AI Chat

<AIChat
      title={TITLE}
      welcomeMessage={WELCOME}
      suggestions={SUGGESTIONS}
      inputPlaceholder={PLACEHOLDER}
      notice={NOTICE}
      onClose={() => {}}
      onSend={() => {}}
      onSelectSuggestion={() => {}}
    />

{
    const [value, setValue] = useState('which melons are FTL');
    return (
      <AIChat
        title={TITLE}
        welcomeMessage={WELCOME}
        suggestions={SUGGESTIONS}
        inputPlaceholder={PLACEHOLDER}
        inputValue={value}
        onInputChange={setValue}
        notice={NOTICE}
        onClose={() => {}}
        onSend={() => {}}
        onSelectSuggestion={(s) => setValue(String(s.label))}
      />
    );
  }

{
    const messages: AIChatMessage[] = [
      {
        id: 'u1',
        role: 'user',
        content: 'which melons are FTL',
        timestamp: '2:54 PM',
      },
    ];
    return (
      <AIChat
        title={TITLE}
        welcomeMessage={WELCOME}
        messages={messages}
        processing
        inputPlaceholder={PLACEHOLDER}
        notice={NOTICE}
        onClose={() => {}}
        onStop={() => {}}
      />
    );
  }

{
    const messages: AIChatMessage[] = [
      {
        id: 'u1',
        role: 'user',
        content: 'which melons are FTL',
        timestamp: '2:54 PM',
      },
      {
        id: 'a1',
        role: 'assistant',
        timestamp: '2:54 PM',
        streaming: true,
        content: (
          <div>
            <p style={{ margin: 0 }}>
              Three melons are on the FDA Food Traceability List under 21 CFR
              §1.1300:
            </p>
            <ul
              style={{
                margin: '8px 0 0',
                paddingLeft: '16px',
                listStyleType: 'disc',
              }}
            >
              <li>Cantaloupe</li>
              <li>Honeydew</li>
              <li>Watermelon</li>
            </ul>
            <p style={{ margin: '8px 0 0' }}>
              Each requires CTE records at harvesting, cooling, initial
              packing, and receiving
            </p>
          </div>
        ),
      },
    ];
    return (
      <AIChat
        title={TITLE}
        messages={messages}
        inputPlaceholder={PLACEHOLDER}
        notice={NOTICE}
        onClose={() => {}}
        onSend={() => {}}
      />
    );
  }

{
    const [messages, setMessages] = useState<AIChatMessage[]>([]);
    const [processing, setProcessing] = useState(false);

    // The streaming engine lives in refs so it survives re-renders
    // without restarting. `timerRef` is the current setInterval handle;
    // `abortedRef` is flipped true by Stop so the tick loop bails.
    const timerRef = useRef<ReturnType<typeof setInterval> | null>(null);
    const abortedRef = useRef(false);

    useEffect(
      () => () => {
        if (timerRef.current) clearInterval(timerRef.current);
      },
      [],
    );

    const stop = useCallback(() => {
      abortedRef.current = true;
      if (timerRef.current) {
        clearInterval(timerRef.current);
        timerRef.current = null;
      }
      // Un-flag streaming on the last assistant message.
      setMessages((m) =>
        m.map((msg, i) =>
          i === m.length - 1 && msg.role === 'assistant'
            ? { ...msg, streaming: false }
            : msg,
        ),
      );
      setProcessing(false);
    }, []);

    const streamAnswer = useCallback((answer: string, assistantId: string) => {
      abortedRef.current = false;
      let i = 0;
      // 18 chars / tick @ 32ms = ~560 chars/sec — reads as fast typing.
      timerRef.current = setInterval(() => {
        if (abortedRef.current) return;
        i = Math.min(i + 18, answer.length);
        const slice = answer.slice(0, i);
        const done = i >= answer.length;
        setMessages((m) =>
          m.map((msg) =>
            msg.id === assistantId
              ? {
                  ...msg,
                  content: <FormattedAnswer text={slice} />,
                  streaming: !done,
                }
              : msg,
          ),
        );
        if (done) {
          if (timerRef.current) clearInterval(timerRef.current);
          timerRef.current = null;
          setProcessing(false);
        }
      }, 32);
    }, []);

    const send = useCallback(
      (message: string) => {
        // Don't accept new sends while one is still streaming.
        if (processing) return;
        const ts = new Date().toLocaleTimeString(undefined, {
          hour: 'numeric',
          minute: '2-digit',
        });
        const userId = `u-${Date.now()}`;
        const assistantId = `a-${Date.now() + 1}`;
        setMessages((m) => [
          ...m,
          { id: userId, role: 'user', content: message, timestamp: ts },
          {
            id: assistantId,
            role: 'assistant',
            timestamp: ts,
            streaming: true,
            content: '',
          },
        ]);
        setProcessing(true);
        // Tiny "thinking" delay before the stream starts so users see
        // the Stop button briefly even on short answers.
        window.setTimeout(() => {
          streamAnswer(lookupAnswer(message), assistantId);
        }, 450);
      },
      [processing, streamAnswer],
    );

    return (
      <AIChat
        title={TITLE}
        welcomeMessage={WELCOME}
        suggestions={SUGGESTIONS}
        messages={messages}
        processing={processing}
        inputPlaceholder={PLACEHOLDER}
        notice={NOTICE}
        onClose={() => {}}
        onSend={send}
        onStop={stop}
        onSelectSuggestion={(s) => send(String(s.label))}
      />
    );
  }