bolt.new/packages/bolt/app/lib/hooks/useMessageParser.ts

import type { Message } from 'ai';
import { useCallback, useState } from 'react';
import { createScopedLogger } from '../../utils/logger';
import { StreamingMessageParser } from '../runtime/message-parser';
import { workbenchStore } from '../stores/workbench';

const logger = createScopedLogger('useMessageParser');

const messageParser = new StreamingMessageParser({
  callbacks: {
    onArtifactOpen: (data) => {
      logger.trace('onArtifactOpen', data);

      workbenchStore.showWorkbench.set(true);
      workbenchStore.addArtifact(data);
    },
    onArtifactClose: (data) => {
      logger.trace('onArtifactClose');

      workbenchStore.updateArtifact(data, { closed: true });
    },
    onActionOpen: (data) => {
      logger.debug('onActionOpen', data.action);

      // we only add shell actions when when the close tag got parsed because only then we have the content
      if (data.action.type !== 'shell') {
        workbenchStore.addAction(data);
      }
    },
    onActionClose: (data) => {
      logger.debug('onActionClose', data.action);

      if (data.action.type === 'shell') {
        workbenchStore.addAction(data);
      }

      workbenchStore.runAction(data);
    },
  },
});

export function useMessageParser() {
  const [parsedMessages, setParsedMessages] = useState<{ [key: number]: string }>({});

  const parseMessages = useCallback((messages: Message[], isLoading: boolean) => {
    let reset = false;

    if (import.meta.env.DEV && !isLoading) {
      reset = true;
      messageParser.reset();
    }

    for (const [index, message] of messages.entries()) {
      if (message.role === 'assistant') {
        /**
         * In production, we only parse the last assistant message since previous messages can't change.
         * During development they can change, e.g., if the parser gets modified.
         */
        if (import.meta.env.PROD && index < messages.length - 1) {
          continue;
        }

        const newParsedContent = messageParser.parse(message.id, message.content);

        setParsedMessages((prevParsed) => ({
          ...prevParsed,
          [index]: !reset ? (prevParsed[index] || '') + newParsedContent : newParsedContent,
        }));
      }
    }
  }, []);

  return { parsedMessages, parseMessages };
}