Contract Source Code:

pragma solidity ^0.5.0;

import "./IERC20.sol";
import "./SafeMath.sol";

/**
 * @dev Implementation of the `IERC20` interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using `_mint`.
 * For a generic mechanism see `ERC20Mintable`.
 *
 * *For a detailed writeup see our guide [How to implement supply
 * mechanisms](https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226).*
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an `Approval` event is emitted on calls to `transferFrom`.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard `decreaseAllowance` and `increaseAllowance`
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See `IERC20.approve`.
 */
contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    /**
     * @dev See `IERC20.totalSupply`.
     */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See `IERC20.balanceOf`.
     */
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See `IERC20.transfer`.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    /**
     * @dev See `IERC20.allowance`.
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See `IERC20.approve`.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev See `IERC20.transferFrom`.
     *
     * Emits an `Approval` event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of `ERC20`;
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `value`.
     * - the caller must have allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender].sub(amount));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender].sub(subtractedValue));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to `transfer`, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a `Transfer` event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _balances[sender] = _balances[sender].sub(amount);
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a `Transfer` event with `from` set to the zero address.
     *
     * Requirements
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

     /**
     * @dev Destoys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a `Transfer` event with `to` set to the zero address.
     *
     * Requirements
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    // function _burn(address account, uint256 value) internal {
    //     require(account != address(0), "ERC20: burn from the zero address");

    //     _totalSupply = _totalSupply.sub(value);
    //     _balances[account] = _balances[account].sub(value);
    //     emit Transfer(account, address(0), value);
    // }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an `Approval` event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 value) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    /**
     * @dev Destoys `amount` tokens from `account`.`amount` is then deducted
     * from the caller's allowance.
     *
     * See `_burn` and `_approve`.
     */
    // function _burnFrom(address account, uint256 amount) internal {
    //     _burn(account, amount);
    //     _approve(account, msg.sender, _allowances[account][msg.sender].sub(amount));
    // }
}

pragma solidity ^0.5.0;

import "./ERC20Mintable.sol";

/**
 * @dev Extension of `ERC20Mintable` that adds a cap to the supply of tokens.
 */
contract ERC20Capped is ERC20Mintable {
    uint256 private _cap;

    /**
     * @dev Sets the value of the `cap`. This value is immutable, it can only be
     * set once during construction.
     */
    constructor (uint256 cap) public {
        require(cap > 0, "ERC20Capped: cap is 0");
        _cap = cap;
    }

    /**
     * @dev Returns the cap on the token's total supply.
     */
    function cap() public view returns (uint256) {
        return _cap;
    }

    /**
     * @dev See `ERC20Mintable.mint`.
     *
     * Requirements:
     *
     * - `value` must not cause the total supply to go over the cap.
     */
    function _mint(address account, uint256 value) internal {
        require(totalSupply().add(value) <= _cap, "ERC20Capped: cap exceeded");
        super._mint(account, value);
    }
}

pragma solidity ^0.5.0;

import "./ERC20.sol";
import "./MinterRole.sol";

/**
 * @dev Extension of `ERC20` that adds a set of accounts with the `MinterRole`,
 * which have permission to mint (create) new tokens as they see fit.
 *
 * At construction, the deployer of the contract is the only minter.
 */
contract ERC20Mintable is ERC20, MinterRole {
    /**
     * @dev See `ERC20._mint`.
     *
     * Requirements:
     *
     * - the caller must have the `MinterRole`.
     */
    function mint(address account, uint256 amount) public onlyMinter returns (bool) {
        _mint(account, amount);
        return true;
    }
}

pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see `ERC20Detailed`.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through `transferFrom`. This is
     * zero by default.
     *
     * This value changes when `approve` or `transferFrom` are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * > Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an `Approval` event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to `approve`. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

pragma solidity ^0.5.0;

import "./Roles.sol";

contract MinterRole {
    using Roles for Roles.Role;

    event MinterAdded(address indexed account);
    event MinterRemoved(address indexed account);

    Roles.Role private _minters;

    constructor () internal {
        _addMinter(msg.sender);
    }

    modifier onlyMinter() {
        require(isMinter(msg.sender), "MinterRole: caller does not have the Minter role");
        _;
    }

    function isMinter(address account) public view returns (bool) {
        return _minters.has(account);
    }

    function addMinter(address account) public onlyMinter {
        _addMinter(account);
    }

    function renounceMinter() public {
        _removeMinter(msg.sender);
    }

    function _addMinter(address account) internal {
        _minters.add(account);
        emit MinterAdded(account);
    }

    function _removeMinter(address account) internal {
        _minters.remove(account);
        emit MinterRemoved(account);
    }
}

pragma solidity ^0.5.0;

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles {
    struct Role {
        mapping (address => bool) bearer;
    }

    /**
     * @dev Give an account access to this role.
     */
    function add(Role storage role, address account) internal {
        require(!has(role, account), "Roles: account already has role");
        role.bearer[account] = true;
    }

    /**
     * @dev Remove an account's access to this role.
     */
    function remove(Role storage role, address account) internal {
        require(has(role, account), "Roles: account does not have role");
        role.bearer[account] = false;
    }

    /**
     * @dev Check if an account has this role.
     * @return bool
     */
    function has(Role storage role, address account) internal view returns (bool) {
        require(account != address(0), "Roles: account is the zero address");
        return role.bearer[account];
    }
}

pragma solidity ^0.5.0;

import "./S3Stake.sol";
import "./ERC20Capped.sol";
import "./ERC20Mintable.sol";

contract S3Coin is ERC20Capped {
    using SafeMath for uint256;

    string public name = "S3 COIN";
    string public symbol = "S3C";
    uint8 public decimals = 18;

    // stake contract addresses
    uint32 private _stakeCount = 0;
    uint256 private _stakeTotal = 0;

    mapping (uint32 => address) private _stakes;

    // NewStake event
    event NewStake(address indexed account);


    /**
     * - cap: 1000000000000000000000000000 (1 bil)
     * - init: 300000000000000000000000000 (3 mil)
     */
    constructor (uint256 cap, uint256 init) public ERC20Capped(cap) {
        require(cap > 1000000000000000000, "S3Coin: cap must greater than 10^18");

        // mint to sender init tokens
        mint(msg.sender, init);
    }

    /**
     * Requirements:
     * - the caller must have the `StakerRole`.
     *
     * return new stake address.
     */
    function stake(uint32 id, address beneficiary, uint256 amount, uint256 releaseAmount, uint32 releaseTime)
        public onlyMinter returns (address) {
        require(_stakes[id] == address(0), "S3Coin: stake with ID already exist");
        require(balanceOf(msg.sender) >= amount, "S3Coin: there is not enough tokens to stake");
        require(amount >= releaseAmount, "S3Coin: there is not enough tokens to stake");

        // create new stake
        S3Stake newStake = new S3Stake(S3Coin(address(this)), beneficiary, releaseAmount, releaseTime);

        emit NewStake(address(newStake));

        // transfer amount of token to stake address
        require(transfer(address(newStake), amount), "S3Coin: transfer tokens to new stake failed");

        // update data
        _stakeCount += 1;
        _stakeTotal = _stakeTotal.add(amount);
        _stakes[id] = address(newStake);

        return _stakes[id];
    }

    /**
     * Get a stake contract address.
     */
    function stakeAddress(uint32 id) public view returns (address) {
        return _stakes[id];
    }

    /**
     * Get number of stakes.
     */
    function stakeCount() public view returns (uint) {
        return _stakeCount;
    }

    /**
     * Get total tokens were staked.
     */
    function stakeTotal() public view returns (uint256) {
        return _stakeTotal;
    }

}

pragma solidity ^0.5.0;

import "./S3Coin.sol";
//import "./SafeMath.sol";
//import "./SafeERC20.sol";


/**
 * @title S3Stake
 * S3Stake is a token stake contract that will allow daily minting
 * to beneficiary, and allow beneficiary to extract the tokens after a given release time.
 */
contract S3Stake /*is TokenTimelock*/ {

    //using SafeMath for uint256;
    //using SafeERC20 for IERC20;

    // ERC20 basic token contract being held
    S3Coin private _token;

    // beneficiary of tokens after they are released
    address private _beneficiary;

    // amount will be release each success call
    uint256 private _releaseAmount;

    // timestamp when token release is enabled
    uint32 private _releaseTime;

    // last given release at (timestamp)
    uint32 private _lastReleaseTime;


    constructor (S3Coin token, address beneficiary, uint256 releaseAmount, uint32 releaseTime) public {
        // solhint-disable-next-line not-rely-on-time
        //require(releaseTime > block.timestamp, "TokenTimelock: release time is before current time");

        _token = token;
        _beneficiary = beneficiary;
        _releaseTime = releaseTime;
        _releaseAmount = releaseAmount;
        _lastReleaseTime = _releaseTime;
    }

    /**
     * @return the token being held.
     */
    function token() public view returns (S3Coin) {
        return _token;
    }

    /**
     * @return the beneficiary of the tokens.
     */
    function beneficiary() public view returns (address) {
        return _beneficiary;
    }

    /**
     * @return the time since then the tokens can be released.
     */
    function releaseTime() public view returns (uint32) {
        return _releaseTime;
    }

    /**
     * @return amount of token can be released a time.
     */
    function releaseAmount() public view returns (uint256) {
        return _releaseAmount;
    }

    /**
     * @return last released time.
     */
    function lastReleaseTime() public view returns (uint32) {
        return _lastReleaseTime;
    }

    /**
     * @return balance of the stake.
     */
    function balance() public view returns (uint256) {
        return _token.balanceOf(address(this));
    }

    /**
     * @notice Transfers tokens held by timelock to beneficiary base on release rate (5%) / week (7 days).
     */
    function release() public returns (bool) {
        uint256 amount = _token.balanceOf(address(this));
        require(amount > 0, "S3Stake: no tokens to release");

        // solhint-disable-next-line not-rely-on-time
        uint lastBlockTime = block.timestamp;

        require(lastBlockTime >= _releaseTime, "S3Stake: current time is before release time");

        // only able to release after each 7-days (7 * 24* 3600 = 604,800)
        uint32 nowReleaseTime = _lastReleaseTime + 604800;
        require(lastBlockTime >= nowReleaseTime, "S3Stake: token is only able to release each week (7 days)");

        // calculate number of tokens to release
        uint256 releasableAmount = (amount > _releaseAmount) ? _releaseAmount : amount;

        // transfer token to beneficiary address
        _token.transfer(_beneficiary, releasableAmount);

        // save release time
        _lastReleaseTime = nowReleaseTime;

        return true;
    }
}

pragma solidity ^0.5.0;

/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}