import * as util from "./util.js";
import {blake2s} from "./blake.js";
import {pbkdf2} from "./pbkdf2.js";
import {Chacha20,encrypt as _encrypt,decrypt as _decrypt} from "./chacha.js";

const VERSION=1;
const MAX_ITERS=24;

function encrypt(s,password){
	let bs=util.str2utf8(s);
	let pass=util.str2utf8(password);
	let salt=util.createRandomNonce(12);
	let [iters,key]=stretchKey(pass,salt);
	let [_,ciphertext]=_encrypt(bs,key,salt);
	let signature=blake2s([VERSION,iters].concat(salt,ciphertext),16,key);
	let arr=[VERSION,iters].concat(signature,salt,ciphertext);
	return util.bytes2base64(arr);
}

function decrypt(s,password){
	let pass=util.str2utf8(password);
	let arr=util.base642bytes(s);
	let version=arr[0];
	let iters=arr[1];
	let signature=arr.slice(2,18);
	let salt=arr.slice(18,30);
	let ciphertext=arr.slice(30);
	
	if(ciphertext.length==0){return 4;}
	if(version>VERSION){return 2;}
	if(iters>MAX_ITERS){return 3;}
	let key=pbkdf2(pass,salt,1<<iters,32);
	let check=blake2s([version,iters].concat(salt,ciphertext),16,key);
	if(!signature.every((b,i)=>b===check[i])){return 1;}
	let plainbytes=_decrypt(ciphertext,key,salt);
	return util.utf82str(plainbytes);
}

function stretchKey(password,salt){
	let start=Date.now(); // ms
	let i,key;
	for(i=0;i<=MAX_ITERS;i++){
		key=pbkdf2(password,salt,1<<i,32);
		if(Date.now()-start>=500){break;}
	}
	return [i,key];
}

export default {util,blake2s,pbkdf2,Chacha20,encrypt,decrypt};

// export for tests running on Node
if(typeof module!=='undefined'&&module.hasOwnProperty('exports')){
	module.exports.util=util;
	module.exports.blake2s=blake2s;
	module.exports.pbkdf2=pbkdf2;
	module.exports.Chacha20=Chacha20;
	module.exports.encrypt=_encrypt;
	module.exports.decrypt=_decrypt;
}