/*

    Copyright 2020 DODO ZOO.
    SPDX-License-Identifier: Apache-2.0

*/

pragma solidity 0.6.9;

import {SafeMath} from "../lib/SafeMath.sol";

contract TestERC20 {
    using SafeMath for uint256;

    string public name;
    uint8 public decimals;

    mapping(address => uint256) balances;
    mapping(address => mapping(address => uint256)) internal allowed;

    event Transfer(address indexed from, address indexed to, uint256 amount);
    event Approval(address indexed owner, address indexed spender, uint256 amount);

    constructor(string memory _name, uint8 _decimals) public {
        name = _name;
        decimals = _decimals;
    }

    function transfer(address to, uint256 amount) public returns (bool) {
        require(to != address(0), "TO_ADDRESS_IS_EMPTY");
        require(amount <= balances[msg.sender], "BALANCE_NOT_ENOUGH");

        balances[msg.sender] = balances[msg.sender].sub(amount);
        balances[to] = balances[to].add(amount);
        emit Transfer(msg.sender, to, amount);
        return true;
    }

    function balanceOf(address owner) public view returns (uint256 balance) {
        return balances[owner];
    }

    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public returns (bool) {
        require(to != address(0), "TO_ADDRESS_IS_EMPTY");
        require(amount <= balances[from], "BALANCE_NOT_ENOUGH");
        require(amount <= allowed[from][msg.sender], "ALLOWANCE_NOT_ENOUGH");

        balances[from] = balances[from].sub(amount);
        balances[to] = balances[to].add(amount);
        allowed[from][msg.sender] = allowed[from][msg.sender].sub(amount);
        emit Transfer(from, to, amount);
        return true;
    }

    function approve(address spender, uint256 amount) public returns (bool) {
        allowed[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function allowance(address owner, address spender) public view returns (uint256) {
        return allowed[owner][spender];
    }

    function mint(address account, uint256 amount) external {
        balances[account] = balances[account].add(amount);
    }
}