document.addEventListener("DOMContentLoaded", async () => {
    const params = new URLSearchParams(window.location.search);
    const room = params.get("room") || "";
    const username = localStorage.getItem("username");
    const userKey = localStorage.getItem("userKey");
    const initialWatchPartyRequested = params.has("watchparty");

    let firstLoad = true;
    let isRefreshing = false;
    let currentRoomKey = null; // AES-GCM 256-bit CryptoKey derived from room password
    let isRoomOwner = false;
    let watchPartyActive = false;

    if (!room || !username || !userKey) {
        alert("Missing room or user credentials.");
        window.location.href = `/index.html${room ? '?room=' + encodeURIComponent(room) : ''}`;
        return;
    }

    document.title = `${room} - Transient.chat`;

    // 1. Validate user session
    try {
        const res = await fetch('/validate', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ username, key: userKey })
        });
        if (!res.ok) {
            localStorage.clear();
            alert("User validation failed.");
            window.location.href = '/';
            return;
        }
    } catch (err) {
        console.error('Validation error:', err);
        localStorage.clear();
        alert("Validation error.");
        window.location.href = '/';
        return;
    }

    // 🔒 Security: Escape HTML
    function escapeHtml(text) {
        if (!text) return text;
        return text
            .replace(/&/g, "&")
            .replace(/</g, "&lt;")
            .replace(/>/g, "&gt;")
            .replace(/"/g, "&quot;")
            .replace(/'/g, "&#039;");
    }

    function updateRoomTitle() {
        const roomTitleEl = document.getElementById("room-title");
        if (roomTitleEl) {
            roomTitleEl.innerHTML = `
              <div class="title-row">
                <a href="server_list.html">
                  <img src="/assets/images/transientchat-blue.png" alt="Transient.chat" style="height: 60px;"/>
                </a>
                <span>Room: ${escapeHtml(room)}</span>
                <span style="color: #4caf50; font-size: 0.8em; margin-left: 12px;">🔒 Private & Encrypted</span>
              </div>
            `;
        }
    }

    updateRoomTitle();

    // DOM Elements
    const messagesDiv = document.getElementById("messages");
    const form = document.getElementById("chat-form");
    const input = document.getElementById("message-input");
    const usersDiv = document.getElementById("user-list");
    const soundToggleBtn = document.getElementById("sound-toggle");
    const externalToggleBtn = document.getElementById("external-toggle");
    const watchpartyToggleBtn = document.getElementById("watchparty-toggle");
    const videoSection = document.getElementById("video-section");

    // Modal elements
    const passwordModal = document.getElementById("password-modal");
    const passwordForm = document.getElementById("password-form");
    const passwordInput = document.getElementById("modal-password-input");

    // Audio & Sounds setup
    const sounds = {
        message: new Audio('/assets/sounds/message.wav'),
        in: new Audio('/assets/sounds/user-in.wav'),
        out: new Audio('/assets/sounds/user-out.wav'),
    };

    let soundEnabled = localStorage.getItem("soundEnabled") !== "false";
    let externalContentEnabled = localStorage.getItem("externalContentEnabled") !== "false";
    let autoplayEnabled = localStorage.getItem("autoplayEnabled") !== "false";

    soundToggleBtn.textContent = soundEnabled ? "🔊 Sound: On" : "🔇 Sound: Off";
    soundToggleBtn.classList.toggle("toggle-off", !soundEnabled);

    const updateExternalToggleBtn = () => {
        externalToggleBtn.textContent = externalContentEnabled
            ? "🖥️ External Content: On"
            : "🔒 External Content: Off";
        externalToggleBtn.classList.toggle("toggle-off", !externalContentEnabled);
    };
    updateExternalToggleBtn();

    soundToggleBtn.addEventListener("click", () => {
        soundEnabled = !soundEnabled;
        localStorage.setItem("soundEnabled", soundEnabled);
        soundToggleBtn.textContent = soundEnabled ? "🔊 Sound: On" : "🔇 Sound: Off";
        soundToggleBtn.classList.toggle("toggle-off", !soundEnabled);
    });

    externalToggleBtn.addEventListener("click", () => {
        externalContentEnabled = !externalContentEnabled;
        localStorage.setItem("externalContentEnabled", externalContentEnabled);
        updateExternalToggleBtn();
    });

    // 🗣️ Autoplay Toggle
    const autoplayToggleBtn = document.createElement("button");
    autoplayToggleBtn.id = "autoplay-toggle";
    autoplayToggleBtn.style.marginBottom = "10px";
    autoplayToggleBtn.style.textAlign = "left";
    autoplayToggleBtn.style.display = "inline-block";
    if (externalToggleBtn && externalToggleBtn.parentNode) {
        externalToggleBtn.parentNode.insertBefore(autoplayToggleBtn, externalToggleBtn.nextSibling);
    }

    const updateAutoplayToggleBtn = () => {
        autoplayToggleBtn.textContent = autoplayEnabled
            ? "🗣️ Autoplay: On"
            : "🔇 Autoplay: Off";
        autoplayToggleBtn.classList.toggle("toggle-off", !autoplayEnabled);
    };
    updateAutoplayToggleBtn();

    autoplayToggleBtn.addEventListener("click", () => {
        autoplayEnabled = !autoplayEnabled;
        localStorage.setItem("autoplayEnabled", autoplayEnabled);
        updateAutoplayToggleBtn();
    });

    // 🎤 Voice Message Button Setup
    const micBtn = document.createElement("button");
    micBtn.textContent = "🎤";
    micBtn.type = "button";
    micBtn.className = "mic-button";
    micBtn.title = "Hold to record voice message (max 15s)";
    if (input && input.parentNode) {
        input.parentNode.insertBefore(micBtn, input.nextSibling);
    }

    // Mobile Toggle for User List & Settings
    const userListContainer = document.getElementById("user-list-container");
    if (userListContainer) {
        const toggleBtn = document.createElement("button");
        toggleBtn.id = "user-list-toggle";
        toggleBtn.textContent = "Show Users & Settings";
        userListContainer.prepend(toggleBtn);

        toggleBtn.addEventListener("click", () => {
            const isExpanded = userListContainer.classList.toggle("expanded");
            toggleBtn.textContent = isExpanded ? "Hide Users & Settings" : "Show Users & Settings";
        });
    }

    // 🔐 Room Password & Encryption Key Derivation Logic
    const sessionPasswordKey = `room_password_${room}`;

    async function authenticateAndDeriveKey(password) {
        try {
            const res = await fetch("/rooms/join", {
                method: "POST",
                headers: { "Content-Type": "application/json" },
                body: JSON.stringify({
                    room: room,
                    password: password,
                    username: username,
                    key: userKey
                })
            });

            if (!res.ok) {
                const errData = await res.json().catch(() => ({}));
                return { success: false, error: errData.error || "Room authentication failed" };
            }

            const data = await res.json();
            isRoomOwner = !!data.is_owner;

            // Store password in sessionStorage for this browser tab session
            sessionStorage.setItem(sessionPasswordKey, password);

            // Derive 256-bit AES-GCM encryption key using PBKDF2
            currentRoomKey = await window.deriveRoomKey(password, room);
            return { success: true };
        } catch (err) {
            console.error("Auth error:", err);
            return { success: false, error: "Network or server error" };
        }
    }

    // Check if password exists in sessionStorage
    const storedPassword = sessionStorage.getItem(sessionPasswordKey);
    if (storedPassword) {
        const result = await authenticateAndDeriveKey(storedPassword);
        if (!result.success) {
            sessionStorage.removeItem(sessionPasswordKey);
            showPasswordModal();
        } else {
            startChatSession();
        }
    } else {
        showPasswordModal();
    }

    function showPasswordModal() {
        if (passwordModal) {
            passwordModal.classList.remove("hidden");
            if (passwordInput) passwordInput.focus();
        }
    }

    function hidePasswordModal() {
        if (passwordModal) {
            passwordModal.classList.add("hidden");
        }
    }

    if (passwordForm) {
        passwordForm.addEventListener("submit", async (e) => {
            e.preventDefault();
            const enteredPass = passwordInput.value.trim();
            if (!enteredPass) return;

            const submitBtn = document.getElementById("modal-submit-btn");
            if (submitBtn) submitBtn.disabled = true;

            const result = await authenticateAndDeriveKey(enteredPass);
            if (submitBtn) submitBtn.disabled = false;

            if (result.success) {
                hidePasswordModal();
                startChatSession();
            } else {
                alert(result.error || "Incorrect room password.");
                passwordInput.value = "";
                passwordInput.focus();
            }
        });
    }

    // 🎬 Watch Party State & Video Synchronization
    const videoControls = document.getElementById("video-controls");
    const videoInput = document.getElementById("video-url-input");
    const videoButton = document.getElementById("start-video-button");
    const pauseButton = document.getElementById("pause-video-button");
    const resumeButton = document.getElementById("resume-video-button");
    const clearButton = document.getElementById("clear-video-button");
    const iframe = document.getElementById("video-iframe");
    const pausedOverlay = document.getElementById("paused-overlay");

    let lastVideoId = null;

    function extractYouTubeId(url) {
        if (!url) return null;
        const match = url.match(/(?:youtube\.com\/.*v=|youtu\.be\/)([\w-]{11})/);
        return match ? match[1] : null;
    }

    function loadYouTubeVideo(videoId, startSeconds = 0) {
        if (lastVideoId === videoId && !iframe.classList.contains("hidden")) return;
        iframe.src = `https://www.youtube.com/embed/${videoId}?autoplay=1&start=${startSeconds}`;
        iframe.classList.remove("hidden");
        lastVideoId = videoId;
    }

    function clearVideoUI() {
        if (iframe) {
            iframe.src = "";
            iframe.classList.add("hidden");
        }
        lastVideoId = null;
        if (pausedOverlay) pausedOverlay.classList.add("hidden");
        updateVideoControlsVisibility(false, false);
    }

    function updateVideoControlsVisibility(hasVideo, isPaused) {
        if (!videoControls) return;
        if (isRoomOwner) {
            videoControls.classList.remove("hidden");
            if (hasVideo) {
                if (videoInput) videoInput.classList.add("hidden");
                if (videoButton) videoButton.classList.add("hidden");
                if (clearButton) clearButton.classList.remove("hidden");

                if (isPaused) {
                    if (pauseButton) pauseButton.classList.add("hidden");
                    if (resumeButton) resumeButton.classList.remove("hidden");
                } else {
                    if (pauseButton) pauseButton.classList.remove("hidden");
                    if (resumeButton) resumeButton.classList.add("hidden");
                }
            } else {
                if (videoInput) videoInput.classList.remove("hidden");
                if (videoButton) videoButton.classList.remove("hidden");
                if (clearButton) clearButton.classList.add("hidden");
                if (pauseButton) pauseButton.classList.add("hidden");
                if (resumeButton) resumeButton.classList.add("hidden");
            }
        } else {
            videoControls.classList.add("hidden");
        }
    }

    function setWatchPartyActive(active) {
        watchPartyActive = active;
        if (active) {
            document.body.classList.add("watchparty-active");
            if (videoSection) videoSection.classList.remove("hidden");
            if (watchpartyToggleBtn) {
                watchpartyToggleBtn.textContent = "🎬 Watch Party: On";
                watchpartyToggleBtn.classList.remove("toggle-off");
            }
        } else {
            document.body.classList.remove("watchparty-active");
            if (videoSection) videoSection.classList.add("hidden");
            if (watchpartyToggleBtn) {
                watchpartyToggleBtn.textContent = "🎬 Watch Party: Off";
                watchpartyToggleBtn.classList.add("toggle-off");
            }
        }
    }

    if (watchpartyToggleBtn) {
        watchpartyToggleBtn.addEventListener("click", () => {
            setWatchPartyActive(!watchPartyActive);
        });
    }

    if (videoButton && videoInput) {
        videoButton.addEventListener("click", async () => {
            const url = videoInput.value.trim();
            const videoId = extractYouTubeId(url);
            if (!videoId) return alert("Please enter a valid YouTube URL.");

            try {
                await fetch(`/watchparty/${encodeURIComponent(room)}/video`, {
                    method: "POST",
                    headers: { "Content-Type": "application/json" },
                    body: JSON.stringify({ url }),
                });
                loadYouTubeVideo(videoId, 0);
                updateVideoControlsVisibility(true, false);
            } catch (err) {
                console.error("Failed to start video:", err);
            }
        });
    }

    if (pauseButton) {
        pauseButton.addEventListener("click", async () => {
            try {
                await fetch(`/watchparty/${encodeURIComponent(room)}/video/pause`, {
                    method: "POST",
                    headers: { "Content-Type": "application/json" },
                    body: JSON.stringify({ username }),
                });
            } catch (err) {
                console.error("Failed to pause video:", err);
            }
        });
    }

    if (resumeButton) {
        resumeButton.addEventListener("click", async () => {
            try {
                await fetch(`/watchparty/${encodeURIComponent(room)}/video/resume`, {
                    method: "POST",
                    headers: { "Content-Type": "application/json" },
                    body: JSON.stringify({ username }),
                });
            } catch (err) {
                console.error("Failed to resume video:", err);
            }
        });
    }

    if (clearButton) {
        clearButton.addEventListener("click", async () => {
            try {
                await fetch(`/watchparty/${encodeURIComponent(room)}/video/clear`, {
                    method: "POST",
                    headers: { "Content-Type": "application/json" },
                    body: JSON.stringify({ username }),
                });
                clearVideoUI();
            } catch (err) {
                console.error("Failed to clear video:", err);
            }
        });
    }

    async function syncWatchPartyFromServer() {
        try {
            const res = await fetch(`/watchparty/${encodeURIComponent(room)}/video`);
            if (!res.ok) return;

            const data = await res.json();
            const { url, elapsed, is_paused, is_active } = data;

            if (url) {
                const videoId = extractYouTubeId(url);
                if (videoId) {
                    // Auto-open watch party panel if video is playing
                    if (!watchPartyActive) {
                        setWatchPartyActive(true);
                    }

                    if (is_paused) {
                        if (iframe && !iframe.classList.contains("hidden")) {
                            iframe.classList.add("hidden");
                            iframe.src = "";
                            lastVideoId = null;
                        }
                        if (pausedOverlay) pausedOverlay.classList.remove("hidden");
                        updateVideoControlsVisibility(true, true);
                    } else {
                        if (pausedOverlay) pausedOverlay.classList.add("hidden");
                        loadYouTubeVideo(videoId, elapsed || 0);
                        updateVideoControlsVisibility(true, false);
                    }
                    return;
                }
            }

            // No active video URL
            if (lastVideoId !== null) {
                clearVideoUI();
            } else {
                updateVideoControlsVisibility(false, false);
            }
        } catch (err) {
            // Silently ignore sync failures
        }
    }

    // 🎤 Audio & Voice Messages Recording
    let mediaRecorder;
    let audioChunks = [];
    let isRecording = false;
    let recordingTimeout;

    async function startRecording() {
        if (isRecording || !currentRoomKey) return;
        try {
            const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
            const options = { mimeType: 'audio/webm;codecs=opus', bitsPerSecond: 16000 };
            if (!MediaRecorder.isTypeSupported(options.mimeType)) delete options.mimeType;

            mediaRecorder = new MediaRecorder(stream, options);
            audioChunks = [];
            isRecording = true;
            micBtn.classList.add("recording");
            micBtn.textContent = "⏹️";

            mediaRecorder.ondataavailable = e => audioChunks.push(e.data);
            mediaRecorder.onstop = () => {
                micBtn.classList.remove("recording");
                micBtn.textContent = "🎤";
                isRecording = false;
                clearTimeout(recordingTimeout);

                const blob = new Blob(audioChunks, { type: 'audio/webm' });
                const reader = new FileReader();
                reader.readAsDataURL(blob);
                reader.onloadend = async () => {
                    const base64Audio = reader.result;
                    const clearPayload = { text: "🎤 Voice Message", audio: base64Audio };

                    try {
                        const encrypted = await window.encryptRoomPayload(currentRoomKey, clearPayload);
                        await fetch(`/chat/${encodeURIComponent(room)}`, {
                            method: "POST",
                            headers: { "Content-Type": "application/json" },
                            body: JSON.stringify({
                                username: username,
                                key: userKey,
                                ciphertext: encrypted.ciphertext,
                                iv: encrypted.iv
                            })
                        });
                        refresh();
                    } catch (err) {
                        console.error("Audio encryption error:", err);
                        alert("Failed to send encrypted voice note.");
                    }
                };
                stream.getTracks().forEach(t => t.stop());
            };

            mediaRecorder.start();
            recordingTimeout = setTimeout(() => {
                if (isRecording && mediaRecorder.state === "recording") mediaRecorder.stop();
            }, 15000);
        } catch (err) {
            console.error("Mic error:", err);
            alert("Could not access microphone.");
        }
    }

    function stopRecording() {
        if (isRecording && mediaRecorder && mediaRecorder.state === "recording") {
            mediaRecorder.stop();
        }
    }

    micBtn.addEventListener("mousedown", startRecording);
    micBtn.addEventListener("mouseup", stopRecording);
    micBtn.addEventListener("mouseleave", stopRecording);
    micBtn.addEventListener("touchstart", (e) => { e.preventDefault(); startRecording(); });
    micBtn.addEventListener("touchend", (e) => { e.preventDefault(); stopRecording(); });

    // Audio Playback Queue
    const audioQueue = [];
    let isPlayingAudio = false;

    function processAudioQueue() {
        if (isPlayingAudio || audioQueue.length === 0) return;
        const audio = audioQueue.shift();
        isPlayingAudio = true;

        const onComplete = () => {
            isPlayingAudio = false;
            processAudioQueue();
        };

        audio.addEventListener('ended', onComplete, { once: true });
        audio.addEventListener('error', onComplete, { once: true });
        audio.play().catch(onComplete);
    }

    // 🔗 Linkify URLs & Media Embeds
    function linkify(text) {
        const safeText = escapeHtml(text);
        return safeText.replace(/(https?:\/\/[^\s]+)/g, (url) => {
            const imagePattern = /\.(png|jpe?g|gif)$/i;
            const youtubeRegex = /(?:https?:\/\/)?(?:www\.)?(?:youtube\.com\/watch\?v=|youtu\.be\/)([\w-]{11})/;
            const id = `preview-${Math.random().toString(36).substr(2, 9)}`;

            // YouTube
            const ytMatch = url.match(youtubeRegex);
            if (ytMatch) {
                const videoId = ytMatch[1];
                const embedUrl = `https://www.youtube.com/embed/${videoId}`;
                if (externalContentEnabled) {
                    return `
                        <a href="${url}" target="_blank" rel="noopener noreferrer">${url}</a>
                        <div style="padding: 0.5em; text-align: center;">
                            <iframe 
                                src="${embedUrl}" 
                                title="YouTube video player"
                                frameborder="0"
                                allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
                                referrerpolicy="strict-origin-when-cross-origin"
                                allowfullscreen
                                style="width: 500px; height: 280px; max-width: 100%; border-radius: 4px;"
                            ></iframe>
                        </div>
                    `;
                } else {
                    return `
                        <a href="${url}" target="_blank" rel="noopener noreferrer">${url}</a>
                        <div class="external-image-placeholder" style="padding: 0.5em; text-align: center;">
                            <button onclick="
                                this.style.display='none';
                                const iframe = document.createElement('iframe');
                                iframe.src = '${embedUrl}';
                                iframe.style.width = '500px';
                                iframe.style.height = '280px';
                                iframe.style.maxWidth = '100%';
                                iframe.style.borderRadius = '4px';
                                iframe.frameBorder = 0;
                                iframe.allowFullscreen = true;
                                document.getElementById('${id}').appendChild(iframe);
                            ">Show external video</button>
                            <div id="${id}" style="margin-top: 0.5em;"></div>
                        </div>
                    `;
                }
            }

            // Image
            if (imagePattern.test(url)) {
                if (externalContentEnabled) {
                    return `
                        <a href="${url}" target="_blank" rel="noopener noreferrer">${url}</a>
                        <div style="padding: 0.5em; text-align: center;">
                            <img src="${url}" style="max-width: 100%; max-height: 400px; border-radius: 4px;" />
                        </div>
                    `;
                } else {
                    return `
                        <a href="${url}" target="_blank" rel="noopener noreferrer">${url}</a>
                        <div class="external-image-placeholder" style="padding: 0.5em; text-align: center;">
                            <button onclick="
                                this.style.display='none';
                                const img = document.createElement('img');
                                img.src = '${url}';
                                img.style.maxWidth = '100%';
                                img.style.maxHeight = '400px';
                                img.style.borderRadius = '4px';
                                document.getElementById('${id}').appendChild(img);
                            ">Show image</button>
                            <div id="${id}" style="margin-top: 0.5em;"></div>
                        </div>
                    `;
                }
            }

            return `<a href="${url}" target="_blank" rel="noopener noreferrer">${url}</a>`;
        });
    }

    // Message Rendering & State
    let lastUserList = [];
    const seenMessageTimestamps = new Set();
    let unreadCount = 0;
    let windowFocused = true;

    window.addEventListener('focus', () => {
        windowFocused = true;
        unreadCount = 0;
        document.title = `${room} - Transient.chat`;
    });

    window.addEventListener('blur', () => {
        windowFocused = false;
    });

    function renderUsers(users, owner) {
        const currentList = users || [];
        isRoomOwner = owner === username;
        usersDiv.innerHTML = "";

        const joined = currentList.filter(user => !lastUserList.includes(user));
        const left = lastUserList.filter(user => !currentList.includes(user));

        if (!firstLoad && soundEnabled) {
            if (joined.length > 0) sounds.in.play().catch(() => {});
            if (left.length > 0) sounds.out.play().catch(() => {});
        }

        lastUserList = currentList;

        currentList.forEach(user => {
            const div = document.createElement("div");
            div.textContent = user + (user === owner ? " 👑" : "");

            if (isRoomOwner && user !== username) {
                const btn = document.createElement("button");
                btn.textContent = "Kick";
                btn.className = "kick-button";
                btn.onclick = async () => {
                    if (confirm(`Kick ${user} from this room?`)) {
                        await fetch(`/chat/${encodeURIComponent(room)}/kick`, {
                            method: "POST",
                            headers: { "Content-Type": "application/json" },
                            body: JSON.stringify({ owner: username, key: userKey, target: user }),
                        });
                        refresh();
                    }
                };
                div.appendChild(btn);
            }

            usersDiv.appendChild(div);
        });
    }

    async function renderMessages(messagesList) {
        if (!Array.isArray(messagesList)) return;

        const now = Date.now();
        const oneHourAgo = now - 60 * 60 * 1000;
        let hasNewIncoming = false;

        for (const msg of messagesList) {
            if (seenMessageTimestamps.has(msg.timestamp)) continue;

            const msgTime = new Date(msg.timestamp).getTime();
            if (!isNaN(msgTime) && !firstLoad && msgTime < oneHourAgo) {
                continue;
            }

            seenMessageTimestamps.add(msg.timestamp);

            const div = document.createElement("div");
            div.classList.add("message");
            div.setAttribute("data-timestamp", msg.timestamp);

            if (msg.username === username) {
                div.classList.add("my-message");
            } else if (!firstLoad) {
                hasNewIncoming = true;
            }

            // System notices
            if (msg.username === "SYSTEM" || msg.system_notice) {
                div.classList.add("system-message");
                div.innerHTML = `<strong>📢 SYSTEM:</strong> ${escapeHtml(msg.system_notice || msg.text || "")}`;
                messagesDiv.appendChild(div);
                continue;
            }

            // Encrypted chat messages
            let textToRender = "";
            let audioToRender = null;

            if (msg.ciphertext && msg.iv && currentRoomKey) {
                try {
                    const decrypted = await window.decryptRoomPayload(currentRoomKey, msg.ciphertext, msg.iv);
                    textToRender = decrypted.text || "";
                    audioToRender = decrypted.audio || null;
                } catch (err) {
                    textToRender = "⚠️ Decryption error (corrupted payload)";
                }
            } else {
                textToRender = "🔒 Encrypted Message";
            }

            div.innerHTML = `<strong>${escapeHtml(msg.username)}:</strong> ${linkify(textToRender)}`;

            if (audioToRender) {
                const audioContainer = document.createElement("div");
                audioContainer.className = "audio-container";
                const audioElement = document.createElement("audio");
                audioElement.controls = true;
                audioElement.src = audioToRender;
                audioElement.className = "voice-message-audio";
                audioContainer.appendChild(audioElement);
                div.appendChild(audioContainer);

                if (autoplayEnabled && !firstLoad && msg.username !== username) {
                    audioQueue.push(audioElement);
                    processAudioQueue();
                }
            }

            messagesDiv.appendChild(div);
        }

        if (hasNewIncoming && soundEnabled) {
            sounds.message.play().catch(() => {});
        }

        if (hasNewIncoming && !windowFocused) {
            unreadCount++;
            document.title = `(${unreadCount}) ${room} - Transient.chat`;
        }

        messagesDiv.scrollTop = messagesDiv.scrollHeight;
    }

    function cleanExpiredMessages() {
        const oneHourAgo = Date.now() - 60 * 60 * 1000;
        const msgDivs = document.querySelectorAll("#messages .message");
        msgDivs.forEach(div => {
            const ts = div.getAttribute("data-timestamp");
            if (ts) {
                const t = new Date(ts).getTime();
                if (!isNaN(t) && t < oneHourAgo) {
                    div.remove();
                    seenMessageTimestamps.delete(ts);
                }
            }
        });
    }

    async function refresh() {
        if (isRefreshing || !currentRoomKey) return;
        isRefreshing = true;

        try {
            const res = await fetch(`/chat/${encodeURIComponent(room)}/poll`, {
                method: "POST",
                headers: { "Content-Type": "application/json" },
                body: JSON.stringify({
                    username: username,
                    key: userKey
                })
            });

            if (res.status === 401) {
                // Room authorization required or expired
                sessionStorage.removeItem(sessionPasswordKey);
                showPasswordModal();
                isRefreshing = false;
                return;
            }

            if (res.status === 403) {
                alert("You are not authorized in this room or have been kicked.");
                window.location.href = "/server_list.html";
                return;
            }

            if (res.ok) {
                const data = await res.json();
                renderUsers(data.users, data.owner);
                await renderMessages(data.messages);
                cleanExpiredMessages();
                firstLoad = false;
            }
        } catch (err) {
            console.error("Poll error:", err);
        } finally {
            isRefreshing = false;
        }
    }

    // Message form submit
    if (form) {
        form.addEventListener("submit", async (e) => {
            e.preventDefault();
            const text = input.value.trim();
            if (!text || !currentRoomKey) return;

            input.value = "";
            try {
                const payload = { text: text, audio: null };
                const encrypted = await window.encryptRoomPayload(currentRoomKey, payload);

                await fetch(`/chat/${encodeURIComponent(room)}`, {
                    method: "POST",
                    headers: { "Content-Type": "application/json" },
                    body: JSON.stringify({
                        username: username,
                        key: userKey,
                        ciphertext: encrypted.ciphertext,
                        iv: encrypted.iv
                    })
                });
                refresh();
            } catch (err) {
                console.error("Send error:", err);
                alert("Failed to send encrypted message.");
            }
        });
    }

    function startChatSession() {
        if (initialWatchPartyRequested) {
            setWatchPartyActive(true);
        }

        refresh();
        setInterval(refresh, 1000);
        setInterval(syncWatchPartyFromServer, 1000);
    }
});