"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;
}

export class CourseLocalStorage {
	static getItem(key: string) {
		return localStorage.getItem(`${key}-${getCourseId()}`);
	}

	static setItem(key: string, val: string) {
		return localStorage.setItem(`${key}-${getCourseId()}`, val);
	}
}

export async function getUserIconUrl(userId: number): Promise<string> {
	let url = CourseLocalStorage.getItem(`bycs-sol-user-icon-${userId}`);
	if (url) return url;

	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 "";
	}

	url = (userpicture as HTMLImageElement).src ?? "";
	CourseLocalStorage.setItem(`bycs-sol-user-icon-${userId}`, url);

	return url;
}

// 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;
	};
}