document.addEventListener('DOMContentLoaded', () => {
    const chatForm = document.getElementById('chat-form');
    const userInput = document.getElementById('user-input');
    const chatContainer = document.getElementById('chat-container');
    const sendBtn = document.getElementById('send-btn');
    const clearChatBtn = document.getElementById('clear-chat');

    let chatHistory = []; // Store conversation history

    // Auto-resize textarea
    userInput.addEventListener('input', function() {
        this.style.height = 'auto';
        this.style.height = (this.scrollHeight > 150 ? 150 : this.scrollHeight) + 'px';
        if (this.value.trim() === '') {
            sendBtn.disabled = true;
        } else {
            sendBtn.disabled = false;
        }
    });

    // Handle Enter key (Shift+Enter for new line)
    userInput.addEventListener('keydown', function(e) {
        if (e.key === 'Enter' && !e.shiftKey) {
            e.preventDefault();
            if (!sendBtn.disabled) {
                chatForm.dispatchEvent(new Event('submit'));
            }
        }
    });

    clearChatBtn.addEventListener('click', () => {
        if (confirm('Are you sure you want to clear the chat history?')) {
            chatHistory = [];
            chatContainer.innerHTML = '';
            addMessage('system', 'Hello! I am LocalFoodAI, your completely local nutrition and menu assistant. How can I help you today?');
        }
    });

    chatForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        const message = userInput.value.trim();
        if (!message) return;

        // Reset input
        userInput.value = '';
        userInput.style.height = 'auto';
        sendBtn.disabled = true;

        // Add user message to UI
        addMessage('user', message);
        chatHistory.push({ role: 'user', content: message });

        // Add loading indicator
        const loadingId = addTypingIndicator();

        try {
            const token = localStorage.getItem('localFoodToken');
            // Fetch response from backend
            const response = await fetch('/chat', {
                method: 'POST',
                headers: { 
                    'Content-Type': 'application/json',
                    'Authorization': `Bearer ${token}`
                },
                body: JSON.stringify({ messages: chatHistory })
            });

            if (response.status === 401) {
                setLoggedOutState();
                addMessage('system', 'Your session has expired. Please log in again.');
                return;
            }

            if (!response.ok) {
                throw new Error(`HTTP error! status: ${response.status}`);
            }

            // Remove loading indicator
            removeElement(loadingId);

            // Create new bot message container
            const botMessageId = 'msg-' + Date.now();
            const botContentEl = addMessage('system', '', botMessageId);

            let botFullResponse = '';

            // Handle Server-Sent Events (Streaming)
            const reader = response.body.getReader();
            const decoder = new TextDecoder('utf-8');
            let done = false;

            while (!done) {
                const { value, done: readerDone } = await reader.read();
                done = readerDone;
                if (value) {
                    const chunk = decoder.decode(value, { stream: true });
                    // Split the chunk by double newline to get individual SSE messages
                    const lines = chunk.split('\n\n');
                    for (const line of lines) {
                        if (line.startsWith('data: ')) {
                            const dataStr = line.substring(6);
                            if (dataStr.trim() === '') continue;
                            try {
                                const data = JSON.parse(dataStr);
                                if (data.error) {
                                    botContentEl.innerHTML += `<br><span style="color:#f85149">Error: ${data.error}</span>`;
                                } else if (data.content !== undefined) {
                                    botFullResponse += data.content;
                                    // Basic text to HTML conversion
                                    botContentEl.innerHTML = formatText(botFullResponse);
                                    chatContainer.scrollTop = chatContainer.scrollHeight;
                                }
                            } catch (err) {
                                console.error('Error parsing SSE data:', err, dataStr);
                            }
                        }
                    }
                }
            }

            // Save bot response to history once complete
            chatHistory.push({ role: 'assistant', content: botFullResponse });

        } catch (error) {
            console.error('Chat error:', error);
            removeElement(loadingId);
            addMessage('system', 'Sorry, there was an error communicating with the local LLM. Make sure the server and Ollama are running.');
        } finally {
            sendBtn.disabled = false;
            userInput.focus();
        }
    });

    function addMessage(role, content, id = null) {
        const msgDiv = document.createElement('div');
        msgDiv.className = `message ${role}`;
        if (id) msgDiv.id = id;

        const avatarDiv = document.createElement('div');
        avatarDiv.className = 'avatar';
        avatarDiv.textContent = role === 'user' ? '👤' : '🤖';

        const contentDiv = document.createElement('div');
        contentDiv.className = 'message-content';
        contentDiv.innerHTML = formatText(content);

        msgDiv.appendChild(avatarDiv);
        msgDiv.appendChild(contentDiv);
        chatContainer.appendChild(msgDiv);
        chatContainer.scrollTop = chatContainer.scrollHeight;

        return contentDiv;
    }

    function addTypingIndicator() {
        const id = 'typing-' + Date.now();
        const msgDiv = document.createElement('div');
        msgDiv.className = 'message system';
        msgDiv.id = id;

        const avatarDiv = document.createElement('div');
        avatarDiv.className = 'avatar';
        avatarDiv.textContent = '🤖';

        const contentDiv = document.createElement('div');
        contentDiv.className = 'message-content typing-indicator';
        contentDiv.innerHTML = `
            <div class="typing-dot"></div>
            <div class="typing-dot"></div>
            <div class="typing-dot"></div>
        `;

        msgDiv.appendChild(avatarDiv);
        msgDiv.appendChild(contentDiv);
        chatContainer.appendChild(msgDiv);
        chatContainer.scrollTop = chatContainer.scrollHeight;

        return id;
    }

    function removeElement(id) {
        const el = document.getElementById(id);
        if (el) el.remove();
    }

    function formatText(text) {
        if (!text) return '';
        // Very basic markdown parsing for bold, italics, code, and newlines
        let formatted = text
            .replace(/&/g, "&amp;")
            .replace(/</g, "&lt;")
            .replace(/>/g, "&gt;")
            .replace(/\n/g, "<br>")
            .replace(/\*\*(.*?)\*\*/g, "<strong>$1</strong>") // bold
            .replace(/\*(.*?)\*/g, "<em>$1</em>") // italic
            .replace(/`(.*?)`/g, "<code style='background:rgba(255,255,255,0.1);padding:2px 4px;border-radius:4px'>$1</code>"); // inline code
        return formatted;
    }

    // Authentication & Session Logic
    const authScreen = document.getElementById('auth-screen');
    const chatApp = document.getElementById('chat-app');
    
    const loginForm = document.getElementById('login-form');
    const registerForm = document.getElementById('register-form');
    
    const showRegisterLink = document.getElementById('show-register');
    const showLoginLink = document.getElementById('show-login');
    
    const loginError = document.getElementById('login-error');
    const regError = document.getElementById('reg-error');
    const regSuccess = document.getElementById('reg-success');
    
    const logoutBtn = document.getElementById('nav-logout-btn');
    const userGreeting = document.getElementById('user-greeting');

    // Check session on load
    const savedUser = localStorage.getItem('localFoodUser');
    const savedToken = localStorage.getItem('localFoodToken');
    if (savedUser && savedToken) {
        setLoggedInState(savedUser, savedToken);
    }

    function setLoggedInState(username, token) {
        localStorage.setItem('localFoodUser', username);
        localStorage.setItem('localFoodToken', token);
        userGreeting.textContent = `Welcome, ${username}`;
        
        authScreen.classList.add('fade-out');
        setTimeout(() => {
            authScreen.style.display = 'none';
            chatApp.style.display = 'flex';
            chatApp.classList.add('fade-in');
            userInput.focus();
        }, 500);
    }

    async function setLoggedOutState() {
        const token = localStorage.getItem('localFoodToken');
        if (token) {
            try {
                await fetch('/api/logout', {
                    method: 'POST',
                    headers: { 'Authorization': `Bearer ${token}` }
                });
            } catch (err) {
                console.error("Error during logout:", err);
            }
        }

        localStorage.removeItem('localFoodUser');
        localStorage.removeItem('localFoodToken');
        chatApp.style.display = 'none';
        chatApp.classList.remove('fade-in');
        
        authScreen.style.display = 'block';
        setTimeout(() => {
            authScreen.classList.remove('fade-out');
        }, 50);
        loginForm.reset();
        registerForm.reset();
        loginError.textContent = '';
        regError.textContent = '';
    }

    logoutBtn.addEventListener('click', () => {
        setLoggedOutState();
    });

    // Toggles
    showRegisterLink.addEventListener('click', (e) => {
        e.preventDefault();
        loginForm.style.display = 'none';
        registerForm.style.display = 'block';
    });
    
    showLoginLink.addEventListener('click', (e) => {
        e.preventDefault();
        registerForm.style.display = 'none';
        loginForm.style.display = 'block';
    });

    // Login Submission
    loginForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        loginError.textContent = '';
        const submitBtn = document.getElementById('login-submit-btn');
        submitBtn.disabled = true;

        const username = document.getElementById('login-username').value;
        const password = document.getElementById('login-password').value;

        try {
            const response = await fetch('/api/login', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ username, password })
            });

            const data = await response.json();

            if (!response.ok) {
                loginError.textContent = data.detail || 'Login failed.';
            } else {
                setLoggedInState(data.username, data.token);
            }
        } catch (err) {
            loginError.textContent = 'Server error. Is the backend running?';
        } finally {
            submitBtn.disabled = false;
        }
    });

    // Registration Submission
    registerForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        regError.textContent = '';
        regSuccess.textContent = '';
        const submitBtn = document.getElementById('reg-submit-btn');
        submitBtn.disabled = true;

        const username = document.getElementById('reg-username').value;
        const password = document.getElementById('reg-password').value;
        const confirmInfo = document.getElementById('reg-confirm').value;

        if (password !== confirmInfo) {
            regError.textContent = "Passwords do not match.";
            submitBtn.disabled = false;
            return;
        }

        try {
            const response = await fetch('/api/register', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ username, password })
            });

            const data = await response.json();

            if (!response.ok) {
                regError.textContent = data.detail || 'Registration failed.';
            } else {
                regSuccess.textContent = 'Account created! Logging in...';
                setTimeout(() => {
                    setLoggedInState(data.username, data.token);
                }, 1000);
            }
        } catch (err) {
            regError.textContent = 'Server error. Please try again later.';
        } finally {
            submitBtn.disabled = false;
        }
    });

    // Initialize state
    sendBtn.disabled = true;
});