document.addEventListener('DOMContentLoaded', function () {

    // متغیرهای وضعیت
    let currentRoomId = null;
    let lastMessageId = 0;
    let messagePollInterval = null;
    let roomPollInterval = null;

    // 🟢 متغیر قفل برای جلوگیری از دریافت پیام‌های تکراری (Race Condition)
    let isFetchingMessages = false;

    // المان‌های DOM
    const UI = {
        roomList: document.getElementById('room-list'),
        noChatSelected: document.getElementById('no-chat-selected'),
        chatHeader: document.getElementById('active-chat-header'),
        chatTitle: document.getElementById('active-chat-title'),
        messages: document.getElementById('chat-messages'),
        inputArea: document.getElementById('chat-input-area'),
        form: document.getElementById('chat-form'),
        input: document.getElementById('chat-input'),
        indicator: document.getElementById('polling-indicator')
    };

    // گرفتن لیست چت‌ها از سرور
    async function fetchRooms() {
        try {
            const res = await fetch(window.CHAT_CONFIG.apiUrlRooms);
            const data = await res.json();
            renderRooms(data.rooms);
        } catch (e) {
            console.error("Failed to fetch rooms:", e);
        }
    }

    // رندر کردن لیست چت‌ها
    function renderRooms(rooms) {
        if (rooms.length === 0) {
            UI.roomList.innerHTML = '<p class="text-center text-sm text-gray-500 mt-10 px-4">No active chats found.</p>';
            return;
        }

        UI.roomList.innerHTML = rooms.map(room => {
            const isActive = currentRoomId === room.id;
            const safeTitle = room.title.replace(/'/g, "\\'");
            return `
                <div onclick="selectRoom(${room.id}, '${safeTitle}')" 
                     class="group px-5 py-4 cursor-pointer border-b border-gray-200 dark:border-gray-800 transition-all duration-150 border-l-4 ${isActive ? 'room-item-active' : 'border-l-transparent hover:bg-gray-100 dark:hover:bg-gray-800/60'}">
                    <div class="flex justify-between items-center mb-1.5">
                        <span class="font-semibold text-[14px] text-gray-900 dark:text-gray-100 truncate pr-2">${room.title}</span>
                        <span class="text-[11px] text-gray-400 whitespace-nowrap flex-shrink-0">${room.time}</span>
                    </div>
                    <div class="flex justify-between items-center">
                        <span class="text-[10px] font-medium text-gray-500 uppercase bg-gray-200 dark:bg-gray-700 px-2 py-0.5 rounded">${room.type}</span>
                        ${room.unread > 0 ? `<span class="bg-red-500 shadow-sm text-white text-[10px] font-bold px-2 py-0.5 rounded-full">${room.unread}</span>` : ''}
                    </div>
                </div>
            `;
        }).join('');
    }

    // انتخاب یک چت
    window.selectRoom = function (id, title) {
        currentRoomId = id;
        lastMessageId = 0;
        isFetchingMessages = false; // ریست کردن قفل

        UI.noChatSelected.classList.add('hidden');
        UI.chatHeader.classList.remove('invisible');
        UI.messages.classList.remove('invisible');
        UI.inputArea.classList.remove('invisible');

        UI.chatTitle.textContent = title;
        UI.messages.innerHTML = '<div class="flex items-center justify-center h-full"><span class="material-symbols-outlined animate-spin text-gray-400 text-3xl">autorenew</span></div>';

        fetchRooms();

        stopPolling();
        fetchMessages().then(() => {
            startPolling();
            scrollToBottom();
        });

        UI.input.focus();
    };

    // گرفتن پیام‌ها از سرور
    async function fetchMessages() {
        // 🟢 اگر هیچ رومی انتخاب نشده، یا درخواست قبلی هنوز تمام نشده، برگرد!
        if (!currentRoomId || isFetchingMessages) return;

        isFetchingMessages = true; // 🟢 فعال کردن قفل

        try {
            UI.indicator.classList.remove('hidden');
            setTimeout(() => UI.indicator.classList.add('hidden'), 500);

            const res = await fetch(`${window.CHAT_CONFIG.apiUrlMessagesBase}${currentRoomId}/?last_id=${lastMessageId}`);
            const data = await res.json();

            if (data.messages && data.messages.length > 0) {
                if (lastMessageId === 0) UI.messages.innerHTML = '';

                renderMessages(data.messages);
                lastMessageId = data.messages[data.messages.length - 1].id;
                scrollToBottom();
            } else if (lastMessageId === 0) {
                UI.messages.innerHTML = `
                    <div class="flex flex-col items-center justify-center h-full text-gray-400 opacity-60">
                        <span class="material-symbols-outlined text-5xl mb-2">forum</span>
                        <p class="text-sm font-medium">No messages yet. Say hi!</p>
                    </div>`;
            }
        } catch (e) {
            console.error("Failed to fetch messages:", e);
        } finally {
            isFetchingMessages = false; // 🟢 باز کردن قفل در هر شرایطی (چه موفق چه ارور)
        }
    }

    // رندر کردن حباب‌های پیام
    function renderMessages(messages) {
        const html = messages.map(m => {
            const isMe = m.is_me;
            const alignClass = isMe ? 'message-sent' : 'message-received';
            const bubbleClass = isMe ? 'message-bubble-sent' : 'message-bubble-received';

            const senderName = !isMe ? `<div class="text-[11px] font-bold text-blue-600 dark:text-blue-400 mb-1 opacity-90">${m.sender_name}</div>` : '';
            const safeContent = m.content.replace(/</g, "&lt;").replace(/>/g, "&gt;");
            const timeColor = isMe ? 'text-blue-100' : 'text-gray-400';
            const tickIcon = isMe ? `<span class="material-symbols-outlined text-[13px] ml-1 text-white opacity-80">done_all</span>` : '';

            return `
                <div class="message-bubble ${alignClass} w-full">
                    <div class="${bubbleClass}">
                        <div class="message-content">
                            ${senderName}
                            <p class="m-0">${safeContent}</p>
                            <div class="message-meta ${timeColor} flex items-center justify-end">
                                ${m.sent_at} ${tickIcon}
                            </div>
                        </div>
                    </div>
                </div>
            `;
        }).join('');

        UI.messages.insertAdjacentHTML('beforeend', html);
    }

    // اسکرول به پایین
    function scrollToBottom() {
        UI.messages.scrollTo({
            top: UI.messages.scrollHeight,
            behavior: 'smooth'
        });
    }

    // ارسال پیام جدید
    UI.form.addEventListener('submit', async (e) => {
        e.preventDefault();
        const text = UI.input.value.trim();
        if (!text || !currentRoomId) return;

        UI.input.value = '';

        try {
            await fetch(`${window.CHAT_CONFIG.apiUrlSendBase}${currentRoomId}/`, {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                    'X-CSRFToken': window.CHAT_CONFIG.csrfToken
                },
                body: JSON.stringify({ content: text })
            });
            // 🟢 صدا زدن دریافت پیام به صورت ایمن
            await fetchMessages();
            fetchRooms();
        } catch (e) {
            console.error("Failed to send message:", e);
        }
    });

    // راه‌اندازی Polling
    function startPolling() {
        messagePollInterval = setInterval(fetchMessages, 3000);
    }

    function stopPolling() {
        if (messagePollInterval) clearInterval(messagePollInterval);
    }

    // مقداردهی اولیه
    fetchRooms();
    roomPollInterval = setInterval(fetchRooms, 10000);

});