import {
  authService,
  isSessionInvalidError,
  normalizeDmChatId,
  setContacts,
  state,
  terminateCurrentSession,
} from '../state.js';
import { renderUserAvatar } from '../components/avatar-image.js';
import { loadProfileSnapshot } from '../services/user-profile-params.js';
import { parseDmTechBlocks } from '../services/dm-tech-blocks.js';

export const pageMeta = { id: 'messages-list', title: 'Личные сообщения' };
const PREVIEW_MAX_LEN = 200;
const DM_BLOB_PREVIEW_CACHE = new Map();
const DM_BLOB_PREVIEW_PENDING = new Map();
const dmAvatarSnapshotCache = new Map();
const dmAvatarPendingByLogin = new Map();

const RELATION_ORDER = new Map([
  ['close_friend', 0],
  ['contact', 1],
  ['none', 2],
]);

async function loadDmAvatarSnapshot(login) {
  const cleanLogin = String(login || '').trim();
  if (!cleanLogin) return null;
  const key = cleanLogin.toLowerCase();
  if (dmAvatarSnapshotCache.has(key)) return dmAvatarSnapshotCache.get(key);
  if (dmAvatarPendingByLogin.has(key)) return dmAvatarPendingByLogin.get(key);
  const pending = loadProfileSnapshot(cleanLogin)
    .then((snapshot) => {
      dmAvatarSnapshotCache.set(key, snapshot || null);
      dmAvatarPendingByLogin.delete(key);
      return snapshot || null;
    })
    .catch(() => {
      dmAvatarSnapshotCache.set(key, null);
      dmAvatarPendingByLogin.delete(key);
      return null;
    });
  dmAvatarPendingByLogin.set(key, pending);
  return pending;
}

function createDmAvatar(login) {
  const cleanLogin = String(login || '').trim();
  const title = cleanLogin ? `Профиль ${cleanLogin}` : '';
  const avatarEl = renderUserAvatar({
    login: cleanLogin || 'unknown',
    size: 'small',
    title,
  });
  if (!cleanLogin) return avatarEl;
  void loadDmAvatarSnapshot(cleanLogin).then((snapshot) => {
    if (!avatarEl.isConnected) return;
    const upgraded = renderUserAvatar({
      login: cleanLogin,
      avatar: snapshot?.avatar?.txId
        ? {
          ar: String(snapshot.avatar.txId || '').trim(),
          sha256Hex: String(snapshot?.avatar?.sha256Hex || '').trim().toLowerCase(),
        }
        : null,
      size: 'small',
      title,
    });
    upgraded.classList.add('avatar');
    avatarEl.replaceWith(upgraded);
  });
  return avatarEl;
}

function normalizeRelationFlag(value) {
  const clean = String(value || '').trim().toLowerCase();
  if (clean === 'close_friend' || clean === 'contact') return clean;
  return 'none';
}

function relationOrder(flag) {
  return RELATION_ORDER.get(normalizeRelationFlag(flag)) ?? 99;
}

function relationLabel(flag) {
  switch (normalizeRelationFlag(flag)) {
    case 'close_friend':
      return 'близкий друг';
    case 'contact':
      return 'контакт';
    default:
      return 'не в контактах';
  }
}

function clipPreviewText(text, maxLen = PREVIEW_MAX_LEN) {
  const normalized = String(text || '').replace(/\s+/g, ' ').trim();
  if (!normalized) return '';
  if (normalized.length <= maxLen) return normalized;
  return `${normalized.slice(0, maxLen - 1)}…`;
}

async function resolveDialogPreview(dialog) {
  const blobB64 = String(dialog?.lastMessageBlobB64 || '').trim();
  if (!blobB64) return 'Диалог пока пуст.';

  const cacheKey = [
    blobB64,
    String(state.session.login || '').trim().toLowerCase(),
    String(state.session.storagePwdInMemory || '').trim(),
  ].join('|');

  if (DM_BLOB_PREVIEW_CACHE.has(cacheKey)) return DM_BLOB_PREVIEW_CACHE.get(cacheKey);
  if (DM_BLOB_PREVIEW_PENDING.has(cacheKey)) return DM_BLOB_PREVIEW_PENDING.get(cacheKey);

  const pending = (async () => {
    try {
      const parsed = authService.parseSignedMessageBlob(blobB64);
      const decrypted = await authService.decryptSignedMessageContent({
        parsed,
        blobB64,
        login: state.session.login,
        storagePwd: state.session.storagePwdInMemory,
      });
      const parsedText = parseDmTechBlocks(String(decrypted?.text || ''));
      const display = clipPreviewText(String(parsedText.displayText || '').trim());
      const result = display || 'Сообщение';
      DM_BLOB_PREVIEW_CACHE.set(cacheKey, result);
      return result;
    } catch {
      const fallback = 'Сообщение недоступно';
      DM_BLOB_PREVIEW_CACHE.set(cacheKey, fallback);
      return fallback;
    } finally {
      DM_BLOB_PREVIEW_PENDING.delete(cacheKey);
    }
  })();

  DM_BLOB_PREVIEW_PENDING.set(cacheKey, pending);
  return pending;
}

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));
}

function compareChatRows(a, b) {
  const timeA = Number(a?.lastMessageTimeMs || 0);
  const timeB = Number(b?.lastMessageTimeMs || 0);
  if (timeA !== timeB) return timeB - timeA;
  const nameA = String(a?.peerLogin || '').toLowerCase();
  const nameB = String(b?.peerLogin || '').toLowerCase();
  return nameA.localeCompare(nameB, 'ru');
}

const SVG_CHEVRON = '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M9 6l6 6-6 6"/></svg>';

export function render({ navigate, chrome }) {
  const screen = document.createElement('section');
  screen.className = 'stack dm-screen dm-list-screen';
  const login = String(state.session.login || '').trim();

  const head = document.createElement('header');
  head.className = 'dm-head';
  head.innerHTML = `
    <div class="dm-head-brand">
      <div class="dm-head-hex">${(login[0] || 'A').toUpperCase()}</div>
      <div class="dm-head-id">
        <span class="dm-head-name"></span>
      </div>
    </div>
    <h1 class="dm-head-title">Чаты</h1>
    <div class="dm-head-menu-wrap">
      <button type="button" class="dm-head-menu-btn" aria-label="Меню чатов" aria-haspopup="menu" aria-expanded="false">
        <span class="dm-head-menu-dots" aria-hidden="true"><i></i><i></i><i></i></span>
      </button>
      <div class="dm-head-menu" role="menu" hidden>
        <button type="button" class="dm-head-menu-item" role="menuitem" data-action="search-contacts">
          <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
            <circle cx="11" cy="11" r="6.5"></circle>
            <path d="M16 16l4 4"></path>
          </svg>
          <span>Поиск пользователей</span>
        </button>
      </div>
    </div>
  `;
  const headName = head.querySelector('.dm-head-name');
  if (headName) headName.textContent = login;

  const menuWrap = head.querySelector('.dm-head-menu-wrap');
  const menuButton = head.querySelector('.dm-head-menu-btn');
  const menuTemplate = head.querySelector('.dm-head-menu');
  // The header itself is mounted into chrome/topbar, whose hit-test area ends at the
  // header bounds. A dropdown overflowing below it can look visible but clicks may
  // land on the content layer underneath. Render the open menu as a body portal.
  menuTemplate?.remove();

  let menuPortal = null;

  const closeHeadMenu = () => {
    menuPortal?.remove();
    menuPortal = null;
    menuButton?.setAttribute('aria-expanded', 'false');
    menuWrap?.classList.remove('is-open');
  };

  const positionHeadMenu = () => {
    if (!menuPortal || !menuButton) return;
    const rect = menuButton.getBoundingClientRect();
    const margin = 10;
    const menuWidth = menuPortal.offsetWidth || 206;
    const left = Math.max(margin, Math.min(window.innerWidth - menuWidth - margin, rect.right - menuWidth));
    menuPortal.style.left = `${Math.round(left)}px`;
    menuPortal.style.top = `${Math.round(rect.bottom + 7)}px`;
  };

  const openHeadMenu = () => {
    if (!menuButton || menuPortal) return;
    const portal = document.createElement('div');
    portal.className = 'dm-head-menu dm-head-menu--portal';
    portal.setAttribute('role', 'menu');
    portal.innerHTML = `
        <button type="button" class="dm-head-menu-item" role="menuitem" data-action="search-contacts">
        <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
          <circle cx="11" cy="11" r="6.5"></circle>
          <path d="M16 16l4 4"></path>
        </svg>
        <span>Поиск пользователей</span>
      </button>
    `;

    portal.querySelector('[data-action="search-contacts"]')?.addEventListener('click', (event) => {
      event.preventDefault();
      event.stopPropagation();
      closeHeadMenu();
      navigate('contact-search-view');
    });
    portal.addEventListener('click', (event) => event.stopPropagation());

    document.body.append(portal);
    menuPortal = portal;
    menuButton.setAttribute('aria-expanded', 'true');
    menuWrap?.classList.add('is-open');
    positionHeadMenu();
  };

  menuButton?.addEventListener('click', (event) => {
    event.preventDefault();
    event.stopPropagation();
    if (menuPortal) closeHeadMenu();
    else openHeadMenu();
  });

  const onOutsideClick = (event) => {
    if (!menuPortal) return;
    if (menuPortal.contains(event.target) || menuButton?.contains(event.target)) return;
    closeHeadMenu();
  };
  const onMenuKeydown = (event) => {
    if (event.key !== 'Escape' || !menuPortal) return;
    closeHeadMenu();
    menuButton?.focus();
  };
  const onMenuViewportChange = () => positionHeadMenu();
  document.addEventListener('click', onOutsideClick);
  document.addEventListener('keydown', onMenuKeydown);
  window.addEventListener('resize', onMenuViewportChange, { passive: true });
  window.addEventListener('scroll', onMenuViewportChange, { passive: true, capture: true });

  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';
    const relationFlag = normalizeRelationFlag(item.relationFlag);
    const relationBadge = relationFlag === 'none'
      ? 'не в контактах'
      : relationLabel(relationFlag);
    const avatarEl = createDmAvatar(item.peerLogin);
    avatarEl.classList.add('avatar');
    const avatarWrap = document.createElement('div');
    avatarWrap.className = 'dm-av dm-av--default';
    avatarWrap.append(avatarEl);
    row.innerHTML = `
      <div class="dm-row-main">
        <div class="dm-row-titleline dm-row-titlewrap">
          <strong class="dm-row-title"></strong>
          <span class="dm-contact-note">${relationBadge}</span>
        </div>
        <p class="dm-row-last-message"></p>
      </div>
      <div class="dm-row-meta-col">
        ${item.unreadCount ? `<span class="dm-unread-badge">${item.unreadCount > 99 ? '99+' : item.unreadCount}</span>` : '<span class="dm-row-meta-spacer" aria-hidden="true"></span>'}
        <div class="dm-row-meta-line">
          ${item.lastMessageTimeMs ? '<span class="dm-row-time"></span>' : '<span class="dm-row-time dm-row-time--empty"></span>'}
          <span class="dm-chevron">${SVG_CHEVRON}</span>
        </div>
      </div>
    `;
    const titleEl = row.querySelector('.dm-row-title');
    const previewEl = row.querySelector('.dm-row-last-message');
    const timeEl = row.querySelector('.dm-row-time');
    if (titleEl) titleEl.textContent = String(item.peerLogin || '');
    if (previewEl) previewEl.textContent = 'Загрузка…';
    if (timeEl) timeEl.textContent = formatChatRowTime(item.lastMessageTimeMs);
    row.prepend(avatarWrap);
    void resolveDialogPreview(item).then((text) => {
      if (!previewEl?.isConnected) return;
      previewEl.textContent = String(text || '').trim() || 'Диалог пока пуст.';
    });
    row.addEventListener('click', () => navigate(`chat/${encodeURIComponent(normalizeDmChatId(item.peerLogin))}`));
    return row;
  }

  async function loadList() {
    if (state.session.isLocalDemo) {
      const empty = document.createElement('div');
      empty.className = 'card meta-muted';
      empty.textContent = 'Локальный тестовый режим: реальные сообщения и контакты не загружаются.';
      list.replaceChildren(empty);
      return;
    }

    try {
      const payload = await authService.listContacts();
      const dialogs = Array.isArray(payload?.dialogs) ? payload.dialogs : [];
      const contacts = Array.isArray(payload?.contacts) ? payload.contacts : [];
      setContacts(contacts);
      list.innerHTML = '';

      const byPeer = new Map();
      dialogs.forEach((dialog) => {
        const peerLogin = String(dialog?.peerLogin || '').trim();
        if (!peerLogin) return;
        const key = peerLogin.toLowerCase();
        const relationFlag = normalizeRelationFlag(dialog?.relationFlag);
        const next = {
          id: peerLogin,
          peerLogin,
          relationFlag,
          lastMessageBlobB64: String(dialog?.lastMessageBlobB64 || ''),
          lastMessageTimeMs: Number(dialog?.lastMessageTimeMs || 0),
          unreadCount: Number(dialog?.unreadCount || 0),
          hasDialog: Boolean(dialog?.hasDialog),
        };
        const current = byPeer.get(key);
        if (!current) {
          byPeer.set(key, next);
          return;
        }
        const currentRank = relationOrder(current.relationFlag);
        const nextRank = relationOrder(relationFlag);
        if (nextRank < currentRank || (nextRank === currentRank && next.lastMessageTimeMs > current.lastMessageTimeMs)) {
          byPeer.set(key, next);
        }
      });

      const rows = Array.from(byPeer.values()).sort((a, b) => {
        const orderA = relationOrder(a.relationFlag);
        const orderB = relationOrder(b.relationFlag);
        if (orderA !== orderB) return orderA - orderB;
        return compareChatRows(a, b);
      });

      if (!rows.length) {
        const empty = document.createElement('div');
        empty.className = 'card meta-muted';
        empty.textContent = 'Пока нет диалогов';
        list.append(empty);
        return;
      }

      let dividerInserted = false;
      rows.forEach((item) => {
        if (!dividerInserted && normalizeRelationFlag(item.relationFlag) === 'none' && list.childNodes.length > 0) {
          const divider = document.createElement('div');
          divider.className = 'dm-divider';
          list.append(divider);
          dividerInserted = true;
        }
        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);
    }
  }

  chrome?.setTopbar(head);
  screen.append(list);
  loadList();

  screen.cleanup = () => {
    closeHeadMenu();
    document.removeEventListener('click', onOutsideClick);
    document.removeEventListener('keydown', onMenuKeydown);
    window.removeEventListener('resize', onMenuViewportChange);
    window.removeEventListener('scroll', onMenuViewportChange, true);
  };

  return screen;
}