app/api/langchain-tools/google_search.ts

import { decode } from "html-entities";
import { convert as htmlToText } from "html-to-text";
import { Tool } from "langchain/tools";
import * as cheerio from "cheerio";
import { getRandomUserAgent } from "./ua_tools";

interface SearchResults {
 /** The web results of the search. */
 results: SearchResult[];
}

interface SearchResult {
 /** The URL of the result. */
 url: string;
 /** The title of the result. */
 title: string;
 /**
 * The sanitized description of the result.
 * Bold tags will still be present in this string.
 */
 description: string;
}

async function search(
 input: string,
 maxResults: number,
): Promise<SearchResults> {
 const results: SearchResults = {
 results: [],
 };
 const headers = new Headers();
 headers.append("User-Agent", getRandomUserAgent());
 const resp = await fetch(
 `https://www.google.com/search?nfpr=1&num=${maxResults}&pws=0&q=${encodeURIComponent(
 input,
 )}`,
 {
 headers: headers,
 },
 );
 const respCheerio = cheerio.load(await resp.text());
 respCheerio("div.g").each((i, elem) => {
 const item = cheerio.load(elem);
 const linkElement = item("a");
 const url = (linkElement.attr("href") ?? "").trim();
 if (url !== "" && url !== "#") {
 const title = decode(item("h3").text());
 const description = item(`div[data-sncf~="1"]`).text().trim();
 results.results.push({
 url,
 title,
 description,
 });
 }
 });
 return results;
}

export class GoogleSearch extends Tool {
 name = "google_search";
 maxResults = 6;

 /** @ignore */
 async _call(input: string) {
 const searchResults = await search(input, this.maxResults);

 if (searchResults.results.length === 0) {
 return "No good search result found";
 }

 const results = searchResults.results
 .slice(0, this.maxResults)
 .map(({ title, description, url }) => htmlToText(description))
 .join("\n\n");
 return results;
 }

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