"""FastAPI application entry point."""

from __future__ import annotations

import logging
from contextlib import asynccontextmanager
from pathlib import Path
from typing import TYPE_CHECKING

from fastapi import FastAPI, WebSocket, WebSocketDisconnect
from fastapi.staticfiles import StaticFiles

from app.callbacks import TokenUsageCallbackHandler
from app.config import Settings
from app.db import create_checkpointer, create_pool, setup_app_tables
from app.escalation import NoOpEscalator, WebhookEscalator
from app.graph import build_graph
from app.intent import LLMIntentClassifier
from app.interrupt_manager import InterruptManager
from app.llm import create_llm
from app.registry import AgentRegistry
from app.session_manager import SessionManager
from app.ws_handler import dispatch_message

if TYPE_CHECKING:
    from collections.abc import AsyncGenerator

logger = logging.getLogger(__name__)

AGENTS_YAML = Path(__file__).parent.parent / "agents.yaml"
FRONTEND_DIST = Path(__file__).parent.parent.parent / "frontend" / "dist"


@asynccontextmanager
async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
    settings = Settings()

    pool = await create_pool(settings)
    checkpointer = await create_checkpointer(pool)
    await setup_app_tables(pool)

    # Load agents from template or default YAML
    if settings.template_name:
        registry = AgentRegistry.load_template(settings.template_name)
    else:
        registry = AgentRegistry.load(AGENTS_YAML)

    llm = create_llm(settings)
    intent_classifier = LLMIntentClassifier(llm)
    graph = build_graph(registry, llm, checkpointer, intent_classifier=intent_classifier)

    session_manager = SessionManager(
        session_ttl_seconds=settings.session_ttl_minutes * 60,
    )
    interrupt_manager = InterruptManager(
        ttl_seconds=settings.interrupt_ttl_minutes * 60,
    )

    # Configure escalation
    if settings.webhook_url:
        escalator = WebhookEscalator(
            url=settings.webhook_url,
            timeout_seconds=settings.webhook_timeout_seconds,
            max_retries=settings.webhook_max_retries,
        )
    else:
        escalator = NoOpEscalator()

    app.state.graph = graph
    app.state.session_manager = session_manager
    app.state.interrupt_manager = interrupt_manager
    app.state.escalator = escalator
    app.state.settings = settings
    app.state.pool = pool

    logger.info(
        "Smart Support started: %d agents loaded, LLM=%s/%s, template=%s",
        len(registry),
        settings.llm_provider,
        settings.llm_model,
        settings.template_name or "(default)",
    )

    yield

    await pool.close()


app = FastAPI(title="Smart Support", version="0.2.0", lifespan=lifespan)


@app.websocket("/ws")
async def websocket_endpoint(ws: WebSocket) -> None:
    await ws.accept()
    graph = app.state.graph
    session_manager = app.state.session_manager
    interrupt_manager = app.state.interrupt_manager
    settings = app.state.settings
    callback_handler = TokenUsageCallbackHandler(model_name=settings.llm_model)

    try:
        while True:
            raw_data = await ws.receive_text()
            await dispatch_message(
                ws, graph, session_manager, callback_handler, raw_data,
                interrupt_manager=interrupt_manager,
            )
    except WebSocketDisconnect:
        logger.info("WebSocket client disconnected")


if FRONTEND_DIST.is_dir():
    app.mount("/", StaticFiles(directory=str(FRONTEND_DIST), html=True), name="frontend")