Building AI Chat

import { useChat } from 'ai/react';

export function MinimalAIChat() {
  const { messages, input, handleInputChange, handleSubmit, isLoading, stop } = useChat();

  return (
    <div className="chat-container">
      <div className="messages">
        {messages.map(m => (
          <div key={m.id} className={`message ${m.role}`}>
            <div className="content">{m.content}</div>
          </div>
        ))}
        {isLoading && <div className="thinking">AI is thinking...</div>}
      </div>

      <form onSubmit={handleSubmit} className="input-form">
        <input
          value={input}
          onChange={handleInputChange}
          placeholder="Ask anything..."
          disabled={isLoading}
        />
        {isLoading ? (
          <button type="button" onClick={stop}>Stop</button>
        ) : (
          <button type="submit">Send</button>
        )}
      </form>
    </div>
  );
}

// User message
<div className="message user">
  <div className="content">{message.content}</div>
  <time className="timestamp">{formatTime(message.timestamp)}</time>
</div>

// AI message with streaming
<div className="message ai">
  <Streamdown className="content">{message.content}</Streamdown>
  {message.isStreaming && <span className="cursor">▊</span>}
</div>

// System message
<div className="message system">
  <Icon type="info" />
  <span>{message.content}</span>
</div>

<div className="input-container">
  <button onClick={attachFile} aria-label="Attach file">
    <PaperclipIcon />
  </button>

  <textarea
    value={input}
    onChange={handleChange}
    onKeyDown={handleKeyDown}
    placeholder="Type a message..."
    rows={1}
    style={{ height: textareaHeight }}
  />

  <button onClick={toggleVoice} aria-label="Voice input">
    <MicIcon />
  </button>

  <button type="submit" disabled={!input.trim() || isLoading}>
    <SendIcon />
  </button>
</div>

<div className="response-controls">
  {isStreaming && (
    <button onClick={stop} className="stop-btn">
      Stop generating
    </button>
  )}

  {!isStreaming && (
    <>
      <button onClick={regenerate} aria-label="Regenerate response">
        <RefreshIcon /> Regenerate
      </button>
      <button onClick={continueGeneration} aria-label="Continue">
        Continue
      </button>
      <button onClick={editMessage} aria-label="Edit message">
        <EditIcon /> Edit
      </button>
    </>
  )}
</div>

<div className="feedback-controls">
  <button
    onClick={() => sendFeedback('positive')}
    aria-label="Good response"
    className={feedback === 'positive' ? 'selected' : ''}
  >
    <ThumbsUpIcon />
  </button>

  <button
    onClick={() => sendFeedback('negative')}
    aria-label="Bad response"
    className={feedback === 'negative' ? 'selected' : ''}
  >
    <ThumbsDownIcon />
  </button>

  <button onClick={copyToClipboard} aria-label="Copy">
    <CopyIcon />
  </button>

  <button onClick={share} aria-label="Share">
    <ShareIcon />
  </button>
</div>

// Use Streamdown for AI streaming (handles incomplete markdown)
import { Streamdown } from '@vercel/streamdown';

// Auto-scroll management
useEffect(() => {
  if (shouldAutoScroll()) {
    messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
  }
}, [messages]);

// Smart auto-scroll heuristic
function shouldAutoScroll() {
  const threshold = 100; // px from bottom
  const isNearBottom =
    container.scrollHeight - container.scrollTop - container.clientHeight < threshold;
  const userNotReading = !hasUserScrolledUp && !isTextSelected;
  return isNearBottom && userNotReading;
}

// User-friendly token display
function TokenIndicator({ used, total }) {
  const percentage = (used / total) * 100;
  const remaining = total - used;

  return (
    <div className="token-indicator">
      <div className="progress-bar">
        <div className="progress-fill" style={{ width: `${percentage}%` }} />
      </div>
      <span className="token-text">
        {percentage > 80
          ? `⚠️ About ${Math.floor(remaining / 250)} messages left`
          : `${Math.floor(remaining / 250)} pages of conversation remaining`}
      </span>
    </div>
  );
}

// Image upload with preview
function ImageUpload({ onUpload }) {
  return (
    <div
      className="upload-zone"
      onDrop={handleDrop}
      onDragOver={preventDefault}
    >
      <input
        type="file"
        accept="image/*"
        onChange={handleFileSelect}
        multiple
        hidden
        ref={fileInputRef}
      />
      {previews.map(preview => (
        <img key={preview.id} src={preview.url} alt="Upload preview" />
      ))}
    </div>
  );
}

// Refusal handling
if (response.type === 'refusal') {
  return (
    <div className="error refusal">
      <Icon type="info" />
      <p>I cannot help with that request.</p>
      <details>
        <summary>Why?</summary>
        <p>{response.reason}</p>
      </details>
      <p>Try asking: {response.suggestion}</p>
    </div>
  );
}

// Rate limit communication
if (error.code === 'RATE_LIMIT') {
  return (
    <div className="error rate-limit">
      <p>Please wait {error.retryAfter} seconds</p>
      <CountdownTimer seconds={error.retryAfter} onComplete={retry} />
    </div>
  );
}

function ToolUsage({ tool }) {
  return (
    <div className="tool-usage">
      <div className="tool-header">
        <Icon type={tool.type} />
        <span>{tool.name}</span>
        {tool.status === 'running' && <Spinner />}
      </div>
      {tool.status === 'complete' && (
        <details>
          <summary>View details</summary>
          <pre>{JSON.stringify(tool.result, null, 2)}</pre>
        </details>
      )}
    </div>
  );
}

# Core AI chat functionality
npm install ai @ai-sdk/react @ai-sdk/openai

# Streaming markdown rendering
npm install @vercel/streamdown

# Syntax highlighting
npm install react-syntax-highlighter

# Security for LLM outputs
npm install dompurify

// Memoize message rendering
const MemoizedMessage = memo(Message, (prev, next) =>
  prev.content === next.content && prev.isStreaming === next.isStreaming
);

// Debounce streaming updates
const debouncedUpdate = useMemo(
  () => debounce(updateMessage, 50),
  []
);

// Virtual scrolling for long conversations
import { VariableSizeList } from 'react-window';

import DOMPurify from 'dompurify';

function SafeAIContent({ content }) {
  const sanitized = DOMPurify.sanitize(content, {
    ALLOWED_TAGS: ['p', 'br', 'strong', 'em', 'code', 'pre', 'blockquote', 'ul', 'ol', 'li'],
    ALLOWED_ATTR: ['class']
  });

  return <Streamdown>{sanitized}</Streamdown>;
}

// ARIA live regions for screen readers
<div role="log" aria-live="polite" aria-relevant="additions">
  {messages.map(msg => (
    <article key={msg.id} role="article" aria-label={`${msg.role} message`}>
      {msg.content}
    </article>
  ))}
</div>

// Loading announcements
<div role="status" aria-live="polite" className="sr-only">
  {isLoading ? 'AI is responding' : ''}
</div>