# File Objective  : Main FastAPI entry point with lifespan management.
# Scope           : apps/api — read-side API server (BFF).
# What this file does:
#   1. Sets up the FastAPI application with title and CORS middleware.
#   2. Instantiates the LangGraph agent once during the lifespan startup.
#   3. Exposes the agent reference via app state to avoid circular imports.
#   4. Mounts the routers for chat, gaps, graph, and signals.
#   5. Serves the built React frontend (apps/web/dist) as static files when present,
#      so a single container can host both API and UI.
# What it does not do:
#   1. Maintain DB connections directly (delegated to core adapters).

from __future__ import annotations

from contextlib import asynccontextmanager
from pathlib import Path

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles

from vantage_core.agent.graph import build_agent
from vantage_core.log import get_logger, timed
from apps.api.routers import chat, gaps, graph, signals

log = get_logger(__name__)


@asynccontextmanager
async def lifespan(app: FastAPI):
    # Build the agent singleton with its in-memory checkpointer.
    # Wires heavy adapters (Qdrant, Neo4j, OpenAI) once at startup.
    log.info("API startup — building agent (models + adapters)")
    with timed("build_agent startup", log):
        app.state.agent = build_agent()
    log.info("API ready")
    yield
    # No explicit teardown required for memory saver checkpointer


app = FastAPI(
    title="Vantage API",
    description="Agentic Market Intelligence Read-side API Layer",
    version="1.0.0",
    lifespan=lifespan,
)

# Allow all origins for the local dashboard integration
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Register endpoints
app.include_router(chat.router, prefix="/api")
app.include_router(gaps.router, prefix="/api")
app.include_router(graph.router, prefix="/api")
app.include_router(signals.router, prefix="/api")


@app.get("/api/health")
def health() -> dict[str, str]:
    """Lightweight liveness probe for uptime monitors and platform healthchecks."""
    return {"status": "ok"}


# Serve the built React app (apps/web/dist) as static files. Mounted LAST so it
# never shadows the /api routes above. html=True serves index.html at "/".
# Skipped gracefully in dev when the frontend hasn't been built yet.
_WEB_DIST = Path(__file__).resolve().parents[2] / "apps" / "web" / "dist"
if _WEB_DIST.is_dir():
    app.mount("/", StaticFiles(directory=str(_WEB_DIST), html=True), name="web")
    log.info("Serving frontend from %s", _WEB_DIST)
else:
    log.info("No frontend build at %s — API-only mode", _WEB_DIST)