ServiceFriendlyToken.sol

/*

                    GNU GENERAL PUBLIC LICENSE
                       Version 3, 29 June 2007

 Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

                            Preamble

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                       TERMS AND CONDITIONS

  0. Definitions.

  "This License" refers to version 3 of the GNU General Public License.

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  Moreover, your license from a particular copyright holder is
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  10. Automatic Licensing of Downstream Recipients.

  Each time you convey a covered work, the recipient automatically
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  11. Patents.

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consistent with the requirements of this License, to extend the patent
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  If, pursuant to or in connection with a single transaction or
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or that patent license was granted, prior to 28 March 2007.

  Nothing in this License shall be construed as excluding or limiting
any implied license or other defenses to infringement that may
otherwise be available to you under applicable patent law.

  12. No Surrender of Others' Freedom.

  If conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License.  If you cannot convey a
covered work so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you may
not convey it at all.  For example, if you agree to terms that obligate you
to collect a royalty for further conveying from those to whom you convey
the Program, the only way you could satisfy both those terms and this
License would be to refrain entirely from conveying the Program.

  13. Use with the GNU Affero General Public License.

  Notwithstanding any other provision of this License, you have
permission to link or combine any covered work with a work licensed
under version 3 of the GNU Affero General Public License into a single
combined work, and to convey the resulting work.  The terms of this
License will continue to apply to the part which is the covered work,
but the special requirements of the GNU Affero General Public License,
section 13, concerning interaction through a network will apply to the
combination as such.

  14. Revised Versions of this License.

  The Free Software Foundation may publish revised and/or new versions of
the GNU General Public License from time to time.  Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.

  Each version is given a distinguishing version number.  If the
Program specifies that a certain numbered version of the GNU General
Public License "or any later version" applies to it, you have the
option of following the terms and conditions either of that numbered
version or of any later version published by the Free Software
Foundation.  If the Program does not specify a version number of the
GNU General Public License, you may choose any version ever published
by the Free Software Foundation.

  If the Program specifies that a proxy can decide which future
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to choose that version for the Program.

  Later license versions may give you additional or different
permissions.  However, no additional obligations are imposed on any
author or copyright holder as a result of your choosing to follow a
later version.

  15. Disclaimer of Warranty.

  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

  16. Limitation of Liability.

  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.

  17. Interpretation of Sections 15 and 16.

  If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.

                     END OF TERMS AND CONDITIONS

            How to Apply These Terms to Your New Programs

  If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.

  To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.

    ServiceFriendlyToken
    Copyright (C) 2018 FST Network Pte Ltd

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.

Also add information on how to contact you by electronic and paper mail.

  If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:

    ServiceFriendlyToken  Copyright (C) 2018 FST Network Pte Ltd
    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
    This is free software, and you are welcome to redistribute it
    under certain conditions; type `show c' for details.

The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License.  Of course, your program's commands
might be different; for a GUI interface, you would use an "about box".

  You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
<https://www.gnu.org/licenses/>.

  The GNU General Public License does not permit incorporating your program
into proprietary programs.  If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications with
the library.  If this is what you want to do, use the GNU Lesser General
Public License instead of this License.  But first, please read
<https://www.gnu.org/licenses/why-not-lgpl.html>.

*/

pragma solidity ^0.4.24;
pragma experimental "v0.5.0";
pragma experimental ABIEncoderV2;

library AddressExtension {

  function isValid(address _address) internal pure returns (bool) {
    return 0 != _address;
  }

  function isAccount(address _address) internal view returns (bool result) {
    assembly {
      result := iszero(extcodesize(_address))
    }
  }

  function toBytes(address _address) internal pure returns (bytes b) {
   assembly {
      let m := mload(0x40)
      mstore(add(m, 20), xor(0x140000000000000000000000000000000000000000, _address))
      mstore(0x40, add(m, 52))
      b := m
    }
  }
}

library Math {

  struct Fraction {
    uint256 numerator;
    uint256 denominator;
  }

  function isPositive(Fraction memory fraction) internal pure returns (bool) {
    return fraction.numerator > 0 && fraction.denominator > 0;
  }

  function mul(uint256 a, uint256 b) internal pure returns (uint256 r) {
    r = a * b;
    require((a == 0) || (r / a == b));
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256 r) {
    r = a / b;
  }

  function sub(uint256 a, uint256 b) internal pure returns (uint256 r) {
    require((r = a - b) <= a);
  }

  function add(uint256 a, uint256 b) internal pure returns (uint256 r) {
    require((r = a + b) >= a);
  }

  function min(uint256 x, uint256 y) internal pure returns (uint256 r) {
    return x <= y ? x : y;
  }

  function max(uint256 x, uint256 y) internal pure returns (uint256 r) {
    return x >= y ? x : y;
  }

  function mulDiv(uint256 value, uint256 m, uint256 d) internal pure returns (uint256 r) {
    r = value * m;
    if (r / value == m) {
      r /= d;
    } else {
      r = mul(value / d, m);
    }
  }

  function mulDivCeil(uint256 value, uint256 m, uint256 d) internal pure returns (uint256 r) {
    r = value * m;
    if (r / value == m) {
      if (r % d == 0) {
        r /= d;
      } else {
        r = (r / d) + 1;
      }
    } else {
      r = mul(value / d, m);
      if (value % d != 0) {
        r += 1;
      }
    }
  }

  function mul(uint256 x, Fraction memory f) internal pure returns (uint256) {
    return mulDiv(x, f.numerator, f.denominator);
  }

  function mulCeil(uint256 x, Fraction memory f) internal pure returns (uint256) {
    return mulDivCeil(x, f.numerator, f.denominator);
  }

  function div(uint256 x, Fraction memory f) internal pure returns (uint256) {
    return mulDiv(x, f.denominator, f.numerator);
  }

  function divCeil(uint256 x, Fraction memory f) internal pure returns (uint256) {
    return mulDivCeil(x, f.denominator, f.numerator);
  }

  function mul(Fraction memory x, Fraction memory y) internal pure returns (Math.Fraction) {
    return Math.Fraction({
      numerator: mul(x.numerator, y.numerator),
      denominator: mul(x.denominator, y.denominator)
    });
  }
}

contract ERC20 {

  event Transfer(address indexed from, address indexed to, uint256 value);
  event Approval(address indexed owner, address indexed spender, uint256 value);

  function balanceOf(address owner) public view returns (uint256);
  function allowance(address owner, address spender) 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);
}

contract SecureERC20 is ERC20 {

  event SetERC20ApproveChecking(bool approveChecking);

  function approve(address spender, uint256 expectedValue, uint256 newValue) public returns (bool);
  function increaseAllowance(address spender, uint256 value) public returns (bool);
  function decreaseAllowance(address spender, uint256 value, bool strict) public returns (bool);
  function setERC20ApproveChecking(bool approveChecking) public;
}

contract FsTKToken {

  enum DelegateMode { PublicMsgSender, PublicTxOrigin, PrivateMsgSender, PrivateTxOrigin }

  event IncreaseNonce(address indexed from, uint256 nonce);
  event SetupDirectDebit(address indexed debtor, address indexed receiver, DirectDebitInfo info);
  event TerminateDirectDebit(address indexed debtor, address indexed receiver);
  event WithdrawDirectDebitFailure(address indexed debtor, address indexed receiver);

  event SetDelegate(bool isDelegateEnable);
  event SetDirectDebit(bool isDirectDebitEnable);

  struct DirectDebitInfo {
    uint256 amount;
    uint256 startTime;
    uint256 interval;
  }

  struct DirectDebit {
    DirectDebitInfo info;
    uint256 epoch;
  }

  struct Instrument {
    uint256 allowance;
    DirectDebit directDebit;
  }

  struct Account {
    uint256 balance;
    uint256 nonce;
    mapping (address => Instrument) instruments;
  }

  function spendableAllowance(address owner, address spender) public view returns (uint256);
  function transfer(uint256[] data) public returns (bool);
  function transferAndCall(address to, uint256 value, bytes data) public payable returns (bool);

  function nonceOf(address owner) public view returns (uint256);
  function increaseNonce() public returns (bool);
  function delegateTransferAndCall(
    uint256 nonce,
    uint256 fee,
    uint256 gasAmount,
    address to,
    uint256 value,
    bytes data,
    DelegateMode mode,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) public returns (bool);

  function directDebit(address debtor, address receiver) public view returns (DirectDebit);
  function setupDirectDebit(address receiver, DirectDebitInfo info) public returns (bool);
  function terminateDirectDebit(address receiver) public returns (bool);
  function withdrawDirectDebit(address debtor) public returns (bool);
  function withdrawDirectDebit(address[] debtors, bool strict) public returns (bool);
}

contract ERC20Like is SecureERC20, FsTKToken {
  using AddressExtension for address;
  using Math for uint256;

  bool public erc20ApproveChecking;
  bool public isDelegateEnable;
  bool public isDirectDebitEnable;

  mapping(address => Account) internal accounts;

  function balanceOf(address owner) public view returns (uint256) {
    return accounts[owner].balance;
  }

  function allowance(address owner, address spender) public view returns (uint256) {
    return accounts[owner].instruments[spender].allowance;
  }

  function transfer(address to, uint256 value) public returns (bool) {
    Account storage senderAccount = accounts[msg.sender];

    senderAccount.balance = senderAccount.balance.sub(value);
    accounts[to].balance += value;

    emit Transfer(msg.sender, to, value);
    return true;
  }

  function transferFrom(address from, address to, uint256 value) public returns (bool) {
    Account storage fromAccount = accounts[from];
    Instrument storage senderInstrument = fromAccount.instruments[msg.sender];

    fromAccount.balance = fromAccount.balance.sub(value);
    senderInstrument.allowance = senderInstrument.allowance.sub(value);
    accounts[to].balance += value;

    emit Transfer(from, to, value);
    return true;
  }

  function approve(address spender, uint256 value) public returns (bool) {
    Instrument storage spenderInstrument = accounts[msg.sender].instruments[spender];
    if (erc20ApproveChecking) {
      require((value == 0) || (spenderInstrument.allowance == 0));
    }

    emit Approval(
      msg.sender,
      spender,
      spenderInstrument.allowance = value
    );
    return true;
  }

  function setERC20ApproveChecking(bool approveChecking) public {
    emit SetERC20ApproveChecking(erc20ApproveChecking = approveChecking);
  }

  function approve(address spender, uint256 expectedValue, uint256 newValue) public returns (bool) {
    Instrument storage spenderInstrument = accounts[msg.sender].instruments[spender];
    require(spenderInstrument.allowance == expectedValue);

    emit Approval(
      msg.sender,
      spender,
      spenderInstrument.allowance = newValue
    );
    return true;
  }

  function increaseAllowance(address spender, uint256 value) public returns (bool) {
    Instrument storage spenderInstrument = accounts[msg.sender].instruments[spender];

    emit Approval(
      msg.sender,
      spender,
      spenderInstrument.allowance = spenderInstrument.allowance.add(value)
    );
    return true;
  }

  function decreaseAllowance(address spender, uint256 value, bool strict) public returns (bool) {
    Instrument storage spenderInstrument = accounts[msg.sender].instruments[spender];

    uint256 currentValue = spenderInstrument.allowance;
    uint256 newValue;
    if (strict) {
      newValue = currentValue.sub(value);
    } else if (value < currentValue) {
      newValue = currentValue - value;
    }

    emit Approval(
      msg.sender,
      spender,
      spenderInstrument.allowance = newValue
    );
    return true;
  }

  function setDelegate(bool delegate) public {
    emit SetDelegate(isDelegateEnable = delegate);
  }

  function setDirectDebit(bool directDebit) public {
    emit SetDirectDebit(isDirectDebitEnable = directDebit);
  }

  function spendableAllowance(address owner, address spender) public view returns (uint256) {
    Account storage ownerAccount = accounts[owner];
    return Math.min(
      ownerAccount.instruments[spender].allowance,
      ownerAccount.balance
    );
  }

  function transfer(uint256[] data) public returns (bool) {
    Account storage senderAccount = accounts[msg.sender];
    uint256 totalValue;

    for (uint256 i = 0; i < data.length; i++) {
      address receiver = address(data[i] >> 96);
      uint256 value = data[i] & 0xffffffffffffffffffffffff;

      totalValue = totalValue.add(value);
      accounts[receiver].balance += value;

      emit Transfer(msg.sender, receiver, value);
    }

    senderAccount.balance = senderAccount.balance.sub(totalValue);

    return true;
  }

  function transferAndCall(
    address to,
    uint256 value,
    bytes data
  )
    public
    payable
    returns (bool)
  {
    require(
      to != address(this) &&
      data.length >= 68 &&
      transfer(to, value)
    );
    assembly {
        mstore(add(data, 36), value)
        mstore(add(data, 68), caller)
    }
    require(to.call.value(msg.value)(data));
    return true;
  }

  function nonceOf(address owner) public view returns (uint256) {
    return accounts[owner].nonce;
  }

  function increaseNonce() public returns (bool) {
    emit IncreaseNonce(msg.sender, accounts[msg.sender].nonce += 1);
  }

  function delegateTransferAndCall(
    uint256 nonce,
    uint256 fee,
    uint256 gasAmount,
    address to,
    uint256 value,
    bytes data,
    DelegateMode mode,
    uint8 v,
    bytes32 r,
    bytes32 s
  )
    public
    returns (bool)
  {
    require(isDelegateEnable);
    require(to != address(this));
    address signer;
    address relayer;
    if (mode == DelegateMode.PublicMsgSender) {
      signer = ecrecover(
        keccak256(abi.encodePacked(this, nonce, fee, gasAmount, to, value, data, mode, address(0))),
        v,
        r,
        s
      );
      relayer = msg.sender;
    } else if (mode == DelegateMode.PublicTxOrigin) {
      signer = ecrecover(
        keccak256(abi.encodePacked(this, nonce, fee, gasAmount, to, value, data, mode, address(0))),
        v,
        r,
        s
      );
      relayer = tx.origin;
    } else if (mode == DelegateMode.PrivateMsgSender) {
      signer = ecrecover(
        keccak256(abi.encodePacked(this, nonce, fee, gasAmount, to, value, data, mode, msg.sender)),
        v,
        r,
        s
      );
      relayer = msg.sender;
    } else if (mode == DelegateMode.PrivateTxOrigin) {
      signer = ecrecover(
        keccak256(abi.encodePacked(this, nonce, fee, gasAmount, to, value, data, mode, tx.origin)),
        v,
        r,
        s
      );
      relayer = tx.origin;
    } else {
      revert();
    }

    Account storage signerAccount = accounts[signer];
    require(nonce == signerAccount.nonce);
    emit IncreaseNonce(signer, signerAccount.nonce += 1);

    signerAccount.balance = signerAccount.balance.sub(value.add(fee));
    accounts[to].balance += value;
    if (fee != 0) {
      accounts[relayer].balance += fee;
      emit Transfer(signer, relayer, fee);
    }

    if (!to.isAccount() && data.length >= 68) {
      assembly {
        mstore(add(data, 36), value)
        mstore(add(data, 68), signer)
      }
      if (to.call.gas(gasAmount)(data)) {
        emit Transfer(signer, to, value);
      } else {
        signerAccount.balance += value;
        accounts[to].balance -= value;
      }
    } else {
      emit Transfer(signer, to, value);
    }

    return true;
  }

  function directDebit(address debtor, address receiver) public view returns (DirectDebit) {
    return accounts[debtor].instruments[receiver].directDebit;
  }

  function setupDirectDebit(
    address receiver,
    DirectDebitInfo info
  )
    public
    returns (bool)
  {
    accounts[msg.sender].instruments[receiver].directDebit = DirectDebit({
      info: info,
      epoch: 0
    });

    emit SetupDirectDebit(msg.sender, receiver, info);
    return true;
  }

  function terminateDirectDebit(address receiver) public returns (bool) {
    delete accounts[msg.sender].instruments[receiver].directDebit;

    emit TerminateDirectDebit(msg.sender, receiver);
    return true;
  }

  function withdrawDirectDebit(address debtor) public returns (bool) {
    require(isDirectDebitEnable);
    Account storage debtorAccount = accounts[debtor];
    DirectDebit storage debit = debtorAccount.instruments[msg.sender].directDebit;
    uint256 epoch = (block.timestamp.sub(debit.info.startTime) / debit.info.interval).add(1);
    uint256 amount = epoch.sub(debit.epoch).mul(debit.info.amount);
    require(amount > 0);
    debtorAccount.balance = debtorAccount.balance.sub(amount);
    accounts[msg.sender].balance += amount;
    debit.epoch = epoch;

    emit Transfer(debtor, msg.sender, amount);
    return true;
  }

  function withdrawDirectDebit(address[] debtors, bool strict) public returns (bool result) {
    require(isDirectDebitEnable);
    Account storage receiverAccount = accounts[msg.sender];
    result = true;
    uint256 total;

    for (uint256 i = 0; i < debtors.length; i++) {
      address debtor = debtors[i];
      Account storage debtorAccount = accounts[debtor];
      DirectDebit storage debit = debtorAccount.instruments[msg.sender].directDebit;
      uint256 epoch = (block.timestamp.sub(debit.info.startTime) / debit.info.interval).add(1);
      uint256 amount = epoch.sub(debit.epoch).mul(debit.info.amount);
      require(amount > 0);
      uint256 debtorBalance = debtorAccount.balance;

      if (amount > debtorBalance) {
        if (strict) {
          revert();
        }
        result = false;
        emit WithdrawDirectDebitFailure(debtor, msg.sender);
      } else {
        debtorAccount.balance = debtorBalance - amount;
        total += amount;
        debit.epoch = epoch;

        emit Transfer(debtor, msg.sender, amount);
      }
    }

    receiverAccount.balance += total;
  }
}

contract ServiceFriendlyToken is ERC20Like {

  string public name;
  string public symbol;
  uint256 public totalSupply;
  uint8 public constant decimals = 18;

  address public issuer;

  constructor(
    address _issuer,
    string _name,
    string _symbol,
    uint256 _totalSupply
  )
    public
  {
    name = _name;
    symbol = _symbol;
    totalSupply = _totalSupply;

    issuer = _issuer;

    accounts[_issuer].balance = _totalSupply;
    emit Transfer(address(0), _issuer, _totalSupply);
  }

  function setERC20ApproveChecking(bool approveChecking) public {
    require(msg.sender == issuer);
    super.setERC20ApproveChecking(approveChecking);
  }

  function setDelegate(bool delegate) public {
    require(msg.sender == issuer);
    super.setDelegate(delegate);
  }

  function setDirectDebit(bool directDebit) public {
    require(msg.sender == issuer);
    super.setDirectDebit(directDebit);
  }
}