// server and channel management

async function loadServers() {
    try {
        const res = await fetch(`${API_URL}/servers`, {
            headers: { 'Authorization': `Bearer ${token}` }
        });
        if (res.ok) {
            servers = await res.json();
            // seed lastSeen timestamps so we don't mark existing messages as unread
            servers.forEach(s => {
                s.channels.forEach(ch => {
                    const key = conversationKey('c', ch.id);
                    if (!lastSeen[key]) lastSeen[key] = Date.now();
                });
            });
            renderServers();
            if (servers.length > 0) {
                selectServer(servers[0].id);
            }
            
            // Update Service Worker with channels list for background notifications
            updateServiceWorkerChannels();
        }
    } catch (error) {
        console.error('Error loading servers:', error);
    }
}

function renderServers() {
    const bar = document.getElementById('servers-bar');
    bar.querySelectorAll('.server-icon').forEach(n => n.remove());
    servers.forEach(s => {
        const icon = document.createElement('div');
        icon.className = 'server-icon';
        icon.textContent = s.name.charAt(0).toUpperCase();
        icon.onclick = () => selectServer(s.id);
        bar.insertBefore(icon, document.getElementById('create-server-btn'));
    });
}

function addChannelButton() {
    const list = document.getElementById('channels-list');
    let btn = document.getElementById('create-channel-btn');
    if (!btn) {
        btn = document.createElement('div');
        btn.id = 'create-channel-btn';
        btn.className = 'channel create-channel-btn';
        btn.textContent = '+ create channel';
        btn.onclick = async () => {
            const name = prompt('Channel name:');
            if (!name) return;
            const res = await fetch(`${API_URL}/servers/${currentServerId}/channels`, {
                method: 'POST',
                headers: { 'Content-Type': 'application/json', 'Authorization': `Bearer ${token}` },
                body: JSON.stringify({ name })
            });
            if (res.ok) {
                const newch = await res.json();
                const srv = servers.find(s=>s.id===currentServerId);
                srv.channels.push(newch);
                selectServer(currentServerId);
            } else {
                const err = await res.json();
                alert(err.error || 'failed');
            }
        };
        list.prepend(btn);
    }
}

function selectServer(id) {
    currentServerId = id;
    const srv = servers.find(s => s.id === id);
    document.querySelector('.server-name').textContent = srv.name;
    const list = document.getElementById('channels-list');
    list.innerHTML = '';
    addChannelButton();
    srv.channels.forEach(ch => {
        const el = document.createElement('div');
        el.className = 'channel';
        el.textContent = '# ' + ch.name;
        // badge
        const count = unreadCounts[conversationKey('c', ch.id)];
        if (count) {
            const badge = document.createElement('span');
            badge.className = 'unread-badge';
            badge.textContent = count;
            el.appendChild(badge);
        }
        el.onclick = () => selectChannel(ch.id, ch.name);
        list.appendChild(el);
    });
    if (srv.channels.length>0) selectChannel(srv.channels[0].id, srv.channels[0].name);
    messageInput.value = '';
}

function selectChannel(id, name) {
    currentChannelId = id;
    headerTitle.textContent = `#${name}`;
    // clear current messages when switching channels to avoid mixed history
    if (messagesContainer) messagesContainer.innerHTML = '';
    lastFetchedTs = null;
    isAtBottom = true; // reset scroll state for new conversation
    currentDMUserId = null;
    loadChannel(id);
    document.querySelectorAll('.channel').forEach(ch => ch.classList.remove('active'));
    const el = [...document.querySelectorAll('.channel')].find(n=>n.textContent.includes(name));
    if(el) el.classList.add('active');
    messageInput.value = '';
}

function selectGlobalChat() {
    currentDMUserId = null;
    headerTitle.textContent = 'Глобальный чат';
    if (messagesContainer) messagesContainer.innerHTML = '';
    lastFetchedTs = null;
    isAtBottom = true; // reset scroll state for new conversation
    currentChannelId = null;
    loadGlobalChat();
    document.querySelectorAll('.channel').forEach(ch => ch.classList.remove('active'));
    document.querySelector('[data-channel="global"]').classList.add('active');
    messageInput.value = '';
}

function initServerListeners() {
    const btn = document.getElementById('create-server-btn');
    if (btn) {
        btn.addEventListener('click', async () => {
            const name = prompt('Server name:');
            if (!name) return;
            const res = await fetch(`${API_URL}/servers`, {
                method: 'POST',
                headers: { 'Content-Type':'application/json', 'Authorization':`Bearer ${token}` },
                body: JSON.stringify({name})
            });
            if (res.ok) {
                loadServers();
            } else {
                const err = await res.json();
                alert(err.error || 'failed');
            }
        });
    }
}