import asyncio
import socket
from contextlib import asynccontextmanager

from fastapi import FastAPI
from fastapi.responses import HTMLResponse
from fastapi.staticfiles import StaticFiles

from app.config import get_settings
from app.plugins import PLUGINS, ROUTERS as PLUGIN_ROUTERS
from app.render import BASE, render
from app.routers import disks, overview, plugins, processes, services
from app.routers import journal as journal_router
from app.sampling import sampler_loop
from app.state import HistoryStore


@asynccontextmanager
async def lifespan(app: FastAPI):
    """Start shared state and run plugin lifecycle hooks around the app.

    Startup: stores settings and the history ring buffer on `app.state`,
    opens every plugin (a plugin `open()` failure is ignored, not fatal),
    and spawns the background sampler task. Shutdown: cancels the
    sampler task and closes every plugin.

    Args:
        app: the FastAPI instance.

    Yields:
        Control to the ASGI app for the server's lifetime.
    """
    settings = get_settings()
    app.state.settings = settings
    app.state.store = HistoryStore(maxlen=settings.history_maxlen)
    for p in PLUGINS:
        try:
            await p.open()
        except Exception: # noqa
            pass
    task = asyncio.create_task(sampler_loop(app.state.store, settings.sample_interval))
    yield
    _ = task.cancel()
    try:
        await task
    except asyncio.CancelledError:
        pass
    for p in PLUGINS:
        try:
            await p.close()
        except Exception: # noqa
            pass


async def index():
    """Serve the single-page dashboard shell at "/".

    The shell only holds the tab bar and containers; each tab polls its
    own `/api/*` endpoint for content, so this renders once and never again.

    Returns:
        The rendered `index.html` as an HTMLResponse.
    """
    return HTMLResponse(render("index.html", hostname=socket.gethostname()))


def create_app() -> FastAPI:
    """Build the FastAPI application.

    Wires up the `/static` mount, the six core routers (overview, disks,
    processes, journal, services, plugins), and the routers contributed by
    each plugin (see `app/plugins/__init__.py`).

    Returns:
        The configured FastAPI instance.
    """
    app = FastAPI(title="Dashboard", lifespan=lifespan)
    app.mount("/static", StaticFiles(directory=BASE / "static"), name="static")
    for r in (overview.router, disks.router, processes.router, journal_router.router, services.router, plugins.router):
        app.include_router(r)
    for r in PLUGIN_ROUTERS:
        app.include_router(r)
    _ = app.get("/", include_in_schema=False)(index)

    return app


app = create_app()