import { renderHeader } from '../components/header.js';
import { directMessages } from '../mock-data.js';
import {
  getChatMessages,
  isSessionInvalidError,
  setContacts,
  state,
  terminateCurrentSession,
} from '../state.js';
import { loadCurrentRelations } from '../services/user-connections.js';

export const pageMeta = { id: 'messages-list', title: 'Личные сообщения' };

function formatChatRowTime(ts) {
  const value = Number(ts || 0);
  if (!Number.isFinite(value) || value <= 0) return '-';
  return new Intl.DateTimeFormat('ru-RU', {
    day: '2-digit',
    month: '2-digit',
    hour: '2-digit',
    minute: '2-digit',
  }).format(new Date(value));
}

export function render({ navigate }) {
  const screen = document.createElement('section');
  screen.className = 'stack dm-screen dm-list-screen';

  screen.append(
    renderHeader({
      title: 'Личные сообщения',
      leftLabel: String(state.session.login || '').trim(),
      rightActions: [{ label: '+', onClick: () => navigate('contact-search-view') }],
    }),
  );

  const list = document.createElement('div');
  list.className = 'stack dm-list';

  function renderRow(item) {
    const row = document.createElement('article');
    row.className = 'list-item dm-dialog-card';
    row.innerHTML = `
      <div class="avatar">${item.initials}</div>
      <div class="dm-row-main">
        <div class="dm-row-title-wrap">
          <strong class="dm-row-title">${item.name}</strong>
          ${item.notInContacts ? '<span class="meta-muted">не в контактах</span>' : ''}
        </div>
        <p class="meta-muted dm-row-last-message">${item.lastMessage}</p>
      </div>
      <div class="dm-row-meta-col">
        ${item.unread ? `<span class="unread">${item.unread}</span>` : '<span></span>'}
        <span class="meta-muted dm-row-time">${item.time}</span>
      </div>
    `;
    row.addEventListener('click', () => navigate(`chat-view/${encodeURIComponent(item.id)}`));
    return row;
  }

  async function loadList() {
    try {
      const relations = await loadCurrentRelations();
      const contacts = relations.outContacts || [];
      setContacts(contacts);
      list.innerHTML = '';

      const contactRows = contacts.map((login) => {
        const preview = directMessages.find((item) => item.id.toLowerCase() === login.toLowerCase());
        const chat = getChatMessages(login);
        const lastChat = chat[chat.length - 1];
        const unread = chat.filter((m) => m?.from === 'in' && m?.unread).length;
        const lastTimeMs = Number(lastChat?.createdAtMs || 0);
        return {
          id: login,
          initials: (login[0] || '?').toUpperCase(),
          name: preview?.name || login,
          lastMessage: lastChat?.text || preview?.lastMessage || 'Диалог пока пуст.',
          time: formatChatRowTime(lastTimeMs),
          unread,
          notInContacts: false,
        };
      });

      const allChatIds = Object.keys(state.chats || {})
        .filter((id) => id && id.toLowerCase() !== String(state.session.login || '').toLowerCase())
        .filter((id) => (getChatMessages(id) || []).length > 0);

      const contactKeys = new Set(contacts.map((x) => String(x || '').toLowerCase()));
      const extraRows = allChatIds
        .filter((login) => !contactKeys.has(String(login || '').toLowerCase()))
        .map((login) => {
          const chat = getChatMessages(login);
          const lastChat = chat[chat.length - 1];
          const unread = chat.filter((m) => m?.from === 'in' && m?.unread).length;
          const lastTimeMs = Number(lastChat?.createdAtMs || 0);
          return {
            id: login,
            initials: (login[0] || '?').toUpperCase(),
            name: login,
            lastMessage: lastChat?.text || 'Диалог пока пуст.',
            time: formatChatRowTime(lastTimeMs),
            unread,
            notInContacts: true,
          };
        });

      const rows = [...contactRows, ...extraRows];
      if (!rows.length) {
        const empty = document.createElement('div');
        empty.className = 'card meta-muted';
        empty.textContent = 'Пока нет ни контактов, ни сообщений';
        list.append(empty);
        return;
      }

      rows.forEach((item) => list.append(renderRow(item)));
    } catch (error) {
      if (isSessionInvalidError(error)) {
        list.innerHTML = '';

        const card = document.createElement('div');
        card.className = 'card stack';

        const title = document.createElement('strong');
        title.textContent = 'Сессия устарела';

        const details = document.createElement('p');
        details.className = 'meta-muted';
        details.textContent = 'Ваша сессия больше не действует. Авторизуйтесь заново.';

        const okBtn = document.createElement('button');
        okBtn.type = 'button';
        okBtn.className = 'primary-btn';
        okBtn.textContent = 'ОК';
        okBtn.addEventListener('click', async () => {
          await terminateCurrentSession({
            infoMessage: 'Ваша сессия устарела. Выполните вход заново.',
          });
          navigate('start-view');
        });

        card.append(title, details, okBtn);
        list.append(card);
        return;
      }

      list.innerHTML = '';
      const fail = document.createElement('div');
      fail.className = 'card meta-muted';
      fail.textContent = `Не удалось загрузить сообщения: ${error.message || 'unknown'}`;
      list.append(fail);
    }
  }

  screen.append(list);
  loadList();
  return screen;
}