"use strict";

export const DATE_FMT = new Intl.DateTimeFormat("de-DE", {
	month: "numeric",
	day: "numeric",
	year: "numeric",
});

export const DATETIME_FMT = new Intl.DateTimeFormat("de-DE", {
	month: "numeric",
	day: "numeric",
	year: "numeric",
	hour: "numeric",
	minute: "numeric",
});

export function dateStringNow() {
	return DATE_FMT.format(new Date());
}

export function datetimeStringNow() {
	return DATETIME_FMT.format(new Date());
}

declare global {
	var M: { cfg: { userId: number; courseId: number } };
}

export function getUserId(): number {
	// M is exported by Moodle
	return globalThis.M.cfg.userId;
}

export function getCourseId(): number {
	// M is exported by Moodle
	return globalThis.M.cfg.courseId;
}

// TODO(muhq): Cache the retrieved URL
export async function getUserIconUrl(userId: number): Promise<string> {
	const userRes = await fetch(`https://lernplattform.bycs.de/user/profile.php?id=${userId}`);
	const userDoc = new DOMParser().parseFromString(await userRes.text(), "text/html");
	const userpicture = userDoc.querySelector(".userpicture");
	if (userpicture === null) {
		return "";
	}

	return (userpicture as HTMLImageElement).src ?? "";
}

// SplitMix32 implementation taken from:
// https://github.com/bryc/code/blob/master/jshash/PRNGs.md
// We only need a seeded PRNG to choose students to observe.
export function splitmix32(a: number) {
	return function () {
		a |= 0;
		a = (a + 0x9e3779b9) | 0;
		let t = a ^ (a >>> 16);
		t = Math.imul(t, 0x21f0aaad);
		t = t ^ (t >>> 15);
		t = Math.imul(t, 0x735a2d97);
		return ((t = t ^ (t >>> 15)) >>> 0) / 4294967296;
	};
}