ai/src/ui/last-assistant-message-is-complete-with-tool-calls.ts

AI SDK by Vercel - The AI Toolkit for TypeScript and JavaScript

import { isToolUIPart, type UIMessage } from './ui-messages';

/**
Check if the message is an assistant message with completed tool calls.
The last step of the message must have at least one tool invocation and
all tool invocations must have a result.
 */
export function lastAssistantMessageIsCompleteWithToolCalls({
  messages,
}: {
  messages: UIMessage[];
}): boolean {
  const message = messages[messages.length - 1];

  if (!message) {
    return false;
  }

  if (message.role !== 'assistant') {
    return false;
  }

  const lastStepStartIndex = message.parts.reduce((lastIndex, part, index) => {
    return part.type === 'step-start' ? index : lastIndex;
  }, -1);

  const lastStepToolInvocations = message.parts
    .slice(lastStepStartIndex + 1)
    .filter(isToolUIPart)
    .filter(part => !part.providerExecuted);

  return (
    lastStepToolInvocations.length > 0 &&
    lastStepToolInvocations.every(
      part =>
        part.state === 'output-available' || part.state === 'output-error',
    )
  );
}