const chatLauncher = document.getElementById('chatLauncher');
const chatContainer = document.getElementById('chatContainer');
const sidebar = document.getElementById('sidebar');

// just changed the name
function closeChat() {
  chatContainer.style.display = 'none';
  chatLauncher.style.display = 'flex';
}

chatLauncher.addEventListener('click', () => {
  chatContainer.style.display = 'flex';
  chatLauncher.style.display = 'none';
  
  // when opening the chat, it should not be fullscreen
  chatContainer.classList.remove('fullscreen');
  // with collapsed sidebar
  sidebar.querySelector('.content').style.display = 'none';
  
  // this is not needed because you don't have 
  // the option to close chat when sidebar is fullwidth
  // in case you implment it later
  // sidebar.classList.remove('fullwidth');
});

function toggleFullscreen() {
  chatContainer.classList.toggle('fullscreen');
  
  // also toggle sidebar content
  sidebar.querySelector('.content').style.display =
    chatContainer.classList.contains('fullscreen') ? 'block' : 'none';
}

function toggleSidebar() {
  const isFullscreen = chatContainer.classList.contains('fullscreen');
  // isMobile is always false if isFullscreen is true
  // isFullscreen = !isMobile
  // const isMobile = chatContainer.offsetWidth <= 400;

  if (!isFullscreen) {
    sidebar.classList.toggle('fullwidth');
    
    // there is no collapsed class defined??
    // sidebar.classList.remove('collapsed');
    
    sidebar.querySelector('.content').style.display =
      sidebar.classList.contains('fullwidth') ? 'block' : 'none';
  } else {
    // you mentioned, collapsing sidebar in fullscreen should not be possible
    // sidebar.classList.toggle('collapsed');
    // sidebar.querySelector('.content').style.display =
    //   sidebar.classList.contains('collapsed') ? 'none' : 'block';
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: 'Segoe UI', sans-serif;
  background: #f3f3f3;
}

/* ---------- launcher ---------- */
.chat-launcher {
  position: fixed;
  bottom: 20px;
  right: 20px;
  background: #000;
  color: #fff;
  border-radius: 50%;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
  cursor: pointer;
  z-index: 1000;
}

/* ---------- chat container ---------- */
.chat-container {
  display: none;
  height: 600px;
  width: 400px;
  max-width: 90vw;
  position: fixed;
  bottom: 80px;
  right: 20px;
  background: #fff;
  box-shadow: 0 0 12px rgba(0, 0, 0, 0.15);
  border-radius: 12px;
  overflow: hidden;
  z-index: 1001;
  transition: all .3s ease;
}

/* ---------- fullscreen overrides ---------- */
.chat-container.fullscreen {
  width: 100vw;
  height: 100vh;
  bottom: 0;
  right: 0;
  border-radius: 0;
  display: flex;
  flex-direction: row;
}

/* sidebar in fullscreen */
.chat-container.fullscreen .sidebar {
  width: 250px;
  border-right: 1px solid #ddd;
}

.chat-container.fullscreen .sidebar .content {
  display: block;
}

/* chat area in fullscreen */
.chat-container.fullscreen .container {
  display: flex;
  flex: 1 1 auto;
}

/* ---------- sidebar ---------- */
.sidebar {
  width: 60px;
  background: #fff;
  border-right: 1px solid #ddd;
  padding: 20px;
  transition: width .3s;
  flex-shrink: 0;
}

.sidebar .toggle-btn {
  font-size: 20px;
  cursor: pointer;
  margin-bottom: 20px;
}

.sidebar .content {
  display: none;
}

.sidebar.fullwidth {
  width: 100%;
  border-right: none;
}

.sidebar.fullwidth .content {
  display: block;
}

.sidebar.fullwidth~.container {
  display: none;
}

/* ---------- chat area ---------- */
.container {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  min-width: 0;
}

.header {
  background: #f5f5f5;
  padding: 10px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.header h2 {
  flex: 1;
  text-align: center;
  font-size: 18px;
  margin: 0;
}

.header .icons {
  display: flex;
  gap: 10px;
  font-size: 20px;
  color: #333;
  cursor: pointer;
}

.blue-banner {
  background: linear-gradient(to right, #2979ff, #1976d2);
  color: white;
  padding: 15px;
  margin: 10px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 14px;
}

.messages {
  flex: 1;
  padding: 20px;
  overflow-y: auto;
}

.message {
  margin-bottom: 20px;
}

.message.bot {
  background: #fff;
  border-radius: 10px;
  padding: 15px;
  box-shadow: 0 0 4px rgba(0, 0, 0, .1);
  max-width: 80%;
}

.message.user {
  text-align: right;
}

.message.user .bubble {
  display: inline-block;
  background: #1976d2;
  color: white;
  border-radius: 20px;
  padding: 10px 20px;
}

.timestamp {
  font-size: 12px;
  color: gray;
  margin-top: 5px;
}

.input-area {
  display: flex;
  align-items: center;
  padding: 10px;
  background: white;
  border-top: 1px solid #ccc;
}

.input-area input {
  flex: 1;
  padding: 10px;
  border: 1px solid #ccc;
  border-radius: 20px;
  outline: none;
}

.input-area button {
  background: #1976d2;
  color: white;
  border: none;
  border-radius: 50%;
  padding: 10px 15px;
  margin-left: 10px;
  cursor: pointer;
}

.upload-btn {
  margin-right: 10px;
  font-size: 12px;
  color: #1976d2;
  cursor: pointer;
}

<div class="chat-launcher" id="chatLauncher">💬</div>

<div class="chat-container" id="chatContainer">
  <!-- sidebar -->
  <div class="sidebar" id="sidebar">
    <div class="toggle-btn" onclick="toggleSidebar()">☰</div>
    <div class="content">
      <h2>{nameHere}</h2>
      <p>{descriptionHere}</p>
      <h3>Continue Conversations</h3>
      <button style="padding:10px;border:1px solid #1976d2;border-radius:10px;width:100%;margin-bottom:10px;background:#E3F2FD;color:#000;">Sender: Clickable →</button>
      <h3>Talk to our experts</h3>
      <button style="padding:10px;width:100%;margin-bottom:10px;background:#F3E5F5;border:1px solid #CCC;border-radius:10px;">👨‍💼 Support</button>
      <div style="padding: 10px; border-radius: 10px; background: linear-gradient(to right, #d1c4e9, #f8bbd0);">
        <p><strong>Need specialized help?</strong><br/>Our teams are ready to assist you with any questions</p>
        <button style="padding: 5px 10px; background: blue; color: white; border: none; border-radius: 5px;">Call Us</button>
      </div>
    </div>
  </div>

  <!-- chat -->
  <div class="container">
    <div class="header">
      <div class="icons" onclick="closeChat()">✖</div>
      <h2>Support</h2>
      <div class="icons">
        <span onclick="alert('Call Clicked')">📞</span>
        <span onclick="toggleFullscreen()">⤢</span>
      </div>
    </div>
    <div class="blue-banner">
      📄
      <div>
        <strong>Enter your details</strong><br>
        <small>Click here to provide your information</small>
      </div>
    </div>
    <div class="messages">
      <div class="message bot">
        Hey 😃 How can I assist you with services today? Could you please share your username to help you better?
        <ul>
          <li>1. I have an issue with SMS</li>
          <li>2. I need help with Email</li>
          <li>3. Other service query</li>
        </ul>
        <div class="timestamp">10:26 am</div>
      </div>
      <div class="message user">
        <div class="bubble">hey</div>
        <div class="timestamp">10:26 am</div>
      </div>
      <div class="message bot">
        Hey 😃 How can I help you with today? Please share your username so I can assist you better.
        <ul>
          <li>1. I have an issue with SMS</li>
          <li>2. I need help with Email</li>
          <li>3. Other service query</li>
        </ul>
        <div class="timestamp">10:27 am</div>
      </div>
    </div>
    <div class="input-area">
      <span class="upload-btn">📎 Upload Files</span>
      <input type="text" placeholder="Message AI Assistant...">
      <button>➤</button>
    </div>
  </div>
</div>