// https://tools.ietf.org/html/rfc2898
import {int322bytesBE} from "./util.js";
import {blake2s} from "./blake.js";

const HASH_LENGTH = 32;

export function pbkdf2(password, salt, iterationCount, outLength) {
	// max BLAKE2 key length is 32B
	if (password.length > 32) {password = blake2s(password);}

	let blockCount = Math.ceil(outLength / HASH_LENGTH);
	let result = [];

	for (let i = 0; i < blockCount; i++) {
		let block = _computeBlock(password, salt, iterationCount, i+1);
		result = result.concat(block);
	}
	return result.slice(0, outLength);
}

function _computeBlock(password, salt, iterationCount, blockIndex) {
	let u = blake2s(salt.concat(int322bytesBE(blockIndex)), HASH_LENGTH, password);
	for (let i = 1; i < iterationCount; i++) {
		let ui = blake2s(u, HASH_LENGTH, password);
		u = u.map((b, j) => b ^ ui[j]);
	}
	return u;
}