from __future__ import annotations

from typing import Any

from fastapi import FastAPI, Response

from adapters.postgres import PostgresTraceRepository
from bootstrap import build_runtime
from config import Settings, get_settings
from rag.answer import GroundedAnswerService
from routers.rag import router as rag_router


def create_app(
    *,
    settings: Settings | None = None,
    answer_service: GroundedAnswerService | None = None,
    conversational: Any | None = None,
    trace_writer: PostgresTraceRepository | None = None,
    metrics: Any | None = None,
) -> FastAPI:
    configured = settings or get_settings()
    app = FastAPI(title=configured.app_name, version="0.1.0")
    app.state.answer_service = answer_service
    app.state.conversational = conversational
    app.state.trace_writer = trace_writer
    app.state.metrics = metrics

    @app.get("/health")
    def health() -> dict[str, str]:
        return {"status": "ok"}

    @app.get("/metrics")
    def prometheus_metrics() -> Response:
        exporter = getattr(app.state, "metrics", None)
        if exporter is None or not hasattr(exporter, "render"):
            # 404 rather than an empty 200: a scrape that silently succeeds
            # with no samples looks identical to a service answering nothing.
            return Response(status_code=404)
        body, content_type = exporter.render()
        return Response(content=body, media_type=content_type)

    app.include_router(rag_router)
    return app


_settings = get_settings()
_answer_service, _conversational, _trace_writer, _metrics = build_runtime(_settings)
app = create_app(
    settings=_settings,
    answer_service=_answer_service,
    conversational=_conversational,
    trace_writer=_trace_writer,
    metrics=_metrics,
)