bingserpapi.ts

import { getEnvironmentVariable } from "@langchain/core/utils/env";
import { Tool } from "@langchain/core/tools";

/**
 * A tool for web search functionality using Bing's search engine. It
 * extends the base `Tool` class and implements the `_call` method to
 * perform the search operation. Requires an API key for Bing's search
 * engine, which can be set in the environment variables. Also accepts
 * additional parameters for the search query.
 */
class BingSerpAPI extends Tool {
  static lc_name() {
    return "BingSerpAPI";
  }

  /**
   * Not implemented. Will throw an error if called.
   */
  toJSON() {
    return this.toJSONNotImplemented();
  }

  name = "bing-search";

  description =
    "a search engine. useful for when you need to answer questions about current events. input should be a search query.";

  key: string;

  params: Record<string, string>;

  constructor(
    apiKey: string | undefined = getEnvironmentVariable("BingApiKey"),
    params: Record<string, string> = {}
  ) {
    super(...arguments);

    if (!apiKey) {
      throw new Error(
        "BingSerpAPI API key not set. You can set it as BingApiKey in your .env file."
      );
    }

    this.key = apiKey;
    this.params = params;
  }

  /** @ignore */
  async _call(input: string): Promise<string> {
    const headers = { "Ocp-Apim-Subscription-Key": this.key };
    const params = { q: input, textDecorations: "true", textFormat: "HTML" };
    const searchUrl = new URL("https://api.bing.microsoft.com/v7.0/search");

    Object.entries(params).forEach(([key, value]) => {
      searchUrl.searchParams.append(key, value);
    });

    const response = await fetch(searchUrl, { headers });

    if (!response.ok) {
      throw new Error(`HTTP error ${response.status}`);
    }

    const res = await response.json();
    const results: [] = res.webPages.value;

    if (results.length === 0) {
      return "No good results found.";
    }
    const snippets = results
      .map((result: { snippet: string }) => result.snippet)
      .join(" ");

    return snippets;
  }
}

export { BingSerpAPI };