read.markets/app/static/js/chat.js

// Cassandra chat sidebar — ephemeral, client-state conversation.
// No persistence: page refresh starts a new chat.
(() => {
  const thread = document.getElementById('chat-thread');
  const form   = document.getElementById('chat-form');
  const input  = document.getElementById('chat-input');
  const send   = document.getElementById('chat-send');
  if (!thread || !form || !input || !send) return;

  /** @type {{role: string, content: string}[]} */
  const messages = [];

  function escapeHTML(s) {
    return s.replace(/&/g, '&')
            .replace(/</g, '&lt;')
            .replace(/>/g, '&gt;');
  }

  function append(role, html_or_text, opts) {
    const div = document.createElement('div');
    div.className = 'chat-msg chat-msg--' + role;
    if (opts && opts.html) {
      div.innerHTML = html_or_text;
    } else {
      div.textContent = html_or_text;
    }
    thread.appendChild(div);
    thread.scrollTop = thread.scrollHeight;
    return div;
  }

  form.addEventListener('submit', async (e) => {
    e.preventDefault();
    const text = input.value.trim();
    if (!text || send.disabled) return;
    messages.push({role: 'user', content: text});
    append('user', text);
    input.value = '';
    send.disabled = true;
    const thinking = append('assistant', '…');
    thinking.classList.add('chat-msg--pending');
    try {
      const r = await fetch('/api/chat', {
        method: 'POST',
        headers: {'Content-Type': 'application/json'},
        body: JSON.stringify({messages}),
      });
      if (!r.ok) {
        const msg = await r.text();
        thinking.className = 'chat-msg chat-msg--error';
        thinking.textContent = 'HTTP ' + r.status + ': ' + msg.slice(0, 300);
        return;
      }
      const data = await r.json();
      thinking.className = 'chat-msg chat-msg--assistant';
      thinking.innerHTML = data.content_html || escapeHTML(data.content);
      messages.push({role: 'assistant', content: data.content});
    } catch (err) {
      thinking.className = 'chat-msg chat-msg--error';
      thinking.textContent = 'error: ' + err.message;
    } finally {
      send.disabled = false;
      input.focus();
    }
  });

  // Enter to send; Shift+Enter for newline.
  input.addEventListener('keydown', (e) => {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault();
      form.requestSubmit();
    }
  });
})();