#
# This file is distributed under the MIT License. See LICENSE.md for details.
#

import asyncio
import os
import signal
from datetime import timedelta
from importlib import import_module
from typing import Callable, List

from starlette.applications import Starlette
from starlette.config import Config
from starlette.datastructures import Headers
from starlette.middleware import Middleware
from starlette.middleware.cors import CORSMiddleware
from starlette.middleware.gzip import GZipMiddleware
from starlette.requests import ClientDisconnect, Request
from starlette.responses import PlainTextResponse
from starlette.routing import Mount, Route
from starlette.types import ASGIApp, Receive, Scope, Send

from ariadne.asgi import GraphQL
from ariadne.asgi.handlers import GraphQLHTTPHandler, GraphQLTransportWSHandler
from ariadne.contrib.tracing.apollotracing import ApolloTracingExtension

from revng.internal.api import Manager
from revng.internal.api._capi import initialize as capi_initialize
from revng.internal.api._capi import shutdown as capi_shutdown
from revng.internal.api.exceptions import RevngManagerInstantiationException
from revng.internal.api.syncing_manager import SyncingManager

from .graphql import get_schema
from .util import log, project_workdir

config = Config()
DEBUG = config("STARLETTE_DEBUG", cast=bool, default=False)


class ManagerCredentialsMiddleware:
    def __init__(self, app: ASGIApp, manager: Manager | None):
        self.app = app
        self.manager = manager

    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
        if scope["type"] != "http":
            return await self.app(scope, receive, send)

        credentials = Headers(scope=scope).get("x-revng-set-credentials")
        if credentials is not None and self.manager is not None:
            self.manager.set_storage_credentials(credentials)

        return await self.app(scope, receive, send)


class PluginHooks:
    def __init__(self):
        self.middlewares_early = []
        self.middlewares_late = []
        self.save_hooks = []

    def register_early_middleware(self, middleware: Middleware):
        self.middlewares_early.append(middleware)

    def register_late_middleware(self, middleware: Middleware):
        self.middlewares_late.append(middleware)

    def register_save_hook(self, hook: Callable[[Manager, str], None]):
        self.save_hooks.append(hook)


def load_plugins() -> PluginHooks:
    hooks = PluginHooks()

    plugins = os.environ.get("REVNG_DAEMON_PLUGINS", "")
    if plugins == "":
        return hooks

    for module_path in plugins.split(","):
        module = import_module(module_path)
        module_setup = getattr(module, "setup", None)
        if module_setup is None:
            raise ValueError(f"Malformed plugin: {module_path}")
        module_setup(hooks)

    return hooks


def get_middlewares(manager: Manager | None, hooks: PluginHooks) -> List[Middleware]:
    origins: List[str] = []
    if "REVNG_ORIGINS" in os.environ:
        origins = os.environ["REVNG_ORIGINS"].split(",")

    expose_headers: List[str] = []
    if "REVNG_EXPOSE_HEADERS" in os.environ:
        expose_headers = os.environ["REVNG_EXPOSE_HEADERS"].split(",")

    return [
        *hooks.middlewares_early,
        Middleware(  # type: ignore
            CORSMiddleware,  # type: ignore
            allow_origins=origins,
            expose_headers=expose_headers,
            allow_methods=["*"],
            allow_headers=["*"],
        ),
        Middleware(GZipMiddleware, minimum_size=1024),  # type: ignore
        *hooks.middlewares_late,
        Middleware(ManagerCredentialsMiddleware, manager=manager),
    ]


async def client_disconnect_handler(request: Request, exc: ClientDisconnect):
    log("Client disconnected while request was being processed!")
    return PlainTextResponse()


def all_500_starlette(hooks: PluginHooks) -> Starlette:
    async def index_page(request):
        return PlainTextResponse("")

    async def status(request):
        return PlainTextResponse("OK")

    async def catch_all(request):
        return PlainTextResponse("Manager failed to initialize", 500)

    return Starlette(
        debug=DEBUG,
        middleware=get_middlewares(None, hooks),
        routes=[
            Route("/", index_page, methods=["GET"]),
            Route("/status", status, methods=["GET"]),
            Route("/{path:path}", catch_all),
        ],
    )


def make_startlette() -> Starlette:
    capi_initialize(
        signals_to_preserve=(
            # Common terminal signals
            signal.SIGINT,
            signal.SIGTERM,
            signal.SIGHUP,
            signal.SIGCHLD,
            # Issued by writing in closed sockets
            signal.SIGPIPE,
            # Used by uvicorn workers
            signal.SIGUSR1,
            signal.SIGUSR2,
            signal.SIGQUIT,
        )
    )

    hooks = load_plugins()
    try:
        manager = SyncingManager(project_workdir(), save_hooks=hooks.save_hooks)
    except RevngManagerInstantiationException:
        capi_shutdown()
        return all_500_starlette(hooks)

    startup_done = False

    if DEBUG:
        log(f"Manager workdir is: {manager.workdir}")
        signal.signal(signal.SIGUSR2, lambda s, f: manager.save())

    async def index_page(request):
        return PlainTextResponse("")

    async def status(request):
        if startup_done:
            return PlainTextResponse("OK")
        else:
            return PlainTextResponse("KO", 503)

    def generate_context(request: Request):
        return {
            "manager": manager,
            # Lock for operations that have an `index` parameter. This is
            # needed because otherwise there's a TOCTOU between when the index
            # is checked and when the analysis actually bumps the index.
            "index_lock": asyncio.Lock(),
            "headers": request.headers,
        }

    routes = [
        Route("/", index_page, methods=["GET"]),
        Route("/status", status, methods=["GET"]),
        Mount(
            "/graphql",
            GraphQL(
                get_schema(),
                context_value=generate_context,
                http_handler=GraphQLHTTPHandler(extensions=[ApolloTracingExtension]),
                websocket_handler=GraphQLTransportWSHandler(
                    connection_init_wait_timeout=timedelta(seconds=5)
                ),
                debug=DEBUG,
            ),
        ),
    ]

    def startup():
        nonlocal startup_done
        startup_done = True

    def shutdown():
        log("Shutting down")

        log("Saving to disk")
        if not manager.save():
            log("Failed to store manager's containers")

        log("Stopping the manager")
        manager.stop()
        manager._manager = None

        log("Shutting down the C API")
        capi_shutdown()

    return Starlette(
        debug=DEBUG,
        middleware=get_middlewares(manager, hooks),
        routes=routes,
        on_startup=[startup],
        on_shutdown=[shutdown],
        exception_handlers={ClientDisconnect: client_disconnect_handler},  # type: ignore
    )


app = make_startlette()