# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the terms described in the LICENSE file in
# the root directory of this source tree.

import asyncio
import json
import signal
from collections.abc import (
    AsyncGenerator as AsyncGeneratorABC,
    AsyncIterator as AsyncIteratorABC,
)
from contextlib import asynccontextmanager
from typing import Any, AsyncGenerator, AsyncIterator, Dict, get_type_hints, Optional

import fire
import httpx
import yaml
from dotenv import load_dotenv

from fastapi import FastAPI, Request
from fastapi.responses import StreamingResponse
from fastapi.routing import APIRoute

from pydantic import BaseModel
from termcolor import cprint

from .datatypes import PassthroughApiAdapter
from .distribution import api_surface_endpoints
from .dynamic import instantiate_adapter

from .registry import resolve_distribution

load_dotenv()


def is_async_iterator_type(typ):
    if hasattr(typ, "__origin__"):
        origin = typ.__origin__
        if isinstance(origin, type):
            return issubclass(
                origin,
                (AsyncIterator, AsyncGenerator, AsyncIteratorABC, AsyncGeneratorABC),
            )
        return False
    return isinstance(
        typ, (AsyncIterator, AsyncGenerator, AsyncIteratorABC, AsyncGeneratorABC)
    )


def create_sse_event(data: Any) -> str:
    if isinstance(data, BaseModel):
        data = data.json()
    else:
        data = json.dumps(data)

    return f"data: {data}\n\n"


async def passthrough(
    request: Request,
    downstream_url: str,
    downstream_headers: Optional[Dict[str, str]] = None,
):
    client = httpx.AsyncClient()

    headers = dict(request.headers)
    headers.pop("host", None)
    headers.update(downstream_headers or {})

    body = await request.body()

    try:
        response = await client.request(
            method=request.method,
            url=downstream_url,
            headers=headers,
            content=body,
            params=request.query_params,
        )
        return StreamingResponse(
            response.iter_bytes(),
            status_code=response.status_code,
            headers=dict(response.headers),
        )
    finally:
        await client.aclose()


def handle_sigint(*args, **kwargs):
    print("SIGINT or CTRL-C detected. Exiting gracefully", args)
    loop = asyncio.get_event_loop()
    for task in asyncio.all_tasks(loop):
        task.cancel()
    loop.stop()


@asynccontextmanager
async def lifespan(app: FastAPI):
    print("Starting up")
    yield
    print("Shutting down")


def create_dynamic_passthrough(
    downstream_url: str, downstream_headers: Optional[Dict[str, str]] = None
):
    async def endpoint(request: Request):
        return await passthrough(request, downstream_url, downstream_headers)

    return endpoint


def create_dynamic_typed_route(func: Any):
    hints = get_type_hints(func)
    request_model = next(iter(hints.values()))
    response_model = hints["return"]

    is_streaming = is_async_iterator_type(response_model)

    if is_streaming:

        async def endpoint(request: request_model):
            async def event_generator():
                async for item in func(request):
                    yield create_sse_event(item)
                    await asyncio.sleep(0.001)

            return StreamingResponse(event_generator(), media_type="text/event-stream")

    else:

        async def endpoint(request: request_model):
            return func(request)

    return endpoint


def main(
    dist_name: str, yaml_config: str, port: int = 5000, disable_ipv6: bool = False
):
    dist = resolve_distribution(dist_name)
    if dist is None:
        raise ValueError(f"Could not find distribution {dist_name}")

    with open(yaml_config, "r") as fp:
        config = yaml.safe_load(fp)

    app = FastAPI()

    all_endpoints = api_surface_endpoints()

    adapter_configs = config["adapters"]
    for surface, adapter in dist.adapters.items():
        if surface.value not in adapter_configs:
            raise ValueError(
                f"Could not find adapter config for {surface}. Please add it to the config"
            )

        adapter_config = adapter_configs[surface.value]
        endpoints = all_endpoints[surface]
        if isinstance(adapter, PassthroughApiAdapter):
            for endpoint in endpoints:
                url = adapter.base_url.rstrip("/") + endpoint.route
                getattr(app, endpoint.method)(endpoint.route)(
                    create_dynamic_passthrough(url)
                )
        else:
            impl = instantiate_adapter(adapter, adapter_config)
            for endpoint in endpoints:
                if not hasattr(impl, endpoint.name):
                    # ideally this should be a typing violation already
                    raise ValueError(
                        f"Could not find method {endpoint.name} on {impl}!!"
                    )

                impl_method = getattr(impl, endpoint.name)
                getattr(app, endpoint.method)(endpoint.route, response_model=None)(
                    create_dynamic_typed_route(impl_method)
                )

    for route in app.routes:
        if isinstance(route, APIRoute):
            cprint(
                f"Serving {next(iter(route.methods))} {route.path}",
                "white",
                attrs=["bold"],
            )

    signal.signal(signal.SIGINT, handle_sigint)

    import uvicorn

    # FYI this does not do hot-reloads
    listen_host = "::" if not disable_ipv6 else "0.0.0.0"
    print(f"Listening on {listen_host}:{port}")
    uvicorn.run(app, host=listen_host, port=port)


if __name__ == "__main__":
    fire.Fire(main)