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;
}