import { decode } from "./base32decoder.js";
import jsSHA from "jssha";
("use bigint");
/**
 * get HOTP based on counter
 * @param {BigInt} counter BigInt counter of HOTP
 * @param {string} secret base32 encoded string
 * @param {number} [digits=6] number of digits in OTP token
 * @param {string} [hashType='SHA-1'] type of hash (more in jsSHA documentation)
 * @returns HOTP string
 */
export function getHOTP(counter, secret, digits = 6, hashType = "SHA-1") {
    //Stage 1: Prepare data
    const rawDataCounter = new DataView(new ArrayBuffer(8));
    rawDataCounter.setUint32(4, counter);

    const bCounter = new Uint8Array(rawDataCounter.buffer);
    const bSecret = new Uint8Array(
        decode(secret)
            .match(/.{1,2}/g)
            .map((chunk) => parseInt(chunk, 16)),
    ); //confirmed

    //Stage 2: Hash data
    const jssha = new jsSHA(hashType, "UINT8ARRAY");
    jssha.setHMACKey(bSecret, "UINT8ARRAY");
    jssha.update(bCounter);
    const hmacResult = jssha.getHMAC("UINT8ARRAY"); //confirmed

    //Stage 3: Dynamic truncate
    const offsetB = hmacResult[19] & 0xf;
    const P = hmacResult.slice(offsetB, offsetB + 4);
    P[0] = P[0] & 0x7f;

    //Stage 4: Format string
    let res = (
        new DataView(P.buffer).getInt32(0) % Math.pow(10, digits)
    ).toString();
    while (res.length < digits) res = "0" + res;
    return res;
}

/**
 * get OTP based on current time
 * @param {string} secret base32 encoded string
 * @param {number} [digits=6] digits in OTP
 * @param {number} [time=Date.now()] time for counter (default unix time epoch)
 * @param {number} [fetchTime=30] period of token in seconds
 * @param {number} [timeOffset=0] time offset for token in seconds
 * @param {string} [hashType='SHA-1'] type of hash (more in jsSHA documentation)
 * @returns TOTP string
 */
export function getTOTP(
    secret,
    digits = 6,
    time = Date.now(),
    fetchTime = 30,
    timeOffset = 0,
    hashType = "SHA-1",
) {
    const unixTime = Math.round((time / 1000 + timeOffset) / fetchTime);
    return getHOTP(BigInt(unixTime), secret, digits);
}