import { useEffect, useMemo, useRef, useState } from 'react';
import {
  attendantsByArea,
  chatContacts,
  getMockReply,
  transferAreas,
} from '../services/chatMocks';

function buildInitialMessages() {
  return chatContacts.reduce((acc, contact) => {
    acc[contact.id] = contact.messages;
    return acc;
  }, {});
}

export function useChat() {
  const [contacts, setContacts] = useState(chatContacts);
  const [activeContactId, setActiveContactId] = useState(chatContacts[0].id);
  const [messagesByContact, setMessagesByContact] = useState(buildInitialMessages);
  const [draft, setDraft] = useState('');
  const [selectedArea, setSelectedArea] = useState(chatContacts[0].area);
  const [isTransferOpen, setIsTransferOpen] = useState(false);
  const [transferArea, setTransferArea] = useState('Suporte');
  const [transferAttendant, setTransferAttendant] = useState(attendantsByArea.Suporte[0]);
  const [transferNote, setTransferNote] = useState('');
  const [isReplying, setIsReplying] = useState(false);
  const replyTimeoutRef = useRef(null);

  const activeContact = useMemo(
    () => contacts.find((contact) => contact.id === activeContactId) || contacts[0],
    [contacts, activeContactId],
  );

  const messages = messagesByContact[activeContactId] || [];
  const attendants = attendantsByArea[transferArea] || [];

  useEffect(() => {
    setSelectedArea(activeContact.area);
  }, [activeContact]);

  useEffect(() => {
    setTransferAttendant(attendants[0] || '');
  }, [transferArea]);

  useEffect(() => {
    return () => {
      if (replyTimeoutRef.current) {
        window.clearTimeout(replyTimeoutRef.current);
      }
    };
  }, []);

  function updateContactPreview(contactId, preview) {
    setContacts((current) =>
      current.map((contact) =>
        contact.id === contactId ? { ...contact, preview, time: 'Agora', unread: 0 } : contact,
      ),
    );
  }

  function sendMessage() {
    const trimmed = draft.trim();
    if (!trimmed) {
      return;
    }

    const newMessage = {
      id: Date.now(),
      sender: 'agent',
      text: trimmed,
    };

    setMessagesByContact((current) => ({
      ...current,
      [activeContactId]: [...(current[activeContactId] || []), newMessage],
    }));
    updateContactPreview(activeContactId, trimmed);
    setDraft('');
    setIsReplying(true);

    replyTimeoutRef.current = window.setTimeout(() => {
      const reply = {
        id: Date.now() + 1,
        sender: 'customer',
        text: getMockReply(activeContact.name),
      };

      setMessagesByContact((current) => ({
        ...current,
        [activeContactId]: [...(current[activeContactId] || []), reply],
      }));
      setContacts((current) =>
        current.map((contact) =>
          contact.id === activeContactId
            ? { ...contact, preview: reply.text, time: 'Agora', unread: contact.unread + 1 }
            : contact,
        ),
      );
      setIsReplying(false);
    }, 1400);
  }

  function submitTransfer() {
    const note = transferNote.trim();
    const transferMessage = note
      ? `Transferencia solicitada para ${transferArea} com ${transferAttendant}. Obs: ${note}`
      : `Transferencia solicitada para ${transferArea} com ${transferAttendant}.`;

    setMessagesByContact((current) => ({
      ...current,
      [activeContactId]: [
        ...(current[activeContactId] || []),
        { id: Date.now() + 2, sender: 'system', text: transferMessage },
      ],
    }));

    setContacts((current) =>
      current.map((contact) =>
        contact.id === activeContactId ? { ...contact, area: transferArea } : contact,
      ),
    );
    setSelectedArea(transferArea);
    setIsTransferOpen(false);
    setTransferNote('');
  }

  return {
    contacts,
    activeContact,
    activeContactId,
    setActiveContactId,
    messages,
    draft,
    setDraft,
    sendMessage,
    isReplying,
    selectedArea,
    setSelectedArea,
    isTransferOpen,
    setIsTransferOpen,
    transferArea,
    setTransferArea,
    transferAreas,
    attendants,
    transferAttendant,
    setTransferAttendant,
    transferNote,
    setTransferNote,
    submitTransfer,
  };
}