pragma solidity 0.6.6;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage)
        internal
        pure
        returns (uint256)
    {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage)
        internal
        pure
        returns (uint256)
    {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage)
        internal
        pure
        returns (uint256)
    {
        require(b != 0, errorMessage);
        return a % b;
    }
}

contract Ownable {
    address internal _owner;

    event OwnershipTransferred(
        address indexed currentOwner,
        address indexed newOwner
    );

    constructor() internal {
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), msg.sender);
    }

    modifier onlyOwner() {
        require(
            msg.sender == _owner,
            "Ownable : Function called by unauthorized user."
        );
        _;
    }

    function owner() external view returns (address ownerAddress) {
        ownerAddress = _owner;
    }

    function transferOwnership(address newOwner)
        public
        onlyOwner
        returns (bool success)
    {
        require(newOwner != address(0), "Ownable/transferOwnership : cannot transfer ownership to zero address");
        success = _transferOwnership(newOwner);
    }

    function renounceOwnership() external onlyOwner returns (bool success) {
        success = _transferOwnership(address(0));
    }

    function _transferOwnership(address newOwner) internal returns (bool success) {
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
        success = true;
    }
}

contract Freezable is Ownable {
    mapping(address => bool) private _frozen;

    event Freeze(address indexed target);
    event Unfreeze(address indexed target);

    modifier whenNotFrozen(address target) {
        require(!_frozen[target], "Freezable : target is frozen");
        _;
    }

    function freeze(address target) external onlyOwner returns (bool success) {
        _frozen[target] = true;
        emit Freeze(target);
        success = true;
    }

    function unFreeze(address target)
        external
        onlyOwner
        returns (bool success)
    {
        _frozen[target] = false;
        emit Unfreeze(target);
        success = true;
    }

    function isFrozen(address target)
        external
        view
        returns (bool frozen)
    {
        return _frozen[target];
    }
}

abstract contract ERC20 {
    using SafeMath for uint256;

    uint256 private _totalSupply;
    mapping(address => uint256) internal _balances;
    mapping(address => mapping(address => uint256)) internal _allowances;

    event Transfer(address indexed from, address indexed to, uint256 amount);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 amount
    );

    /*
   * Internal Functions for ERC20 standard logics
   */

    function _transfer(address from, address to, uint256 amount)
        internal
        returns (bool success)
    {
        _balances[from] = _balances[from].sub(
            amount,
            "ERC20/transfer : cannot transfer more than token owner balance"
        );
        _balances[to] = _balances[to].add(amount);
        emit Transfer(from, to, amount);
        success = true;
    }

    function _approve(address owner, address spender, uint256 amount)
        internal
        returns (bool success)
    {
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
        success = true;
    }

    function _mint(address recipient, uint256 amount)
        internal
        returns (bool success)
    {
        _totalSupply = _totalSupply.add(amount);
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(address(0), recipient, amount);
        success = true;
    }

    function _burn(address burned, uint256 amount)
        internal
        returns (bool success)
    {
        _balances[burned] = _balances[burned].sub(
            amount,
            "ERC20Burnable/burn : Cannot burn more than user's balance"
        );
        _totalSupply = _totalSupply.sub(
            amount,
            "ERC20Burnable/burn : Cannot burn more than totalSupply"
        );
        emit Transfer(burned, address(0), amount);
        success = true;
    }

    /*
   * public view functions to view common data
   */

    function totalSupply() external view returns (uint256 total) {
        total = _totalSupply;
    }
    function balanceOf(address owner) external view returns (uint256 balance) {
        balance = _balances[owner];
    }

    function allowance(address owner, address spender)
        external
        view
        returns (uint256 remaining)
    {
        remaining = _allowances[owner][spender];
    }

    /*
   * External view Function Interface to implement on final contract
   */
    function name() virtual external view returns (string memory tokenName);
    function symbol() virtual external view returns (string memory tokenSymbol);
    function decimals() virtual external view returns (uint8 tokenDecimals);

    /*
   * External Function Interface to implement on final contract
   */
    function transfer(address to, uint256 amount)
        virtual
        external
        returns (bool success);
    function transferFrom(address from, address to, uint256 amount)
        virtual
        external
        returns (bool success);
    function approve(address spender, uint256 amount)
        virtual
        external
        returns (bool success);
}

contract Pausable is Ownable {
    bool internal _paused;

    event Paused();
    event Unpaused();

    modifier whenPaused() {
        require(_paused, "Paused : This function can only be called when paused");
        _;
    }

    modifier whenNotPaused() {
        require(!_paused, "Paused : This function can only be called when not paused");
        _;
    }

    function pause() external onlyOwner whenNotPaused returns (bool success) {
        _paused = true;
        emit Paused();
        success = true;
    }

    function unPause() external onlyOwner whenPaused returns (bool success) {
        _paused = false;
        emit Unpaused();
        success = true;
    }

    function paused() external view returns (bool) {
        return _paused;
    }
}

abstract contract ERC20Burnable is ERC20, Pausable {
    event Burn(address indexed burned, uint256 amount);

    function burn(uint256 amount)
        external
        whenNotPaused
        returns (bool success)
    {
        success = _burn(msg.sender, amount);
        emit Burn(msg.sender, amount);
        success = true;
    }

    function burnFrom(address burned, uint256 amount)
        external
        whenNotPaused
        returns (bool success)
    {
        _burn(burned, amount);
        emit Burn(burned, amount);
        success = _approve(
            burned,
            msg.sender,
            _allowances[burned][msg.sender].sub(
                amount,
                "ERC20Burnable/burnFrom : Cannot burn more than allowance"
            )
        );
    }
}

abstract contract ERC20Mintable is ERC20, Pausable {
    event Mint(address indexed receiver, uint256 amount);
    event MintFinished();

    bool internal _mintingFinished;
    ///@notice mint token
    ///@dev only owner can call this function
    function mint(address receiver, uint256 amount)
        external
        onlyOwner
        whenNotPaused
        returns (bool success)
    {
        require(
            receiver != address(0),
            "ERC20Mintable/mint : Should not mint to zero address"
        );
        require(
            !_mintingFinished,
            "ERC20Mintable/mint : Cannot mint after finished"
        );
        _mint(receiver, amount);
        emit Mint(receiver, amount);
        success = true;
    }

    ///@notice finish minting, cannot mint after calling this function
    ///@dev only owner can call this function
    function finishMint()
        external
        onlyOwner
        returns (bool success)
    {
        require(
            !_mintingFinished,
            "ERC20Mintable/finishMinting : Already finished"
        );
        _mintingFinished = true;
        emit MintFinished();
        return true;
    }

    function isFinished() external view returns(bool finished) {
        finished = _mintingFinished;
    }
}

abstract contract ERC20Lockable is ERC20, Ownable {
    struct LockInfo {
        uint256 amount;
        uint256 due;
    }

    mapping(address => LockInfo[]) internal _locks;
    mapping(address => uint256) internal _totalLocked;

    event Lock(address indexed from, uint256 amount, uint256 due);
    event Unlock(address indexed from, uint256 amount);

    modifier checkLock(address from, uint256 amount) {
        require(_balances[from] >= _totalLocked[from].add(amount), "ERC20Lockable/Cannot send more than unlocked amount");
        _;
    }

    function _lock(address from, uint256 amount, uint256 due)
        internal
        returns (bool success)
    {
        require(due > now, "ERC20Lockable/lock : Cannot set due to past");
        require(
            _balances[from] >= amount.add(_totalLocked[from]),
            "ERC20Lockable/lock : locked total should be smaller than balance"
        );
        _totalLocked[from] = _totalLocked[from].add(amount);
        _locks[from].push(LockInfo(amount, due));
        emit Lock(from, amount, due);
        success = true;
    }

    function _unlock(address from, uint256 index) internal returns (bool success) {
        LockInfo storage lock = _locks[from][index];
        _totalLocked[from] = _totalLocked[from].sub(lock.amount);
        emit Unlock(from, lock.amount);
        _locks[from][index] = _locks[from][_locks[from].length - 1];
        _locks[from].pop();
        success = true;
    }

    function unlock(address from) external returns (bool success) {
        for(uint256 i = 0; i < _locks[from].length; i++){
            if(_locks[from][i].due < now){
                _unlock(from, i);
            }
        }
        success = true;
    }

    function releaseLock(address from)
        external
        onlyOwner
        returns (bool success)
    {
        for(uint256 i = 0; i < _locks[from].length; i++){
            _unlock(from, i);
        }
        success = true;
    }

    function transferWithLockUp(address recipient, uint256 amount, uint256 due)
        external
        returns (bool success)
    {
        require(
            recipient != address(0),
            "ERC20Lockable/transferWithLockUp : Cannot send to zero address"
        );
        _transfer(msg.sender, recipient, amount);
        _lock(recipient, amount, due);
        success = true;
    }

    function lockInfo(address locked, uint256 index)
        external
        view
        returns (uint256 amount, uint256 due)
    {
        LockInfo memory lock = _locks[locked][index];
        amount = lock.amount;
        due = lock.due;
    }

    function totalLocked(address locked) external view returns(uint256 amount, uint256 length){
        amount = _totalLocked[locked];
        length = _locks[locked].length;
    }
}

contract EnvatoToken is
    ERC20Lockable,
    ERC20Burnable,
    ERC20Mintable,
    Freezable
{
    string constant private _name = "ENVATO";
    string constant private _symbol = "EVT";
    uint8 constant private _decimals = 18;
    uint256 constant private _initial_supply = 1_000_000_000;

    constructor() public Ownable() {
        _mint(msg.sender, _initial_supply * (10**uint256(_decimals)));
    }

    function transfer(address to, uint256 amount)
        override
        external
        whenNotFrozen(msg.sender)
        whenNotPaused
        checkLock(msg.sender, amount)
        returns (bool success)
    {
        require(
            to != address(0),
            "SAM/transfer : Should not send to zero address"
        );
        _transfer(msg.sender, to, amount);
        success = true;
    }

    function transferFrom(address from, address to, uint256 amount)
        override
        external
        whenNotFrozen(from)
        whenNotPaused
        checkLock(from, amount)
        returns (bool success)
    {
        require(
            to != address(0),
            "SAM/transferFrom : Should not send to zero address"
        );
        _transfer(from, to, amount);
        _approve(
            from,
            msg.sender,
            _allowances[from][msg.sender].sub(
                amount,
                "SAM/transferFrom : Cannot send more than allowance"
            )
        );
        success = true;
    }

    function approve(address spender, uint256 amount)
        override
        external
        returns (bool success)
    {
        require(
            spender != address(0),
            "SAM/approve : Should not approve zero address"
        );
        _approve(msg.sender, spender, amount);
        success = true;
    }

    function name() override external view returns (string memory tokenName) {
        tokenName = _name;
    }

    function symbol() override external view returns (string memory tokenSymbol) {
        tokenSymbol = _symbol;
    }

    function decimals() override external view returns (uint8 tokenDecimals) {
        tokenDecimals = _decimals;
    }
}