the message history doesn't work and the bot isn't remembering previous messages

<!DOCTYPE html>
<html>
<head>
  <title>Google Chat with File Upload</title>
  <style>
    /* ... (Styles remain the same as your original code) ... */
    body {
      font-family: sans-serif;
      margin: 0;
      padding: 0;
      display: flex;
      justify-content: center;
      align-items: center;
      min-height: 100vh;
      background-color: #f0f0f0;
    }

    .container {
      display: flex;
      flex-direction: column;
      width: 90%;
      max-width: 600px;
      height: 80vh;
      background-color: #fff;
      border: 1px solid #ccc;
      border-radius: 8px;
      box-shadow: 0 2px 10px rgba(0,0,0,0.1);
      overflow: hidden;
    }

    /* Header for Toggle Buttons */
    .header {
      padding: 10px 20px;
      background-color: #f9f9f9;
      border-bottom: 1px solid #ddd;
      display: flex;
      flex-wrap: wrap;
      justify-content: space-between;
      align-items: center;
    }

    .toggle-container {
      display: flex;
      align-items: center;
      margin: 5px 0;
    }

    .toggle-container label {
      margin-right: 10px;
      font-size: 14px;
    }

    /* Toggle switch styles */
    .switch {
      position: relative;
      display: inline-block;
      width: 50px;
      height: 28px;
      margin-left: 10px;
    }

    .switch input {
      opacity: 0;
      width: 0;
      height: 0;
    }

    .slider {
      position: absolute;
      cursor: pointer;
      top: 0;
      left: 0;
      right: 0;
      bottom: 0;
      background-color: #ccc;
      transition: .4s;
      border-radius: 28px;
    }

    .slider:before {
      position: absolute;
      content: "";
      height: 22px;
      width: 22px;
      left: 3px;
      bottom: 3px;
      background-color: white;
      transition: .4s;
      border-radius: 50%;
    }

    input:checked + .slider {
      background-color: #2196F3;
    }

    input:checked + .slider:before {
      transform: translateX(22px);
    }

    /* Chat Container */
    #chat-container {
      flex: 1;
      padding: 15px;
      overflow-y: auto;
      background-color: #fafafa;
    }

    .message {
      padding: 10px 15px;
      margin-bottom: 10px;
      border-radius: 18px;
      max-width: 80%;
      word-wrap: break-word;
      position: relative;
      clear: both;
    }

    .user-message {
      background-color: #e0f7fa;
      align-self: flex-end;
      margin-left: auto;
      text-align: right;
    }

    .bot-message {
      background-color: #f1f8e9;
      align-self: flex-start;
      margin-right: auto;
    }

    /* Input Area */
    #input-area {
      display: flex;
      align-items: center; /* Updated to align items vertically */
      padding: 10px 20px;
      border-top: 1px solid #ddd;
      background-color: #f9f9f9;
    }

    #input-box {
      flex-grow: 1;
      padding: 10px;
      border: 1px solid #ccc;
      border-radius: 20px;
      resize: none;
      font-size: 14px;
      outline: none;
    }

    /* File Input Styles */
    #file-input {
      display: none;
    }

    #file-label {
      margin-left: 10px;
      padding: 10px 15px;
      background-color: #f0f0f0;
      border-radius: 20px;
      cursor: pointer;
      font-size: 14px;
      transition: background-color 0.3s;
    }

    #file-label:hover {
      background-color: #e0e0e0;
    }

    #send-button {
      padding: 10px 20px;
      margin-left: 10px;
      background-color: #007bff;
      color: #fff;
      border: none;
      border-radius: 20px;
      cursor: pointer;
      font-size: 14px;
      transition: background-color 0.3s;
    }

    #send-button:hover {
      background-color: #0056b3;
    }

    /* Typing Indicator */
    #typing-indicator {
      padding: 5px 20px;
      font-style: italic;
      color: #999;
      background-color: #f9f9f9;
      border-top: 1px solid #ddd;
      display: none;
    }

    /* Responsive Adjustments */
    @media (max-width: 768px) {
      .container {
        width: 95%;
        height: 90vh;
      }
    }

    @media (max-width: 480px) {
      .header {
        flex-direction: column;
        align-items: flex-start;
      }

      .toggle-container {
        width: 100%;
        justify-content: space-between;
      }

      #send-button {
        padding: 10px;
        margin-left: 5px;
      }
    }
  </style>
</head>

<body>
  <div class="container">
    <!-- Header with Toggle Buttons -->
    <div class="header">
      <!-- Toggle Button for Super Smart Mode -->
      <div class="toggle-container">
        <label for="superSmartToggle">Super Smart Mode</label>
        <label class="switch">
          <input type="checkbox" id="superSmartToggle">
          <span class="slider"></span>
        </label>
      </div>

      <!-- Toggle Button for Fast/Smart Model Switching -->
      <div class="toggle-container">
        <label for="modelToggle">Fast Mode</label>
        <label class="switch">
          <input type="checkbox" id="modelToggle">
          <span class="slider"></span>
        </label>
      </div>
    </div>

    <!-- Chat Messages -->
    <div id="chat-container"></div>

    <!-- Typing Indicator -->
    <div id="typing-indicator">Gemini is typing...</div> 

    <!-- Input Area -->
    <div id="input-area">
      <textarea id="input-box" placeholder="Enter your message..." rows="1"></textarea>
      <!-- File Input -->
      <input type="file" id="file-input" accept=".pdf,image/*,audio/*">
      <label for="file-input" id="file-label">📎</label>
      <button id="send-button">Send</button>
    </div>
  </div>

  <script>
    // List of API keys. Replace these with your actual API keys.
    const API_KEYS = [
      'AIzaSyBdc_A8VxExwO6-0LY1--r2-Ym73lMg-h4',
      'AIzaSyBydeCpaNOIPSk794CpTGnfKrxbjCgJLu4',
      'AIzaSyCQ7tBHtctxlNs61Zm2Y__7KYeDLfz5dms',
      'AIzaSyAip_DFfKNC35MFIorEoNK4y6czP9P65-c'
    ];

    const chatContainer = document.getElementById('chat-container');
    const inputBox = document.getElementById('input-box');
    const sendButton = document.getElementById('send-button');
    const typingIndicator = document.getElementById('typing-indicator');
    const superSmartToggle = document.getElementById('superSmartToggle');
    const modelToggle = document.getElementById('modelToggle');
    const fileInput = document.getElementById('file-input');
    const fileLabel = document.getElementById('file-label');

    // Initialize messageHistory based on toggles' initial state
    let messageHistory = "";

    // Current model variable
    let currentModel = 'gemini-1.5-pro-exp-0827'; // Default model

    // Event listener for the Super Smart Mode toggle switch
    superSmartToggle.addEventListener('change', () => {
      if (superSmartToggle.checked) {
        messageHistory = "tt" + messageHistory;
      } else {
        messageHistory = messageHistory.replace("tt", "");
      }
    });

    // Event listener for the Fast/Smart Model toggle switch
    modelToggle.addEventListener('change', () => {
      if (modelToggle.checked) {
        currentModel = 'gemini-1.5-flash';
      } else {
        currentModel = 'gemini-1.5-pro-exp-0827';
      }
      console.log(`Model switched to: ${currentModel}`);
    });

    sendButton.addEventListener('click', sendMessage);
    inputBox.addEventListener('keydown', (event) => {
      if (event.key === 'Enter' && !event.shiftKey) {
        event.preventDefault();
        sendMessage();
      }
    });

    /**
     * Attempts to fetch a response using the provided API key.
     * @param {string} apiKey - The API key to use for the request.
     * @param {Array} contents - The contents to send (messages and files).
     * @param {string} model - The model to use for generating the response.
     * @returns {Promise<Object>} - The response data from the API.
     */
    async function fetchWithKey(apiKey, contents, model) {
      const response = await fetch(`https://generativelanguage.googleapis.com/v1beta/models/${model}:generateContent?key=${apiKey}`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          contents: contents,
          "generationConfig": {
            "temperature": 0.5,
            "topK": 64,
            "topP": 0.95,
            "maxOutputTokens": 8192,
            "responseMimeType": "text/plain"
          }
        })
      });

      if (!response.ok) {
        // Extract error message from response
        const errorData = await response.json();
        throw new Error(errorData.error?.message || 'Unknown API error');
      }

      const data = await response.json();
      return data;
    }

    /**
     * Uploads a file using the File API and returns the file URI.
     * @param {File} file - The file to upload.
     * @param {string} apiKey - The API key to use for the request.
     * @returns {Promise<string>} - The file URI.
     */
    async function uploadFile(file, apiKey) {
      const BASE_URL = 'https://generativelanguage.googleapis.com';

      // Start the resumable upload
      const startResponse = await fetch(`${BASE_URL}/upload/v1beta/files?key=${apiKey}`, {
        method: 'POST',
        headers: {
          'X-Goog-Upload-Protocol': 'resumable',
          'X-Goog-Upload-Command': 'start',
          'X-Goog-Upload-Header-Content-Length': file.size,
          'X-Goog-Upload-Header-Content-Type': file.type,
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          file: { display_name: file.name }
        })
      });

      if (!startResponse.ok) {
        const errorData = await startResponse.json();
        throw new Error(errorData.error?.message || 'Failed to start upload');
      }

      const uploadUrl = startResponse.headers.get('X-Goog-Upload-URL');
      if (!uploadUrl) {
        throw new Error('Upload URL not received');
      }

      // Upload the file data
      const uploadResponse = await fetch(uploadUrl, {
        method: 'POST',
        headers: {
          'Content-Length': file.size,
          'X-Goog-Upload-Offset': '0',
          'X-Goog-Upload-Command': 'upload, finalize'
        },
        body: file
      });

      if (!uploadResponse.ok) {
        const errorData = await uploadResponse.json();
        throw new Error(errorData.error?.message || 'Failed to upload file');
      }

      const fileInfo = await uploadResponse.json();
      return fileInfo.file.uri;
    }

    /**
     * Sends the user's message and handles the bot's response using multiple API keys.
     */
    async function sendMessage() {
      const userMessageText = inputBox.value.trim();
      const selectedFile = fileInput.files[0];

      if (userMessageText === '' && !selectedFile) return;

      // Display user's message
      const userMessage = document.createElement('div');
      userMessage.classList.add('message', 'user-message');

      if (selectedFile) {
        const fileType = selectedFile.type;
        if (fileType.startsWith('image/')) {
          const img = document.createElement('img');
          img.src = URL.createObjectURL(selectedFile);
          img.style.maxWidth = '100%';
          userMessage.appendChild(img);
        } else {
          userMessage.textContent = `Sent a file: ${selectedFile.name}`;
        }
      }

      if (userMessageText !== '') {
        const textNode = document.createTextNode(userMessageText);
        userMessage.appendChild(textNode);
      }

      chatContainer.appendChild(userMessage);
      chatContainer.scrollTop = chatContainer.scrollHeight;      

      inputBox.value = '';
      fileInput.value = '';
      typingIndicator.style.display = 'block';

      let botMessageText = '';
      let success = false;

      // Prepare the contents array
      const parts = [];

      if (userMessageText !== '') {
        parts.push({ text: userMessageText });
      }

      if (selectedFile) {
        parts.push({
          file_data: {
            mime_type: selectedFile.type,
            file_uri: ''  // We'll fill this after uploading
          }
        });
      }

      const contents = [
        {
          role: "user",
          parts: parts
        }
      ];

      // Loop through API keys to fetch response
      for (const apiKey of API_KEYS) {
        try {
          // If there's a file, upload it first
          if (selectedFile) {
            const fileUri = await uploadFile(selectedFile, apiKey);
            // Update the file_data with the correct file_uri
            parts.find(p => p.file_data).file_data.file_uri = fileUri;
          }

          const data = await fetchWithKey(apiKey, contents, currentModel);

          const fullResponse = data?.candidates[0]?.content?.parts[0]?.text; // Optional chaining

          if (!fullResponse) {
            throw new Error("Invalid response format: Missing content.");
          }

          if (superSmartToggle.checked) {
            // Parse response between <final_answer> and </final_answer>
            const finalAnswerStartIndex = fullResponse.indexOf("<final_answer>");
            const finalAnswerEndIndex = fullResponse.indexOf("</final_answer>");

            if (finalAnswerStartIndex !== -1 && finalAnswerEndIndex !== -1) {
              botMessageText = fullResponse.substring(finalAnswerStartIndex + "<final_answer>".length, finalAnswerEndIndex).trim();
            } else {
              botMessageText = "Error: Could not extract final answer. Invalid response format.";
              console.error("Final answer tags not found in response:", fullResponse);
            }
          } else {
            // When Super smart mode is off, use the entire response
            botMessageText = fullResponse.trim();
          }

          if (botMessageText) {
            // Update history *after* successful response
            messageHistory += `Bot: ${botMessageText}\n`;
          }

          success = true;
          break; 
        } catch (error) {
          console.error(`Error with API key:`, error.message);
        }
      }

      const botMessage = document.createElement('div');
      botMessage.classList.add('message', 'bot-message');
      botMessage.textContent = success ? botMessageText : "I'm sorry, I'm currently unable to process your request. Please try again later.";
      chatContainer.appendChild(botMessage);
      chatContainer.scrollTop = chatContainer.scrollHeight;

      typingIndicator.style.display = 'none';
    }
  </script>
</body>
</html>