import * as jsSHA3 from 'js-sha3';

const BASIC_ADDRESS_REGEX = /^(0x)?[0-9a-f]{40}$/i;
const SAME_CASE_ADDRESS_REGEX = /^(0x)?([0-9a-f]{40}|[0-9A-F]{40})$/;

export const addressUtils = {
	isChecksumAddress(address: string): boolean {
		// Check each case
		const unprefixedAddress = address.replace('0x', '');
		const addressHash = jsSHA3.keccak256(unprefixedAddress.toLowerCase());

		for (let i = 0; i < 40; i++) {
			// The nth letter should be uppercase if the nth digit of casemap is 1
			if (
				(parseInt(addressHash[i], 16) > 7 && unprefixedAddress[i].toUpperCase() !== unprefixedAddress[i]) ||
				(parseInt(addressHash[i], 16) <= 7 && unprefixedAddress[i].toLowerCase() !== unprefixedAddress[i])
			) {
				return false;
			}
		}
		return true;
	},
	isAddress(address: string): boolean {
		if (!BASIC_ADDRESS_REGEX.test(address)) {
			// Check if it has the basic requirements of an address
			return false;
		} else if (SAME_CASE_ADDRESS_REGEX.test(address)) {
			// If it's all small caps or all all caps, return true
			return true;
		} else {
			// Otherwise check each case
			const isValidChecksummedAddress = addressUtils.isChecksumAddress(address);
			return isValidChecksummedAddress;
		}
	},
};