/**
 * app.js — Sebayhi
 *
 * Handles:
 *  - Mode selection (knowledge / i3rab) with sidebar toggle
 *  - Conversation history stored in memory (sidebar list)
 *  - SSE streaming from /chat/stream
 *  - New chat / history switching
 */

// ── DOM ───────────────────────────────────────────────────────────────────────
const messageList   = document.getElementById('messageList');
const chatScroll    = document.getElementById('chatScroll');
const userInput     = document.getElementById('userInput');
const sendBtn       = document.getElementById('sendBtn');
const modeKnowledge = document.getElementById('modeKnowledge');
const modeI3rab     = document.getElementById('modeI3rab');
const newChatBtn    = document.getElementById('newChatBtn');
const historyList   = document.getElementById('historyList');
const historyEmpty  = document.getElementById('historyEmpty');

// ── State ─────────────────────────────────────────────────────────────────────
let currentMode  = 'knowledge';
let previousMode = null;
let isStreaming  = false;

// In-memory history: [{ id, mode, title, messages: [{role, text, mode}] }]
let conversations = [];
let activeConvId  = null;

const PLACEHOLDERS = {
  knowledge: 'Ask a grammar question…  /  اسأل سؤالاً نحوياً',
  i3rab:     'Enter a sentence for I3rab…  /  اكتب الجملة للإعراب',
};

const MODE_LABELS = {
  knowledge: 'Switched to Knowledge · معرفة',
  i3rab:     'Switched to I3rab · إعراب',
};

// ═════════════════════════════════════════════════════════════════════════════
// MODE
// ═════════════════════════════════════════════════════════════════════════════

function setMode(mode) {
  currentMode = mode;
  document.body.dataset.mode = mode;

  [modeKnowledge, modeI3rab].forEach(btn => {
    const active = btn.dataset.mode === mode;
    btn.classList.toggle('mode-btn--active', active);
    btn.setAttribute('aria-pressed', active);
  });

  userInput.placeholder = PLACEHOLDERS[mode];
  userInput.focus();
}

modeKnowledge.addEventListener('click', () => setMode('knowledge'));
modeI3rab.addEventListener('click',     () => setMode('i3rab'));
setMode('knowledge');


// ═════════════════════════════════════════════════════════════════════════════
// HISTORY
// ═════════════════════════════════════════════════════════════════════════════

function createConversation(mode, firstMessage) {
  const id = Date.now().toString();
  const conv = {
    id,
    mode,
    title: firstMessage.slice(0, 36) + (firstMessage.length > 36 ? '…' : ''),
    messages: [],
  };
  conversations.unshift(conv);
  activeConvId = id;
  renderHistory();
  return conv;
}

function renderHistory() {
  // Clear all items but keep the empty placeholder
  [...historyList.querySelectorAll('.history-item')].forEach(el => el.remove());

  if (conversations.length === 0) {
    historyEmpty.style.display = '';
    return;
  }
  historyEmpty.style.display = 'none';

  conversations.forEach(conv => {
    const item = document.createElement('div');
    item.className = 'history-item' + (conv.id === activeConvId ? ' history-item--active' : '');
    item.dataset.id = conv.id;
    item.innerHTML = `
      <span class="history-item-badge history-item-badge--${conv.mode}">${conv.mode === 'i3rab' ? 'I3' : 'KN'}</span>
      <span class="history-item-text">${escapeHtml(conv.title)}</span>`;
    item.addEventListener('click', () => loadConversation(conv.id));
    historyList.appendChild(item);
  });
}

function loadConversation(id) {
  const conv = conversations.find(c => c.id === id);
  if (!conv || id === activeConvId) return;

  activeConvId = id;
  previousMode = null;

  // Restore mode
  setMode(conv.mode);

  // Re-render messages
  messageList.innerHTML = '';
  conv.messages.forEach(msg => {
    if (msg.role === 'user') {
      _appendUserBubble(msg.text);
    } else {
      _appendAssistantBubble(msg.text, msg.mode);
    }
  });

  renderHistory();
  scrollToBottom();
}


// ═════════════════════════════════════════════════════════════════════════════
// NEW CHAT
// ═════════════════════════════════════════════════════════════════════════════

function startNewChat() {
  activeConvId = null;
  previousMode = null;
  messageList.innerHTML = `
    <div class="message message--assistant">
      <div class="msg-avatar">س</div>
      <div class="msg-body">
        <div class="msg-text">
          أهلاً وسهلاً — I'm Sebayhi, your Arabic grammar assistant.<br>
          Select a mode on the left, then type your message below.
        </div>
      </div>
    </div>`;
  renderHistory();
  userInput.focus();
}

newChatBtn.addEventListener('click', startNewChat);


// ═════════════════════════════════════════════════════════════════════════════
// SEND
// ═════════════════════════════════════════════════════════════════════════════
//* look at this func later
async function sendMessage() {
  const text = userInput.value.trim();
  if (!text || isStreaming) return;

  // Mode switch divider
  if (previousMode !== null && previousMode !== currentMode) {
    appendModeDivider(currentMode);
  }

  // Start or continue conversation
  let conv;
  if (!activeConvId) {
    conv = createConversation(currentMode, text);
  } else {
    conv = conversations.find(c => c.id === activeConvId);
  }

  previousMode = currentMode;

  // Save user message
  conv.messages.push({ role: 'user', text, mode: currentMode });

  // Render user bubble
  _appendUserBubble(text);
  userInput.value = '';
  autoResizeTextarea();

  // Lock
  isStreaming = true;
  sendBtn.disabled = true;

  const thinkingEl = appendThinking();

  try {
    const response = await fetch('/chat/stream', {
      method:  'POST',
      credentials: "include",
      headers: { 'Content-Type': 'application/json' },
      body:    JSON.stringify({ message: text, intent: currentMode }),
    });

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

    thinkingEl.remove();
    const { textEl, cursorEl } = _appendStreamingBubble(currentMode);

    const reader  = response.body.getReader();
    const decoder = new TextDecoder();
    let   buffer  = '';
    let   replyText = '';

    outer: while (true) {
      const { value, done } = await reader.read();
      if (done) break;

      buffer += decoder.decode(value, { stream: true });
      const parts = buffer.split('\n\n');
      buffer = parts.pop();

      for (const part of parts) {
        if (!part.startsWith('data: ')) continue;
        const payload = part.slice(6);
        if (payload === '[DONE]') { cursorEl.remove(); break outer; }
        textEl.textContent += payload;
        replyText += payload;
        scrollToBottom();
      }
    }

    // Save assistant reply to history
    conv.messages.push({ role: 'assistant', text: replyText, mode: currentMode });

  } catch (err) {
    thinkingEl?.remove();
    appendErrorBubble(err.message);
    console.error(err);
  } finally {
    isStreaming      = false;
    sendBtn.disabled = false;
    userInput.focus();
    scrollToBottom();
  }
}


// ═════════════════════════════════════════════════════════════════════════════
// RENDER HELPERS
// ═════════════════════════════════════════════════════════════════════════════

function _appendUserBubble(text) {
  const el = document.createElement('div');
  el.className = 'message message--user';
  el.innerHTML = `
    <div class="msg-avatar">أ</div>
    <div class="msg-body">
      <div class="msg-text">${escapeHtml(text)}</div>
    </div>`;
  messageList.appendChild(el);
  scrollToBottom();
}

function _appendAssistantBubble(text, mode) {
  // Used when replaying history — full text already available
  const isI3rab  = mode === 'i3rab';
  const badgeText = isI3rab ? 'إعراب · I3rab' : 'معرفة · Knowledge';
  const el = document.createElement('div');
  el.className = 'message message--assistant';
  el.innerHTML = `
    <div class="msg-avatar">س</div>
    <div class="msg-body">
      <div class="intent-badge"><span class="badge-dot"></span>${badgeText}</div>
      <div class="msg-text">${escapeHtml(text)}</div>
    </div>`;
  messageList.appendChild(el);
}

function _appendStreamingBubble(mode) {
  // Used during live streaming — returns live textEl + cursorEl
  const isI3rab  = mode === 'i3rab';
  const badgeText = isI3rab ? 'إعراب · I3rab' : 'معرفة · Knowledge';

  const textEl   = document.createElement('span');
  const cursorEl = document.createElement('span');
  cursorEl.className = 'streaming-cursor';

  const bubble = document.createElement('div');
  bubble.className = 'msg-text';
  bubble.appendChild(textEl);
  bubble.appendChild(cursorEl);

  const body = document.createElement('div');
  body.className = 'msg-body';
  body.innerHTML = `<div class="intent-badge"><span class="badge-dot"></span>${badgeText}</div>`;
  body.appendChild(bubble);

  const msg = document.createElement('div');
  msg.className = 'message message--assistant';
  msg.innerHTML = `<div class="msg-avatar">س</div>`;
  msg.appendChild(body);
  messageList.appendChild(msg);
  scrollToBottom();

  return { textEl, cursorEl };
}

function appendThinking() {
  const el = document.createElement('div');
  el.className = 'message message--assistant';
  el.innerHTML = `
    <div class="msg-avatar">س</div>
    <div class="msg-body">
      <div class="thinking">
        <div class="thinking-dot"></div>
        <div class="thinking-dot"></div>
        <div class="thinking-dot"></div>
      </div>
    </div>`;
  messageList.appendChild(el);
  scrollToBottom();
  return el;
}

function appendModeDivider(mode) {
  const el = document.createElement('div');
  el.className = 'mode-divider';
  el.innerHTML = `
    <div class="mode-divider-line"></div>
    <span class="mode-divider-label">${MODE_LABELS[mode]}</span>
    <div class="mode-divider-line"></div>`;
  messageList.appendChild(el);
}

function appendErrorBubble(detail) {
  const el = document.createElement('div');
  el.className = 'message message--assistant';
  el.innerHTML = `
    <div class="msg-avatar">س</div>
    <div class="msg-body">
      <div class="msg-text msg-text--error">
        ⚠️ Something went wrong. Please try again.<br>
        <small style="opacity:0.5">${escapeHtml(detail)}</small>
      </div>
    </div>`;
  messageList.appendChild(el);
  scrollToBottom();
}


// ═════════════════════════════════════════════════════════════════════════════
// INPUT EVENTS
// ═════════════════════════════════════════════════════════════════════════════

userInput.addEventListener('keydown', e => {
  if (e.key === 'Enter' && !e.shiftKey) { e.preventDefault(); sendMessage(); }
});
sendBtn.addEventListener('click', sendMessage);
userInput.addEventListener('input', autoResizeTextarea);

function autoResizeTextarea() {
  userInput.style.height = 'auto';
  userInput.style.height = Math.min(userInput.scrollHeight, 160) + 'px';
}

function scrollToBottom() {
  chatScroll.scrollTop = chatScroll.scrollHeight;
}

function escapeHtml(str) {
  return str
    .replace(/&/g, '&amp;').replace(/</g, '&lt;')
    .replace(/>/g, '&gt;').replace(/"/g, '&quot;').replace(/'/g, '&#39;');
}

// ═════════════════════════════════════════════════════════════════════════════
// THEME TOGGLE
// ═════════════════════════════════════════════════════════════════════════════

// ── Theme toggle (desktop sidebar + mobile topbar) ────────────────────────────
const themeToggle      = document.getElementById('themeToggle');
const themeIcon        = document.getElementById('themeIcon');
const themeLabel       = document.getElementById('themeLabel');
const mobileThemeBtn   = document.getElementById('mobileThemeBtn');
const mobileThemeIcon  = document.getElementById('mobileThemeIcon');

const ICON_MOON = 'M17.293 13.293A8 8 0 016.707 2.707a8.001 8.001 0 1010.586 10.586z';
const ICON_SUN  = 'M10 2a1 1 0 011 1v1a1 1 0 11-2 0V3a1 1 0 011-1zm4 8a4 4 0 11-8 0 4 4 0 018 0zm-.464 4.95l.707.707a1 1 0 001.414-1.414l-.707-.707a1 1 0 00-1.414 1.414zm2.12-10.607a1 1 0 010 1.414l-.706.707a1 1 0 11-1.414-1.414l.707-.707a1 1 0 011.414 0zM17 11a1 1 0 100-2h-1a1 1 0 100 2h1zm-7 4a1 1 0 011 1v1a1 1 0 11-2 0v-1a1 1 0 011-1zM5.05 6.464A1 1 0 106.464 5.05l-.707-.707a1 1 0 00-1.414 1.414l.707.707zm1.414 8.486l-.707.707a1 1 0 01-1.414-1.414l.707-.707a1 1 0 011.414 1.414zM4 11a1 1 0 100-2H3a1 1 0 000 2h1z';

function applyTheme(theme) {
  document.body.dataset.theme = theme;
  const isLight = theme === 'light';
  const iconPath = isLight ? ICON_SUN : ICON_MOON;
  themeIcon.querySelector('path').setAttribute('d', iconPath);
  mobileThemeIcon.querySelector('path').setAttribute('d', iconPath);
  themeLabel.textContent = isLight ? 'Dark mode' : 'Light mode';
}

applyTheme(localStorage.getItem('sebayhi-theme') || 'dark');

function toggleTheme() {
  const next = document.body.dataset.theme === 'light' ? 'dark' : 'light';
  applyTheme(next);
  localStorage.setItem('sebayhi-theme', next);
}

themeToggle.addEventListener('click', toggleTheme);
mobileThemeBtn.addEventListener('click', toggleTheme);

userInput.focus();

// ═════════════════════════════════════════════════════════════════════════════
// MOBILE SIDEBAR TOGGLE
// ═════════════════════════════════════════════════════════════════════════════

const sidebar        = document.getElementById('sidebar');
const sidebarOverlay = document.getElementById('sidebarOverlay');
const mobileMenuBtn  = document.getElementById('mobileMenuBtn');

function openSidebar() {
  sidebar.classList.add('open');
  sidebarOverlay.classList.add('active');
}

function closeSidebar() {
  sidebar.classList.remove('open');
  sidebarOverlay.classList.remove('active');
}

mobileMenuBtn.addEventListener('click', openSidebar);
sidebarOverlay.addEventListener('click', closeSidebar);

// Close sidebar when a mode or history item is selected on mobile
[modeKnowledge, modeI3rab, newChatBtn].forEach(btn =>
  btn.addEventListener('click', () => {
    if (window.innerWidth <= 680) closeSidebar();
  })
);