"""FastAPI app factory — lifespan, CORS, health, routers."""

import asyncio
import contextlib
import logging
from contextlib import asynccontextmanager

import httpx
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

from .agents.registry import AgentRegistry, register_builtin_agents
from .agents.session import InMemorySessionStore
from .api import (
    assessment_router,
    chat_router,
    lab_router,
    mentor_router,
    proctor_router,
    sandboxes_router,
)
from .config import Settings
from .llm import create_provider
from .sandbox import SandboxManager, UnshareBackend

logger = logging.getLogger(__name__)

#: Interval between wall-clock/G-2 reaper passes (the manager owns the pass;
#: the lifespan owns the loop). 60s against a 900s default timeout → ≤6.7% lag.
REAPER_INTERVAL_S = 60.0


def create_app(settings: Settings | None = None) -> FastAPI:
    settings = settings or Settings()

    @asynccontextmanager
    async def lifespan(app: FastAPI):
        # Shared HTTP client pool (D-017): 10s connect / 300s read for cloud TTFT
        timeout = httpx.Timeout(connect=10.0, read=300.0, write=30.0, pool=10.0)
        app.state.http_client = httpx.AsyncClient(timeout=timeout)
        app.state.settings = settings
        app.state.provider = create_provider(settings, app.state.http_client)
        app.state.session_store = InMemorySessionStore()
        app.state.agent_registry = AgentRegistry()
        register_builtin_agents(app.state.agent_registry)

        # v0.3 sandbox fabric (REQ-3-001): singleton manager, DI'd via
        # app.state. Tests may pre-set app.state.sandbox_manager (dependency
        # override by state injection) to swap the backend; the lifespan then
        # adopts it instead of constructing the real UnshareBackend one.
        manager = getattr(app.state, "sandbox_manager", None)
        if manager is None:
            manager = SandboxManager(backend=UnshareBackend(), settings=settings)
            app.state.sandbox_manager = manager
        await manager.start()  # a-1: reap on-disk orphans from a previous process

        async def _reaper_loop() -> None:
            # Wall-clock timeout + G-2 workdir-size sweep, one pass per tick.
            while True:
                await asyncio.sleep(REAPER_INTERVAL_S)
                try:
                    await manager.reap_expired()
                except Exception:
                    logger.exception("sandbox reaper pass failed; retrying next tick")

        reaper = asyncio.create_task(_reaper_loop())
        try:
            yield
        finally:
            reaper.cancel()
            with contextlib.suppress(asyncio.CancelledError):
                await reaper
            # No orphans outlive the process (a-1, shutdown half): destroy
            # everything live; workdirs stay on disk for snapshot restore.
            await manager.destroy_all()
            await app.state.http_client.aclose()

    app = FastAPI(title="Nextcraft AI Service", version="0.3.0", lifespan=lifespan)

    # A-008: localhost-only CORS, no credentials
    app.add_middleware(
        CORSMiddleware,
        allow_origins=["http://localhost:3000", "http://127.0.0.1:3000"],
        allow_methods=["GET", "POST", "DELETE", "OPTIONS"],
        allow_headers=["Content-Type"],
        allow_credentials=False,
    )

    @app.get("/health")
    async def health() -> dict:
        return {
            "status": "ok",
            "provider": settings.provider,
            "model": settings.model,
        }

    app.include_router(chat_router)
    app.include_router(lab_router)
    app.include_router(assessment_router)
    app.include_router(mentor_router)
    app.include_router(proctor_router)
    app.include_router(sandboxes_router)
    return app


app = create_app()