import { scrypt as _nobleSync, scryptAsync as _nobleAsync } from "@noble/hashes/scrypt";

import { getBytes, hexlify as H } from "../utils/index.js";

import type { BytesLike } from "../utils/index.js";

/**
 *  A callback during long-running operations to update any
 *  UI or provide programatic access to the progress.
 *
 *  The %%percent%% is a value between ``0`` and ``1``.
 */
export type ProgressCallback = (percent: number) => void;


let lockedSync = false, lockedAsync = false;

const _scryptAsync = async function(passwd: Uint8Array, salt: Uint8Array, N: number, r: number, p: number, dkLen: number, onProgress?: ProgressCallback) {
    return await _nobleAsync(passwd, salt, { N, r, p, dkLen, onProgress });
}
const _scryptSync = function(passwd: Uint8Array, salt: Uint8Array, N: number, r: number, p: number, dkLen: number) {
    return _nobleSync(passwd, salt, { N, r, p, dkLen });
}

let __scryptAsync: (passwd: Uint8Array, salt: Uint8Array, N: number, r: number, p: number, dkLen: number, onProgress?: ProgressCallback) => Promise<BytesLike> = _scryptAsync;
let __scryptSync: (passwd: Uint8Array, salt: Uint8Array, N: number, r: number, p: number, dkLen: number) => BytesLike = _scryptSync


/**
 *  The [[link-wiki-scrypt]] uses a memory and cpu hard method of
 *  derivation to increase the resource cost to brute-force a password
 *  for a given key.
 *
 *  This means this algorithm is intentionally slow, and can be tuned to
 *  become slower. As computation and memory speed improve over time,
 *  increasing the difficulty maintains the cost of an attacker.
 *
 *  For example, if a target time of 5 seconds is used, a legitimate user
 *  which knows their password requires only 5 seconds to unlock their
 *  account. A 6 character password has 68 billion possibilities, which
 *  would require an attacker to invest over 10,000 years of CPU time. This
 *  is of course a crude example (as password generally aren't random),
 *  but demonstrates to value of imposing large costs to decryption.
 *
 *  For this reason, if building a UI which involved decrypting or
 *  encrypting datsa using scrypt, it is recommended to use a
 *  [[ProgressCallback]] (as event short periods can seem lik an eternity
 *  if the UI freezes). Including the phrase //"decrypting"// in the UI
 *  can also help, assuring the user their waiting is for a good reason.
 *
 *  @_docloc: api/crypto:Passwords
 *
 *  @example:
 *    // The password must be converted to bytes, and it is generally
 *    // best practices to ensure the string has been normalized. Many
 *    // formats explicitly indicate the normalization form to use.
 *    password = "hello"
 *    passwordBytes = toUtf8Bytes(password, "NFKC")
 *
 *    salt = id("some-salt")
 *
 *    // Compute the scrypt
 *    scrypt(passwordBytes, salt, 1024, 8, 1, 16)
 *    //_result:
 */
export async function scrypt(_passwd: BytesLike, _salt: BytesLike, N: number, r: number, p: number, dkLen: number, progress?: ProgressCallback): Promise<string> {
    const passwd = getBytes(_passwd, "passwd");
    const salt = getBytes(_salt, "salt");
    return H(await __scryptAsync(passwd, salt, N, r, p, dkLen, progress));
}
scrypt._ = _scryptAsync;
scrypt.lock = function(): void { lockedAsync = true; }
scrypt.register = function(func: (passwd: Uint8Array, salt: Uint8Array, N: number, r: number, p: number, dkLen: number, progress?: ProgressCallback) => Promise<BytesLike>) {
    if (lockedAsync) { throw new Error("scrypt is locked"); }
    __scryptAsync = func;
}
Object.freeze(scrypt);

/**
 *  Provides a synchronous variant of [[scrypt]].
 *
 *  This will completely lock up and freeze the UI in a browser and will
 *  prevent any event loop from progressing. For this reason, it is
 *  preferred to use the [async variant](scrypt).
 *
 *  @_docloc: api/crypto:Passwords
 *
 *  @example:
 *    // The password must be converted to bytes, and it is generally
 *    // best practices to ensure the string has been normalized. Many
 *    // formats explicitly indicate the normalization form to use.
 *    password = "hello"
 *    passwordBytes = toUtf8Bytes(password, "NFKC")
 *
 *    salt = id("some-salt")
 *
 *    // Compute the scrypt
 *    scryptSync(passwordBytes, salt, 1024, 8, 1, 16)
 *    //_result:
 */
export function scryptSync(_passwd: BytesLike, _salt: BytesLike, N: number, r: number, p: number, dkLen: number): string {
    const passwd = getBytes(_passwd, "passwd");
    const salt = getBytes(_salt, "salt");
    return H(__scryptSync(passwd, salt, N, r, p, dkLen));
}
scryptSync._ = _scryptSync;
scryptSync.lock = function(): void { lockedSync = true; }
scryptSync.register = function(func: (passwd: Uint8Array, salt: Uint8Array, N: number, r: number, p: number, dkLen: number) => BytesLike) {
    if (lockedSync) { throw new Error("scryptSync is locked"); }
    __scryptSync = func;
}
Object.freeze(scryptSync);