import { useLocation } from '@docusaurus/router';
import { useCallback, useEffect, useRef, useState } from 'react';

import { useOptions } from '@docuservix/hooks/useOptions';
import { IChat, IChatMessage, IChatSource } from '@docuservix/models/chat';

interface UseChatResult {
    dialog: IChat;
    typing: boolean;
    statusMessage?: string;
    sendMessage: (text: string) => void;
}

function useQuery(): string {
    const location = useLocation();
    const params = new URLSearchParams(location.search);

    return params.get('q') ?? '';
}

export function useChat(): UseChatResult {
    const chatEndpoint = useOptions().api + '/v1/chat';
    const urlQuery = useQuery();

    const [messages, setMessages] = useState<IChatMessage[]>([]);
    const [loading, setLoading] = useState(false);
    const [error, setError] = useState<string | null>(null);

    const initialSentRef = useRef(false);
    const messagesEndRef = useRef(messages);

    messagesEndRef.current = messages;

    const sendMessage = useCallback(
        async (text: string) => {
            const content = text.trim();

            if (!content) {
                return;
            }

            const userMessage: IChatMessage = { role: 'user', content };
            const newHistory = [...messagesEndRef.current, userMessage];

            setMessages(newHistory);
            setLoading(true);
            setError(null);

            try {
                const res = await fetch(chatEndpoint, {
                    method: 'POST',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify({ messages: newHistory }),
                });

                if (!res.ok) {
                    throw new Error(`HTTP ${res.status}`);
                }

                const data: { answer: string; sources?: IChatSource[] } = await res.json();

                setMessages((prev) => [
                    ...prev,
                    { role: 'assistant', content: data.answer, sources: data.sources },
                ]);
            } catch (err) {
                setError(err instanceof Error ? err.message : 'Ошибка при обращении к серверу');
            } finally {
                setLoading(false);
            }
        },
        [chatEndpoint],
    );

    useEffect(() => {
        if (urlQuery && !initialSentRef.current) {
            initialSentRef.current = true;
            sendMessage(urlQuery);
        }
    }, [urlQuery, sendMessage]);

    return {
        dialog: { messages },
        typing: loading,
        statusMessage: error ?? undefined,
        sendMessage,
    };
}