How to use the libsodium-wrappers.base64_variants function in libsodium-wrappers

private authCheck(client: Client, publicKey: string) {
    if (client.status === ClientStatus.Authed) return true
    else if (client.status === ClientStatus.PendingAuth) return false
    else if (!isValidRoom(publicKey)) return false

    const nonce = sodium.randombytes_buf(sodium.crypto_box_NONCEBYTES)
    const box = sodium.crypto_box_seal(nonce, sodium.from_hex(publicKey))
    const challenge = sodium.to_base64(box, sodium.base64_variants.URLSAFE_NO_PADDING)

    client.status = ClientStatus.PendingAuth
    client.authSecret = nonce

    this.sendTo(client, {
      t: MessageType.AuthChallenge,
      c: challenge
    })

    return false
  }

return promise.then((pieces) => {
			let metadata = {
				header: sodium.to_base64(header, sodium.base64_variants.ORIGINAL_NO_PADDING),
				encryptedMetadata: sodium.to_base64(metadataEncrypted, sodium.base64_variants.ORIGINAL_NO_PADDING),
			};

			return {
				pieces,
				metadata,
				key: sodium.to_base64(key, sodium.base64_variants.URLSAFE_NO_PADDING),
			};
		});
	});

function b64url (input) {
  return sodium.to_base64(input, sodium.base64_variants.URLSAFE)
}

return promise.then((pieces) => {
			let metadata = {
				header: sodium.to_base64(header, sodium.base64_variants.ORIGINAL_NO_PADDING),
				encryptedMetadata: sodium.to_base64(metadataEncrypted, sodium.base64_variants.ORIGINAL_NO_PADDING),
			};

			return {
				pieces,
				metadata,
				key: sodium.to_base64(key, sodium.base64_variants.URLSAFE_NO_PADDING),
			};
		});
	});

decryptMetadata(data) {
		if (this.metadata) {
			return this.metadata;
		}

		let header = sodium.from_base64(data.header, sodium.base64_variants.ORIGINAL_NO_PADDING);
		let encryptedMetadata = sodium.from_base64(data.encryptedMetadata, sodium.base64_variants.ORIGINAL_NO_PADDING);
		this.state = sodium.crypto_secretstream_xchacha20poly1305_init_pull(header, this.key);
		let { message, tag } = sodium.crypto_secretstream_xchacha20poly1305_pull(this.state, encryptedMetadata);
		message = JSON.parse(sodium.to_string(message));

		if (tag !== sodium.crypto_secretstream_xchacha20poly1305_TAG_FINAL) {
			throw new Error('metadata chunk not ended with final tag');
		}

		this.metadata = Object.assign({}, data, message);

		return this.metadata;
	}

decryptMetadata(data) {
		if (this.metadata) {
			return this.metadata;
		}

		let header = sodium.from_base64(data.header, sodium.base64_variants.ORIGINAL_NO_PADDING);
		let encryptedMetadata = sodium.from_base64(data.encryptedMetadata, sodium.base64_variants.ORIGINAL_NO_PADDING);
		this.state = sodium.crypto_secretstream_xchacha20poly1305_init_pull(header, this.key);
		let { message, tag } = sodium.crypto_secretstream_xchacha20poly1305_pull(this.state, encryptedMetadata);
		message = JSON.parse(sodium.to_string(message));

		if (tag !== sodium.crypto_secretstream_xchacha20poly1305_TAG_FINAL) {
			throw new Error('metadata chunk not ended with final tag');
		}

		this.metadata = Object.assign({}, data, message);

		return this.metadata;
	}

private solveChallenge(keyPair: KeyPair, data: string) {
    const challenge = sodium.from_base64(data, sodium.base64_variants.URLSAFE_NO_PADDING)
    const nonce = sodium.crypto_box_seal_open(challenge, keyPair.publicKey, keyPair.privateKey)

    const decoded = sodium.to_base64(nonce, sodium.base64_variants.URLSAFE_NO_PADDING)
    this.send({
      t: MessageType.AuthResponse,
      c: decoded
    })
  }

function toB64URLSafe(buf) {
  if (!(buf instanceof Buffer)) { throw new TypeError('Can only encode buffer'); }
  return sodium.to_base64(buf, sodium.base64_variants.URLSAFE_NO_PADDING);
}

private solveChallenge(keyPair: KeyPair, data: string) {
    const challenge = sodium.from_base64(data, sodium.base64_variants.URLSAFE_NO_PADDING)
    const nonce = sodium.crypto_box_seal_open(challenge, keyPair.publicKey, keyPair.privateKey)

    const decoded = sodium.to_base64(nonce, sodium.base64_variants.URLSAFE_NO_PADDING)
    this.send({
      t: MessageType.AuthResponse,
      c: decoded
    })
  }