export const MASK = 0xffffffff;

export function zeroPad(arr, length) {
	return arr.concat((new Array(length)).fill(0)).slice(0, length);
}

export function bytes2int32(arr) {
	return arr.reduce((acc, b, i) => acc | b << (i*8));
}

export function bytes2int32s(arr) {
	let res = [];
	for (let i = 0; i < arr.length; i += 4) {
		res.push(bytes2int32(arr.slice(i, i+4)));
	}
	return res;
}

/**
 * Converts a 32 bit integer into 4 bytes in little endian order.
 */
export function int322bytes(x) {
	let res = [];
	for (let i = 0; i < 4; i++) {
		res.push(x & 0xff);
		x >>>= 8;
	}
	return res;
}

/**
 * Converts a 32 bit integer into 4 bytes in big endian order.
 */
export function int322bytesBE(x) {
	let res = int322bytes(x);
	res.reverse();
	return res;
}

export function int32s2bytes(arr) {
	return arr.map(int322bytes).reduce((acc, bytes) => acc.concat(bytes));
}

export function bytes2hex(arr) {
	return arr.map(x => x.toString(16).padStart(2, "0")).join("");
}

export function str2utf8(s) {
	let res = [];
	let c = s.codePointAt(0);
	for (let i=0; c!==undefined; i++, c=s.codePointAt(i)) {
		if (c < 0x80) {res.push(c);}
		else if (c < 0x800) {
			res.push(0b11000000 | (c >>> 6));
			res.push(0b10000000 | (c & 0b111111));
		}
		else if (c < 0x10000) {
			res.push(0b11100000 | (c >>> 12));
			res.push(0b10000000 | ((c >>> 6) & 0b111111));
			res.push(0b10000000 | (c & 0b111111));
		}
		else {
			res.push(0b11110000 | (c >>> 18));
			res.push(0b10000000 | ((c >>> 12) & 0b111111));
			res.push(0b10000000 | ((c >>> 6) & 0b111111));
			res.push(0b10000000 | (c & 0b111111));
		}
		if (c > 0xffff) {i++;} // skip surrogate
	}
	return res;
}

export function utf82str(arr) {
	let res = [];
	for (let i = 0; i < arr.length; i++) {
		let x = arr[i];
		if (x <= 0b1111111) {res.push(x);}
		else if (x <= 0b11011111) {
			let a = x & 0b11111;
			let b = arr[++i] & 0b111111;
			res.push(a << 6 | b);
		}
		else if (x <= 0b11101111) {
			let a = x & 0b1111;
			let b = arr[++i] & 0b111111;
			let c = arr[++i] & 0b111111;
			res.push(a << 12 | b << 6 | c);
		}
		else {
			let a = x & 0b111;
			let b = arr[++i] & 0b111111;
			let c = arr[++i] & 0b111111;
			let d = arr[++i] & 0b111111;
			res.push(a << 18 | b << 12 | c << 6 | d);
		}
	}
	return res.map(x => String.fromCodePoint(x)).join("");
}

const mapping = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".split("");
const remapping = new Array(128);
mapping.forEach((c, i) => {remapping[c.charCodeAt(0)] = i;});

export function bytes2base64(byteArr) {
	let arr = byteArr.concat();
	let out = [];
	let rem = (3 - arr.length%3) % 3;
	for (let i = 0; i < rem; i++) {arr.push(0);} // pad array to a multiple of 3

	for (let i = 0; i < arr.length; i += 3) { // encode 3 bytes into 4 characters
		out.push(mapping[arr[i]>>>2 & 63]);
		out.push(mapping[((arr[i]&3) << 4) + (arr[i+1]>>>4 & 15)]);
		out.push(mapping[((arr[i+1]&15) << 2) + (arr[i+2]>>>6 & 3)]);
		out.push(mapping[arr[i+2] & 63]);
	}

	for (let i = 0; i < rem; i++) {out.pop();}
	for (let i = 0; i < rem; i++) {out.push("=");}

	return out.join("");
}

export function base642bytes(str) {
	let out = [];

	for (let i = 0; i < str.length; i += 4) {
		let b1 = remapping[str.charCodeAt(i)];
		let b2 = remapping[str.charCodeAt(i+1)];
		let b3 = remapping[str.charCodeAt(i+2)];
		let b4 = remapping[str.charCodeAt(i+3)];

		out.push((b1<<2) + (b2>>4 & 3));
		out.push(((b2&15) << 4) + (b3>>2 & 15));
		out.push(((b3&3) << 6) + b4);
	}

	for (let i=1; i<3 && str[str.length-i]=="="; i++) {out.pop();}

	return out;
}

export function createRandomNonce(n) {
	let nonce = new Uint8Array(n);
	window.crypto.getRandomValues(nonce);
	return Array.from(nonce);
}