backend/main.py

import asyncio
import logging
import sys

from dotenv import load_dotenv
load_dotenv()

logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(name)s] %(levelname)s: %(message)s")
log = logging.getLogger("app")

# psycopg (used by LangGraph checkpointer) requires SelectorEventLoop on Windows
if sys.platform == "win32":
    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

from contextlib import asynccontextmanager

from fastapi import FastAPI

from backend.checkpointer import init_checkpointer
from backend.db.connection import init_db_pool
from backend.graph.graph import build_graph
from backend.routers import auth, batches, instructor, interview, sessions, student, topics, upload


@asynccontextmanager
async def lifespan(app: FastAPI):
    log.info("Starting up — connecting to DB...")
    await init_db_pool()
    log.info("DB pool ready")
    checkpointer = await init_checkpointer()
    log.info("LangGraph checkpointer ready")
    app.state.graph = build_graph(checkpointer)
    log.info("Interview graph compiled")
    yield
    log.info("Shutting down")


app = FastAPI(lifespan=lifespan)

app.include_router(auth.router,        prefix="/api/auth")
app.include_router(batches.router,     prefix="/api/batches")
app.include_router(topics.router,      prefix="/api/topics")
app.include_router(upload.router,      prefix="/api/upload")
app.include_router(student.router,     prefix="/api/student")
app.include_router(sessions.router,    prefix="/api/sessions")
app.include_router(instructor.router,  prefix="/api/instructor")
app.include_router(interview.router,   prefix="/interview")

# React static build — MUST be last (serves the SPA for all non-API routes)
from pathlib import Path
from fastapi.staticfiles import StaticFiles
from fastapi.responses import FileResponse

_dist = Path(__file__).resolve().parent.parent / "frontend" / "dist"
if _dist.is_dir():
    # Catch-all for React Router — serve index.html for any path that isn't a real file
    @app.get("/{full_path:path}", include_in_schema=False)
    async def spa_fallback(full_path: str):
        file = _dist / full_path
        if file.is_file():
            return FileResponse(str(file))
        return FileResponse(str(_dist / "index.html"))

    app.mount("/", StaticFiles(directory=str(_dist)), name="static")
    log.info("Static files mounted from %s", _dist)
else:
    log.warning("frontend/dist not found at %s — SPA will not be served", _dist)