from __future__ import annotations

from collections.abc import AsyncIterator, Callable
from contextlib import AsyncExitStack, asynccontextmanager, suppress
import logging
from uuid import uuid4

import uvicorn
from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
from starlette.concurrency import run_in_threadpool

from qonto_assistant import __version__
from qonto_assistant.audit import AuditLogger
from qonto_assistant.auth import actor_claims_from_request
from qonto_assistant.config import Settings
from qonto_assistant.credentials import build_credential_provider
from qonto_assistant.errors import QontoAssistantError, UpstreamError
from qonto_assistant.mcp_auth import BearerTokenAuthMiddleware
from qonto_assistant.mcp_server import create_mcp_server
from qonto_assistant.policy import PolicyEngine
from qonto_assistant.qonto_client import FixtureQontoClient, QontoClient
from qonto_assistant.rate_limits import ConcurrencyLimiter, RateLimiter
from qonto_assistant.service import CapabilityService


def create_app(
    *,
    settings: Settings | None = None,
    service: CapabilityService | None = None,
    audit_logger: AuditLogger | None = None,
    rate_limiter: RateLimiter | None = None,
    concurrency_limiter: ConcurrencyLimiter | None = None,
) -> FastAPI:
    settings = settings or Settings.from_env()
    audit_logger = audit_logger or AuditLogger()
    service = service or _build_service(
        settings=settings,
        audit_logger=audit_logger,
        rate_limiter=rate_limiter,
        concurrency_limiter=concurrency_limiter,
    )

    mcp_server = create_mcp_server(settings=settings, service=service)
    mcp_app = mcp_server.streamable_http_app()
    if settings.mcp_auth_token:
        mcp_app.add_middleware(BearerTokenAuthMiddleware, token=settings.mcp_auth_token)

    @asynccontextmanager
    async def lifespan(_: FastAPI) -> AsyncIterator[None]:
        async with AsyncExitStack() as stack:
            await stack.enter_async_context(mcp_app.router.lifespan_context(mcp_app))
            yield
            with suppress(Exception):
                service.client.close()

    app = FastAPI(title="qonto-assistant", version=__version__, lifespan=lifespan)
    app.state.settings = settings
    app.state.service = service
    app.mount("/mcp", mcp_app)

    @app.exception_handler(QontoAssistantError)
    def handle_qonto_error(_: Request, exc: QontoAssistantError) -> JSONResponse:
        body = {"error_code": exc.error_code, "detail": exc.message}
        if isinstance(exc, UpstreamError) and exc.upstream_status is not None:
            body["upstream_status"] = exc.upstream_status
        return JSONResponse(status_code=exc.status_code, content=body)

    @app.get("/v1/health")
    async def health() -> dict[str, str]:
        return {
            "status": "ok",
            "service": settings.service_name,
            "version": __version__,
            "policy_file": str(settings.policy_file),
        }

    @app.get("/v1/accounts")
    async def get_accounts(request: Request) -> JSONResponse:
        claims = actor_claims_from_request(request, settings)
        request_id = _request_id(request)
        payload = await run_in_threadpool(service.get_accounts, claims=claims, request_id=request_id)
        return JSONResponse(content=payload, headers={"X-Request-ID": request_id})

    @app.get("/v1/transactions")
    async def get_transactions(
        request: Request,
        account_slug: str | None = None,
        page: int = 1,
        page_size: int = 50,
        window_days: int = 31,
        status: str | None = "completed",
        side: str | None = None,
    ) -> JSONResponse:
        claims = actor_claims_from_request(request, settings)
        request_id = _request_id(request)
        payload = await run_in_threadpool(
            service.list_transactions,
            claims=claims,
            request_id=request_id,
            account_slug=account_slug,
            page=page,
            page_size=page_size,
            window_days=window_days,
            status=status,
            side=side,
        )
        return JSONResponse(content=payload, headers={"X-Request-ID": request_id})

    @app.get("/v1/snapshot")
    async def get_snapshot(
        request: Request,
        window_days: int = 31,
        page_size: int = 50,
    ) -> JSONResponse:
        claims = actor_claims_from_request(request, settings)
        request_id = _request_id(request)
        payload = await run_in_threadpool(
            service.get_snapshot,
            claims=claims,
            request_id=request_id,
            window_days=window_days,
            page_size=page_size,
        )
        return JSONResponse(content=payload, headers={"X-Request-ID": request_id})

    return app


def _request_id(request: Request) -> str:
    existing = getattr(request.state, "request_id", None)
    if existing:
        return existing
    request.state.request_id = request.headers.get("x-request-id", str(uuid4()))
    return request.state.request_id


def _build_service(
    *,
    settings: Settings,
    audit_logger: AuditLogger,
    rate_limiter: RateLimiter | None,
    concurrency_limiter: ConcurrencyLimiter | None,
) -> CapabilityService:
    policy = PolicyEngine.from_file(
        settings.policy_file,
        required_scope=settings.required_scope,
        enforce_scope=settings.enforce_scope,
    )
    if settings.qonto_fixture_dir is not None:
        client = FixtureQontoClient(fixture_dir=settings.qonto_fixture_dir)
    else:
        credential_provider = build_credential_provider(settings)
        client = QontoClient(
            base_url=settings.qonto_base_url,
            organization_path=settings.qonto_organization_path,
            transactions_path=settings.qonto_transactions_path,
            auth_mode=settings.qonto_auth_mode,
            timeout_seconds=settings.qonto_timeout_seconds,
            max_retries=settings.qonto_max_retries,
            credential_provider=credential_provider,
        )
    return CapabilityService(
        client=client,
        policy=policy,
        audit_logger=audit_logger,
        rate_limiter=rate_limiter
        or RateLimiter(
            limit=settings.rate_limit_requests,
            window_seconds=settings.rate_limit_window_seconds,
        ),
        concurrency_limiter=concurrency_limiter
        or ConcurrencyLimiter(limit=settings.max_concurrency),
    )


def main() -> None:
    settings = Settings.from_env()
    logging.basicConfig(level=logging.INFO, format="%(message)s")
    uvicorn.run(
        "qonto_assistant.app:create_app",
        factory=True,
        host=settings.host,
        port=settings.port,
        reload=False,
    )