pragma solidity 0.5.8;

// File: node_modules\openzeppelin-solidity\contracts\token\ERC20\IERC20.sol

/**
 * @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);
}

// File: node_modules\openzeppelin-solidity\contracts\math\SafeMath.sol

/**
 * @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;
    }
}

// File: node_modules\openzeppelin-solidity\contracts\token\ERC20\ERC20.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) internal _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));
    }
}

// File: J\contracts\IPFS5A.sol

contract IPFS5A is ERC20 {
    string public constant name = "Filecoin buy agreement 5A"; 
    string public constant symbol = "IPFS5A"; 
    uint8 public constant decimals = 8; 
    uint256 public constant initialSupply = 2000000 * (10 ** uint256(decimals));
    
    constructor() public {
        super._mint(msg.sender, initialSupply);
        owner = msg.sender;
    }

    //ownership
    address public owner;

    event OwnershipRenounced(address indexed previousOwner);
    event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
    );

    modifier onlyOwner() {
        require(msg.sender == owner, "Not owner");
        _;
    }

  /**
   * @dev Allows the current owner to relinquish control of the contract.
   * @notice Renouncing to ownership will leave the contract without an owner.
   * It will not be possible to call the functions with the `onlyOwner`
   * modifier anymore.
   */
    function renounceOwnership() public onlyOwner {
        emit OwnershipRenounced(owner);
        owner = address(0);
    }

  /**
   * @dev Allows the current owner to transfer control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
    function transferOwnership(address _newOwner) public onlyOwner {
        _transferOwnership(_newOwner);
    }

  /**
   * @dev Transfers control of the contract to a newOwner.
   * @param _newOwner The address to transfer ownership to.
   */
    function _transferOwnership(address _newOwner) internal {
        require(_newOwner != address(0), "Already owner");
        emit OwnershipTransferred(owner, _newOwner);
        owner = _newOwner;
    }

    //pausable
    event Pause();
    event Unpause();

    bool public paused = false;
    
    /**
    * @dev Modifier to make a function callable only when the contract is not paused.
    */
    modifier whenNotPaused() {
        require(!paused, "Paused by owner");
        _;
    }

    /**
    * @dev Modifier to make a function callable only when the contract is paused.
    */
    modifier whenPaused() {
        require(paused, "Not paused now");
        _;
    }

    /**
    * @dev called by the owner to pause, triggers stopped state
    */
    function pause() public onlyOwner whenNotPaused {
        paused = true;
        emit Pause();
    }

    /**
    * @dev called by the owner to unpause, returns to normal state
    */
    function unpause() public onlyOwner whenPaused {
        paused = false;
        emit Unpause();
    }

    //freezable
    event Frozen(address target);
    event Unfrozen(address target);

    mapping(address => bool) internal freezes;

    modifier whenNotFrozen() {
        require(!freezes[msg.sender], "Sender account is locked.");
        _;
    }

    function freeze(address _target) public onlyOwner {
        freezes[_target] = true;
        emit Frozen(_target);
    }

    function unfreeze(address _target) public onlyOwner {
        freezes[_target] = false;
        emit Unfrozen(_target);
    }

    function isFrozen(address _target) public view returns (bool) {
        return freezes[_target];
    }

    function transfer(
        address _to,
        uint256 _value
    )
      public
      whenNotFrozen
      whenNotPaused
      returns (bool)
    {
        releaseLock(msg.sender);
        return super.transfer(_to, _value);
    }

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
      public
      whenNotPaused
      returns (bool)
    {
        require(!freezes[_from], "From account is locked.");
        releaseLock(_from);
        return super.transferFrom(_from, _to, _value);
    }

    //mintable
    event Mint(address indexed to, uint256 amount);

    function mint(
        address _to,
        uint256 _amount
    )
      public
      onlyOwner
      returns (bool)
    {
        super._mint(_to, _amount);
        emit Mint(_to, _amount);
        return true;
    }

    //burnable
    event Burn(address indexed burner, uint256 value);

    function burn(address _who, uint256 _value) public onlyOwner {
        require(_value <= super.balanceOf(_who), "Balance is too small.");

        _burn(_who, _value);
        emit Burn(_who, _value);
    }

    //lockable
    struct LockInfo {
        uint256 releaseTime;
        uint256 balance;
    }
    mapping(address => LockInfo[]) internal lockInfo;

    event Lock(address indexed holder, uint256 value, uint256 releaseTime);
    event Unlock(address indexed holder, uint256 value);

    function balanceOf(address _holder) public view returns (uint256 balance) {
        uint256 lockedBalance = 0;
        for(uint256 i = 0; i < lockInfo[_holder].length ; i++ ) {
            lockedBalance = lockedBalance.add(lockInfo[_holder][i].balance);
        }
        return super.balanceOf(_holder).add(lockedBalance);
    }

    function releaseLock(address _holder) internal {

        for(uint256 i = 0; i < lockInfo[_holder].length ; i++ ) {
            if (lockInfo[_holder][i].releaseTime <= now) {
                _balances[_holder] = _balances[_holder].add(lockInfo[_holder][i].balance);
                emit Unlock(_holder, lockInfo[_holder][i].balance);
                lockInfo[_holder][i].balance = 0;

                if (i != lockInfo[_holder].length - 1) {
                    lockInfo[_holder][i] = lockInfo[_holder][lockInfo[_holder].length - 1];
                    i--;
                }
                lockInfo[_holder].length--;

            }
        }
    }
    function lockCount(address _holder) public view returns (uint256) {
        return lockInfo[_holder].length;
    }
    function lockState(address _holder, uint256 _idx) public view returns (uint256, uint256) {
        return (lockInfo[_holder][_idx].releaseTime, lockInfo[_holder][_idx].balance);
    }

    function lock(address _holder, uint256 _amount, uint256 _releaseTime) public onlyOwner {
        require(super.balanceOf(_holder) >= _amount, "Balance is too small.");
        _balances[_holder] = _balances[_holder].sub(_amount);
        lockInfo[_holder].push(
            LockInfo(_releaseTime, _amount)
        );
        emit Lock(_holder, _amount, _releaseTime);
    }

    function lockAfter(address _holder, uint256 _amount, uint256 _afterTime) public onlyOwner {
        require(super.balanceOf(_holder) >= _amount, "Balance is too small.");
        _balances[_holder] = _balances[_holder].sub(_amount);
        lockInfo[_holder].push(
            LockInfo(now + _afterTime, _amount)
        );
        emit Lock(_holder, _amount, now + _afterTime);
    }

    function unlock(address _holder, uint256 i) public onlyOwner {
        require(i < lockInfo[_holder].length, "No lock information.");

        _balances[_holder] = _balances[_holder].add(lockInfo[_holder][i].balance);
        emit Unlock(_holder, lockInfo[_holder][i].balance);
        lockInfo[_holder][i].balance = 0;

        if (i != lockInfo[_holder].length - 1) {
            lockInfo[_holder][i] = lockInfo[_holder][lockInfo[_holder].length - 1];
        }
        lockInfo[_holder].length--;
    }

    function transferWithLock(address _to, uint256 _value, uint256 _releaseTime) public onlyOwner returns (bool) {
        require(_to != address(0), "wrong address");
        require(_value <= super.balanceOf(owner), "Not enough balance");

        _balances[owner] = _balances[owner].sub(_value);
        lockInfo[_to].push(
            LockInfo(_releaseTime, _value)
        );
        emit Transfer(owner, _to, _value);
        emit Lock(_to, _value, _releaseTime);

        return true;
    }

    function transferWithLockAfter(address _to, uint256 _value, uint256 _afterTime) public onlyOwner returns (bool) {
        require(_to != address(0), "wrong address");
        require(_value <= super.balanceOf(owner), "Not enough balance");

        _balances[owner] = _balances[owner].sub(_value);
        lockInfo[_to].push(
            LockInfo(now + _afterTime, _value)
        );
        emit Transfer(owner, _to, _value);
        emit Lock(_to, _value, now + _afterTime);

        return true;
    }

    function currentTime() public view returns (uint256) {
        return now;
    }

    function afterTime(uint256 _value) public view returns (uint256) {
        return now + _value;
    }

    //airdrop
    mapping (address => uint256) public airDropHistory;
    event AirDrop(address _receiver, uint256 _amount);

    function dropToken(address[] memory receivers, uint256[] memory values) onlyOwner public {
    require(receivers.length != 0);
    require(receivers.length == values.length);

    for (uint256 i = 0; i < receivers.length; i++) {
      address receiver = receivers[i];
      uint256 amount = values[i];

      transfer(receiver, amount);
      airDropHistory[receiver] += amount;

      emit AirDrop(receiver, amount);
    }
  }
}