import promiseLimit from "promise-limit";
import { toArray, unique } from "@/prelude/array.js";
import type { CacheableUser } from "@/models/entities/user.js";
import type { IObject, IApMention } from "../type.js";
import { isMention } from "../type.js";
import Resolver from "../resolver.js";
import { resolvePerson } from "./person.js";

export async function extractApMentions(
	tags: IObject | IObject[] | null | undefined,
) {
	const hrefs = unique(
		extractApMentionObjects(tags).map((x) => x.href as string),
	);

	const resolver = new Resolver();

	const limit = promiseLimit<CacheableUser | null>(2);
	const mentionedUsers = (
		await Promise.all(
			hrefs.map((x) =>
				limit(() => resolvePerson(x, resolver).catch(() => null)),
			),
		)
	).filter((x): x is CacheableUser => x != null);

	return mentionedUsers;
}

export function extractApMentionObjects(
	tags: IObject | IObject[] | null | undefined,
): IApMention[] {
	if (tags == null) return [];
	return toArray(tags).filter(isMention);
}
