/**
 * Copyright 2017-2021, bZeroX, LLC. All Rights Reserved.
 * Licensed under the Apache License, Version 2.0.
 */

pragma solidity 0.5.17;

import "../openzeppelin/SafeMath.sol";

contract TestToken {
	using SafeMath for uint256;

	event Transfer(address indexed from, address indexed to, uint256 value);
	event Approval(address indexed owner, address indexed spender, uint256 value);
	event Mint(address indexed minter, uint256 value);
	event Burn(address indexed burner, uint256 value);

	string public name;
	string public symbol;
	uint8 public decimals;

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

	constructor(
		string memory _name,
		string memory _symbol,
		uint8 _decimals,
		uint256 _initialAmount
	) public {
		name = _name;
		symbol = _symbol;
		decimals = _decimals;

		if (_initialAmount != 0) {
			mint(msg.sender, _initialAmount);
		}
	}

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

	function transfer(address _to, uint256 _value) public returns (bool) {
		require(_value <= balances[msg.sender] && _to != address(0), "invalid transfer");

		balances[msg.sender] = balances[msg.sender].sub(_value);
		balances[_to] = balances[_to].add(_value);

		emit Transfer(msg.sender, _to, _value);
		return true;
	}

	function transferFrom(
		address _from,
		address _to,
		uint256 _value
	) public returns (bool) {
		uint256 allowanceAmount = allowed[_from][msg.sender];
		require(_value <= balances[_from] && _value <= allowanceAmount && _to != address(0), "invalid transfer");

		balances[_from] = balances[_from].sub(_value);
		balances[_to] = balances[_to].add(_value);
		if (allowanceAmount < uint256(-1)) {
			allowed[_from][msg.sender] = allowanceAmount.sub(_value);
		}

		emit Transfer(_from, _to, _value);
		return true;
	}

	function mint(address _to, uint256 _value) public {
		require(_to != address(0), "no burn allowed");
		totalSupply_ = totalSupply_.add(_value);
		balances[_to] = balances[_to].add(_value);

		emit Mint(_to, _value);
		emit Transfer(address(0), _to, _value);
	}

	function burn(address _who, uint256 _value) public {
		require(_value <= balances[_who], "balance too low");
		// no need to require _value <= totalSupply, since that would imply the
		// sender's balance is greater than the totalSupply, which *should* be an assertion failure

		balances[_who] = balances[_who].sub(_value);
		totalSupply_ = totalSupply_.sub(_value);

		emit Burn(_who, _value);
		emit Transfer(_who, address(0), _value);
	}

	function totalSupply() public view returns (uint256) {
		return totalSupply_;
	}

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

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