// global variables and constants
let token = localStorage.getItem('token');
let userId = localStorage.getItem('userId');
let username = localStorage.getItem('username');
let currentDMUserId = null;
let currentServerId = null;
let currentChannelId = null;
let servers = [];
let friends = [];
let allUsers = [];

// reply functionality
let replyToMessage = null; // { id, username, content }
let replyToUsername = null;

// unread message bookkeeping
let lastSeen = {};            // key -> timestamp ms of last seen message
let unreadCounts = {};        // key -> number of unread messages

// notification state
let notificationPermission = Notification.permission;
let lastNotifiedMessages = {}; // key -> timestamp of last notified message

function conversationKey(type, id) {
    // type 'c' for channel, 'd' for dm
    return `${type}${id}`;
}

const API_URL = '/api'; // relative base for flask backend

// DOM elements (will be assigned after DOM ready)
let authScreen, chatScreen;
let usernameInput, passwordInput;
let loginBtn, registerBtn, logoutBtn;
let messagesContainer, messageInput, sendBtn, fileInput, attachBtn, filePreview, filePreviewText, filePreviewClear;
let authMessage, currentUserDisplay, headerTitle;
let dmList, friendsList, friendRequestsList;
let addFriendBtn, addFriendModal, closeModal;
let friendUsernameInput, modalAddBtn, modalError;
let tabBtns, chatTab, friendsTab;
let profileBtn, profileModal, profileAvatarInput, profileDescInput, profilePronounsInput, profileSaveBtn, profileCloseBtn;
let userProfileModal, userProfileAvatar, userProfileUsername, userProfilePronouns, userProfileDescription;
let userProfileAddFriendBtn, userProfileCloseBtn;

// Reply functionality DOM elements
let replyPreview, replyUsername, replyPreviewText, replyCancelBtn;

// utility function available globally
function escapeHtml(text) {
    const map = {
        '&': '&',
        '<': '<',
        '>': '>',
        '"': '"',
        "'": '&#039;'
    };
    return text.replace(/[&<>"']/g, m => map[m]);
}
// Stub functions for Service Worker updates (prevent errors if sw not implemented)
function updateServiceWorkerFriends() {
    // Placeholder - implement if Service Worker is used
    console.log('Service Worker friends update skipped');
}

function updateServiceWorkerChannels() {
    // Placeholder - implement if Service Worker is used
    console.log('Service Worker channels update skipped');
}