pragma solidity ^0.4.21;

library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
        if (a == 0) {
            return 0;
        }
        c = a * b;
        assert(c / a == b);
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
        c = a + b;
        assert(c >= a);
        return c;
    }
}

contract Ownable {
    address public owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    function Ownable() public {
        owner = msg.sender;
    }

    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }
}

contract ERC20Interface {
    function totalSupply() public view returns (uint256);
    function balanceOf(address who) public view returns (uint256);
    function transfer(address to, uint256 value) public returns (bool);
    function transferFrom(address from, address to, uint256 value) public returns (bool);
    function approve(address spender, uint256 value) public returns (bool);
    function allowance(address owner, address spender) public view returns (uint256);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract StandardToken is ERC20Interface {
    using SafeMath for uint256;

    mapping(address => uint256) balances;
    mapping (address => mapping (address => uint256)) internal allowed;

    uint256 totalSupply_;

    function totalSupply() public view returns (uint256) {
        return totalSupply_;
    }

    function balanceOf(address _owner) public view returns (uint256) {
        return balances[_owner];
    }

    function transfer(address _to, uint256 _value) public returns (bool) {
        require(_to != address(0));
        require(_value > 0 && _value <= balances[msg.sender]);

        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) {
        require(_to != address(0));
        require(_value > 0 && _value <= balances[_from] && _value <= allowed[_from][msg.sender]);

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) public view returns (uint256) {
        return allowed[_owner][_spender];
    }

    function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
        allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
        uint oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue > oldValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }
}

contract Pausable is Ownable {
    event Pause();
    event Unpause();

    bool public paused = false;

    modifier whenNotPaused() {
        require(!paused);
        _;
    }

    modifier whenPaused() {
        require(paused);
        _;
    }

    function pause() onlyOwner whenNotPaused public {
        paused = true;
        emit Pause();
    }

    function unpause() onlyOwner whenPaused public {
        paused = false;
        emit Unpause();
    }
}

contract PausableToken is StandardToken, Pausable {
    function transfer(address _to, uint256 _value) public whenNotPaused returns (bool) {
        return super.transfer(_to, _value);
    }

    function transferFrom(address _from, address _to, uint256 _value) public whenNotPaused returns (bool) {
        return super.transferFrom(_from, _to, _value);
    }

    function approve(address _spender, uint256 _value) public whenNotPaused returns (bool) {
        return super.approve(_spender, _value);
    }

    function increaseApproval(address _spender, uint _addedValue) public whenNotPaused returns (bool success) {
        return super.increaseApproval(_spender, _addedValue);
    }

    function decreaseApproval(address _spender, uint _subtractedValue) public whenNotPaused returns (bool success) {
        return super.decreaseApproval(_spender, _subtractedValue);
    }
}

contract BurnableToken is StandardToken {
    event Burn(address indexed burner, uint256 value);

    function burn(uint256 _value) public {
        _burn(msg.sender, _value);
    }

    function _burn(address _who, uint256 _value) internal {
        require(_value <= balances[_who]);

        balances[_who] = balances[_who].sub(_value);
        totalSupply_ = totalSupply_.sub(_value);
        emit Burn(_who, _value);
        emit Transfer(_who, address(0), _value);
    }

    function burnFrom(address _from, uint256 _value) public {
        require(_value <= allowed[_from][msg.sender]);

        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        _burn(_from, _value);
    }
}

contract MintableToken is StandardToken, Ownable {
    event Mint(address indexed to, uint256 amount);
    event MintFinished();

    bool public mintingFinished = false;

    modifier canMint() {
        require(!mintingFinished);
        _;
    }

    function mint(address _to, uint256 _amount) onlyOwner canMint public returns (bool) {
        totalSupply_ = totalSupply_.add(_amount);
        balances[_to] = balances[_to].add(_amount);
        emit Mint(_to, _amount);
        emit Transfer(address(0), _to, _amount);
        return true;
    }

    function finishMinting() onlyOwner canMint public returns (bool) {
        mintingFinished = true;
        emit MintFinished();
        return true;
    }
}

library SafeERC20 {
    function safeTransfer(ERC20Interface token, address to, uint256 value) internal {
        assert(token.transfer(to, value));
    }

    function safeTransferFrom(ERC20Interface token, address from, address to, uint256 value ) internal {
        assert(token.transferFrom(from, to, value));
    }

    function safeApprove(ERC20Interface token, address spender, uint256 value) internal {
        assert(token.approve(spender, value));
    }
}

contract TokenVesting is Ownable {
    using SafeMath for uint256;
    using SafeERC20 for ERC20Interface;

    event Released(uint256 amount);
    event Revoked();

    address public beneficiary;

    uint256 public cliff;
    uint256 public start;
    uint256 public duration;

    bool public revocable;

    mapping (address => uint256) public released;
    mapping (address => bool) public revoked;

    function TokenVesting(address _beneficiary, uint256 _start, uint256 _cliff, uint256 _duration, bool _revocable) public {
        require(_beneficiary != address(0));
        require(_cliff <= _duration);

        beneficiary = _beneficiary;
        revocable = _revocable;
        duration = _duration;
        cliff = _start.add(_cliff);
        start = _start;
    }

    function release(ERC20Interface token) public {
        uint256 unreleased = releasableAmount(token);

        require(unreleased > 0);

        released[token] = released[token].add(unreleased);

        token.safeTransfer(beneficiary, unreleased);

        emit Released(unreleased);
    }

    function revoke(ERC20Interface token) public onlyOwner {
        require(revocable);
        require(!revoked[token]);

        uint256 balance = token.balanceOf(this);

        uint256 unreleased = releasableAmount(token);
        uint256 refund = balance.sub(unreleased);

        revoked[token] = true;

        token.safeTransfer(owner, refund);

        emit Revoked();
    }

    function releasableAmount(ERC20Interface token) public view returns (uint256) {
        return vestedAmount(token).sub(released[token]);
    }

    function vestedAmount(ERC20Interface token) public view returns (uint256) {
        uint256 currentBalance = token.balanceOf(this);
        uint256 totalBalance = currentBalance.add(released[token]);

        if (block.timestamp < cliff) {
            return 0;
        } else if (block.timestamp >= start.add(duration) || revoked[token]) {
            return totalBalance;
        } else {
            return totalBalance.mul(block.timestamp.sub(start)).div(duration);
        }
    }
}

contract ETVRToken is PausableToken, BurnableToken, MintableToken {
    string public constant name     = "ETVR TOKEN";
    string public constant symbol   = "ETVR";
    uint8  public constant decimals = 18;

    uint256 public constant INITIAL_SUPPLY = 500000000 * (10 ** uint256(decimals));

    function ETVRToken() public {
        totalSupply_ = INITIAL_SUPPLY;
        balances[msg.sender] = INITIAL_SUPPLY;
        emit Transfer(0x0, msg.sender, INITIAL_SUPPLY);
    }
}