import { useState, useCallback } from 'react';

export interface ChatMessage {
  id: string;
  role: 'user' | 'assistant';
  content: string;
  timestamp: number;
}

interface UseChatHistoryReturn {
  messages: ChatMessage[];
  addMessage: (role: 'user' | 'assistant', content: string) => void;
  clearMessages: () => void;
  deleteMessage: (id: string) => void;
  updateMessage: (id: string, content: string) => void;
}

export function useChatHistory(storageKey: string = 'chat-history'): UseChatHistoryReturn {
  const [messages, setMessages] = useState<ChatMessage[]>(() => {
    try {
      const stored = localStorage.getItem(storageKey);
      return stored ? JSON.parse(stored) : [];
    } catch {
      return [];
    }
  });

  const saveToStorage = useCallback((newMessages: ChatMessage[]) => {
    try {
      localStorage.setItem(storageKey, JSON.stringify(newMessages));
    } catch (error) {
      console.error('Failed to save chat history:', error);
    }
  }, [storageKey]);

  const addMessage = useCallback((role: 'user' | 'assistant', content: string) => {
    const newMessage: ChatMessage = {
      id: `${Date.now()}-${Math.random().toString(36).substr(2, 9)}`,
      role,
      content,
      timestamp: Date.now(),
    };
    setMessages((prev) => {
      const updated = [...prev, newMessage];
      saveToStorage(updated);
      return updated;
    });
  }, [saveToStorage]);

  const clearMessages = useCallback(() => {
    setMessages([]);
    localStorage.removeItem(storageKey);
  }, [storageKey]);

  const deleteMessage = useCallback((id: string) => {
    setMessages((prev) => {
      const updated = prev.filter((msg) => msg.id !== id);
      saveToStorage(updated);
      return updated;
    });
  }, [saveToStorage]);

  const updateMessage = useCallback((id: string, content: string) => {
    setMessages((prev) => {
      const updated = prev.map((msg) =>
        msg.id === id ? { ...msg, content } : msg
      );
      saveToStorage(updated);
      return updated;
    });
  }, [saveToStorage]);

  return {
    messages,
    addMessage,
    clearMessages,
    deleteMessage,
    updateMessage,
  };
}