/* @flow */

import BigNumber from 'bignumber.js';
import EthereumjsUtil from 'ethereumjs-util';

export const namehash = (domain: string): string => {
    if (!domain) {
        return '0x0000000000000000000000000000000000000000000000000000000000000000';
    }
    const [label, ...remainder] = domain.split('.');
    return `0x${EthereumjsUtil.keccak256(
        namehash(remainder.join('.')) + EthereumjsUtil.keccak256(label).toString('hex')
    ).toString('hex')}`;
};

export const decimalToHex = (dec: number): string => new BigNumber(dec).toString(16);

export const padLeftEven = (hex: string): string => (hex.length % 2 !== 0 ? `0${hex}` : hex);

export const sanitizeHex = ($hex: string): string => {
    const hex = $hex.toLowerCase().substring(0, 2) === '0x' ? $hex.substring(2) : $hex;
    if (hex === '') return '';
    return `0x${padLeftEven(hex)}`;
};

export const hexToDecimal = (hex: number): string => {
    const sanitized: ?string = sanitizeHex(hex.toString());
    return !sanitized ? 'null' : new BigNumber(sanitized).toString();
};

export const strip = (str: string): string => {
    if (str.indexOf('0x') === 0) {
        return padLeftEven(str.substring(2, str.length));
    }
    return padLeftEven(str);
};

export const calcGasPrice = (price: BigNumber, limit: string): string =>
    price.times(limit).toString();

export const validateAddress = (address: string): ?string => {
    const hasUpperCase = new RegExp('^(.*[A-Z].*)$');
    if (address.length < 1) {
        return 'Address is not set';
    }
    if (!EthereumjsUtil.isValidAddress(address)) {
        return 'Address is not valid';
    }
    if (address.match(hasUpperCase) && !EthereumjsUtil.isValidChecksumAddress(address)) {
        return 'Address is not a valid checksum';
    }
    return null;
};

export const isHex = (str: string): boolean => {
    const regExp = /^(0x|0X)?[0-9A-Fa-f]+$/g;
    return regExp.test(str);
};