"""FastAPI application factory."""

from __future__ import annotations

from contextlib import asynccontextmanager
from typing import AsyncGenerator

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

from src.api.routes import router
from src.utils.config import get_settings
from src.utils.logging import get_logger

logger = get_logger(__name__)


@asynccontextmanager
async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
    """Application lifespan handler."""
    # Startup
    logger.info("Starting Ask-the-Web Agent API...")
    settings = get_settings()
    logger.info(f"Environment: {settings.environment}")

    yield

    # Shutdown
    logger.info("Shutting down Ask-the-Web Agent API...")


def create_app() -> FastAPI:
    """Create and configure the FastAPI application.
    
    Returns:
        Configured FastAPI application
    """
    settings = get_settings()

    app = FastAPI(
        title="Ask-the-Web Agent API",
        description="""
        An AI-powered agent that answers questions using web search and reasoning.
        
        ## Features
        - Natural language question answering
        - Web search integration
        - Source citation
        - Follow-up question generation
        - Conversation history
        
        ## Usage
        Send a POST request to `/api/v1/query` with your question.
        """,
        version="1.0.0",
        docs_url="/docs" if settings.debug else None,
        redoc_url="/redoc" if settings.debug else None,
        lifespan=lifespan,
    )

    # Add CORS middleware
    app.add_middleware(
        CORSMiddleware,
        allow_origins=["*"],  # Configure appropriately for production
        allow_credentials=True,
        allow_methods=["*"],
        allow_headers=["*"],
    )

    # Include API routes
    app.include_router(router, prefix="/api/v1")

    # Root endpoint
    @app.get("/", tags=["Root"])
    async def root() -> dict:
        """Root endpoint with API information."""
        return {
            "name": "Ask-the-Web Agent API",
            "version": "1.0.0",
            "docs": "/docs" if settings.debug else None,
            "health": "/api/v1/health",
        }

    return app


# Create app instance for uvicorn
app = create_app()