document.addEventListener('DOMContentLoaded', () => {
    
    // --- DOM Elements ---
    const chatArea = document.getElementById('chat-area');
    const closeSidebarBtn = document.getElementById('close-sidebar-btn');
    const messageInput = document.getElementById('message-input');
    const sendBtn = document.getElementById('send-btn');
    const newChatBtn = document.getElementById('new-chat-btn');
    const chatMessages = document.getElementById('chat-messages');
    const chatHistoryList = document.getElementById('chat-history-list');
    const menuToggle = document.getElementById('menu-toggle');
    const appContainer = document.getElementById('app-container');
    const chatTitle = document.getElementById('chat-title');
    const imageUploadBtn = document.getElementById('image-upload-btn');
    const imageUploadInput = document.getElementById('image-upload-input');
    const imagePreviewContainer = document.getElementById('image-preview-container');
    const imagePreview = document.getElementById('image-preview');
    const removeImageBtn = document.getElementById('remove-image-btn');

    // --- State ---
    let currentSessionId = null;
    let conversationsCache = {};
    let selectedImageFile = null;
    let imgbbApiKey = '';

    // --- Initialization ---
    const init = async () => {
        if (!messageInput || !sendBtn || !imageUploadBtn || !imagePreviewContainer) {
            console.error("Critical UI elements not found. Check HTML IDs.");
            return;
        }

        await fetchConfig();
        loadCache();
        await renderChatHistoryFromAPI();

        // Event Listeners
        sendBtn.addEventListener('click', sendMessage);
        messageInput.addEventListener('keydown', e => { if (e.key === 'Enter' && !e.shiftKey) { e.preventDefault(); sendMessage(); } });
        
        imageUploadBtn.addEventListener('click', () => imageUploadInput.click());
        imageUploadInput.addEventListener('change', handleImageSelect);
        removeImageBtn.addEventListener('click', removeSelectedImage);

        // Sidebar Listeners
        newChatBtn.addEventListener('click', () => { startNewChat(); closeSidebar(); });
        menuToggle.addEventListener('click', (event) => {
            event.stopPropagation();
            appContainer.classList.toggle('sidebar-visible');
        });
        closeSidebarBtn.addEventListener('click', (event) => {
            event.stopPropagation();
            closeSidebar();
        });
        chatArea.addEventListener('click', () => {
            if (appContainer.classList.contains('sidebar-visible')) {
                closeSidebar();
            }
        });
    };

    const fetchConfig = async () => {
        try {
            const response = await fetch('/config');
            const config = await response.json();
            imgbbApiKey = config.imgbb_api_key;
            if (!imgbbApiKey) { console.error("ImgBB API Key is missing."); }
        } catch (error) { console.error('Failed to fetch config:', error); }
    };

    // --- Core Chat Functions ---
    const sendMessage = async () => {
        const messageText = messageInput.value.trim();
        if (!messageText && !selectedImageFile) return;
        displayMessage({ role: 'user', content: messageText, imageUrl: selectedImageFile });
        const loadingIndicator = displayMessage({ role: 'assistant', content: 'Thinking...', isLoading: true });
        try {
            let permanentImageUrl = null;
            if (selectedImageFile) { permanentImageUrl = await uploadImageToImgBB(selectedImageFile); }
            const formData = new FormData();
            formData.append('message', messageText);
            formData.append('session_id', currentSessionId);
            if (permanentImageUrl) { formData.append('image_url', permanentImageUrl); }
            const response = await fetch('/chat', { method: 'POST', body: formData });
            if (!response.ok) throw new Error('Network response was not ok.');
            const data = await response.json();
            chatMessages.removeChild(loadingIndicator);
            displayMessage({ role: 'assistant', content: data.response });
            updateCache(data.session_id, { content: messageText, imageUrl: permanentImageUrl }, { content: data.response });
        } catch (error) {
            console.error('Error sending message:', error);
            loadingIndicator.innerHTML = marked.parse("Sorry, something went wrong.");
            loadingIndicator.classList.remove('loading');
        } finally {
            messageInput.value = ''; messageInput.style.height = 'auto'; removeSelectedImage();
        }
    };

    const uploadImageToImgBB = async (imageFile) => {
        if (!imgbbApiKey) throw new Error("ImgBB API Key not configured.");
        const formData = new FormData();
        formData.append('image', imageFile);
        formData.append('key', imgbbApiKey);
        const response = await fetch('https://api.imgbb.com/1/upload', { method: 'POST', body: formData });
        const result = await response.json();
        if (result.success) { return result.data.url; }
        else { throw new Error(result.error.message || 'Image upload failed.'); }
    };

    // --- Caching and State Management ---
    const startNewChat = () => {
        currentSessionId = null;
        chatMessages.innerHTML = `<div class="welcome-message"><h1>EasyFarms Assistant</h1></div>`;
        chatTitle.textContent = "New Chat";
        updateActiveChatItem();
    };

    const switchChat = async (sessionId) => {
        currentSessionId = sessionId;
        chatMessages.innerHTML = '';
        if (conversationsCache[sessionId] && conversationsCache[sessionId].messages) {
            conversationsCache[sessionId].messages.forEach(displayMessage);
        } else {
            const loading = displayMessage({ role: 'assistant', content: 'Loading chat history...', isLoading: true });
            try {
                const response = await fetch(`/history/messages/${sessionId}`);
                const messages = await response.json();
                if (!conversationsCache[sessionId]) conversationsCache[sessionId] = {};
                conversationsCache[sessionId].messages = messages;
                saveCache();
                chatMessages.removeChild(loading);
                messages.forEach(displayMessage);
            } catch (error) {
                loading.innerHTML = marked.parse("Failed to load chat history.");
            }
        }
        chatTitle.textContent = conversationsCache[sessionId]?.title || "Chat";
        updateActiveChatItem();
        closeSidebar();
    };

    const updateCache = (sessionId, userTurn, assistantTurn) => {
        const isNewChat = !currentSessionId;
        currentSessionId = sessionId;
        if (isNewChat) {
            const title = (userTurn.content || "Image Query").substring(0, 30) + '...';
            conversationsCache[sessionId] = { title, messages: [] };
            const item = document.createElement('div');
            item.className = 'chat-history-item';
            item.textContent = title;
            item.dataset.sessionId = sessionId;
            item.addEventListener('click', () => switchChat(sessionId));
            chatHistoryList.prepend(item);
        }
        const userMessage = { role: 'user', content: userTurn.content };
        if (userTurn.imageUrl) userMessage.imageUrl = userTurn.imageUrl;
        const assistantMessage = { role: 'assistant', content: assistantTurn.content };
        conversationsCache[sessionId].messages.push(userMessage, assistantMessage);
        saveCache();
        updateActiveChatItem();
    };

    const displayMessage = (message) => {
        const { role, content, imageUrl, isLoading } = message;
        const sender = role || message.sender;
        const messageDiv = document.createElement('div');
        messageDiv.classList.add('message', `${sender}-message`);
        let htmlContent = '';
        const imageSrc = (typeof imageUrl === 'object' && imageUrl instanceof File) ? URL.createObjectURL(imageUrl) : imageUrl;
        if (imageSrc) { htmlContent += `<img src="${imageSrc}" alt="User upload" class="user-upload">`; }
        if (content) { htmlContent += marked.parse(content); }
        messageDiv.innerHTML = htmlContent || (isLoading ? '...' : '');
        if (isLoading) messageDiv.classList.add('loading');
        chatMessages.appendChild(messageDiv);
        chatMessages.scrollTop = chatMessages.scrollHeight;
        return messageDiv;
    };

    // --- Image Preview Handling ---
    const handleImageSelect = (event) => {
        const file = event.target.files[0];
        if (file) {
            selectedImageFile = file;
            imagePreview.src = URL.createObjectURL(file);
            imagePreviewContainer.style.display = 'block';
        }
    };

    const removeSelectedImage = () => {
        selectedImageFile = null;
        imageUploadInput.value = '';
        imagePreviewContainer.style.display = 'none';
        imagePreview.src = '#';
    };

    // --- LocalStorage Cache & Sidebar Rendering ---
    const saveCache = () => localStorage.setItem('easyfarms_cache', JSON.stringify(conversationsCache));
    const loadCache = () => {
        const saved = localStorage.getItem('easyfarms_cache');
        if (saved) conversationsCache = JSON.parse(saved);
    };

    const renderChatHistoryFromAPI = async () => {
        try {
            const response = await fetch('/history/sessions');
            const sessions = await response.json();
            chatHistoryList.innerHTML = '';
            sessions.reverse().forEach(session => {
                if (!conversationsCache[session.session_id]) conversationsCache[session.session_id] = {};
                conversationsCache[session.session_id].title = session.title;
                const item = document.createElement('div');
                item.className = 'chat-history-item';
                item.textContent = session.title;
                item.dataset.sessionId = session.session_id;
                item.addEventListener('click', () => switchChat(session.session_id));
                chatHistoryList.appendChild(item);
            });
            saveCache();
            updateActiveChatItem();
        } catch (error) { console.error("Failed to render chat history from API:", error); }
    };

    const updateActiveChatItem = () => {
        document.querySelectorAll('.chat-history-item').forEach(item => {
            item.classList.toggle('active', item.dataset.sessionId === currentSessionId);
        });
    };

    const closeSidebar = () => appContainer.classList.remove('sidebar-visible');

    // --- Start the Application ---
    init();
});