create-agent-chat-app/templates/retrieval-agent/utils.ts

Create a LangGraph chat app with one command

import { BaseMessage } from "@langchain/core/messages";
import { Document } from "@langchain/core/documents";

import { BaseChatModel } from "@langchain/core/language_models/chat_models";
import { initChatModel } from "langchain/chat_models/universal";

export function getMessageText(msg: BaseMessage): string {
  /** Get the text content of a message. */
  const content = msg.content;
  if (typeof content === "string") {
    return content;
  } else {
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    const txts = (content as any[]).map((c) =>
      typeof c === "string" ? c : c.text || "",
    );
    return txts.join("").trim();
  }
}

export function formatDoc(doc: Document): string {
  const metadata = doc.metadata || {};
  const meta = Object.entries(metadata)
    .map(([k, v]) => ` ${k}=${v}`)
    .join("");
  const metaStr = meta ? ` ${meta}` : "";

  return `<document${metaStr}>\n${doc.pageContent}\n</document>`;
}

export function formatDocs(docs?: Document[]): string {
  /**Format a list of documents as XML. */
  if (!docs || docs.length === 0) {
    return "<documents></documents>";
  }
  const formatted = docs.map(formatDoc).join("\n");
  return `<documents>\n${formatted}\n</documents>`;
}

/**
 * Load a chat model from a fully specified name.
 * @param fullySpecifiedName - String in the format 'provider/model' or 'provider/account/provider/model'.
 * @returns A Promise that resolves to a BaseChatModel instance.
 */
export async function loadChatModel(
  fullySpecifiedName: string,
): Promise<BaseChatModel> {
  const index = fullySpecifiedName.indexOf("/");
  if (index === -1) {
    // If there's no "/", assume it's just the model
    return await initChatModel(fullySpecifiedName);
  } else {
    const provider = fullySpecifiedName.slice(0, index);
    const model = fullySpecifiedName.slice(index + 1);
    return await initChatModel(model, { modelProvider: provider });
  }
}