path:path}", dependencies=[Depends(login_check)])
        @app.get("/proxy={url_path:path}", dependencies=[Depends(login_check)])
        async def reverse_proxy(url_path: str):
            # Adapted from: https://github.com/tiangolo/fastapi/issues/1788
            try:
                rp_req = app.build_proxy_request(url_path)
            except PermissionError as err:
                raise HTTPException(status_code=400, detail=str(err)) from err
            rp_resp = await client.send(rp_req, stream=True)
            return StreamingResponse(
                rp_resp.aiter_raw(),
                status_code=rp_resp.status_code,
                headers=rp_resp.headers,  # type: ignore
                background=BackgroundTask(rp_resp.aclose),
            )

        @app.head("/file={path_or_url:path}", dependencies=[Depends(login_check)])
        @app.get("/file={path_or_url:path}", dependencies=[Depends(login_check)])
        async def file(path_or_url: str, request: fastapi.Request):
            blocks = app.get_blocks()
            if utils.validate_url(path_or_url):
                return RedirectResponse(
                    url=path_or_url, status_code=status.HTTP_302_FOUND
                )

            abs_path = utils.abspath(path_or_url)

            in_blocklist = any(
                utils.is_in_or_equal(abs_path, blocked_path)
                for blocked_path in blocks.blocked_paths
            )
            is_dotfile = any(part.startswith(".") for part in abs_path.parts)
            is_dir = abs_path.is_dir()

            if in_blocklist or is_dotfile or is_dir:
                raise HTTPException(403, f"File not allowed: {path_or_url}.")
            if not abs_path.exists():
                raise HTTPException(404, f"File not found: {path_or_url}.")

            in_app_dir = utils.is_in_or_equal(abs_path, app.cwd)
            created_by_app = str(abs_path) in set().union(*blocks.temp_file_sets)
            in_allowlist = any(
                utils.is_in_or_equal(abs_path, allowed_path)
                for allowed_path in blocks.allowed_paths
            )
            was_uploaded = utils.is_in_or_equal(abs_path, app.uploaded_file_dir)

            if not (in_app_dir or created_by_app or in_allowlist or was_uploaded):
                raise HTTPException(403, f"File not allowed: {path_or_url}.")

            range_val = request.headers.get("Range", "").strip()
            if range_val.startswith("bytes=") and "-" in range_val:
                range_val = range_val[6:]
                start, end = range_val.split("-")
                if start.isnumeric() and end.isnumeric():
                    start = int(start)
                    end = int(end)
                    response = ranged_response.RangedFileResponse(
                        abs_path,
                        ranged_response.OpenRange(start, end),
                        dict(request.headers),
                        stat_result=os.stat(abs_path),
                    )
                    return response
            return FileResponse(abs_path, headers={"Accept-Ranges": "bytes"})

        @app.get("/file/{path:path}", dependencies=[Depends(login_check)])
        async def file_deprecated(path: str, request: fastapi.Request):
            return await file(path, request)

        @app.post("/reset/")
        @app.post("/reset")
        async def reset_iterator(body: ResetBody):
            if body.session_hash not in app.iterators:
                return {"success": False}
            async with app.lock:
                app.iterators[body.session_hash][body.fn_index] = None
                app.iterators[body.session_hash]["should_reset"].add(body.fn_index)
            return {"success": True}

        async def run_predict(
            body: PredictBody,
            request: Request | List[Request],
            fn_index_inferred: int,
        ):
            if hasattr(body, "session_hash"):
                if body.session_hash not in app.state_holder:
                    app.state_holder[body.session_hash] = {
                        _id: deepcopy(getattr(block, "value", None))
                        for _id, block in app.get_blocks().blocks.items()
                        if getattr(block, "stateful", False)
                    }
                session_state = app.state_holder[body.session_hash]
                iterators = app.iterators[body.session_hash]
                # The should_reset set keeps track of the fn_indices
                # that have been cancelled. When a job is cancelled,
                # the /reset route will mark the jobs as having been reset.
                # That way if the cancel job finishes BEFORE the job being cancelled
                # the job being cancelled will not overwrite the state of the iterator.
                # In all cases, should_reset will be the empty set the next time
                # the fn_index is run.
                app.iterators[body.session_hash]["should_reset"] = set()
            else:
                session_state = {}
                iterators = {}
            event_id = getattr(body, "event_id", None)
            raw_input = body.data
            fn_index = body.fn_index

            dependency = app.get_blocks().dependencies[fn_index_inferred]
            target = dependency["targets"][0] if len(dependency["targets"]) else None
            event_data = EventData(
                app.get_blocks().blocks.get(target) if target else None,
                body.event_data,
            )
            batch = dependency["batch"]
            if not (body.batched) and batch:
                raw_input = [raw_input]
            try:
                with utils.MatplotlibBackendMananger():
                    output = await app.get_blocks().process_api(
                        fn_index=fn_index_inferred,
                        inputs=raw_input,
                        request=request,
                        state=session_state,
                        iterators=iterators,
                        event_id=event_id,
                        event_data=event_data,
                    )
                iterator = output.pop("iterator", None)
                if hasattr(body, "session_hash"):
                    if fn_index in app.iterators[body.session_hash]["should_reset"]:
                        app.iterators[body.session_hash][fn_index] = None
                    else:
                        app.iterators[body.session_hash][fn_index] = iterator
                if isinstance(output, Error):
                    raise output
            except BaseException as error:
                show_error = app.get_blocks().show_error or isinstance(error, Error)
                traceback.print_exc()
                return JSONResponse(
                    content={"error": str(error) if show_error else None},
                    status_code=500,
                )

            if not (body.batched) and batch:
                output["data"] = output["data"][0]
            return output

        # had to use '/run' endpoint for Colab compatibility, '/api' supported for backwards compatibility
        @app.post("/run/{api_name}", dependencies=[Depends(login_check)])
        @app.post("/run/{api_name}/", dependencies=[Depends(login_check)])
        @app.post("/api/{api_name}", dependencies=[Depends(login_check)])
        @app.post("/api/{api_name}/", dependencies=[Depends(login_check)])
        async def predict(
            api_name: str,
            body: PredictBody,
            request: fastapi.Request,
            username: str = Depends(get_current_user),
        ):
            fn_index_inferred = None
            if body.fn_index is None:
                for i, fn in enumerate(app.get_blocks().dependencies):
                    if fn["api_name"] == api_name:
                        fn_index_inferred = i
                        break
                if fn_index_inferred is None:
                    return JSONResponse(
                        content={
                            "error": f"This app has no endpoint /api/{api_name}/."
                        },
                        status_code=500,
                    )
            else:
                fn_index_inferred = body.fn_index
            if (
                not app.get_blocks().api_open
                and app.get_blocks().queue_enabled_for_fn(fn_index_inferred)
                and f"Bearer {app.queue_token}" != request.headers.get("Authorization")
            ):
                raise HTTPException(
                    status_code=status.HTTP_401_UNAUTHORIZED,
                    detail="Not authorized to skip the queue",
                )

            # If this fn_index cancels jobs, then the only input we need is the
            # current session hash
            if app.get_blocks().dependencies[fn_index_inferred]["cancels"]:
                body.data = [body.session_hash]
            if body.request:
                if body.batched:
                    gr_request = [
                        Request(username=username, **req) for req in body.request
                    ]
                else:
                    assert isinstance(body.request, dict)
                    gr_request = Request(username=username, **body.request)
            else:
                gr_request = Request(username=username, request=request)
            result = await run_predict(
                body=body,
                fn_index_inferred=fn_index_inferred,
                request=gr_request,
            )
            return result

        @app.websocket("/queue/join")
        async def join_queue(
            websocket: WebSocket,
            token: Optional[str] = Depends(ws_login_check),
        ):
            blocks = app.get_blocks()
            if app.auth is not None and token is None:
                await websocket.close(code=status.WS_1008_POLICY_VIOLATION)
                return
            if blocks._queue.server_path is None:
                app_url = get_server_url_from_ws_url(str(websocket.url))
                blocks._queue.set_url(app_url)
            await websocket.accept()
            # In order to cancel jobs, we need the session_hash and fn_index
            # to create a unique id for each job
            try:
                await asyncio.wait_for(
                    websocket.send_json({"msg": "send_hash"}), timeout=5
                )
            except AsyncTimeOutError:
                return

            try:
                session_info = await asyncio.wait_for(
                    websocket.receive_json(), timeout=5
                )
            except AsyncTimeOutError:
                return

            event = Event(
                websocket, session_info["session_hash"], session_info["fn_index"]
            )
            # set the token into Event to allow using the same token for call_prediction
            event.token = token
            event.session_hash = session_info["session_hash"]

            # Continuous events are not put in the queue  so that they do not
            # occupy the queue's resource as they are expected to run forever
            if blocks.dependencies[event.fn_index].get("every", 0):
                await cancel_tasks({f"{event.session_hash}_{event.fn_index}"})
                await blocks._queue.reset_iterators(event.session_hash, event.fn_index)
                blocks._queue.continuous_tasks.append(event)
                task = run_coro_in_background(
                    blocks._queue.process_events, [event], False
                )
                set_task_name(task, event.session_hash, event.fn_index, batch=False)
            else:
                rank = blocks._queue.push(event)

                if rank is None:
                    await blocks._queue.send_message(event, {"msg": "queue_full"})
                    await event.disconnect()
                    return
                estimation = blocks._queue.get_estimation()
                await blocks._queue.send_estimation(event, estimation, rank)
            while True:
                await asyncio.sleep(1)
                if websocket.application_state == WebSocketState.DISCONNECTED:
                    return

        @app.get(
            "/queue/status",
            dependencies=[Depends(login_check)],
            response_model=Estimation,
        )
        async def get_queue_status():
            return app.get_blocks()._queue.get_estimation()

        @app.post("/upload", dependencies=[Depends(login_check)])
        async def upload_file(
            files: List[UploadFile] = File(...),
        ):
            output_files = []
            file_manager = gradio.File()
            for input_file in files:
                output_files.append(
                    await file_manager.save_uploaded_file(
                        input_file, app.uploaded_file_dir
                    )
                )
            return output_files

        @app.on_event("startup")
        @app.get("/startup-events")
        async def startup_events():
            if not app.startup_events_triggered:
                app.get_blocks().startup_events()
                app.startup_events_triggered = True
                return True
            return False

        @app.get("/theme.css", response_class=PlainTextResponse)
        def theme_css():
            return PlainTextResponse(app.get_blocks().theme_css, media_type="text/css")

        @app.get("/robots.txt", response_class=PlainTextResponse)
        def robots_txt():
            if app.get_blocks().share:
                return "User-agent: *\nDisallow: /"
            else:
                return "User-agent: *\nDisallow: "

        return app


########
# Helper functions
########


def safe_join(directory: str, path: str) -> str:
    """Safely path to a base directory to avoid escaping the base directory.
    Borrowed from: werkzeug.security.safe_join"""
    _os_alt_seps: List[str] = [
        sep for sep in [os.path.sep, os.path.altsep] if sep is not None and sep != "/"
    ]

    if path == "":
        raise HTTPException(400)

    filename = posixpath.normpath(path)
    fullpath = os.path.join(directory, filename)
    if (
        any(sep in filename for sep in _os_alt_seps)
        or os.path.isabs(filename)
        or filename == ".."
        or filename.startswith("../")
        or os.path.isdir(fullpath)
    ):
        raise HTTPException(403)

    if not os.path.exists(fullpath):
        raise HTTPException(404, "File not found")

    return fullpath


def get_types(cls_set: List[Type]):
    docset = []
    types = []
    for cls in cls_set:
        doc = inspect.getdoc(cls) or ""
        doc_lines = doc.split("\n")
        for line in doc_lines:
            if "value (" in line:
                types.append(line.split("value (")[1].split(")")[0])
        docset.append(doc_lines[1].split(":")[-1])
    return docset, types


def get_server_url_from_ws_url(ws_url: str):
    ws_url_parsed = urlparse(ws_url)
    scheme = "http" if ws_url_parsed.scheme == "ws" else "https"
    port = f":{ws_url_parsed.port}" if ws_url_parsed.port else ""
    return f"{scheme}://{ws_url_parsed.hostname}{port}{ws_url_parsed.path.replace('queue/join', '')}"


set_documentation_group("routes")


class Obj:
    """
    Using a class to convert dictionaries into objects. Used by the `Request` class.
    Credit: https://www.geeksforgeeks.org/convert-nested-python-dictionary-to-object/
    """

    def __init__(self, dict_):
        self.__dict__.update(dict_)
        for key, value in dict_.items():
            if isinstance(value, (dict, list)):
                value = Obj(value)
            setattr(self, key, value)

    def __getitem__(self, item):
        return self.__dict__[item]

    def __setitem__(self, item, value):
        self.__dict__[item] = value

    def __iter__(self):
        for key, value in self.__dict__.items():
            if isinstance(value, Obj):
                yield (key, dict(value))
            else:
                yield (key, value)

    def __contains__(self, item) -> bool:
        if item in self.__dict__:
            return True
        for value in self.__dict__.values():
            if isinstance(value, Obj) and item in value:
                return True
        return False

    def keys(self):
        return self.__dict__.keys()

    def values(self):
        return self.__dict__.values()

    def items(self):
        return self.__dict__.items()

    def __str__(self) -> str:
        return str(self.__dict__)

    def __repr__(self) -> str:
        return str(self.__dict__)


@document()
class Request:
    """
    A Gradio request object that can be used to access the request headers, cookies,
    query parameters and other information about the request from within the prediction
    function. The class is a thin wrapper around the fastapi.Request class. Attributes
    of this class include: `headers`, `client`, `query_params`, and `path_params`. If
    auth is enabled, the `username` attribute can be used to get the logged in user.
    Example:
        import gradio as gr
        def echo(name, request: gr.Request):
            print("Request headers dictionary:", request.headers)
            print("IP address:", request.client.host)
            return name
        io = gr.Interface(echo, "textbox", "textbox").launch()
    """

    def __init__(
        self,
        request: fastapi.Request | None = None,
        username: str | None = None,
        **kwargs,
    ):
        """
        Can be instantiated with either a fastapi.Request or by manually passing in
        attributes (needed for websocket-based queueing).
        Parameters:
            request: A fastapi.Request
        """
        self.request = request
        self.username = username
        self.kwargs: Dict = kwargs

    def dict_to_obj(self, d):
        if isinstance(d, dict):
            return json.loads(json.dumps(d), object_hook=Obj)
        else:
            return d

    def __getattr__(self, name):
        if self.request:
            return self.dict_to_obj(getattr(self.request, name))
        else:
            try:
                obj = self.kwargs[name]
            except KeyError as ke:
                raise AttributeError(
                    f"'Request' object has no attribute '{name}'"
                ) from ke
            return self.dict_to_obj(obj)


@document()
def mount_gradio_app(
    app: fastapi.FastAPI,
    blocks: gradio.Blocks,
    path: str,
    gradio_api_url: str | None = None,
    app_kwargs: dict[str, Any] | None = None,
) -> fastapi.FastAPI:
    """Mount a gradio.Blocks to an existing FastAPI application.

    Parameters:
        app: The parent FastAPI application.
        blocks: The blocks object we want to mount to the parent app.
        path: The path at which the gradio application will be mounted.
        gradio_api_url: The full url at which the gradio app will run. This is only needed if deploying to Huggingface spaces of if the websocket endpoints of your deployed app are on a different network location than the gradio app. If deploying to spaces, set gradio_api_url to 'http://localhost:7860/'
        app_kwargs: Additional keyword arguments to pass to the underlying FastAPI app as a dictionary of parameter keys and argument values. For example, `{"docs_url": "/docs"}`
    Example:
        from fastapi import FastAPI
        import gradio as gr
        app = FastAPI()
        @app.get("/")
        def read_main():
            return {"message": "This is your main app"}
        io = gr.Interface(lambda x: "Hello, " + x + "!", "textbox", "textbox")
        app = gr.mount_gradio_app(app, io, path="/gradio")
        # Then run `uvicorn run:app` from the terminal and navigate to http://localhost:8000/gradio.
    """
    blocks.dev_mode = False
    blocks.config = blocks.get_config_file()
    blocks.validate_queue_settings()
    gradio_app = App.create_app(blocks, app_kwargs=app_kwargs)

    @app.on_event("startup")
    async def start_queue():
        if gradio_app.get_blocks().enable_queue:
            if gradio_api_url:
                gradio_app.get_blocks()._queue.set_url(gradio_api_url)
            gradio_app.get_blocks().startup_events()

    app.mount(path, gradio_app)
    return app