# app.py
from fastapi import FastAPI, Request, status
from fastapi.responses import JSONResponse
from fastapi.middleware.cors import CORSMiddleware # If you need CORS
from contextlib import asynccontextmanager
import uvicorn
import logging
from slowapi import Limiter, _rate_limit_exceeded_handler
from slowapi.util import get_remote_address
from slowapi.errors import RateLimitExceeded
from slowapi.middleware import SlowAPIMiddleware
import sys # Import sys module
import config
from services import generation
from routers import ideas, images, videos

# --- Logging Setup ---
logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(name)s - %(levelname)s - %(message)s')
logger = logging.getLogger(__name__)

# --- Rate Limiting Setup ---
limiter = Limiter(key_func=get_remote_address, default_limits=[config.RATE_LIMIT])

# --- Lifespan Management (Model Loading/Unloading) ---
@asynccontextmanager
async def lifespan(app: FastAPI):
    # Startup: Assign essential state FIRST
    app.state.limiter = limiter
    logger.info("Rate limiter assigned to app state.")

    models_loaded_successfully = False
    try:
        logger.info("Application startup: Loading models...")
        generation.load_models() # This might raise an exception
        models_loaded_successfully = True # Set flag ONLY if load_models completes
        logger.info("Models loaded successfully.")
    except Exception as e:
        logger.error(f"FATAL: Model loading failed during startup: {e}", exc_info=True)
        # Option 1: Exit the application (cleaner for Docker environments)
        # logger.critical("Exiting application due to model loading failure.")
        # sys.exit(1)
        # Option 2: Raise the exception again to make uvicorn aware of failure
        # This might depend on how uvicorn handles lifespan exceptions
        # raise # Re-raise the exception

    # >>> Only yield if models loaded <<<
    if models_loaded_successfully:
        yield # Application is now ready to serve requests
    else:
        # If models didn't load, we don't yield, preventing Uvicorn
        # from reporting "Application startup complete."
        # You might need to manually stop the process if Option 1 above isn't used.
        logger.error("Application startup failed due to model loading errors. Server will not serve requests effectively.")
        # Keep the process running but indicate failure. Or use sys.exit(1) above.
        # If you don't yield or exit, Uvicorn might hang or exit depending on version.
        # Testing needed here - sys.exit(1) is often simplest in Docker.
        # For now, just logging the failure and not yielding.

    # --- Shutdown Logic ---
    # This part might not be reached if sys.exit was called
    logger.info("Application shutdown sequence starting.")
    if "generation" in globals() and hasattr(generation, 'model_cache'):
         generation.model_cache.clear()
    # Add any other cleanup here
    logger.info("Resources cleaned up.")



# --- FastAPI App Initialization ---
app = FastAPI(
    title="AI Content Generation API",
    description="API for generating content ideas, images, and videos using Hugging Face models.",
    version="1.0.0",
    lifespan=lifespan # Use the lifespan context manager
)

# --- Middleware ---
# Rate Limiting Middleware - Now it can safely access app.state.limiter
app.add_middleware(SlowAPIMiddleware)

# CORS Middleware (Uncomment and configure if needed for browser-based clients)
# origins = [
#     "http://localhost",
#     "http://localhost:8080",
#     "https://your-frontend-domain.com", # Add your frontend domain
# ]
# app.add_middleware(
#     CORSMiddleware,
#     allow_origins=origins,
#     allow_credentials=True,
#     allow_methods=["*"],
#     allow_headers=["*"],
# )

# --- Exception Handlers ---
app.add_exception_handler(RateLimitExceeded, _rate_limit_exceeded_handler)

@app.exception_handler(Exception)
async def general_exception_handler(request: Request, exc: Exception):
    logger.error(f"Unhandled exception: {exc}", exc_info=True)
    return JSONResponse(
        status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
        content={"detail": "An internal server error occurred."},
    )

# --- API Routers ---
app.include_router(ideas.router)
app.include_router(images.router)
app.include_router(videos.router)

# --- Root Endpoint ---
@app.get("/", tags=["Status"])
async def read_root():
    """Root endpoint providing basic API information."""
    return {
        "message": "Welcome to the AI Content Generation API!",
        "docs": "/docs",
        "models": {
            "text": config.TEXT_MODEL_NAME,
            "image": config.IMAGE_MODEL_NAME,
            "video": config.VIDEO_MODEL_NAME
        },
         "status": "OK"
    }

# --- Main Execution (for local testing) ---
if __name__ == "__main__":
    # When running locally: uvicorn app:app --reload
    # The following is mostly for structuring; direct execution isn't typical for deployment
    print("To run locally, use: uvicorn app:app --reload --host 0.0.0.0 --port 7860")
    # uvicorn.run(app, host="0.0.0.0", port=7860) # Port 7860 is common for HF Spaces