import { setTimeout as delay } from "node:timers/promises";
import type { SearchResult } from "./constants.js";
import { extractBalanced } from "./extract.js";
import { fetchSearchHtml } from "./fetch.js";

const NOKIA_USER_AGENT =
	"Nokia7610/2.0 (5.0509.0) SymbianOS/7.0s Series60/2.1 Profile/MIDP-2.0 Configuration/CLDC-1.0";
let nextRequestAt = 0;

function decodeEntities(text: string): string {
	const named: Record<string, string> = {
		amp: "&",
		lt: "<",
		gt: ">",
		quot: '"',
		apos: "'",
		nbsp: " ",
	};
	return text.replace(
		/&(#x[\da-f]+|#\d+|amp|lt|gt|quot|apos|nbsp);/gi,
		(entity, code: string) => {
			if (!code.startsWith("#")) return named[code.toLowerCase()] ?? entity;
			const number =
				code[1].toLowerCase() === "x"
					? Number.parseInt(code.slice(2), 16)
					: Number.parseInt(code.slice(1), 10);
			return number > 0 &&
				number <= 0x10ffff &&
				!(number >= 0xd800 && number <= 0xdfff)
				? String.fromCodePoint(number)
				: "�";
		},
	);
}

function plainText(html: string): string {
	return decodeEntities(html.replace(/<[^>]*>/g, " "))
		.replace(/\s+/g, " ")
		.trim();
}

function classPattern(tag: string, name: string): RegExp {
	return new RegExp(
		`<${tag}\\b[^>]*\\bclass=["'][^"']*\\b${name}\\b[^"']*["'][^>]*>`,
		"g",
	);
}

function classContent(html: string, tag: string, name: string): string {
	const match = classPattern(tag, name).exec(html);
	return match
		? (extractBalanced(html, match.index + match[0].length, tag) ?? "")
		: "";
}

export function parseGoogleResults(html: string): SearchResult[] {
	if (
		/unusual traffic|our systems have detected|g-recaptcha|\/sorry\/index/i.test(
			html,
		)
	)
		throw new Error("Google WML returned a CAPTCHA or traffic block");
	if (/before you continue to google|enable javascript/i.test(html))
		throw new Error("Google WML returned a consent or JavaScript page");
	const results: SearchResult[] = [];
	const seen = new Set<string>();
	for (const match of html.matchAll(classPattern("div", "zMzFAb"))) {
		const block = extractBalanced(html, match.index + match[0].length, "div");
		if (!block) continue;
		const anchor = classPattern("a", "fuLhoc").exec(block)?.[0];
		const href = anchor?.match(/\bhref=["']([^"']+)["']/)?.[1];
		const title = plainText(classContent(block, "span", "CVA68e"));
		if (!href || !title) continue;
		try {
			let url = new URL(decodeEntities(href), "https://www.google.com");
			if (url.hostname === "www.google.com" && url.pathname === "/url")
				url = new URL(
					url.searchParams.get("q") ?? url.searchParams.get("url") ?? "",
				);
			if (
				!/^https?:$/.test(url.protocol) ||
				url.username ||
				url.password ||
				/(^|\.)google\.com$/.test(url.hostname) ||
				seen.has(url.href)
			)
				continue;
			seen.add(url.href);
			results.push({
				title,
				url: url.href,
				snippet: plainText(classContent(block, "span", "FrIlee")),
			});
		} catch {
			/* Ignore malformed result links, never navigate them. */
		}
	}
	if (
		!results.length &&
		!/did not match any documents|no results found/i.test(html)
	)
		throw new Error(
			"Google WML returned no parseable results (layout may have changed)",
		);
	return results;
}

export async function googleSearch(
	query: string,
	signal?: AbortSignal,
	count = 5,
	timeout = 30_000,
): Promise<SearchResult[]> {
	const deadline = AbortSignal.timeout(timeout);
	const requestSignal = signal ? AbortSignal.any([signal, deadline]) : deadline;
	requestSignal.throwIfAborted();
	const now = Date.now();
	const wait = Math.max(0, nextRequestAt - now);
	nextRequestAt = Math.max(now, nextRequestAt) + 2000;
	if (wait) await delay(wait, undefined, { signal: requestSignal });
	const url = new URL("https://www.google.com/wml/search");
	url.search = new URLSearchParams({
		q: query,
		hl: "en",
		ie: "utf8",
		oe: "utf8",
		sca_esv: "1",
		lr: "",
		cr: "",
	}).toString();
	const html = await fetchSearchHtml(url.href, requestSignal, timeout, {
		headers: {
			"User-Agent": NOKIA_USER_AGENT,
			Accept: "*/*",
			Cookie: "CONSENT=YES+",
		},
	});
	return parseGoogleResults(html).slice(0, count);
}