// GoToken is an open community aims to explore a decentralized collaboration network incentived and well-governed through blockchain. Learn more about gotoken @ forum.gotoken.io

pragma solidity >=0.4.21 <0.6.0;

contract ApproveAndCallFallBack {
    function receiveApproval(
        address from,
        uint256 _amount,
        address _token,
        bytes memory _data
    ) public;
}

contract ERC20Base {
    string public name;                //The Token's name: e.g. GTToken
    uint8 public decimals;             //Number of decimals of the smallest unit
    string public symbol;              //An identifier: e.g. REP
    string public version = "GTT_0.1"; //An arbitrary versioning scheme

////////////////
// Events
////////////////
    event Transfer(address indexed _from, address indexed _to, uint256 _amount);
    event Approval(
        address indexed _owner,
        address indexed _spender,
        uint256 _amount
        );

    /// @dev `Checkpoint` is the structure that attaches a block number to a
    ///  given value, the block number attached is the one that last changed the
    ///  value
    struct Checkpoint {
        // `fromBlock` is the block number that the value was generated from
        uint128 fromBlock;
        // `value` is the amount of tokens at a specific block number
        uint128 value;
    }

    // `parentToken` is the Token address that was cloned to produce this token;
    //  it will be 0x0 for a token that was not cloned
    ERC20Base public parentToken;

    // `parentSnapShotBlock` is the block number from the Parent Token that was
    //  used to determine the initial distribution of the Clone Token
    uint public parentSnapShotBlock;

    // `creationBlock` is the block number that the Clone Token was created
    uint public creationBlock;

    // `balances` is the map that tracks the balance of each address, in this
    //  contract when the balance changes the block number that the change
    //  occurred is also included in the map
    mapping (address => Checkpoint[]) balances;

    // `allowed` tracks any extra transfer rights as in all ERC20 tokens
    mapping (address => mapping (address => uint256)) allowed;

    // Tracks the history of the `totalSupply` of the token
    Checkpoint[] totalSupplyHistory;

    // Flag that determines if the token is transferable or not.
    bool public transfersEnabled;

////////////////
// Constructor
////////////////

    /// @notice Constructor to create a ERC20Base
    /// @param _parentToken Address of the parent token, set to 0x0 if it is a
    ///  new token
    /// @param _parentSnapShotBlock Block of the parent token that will
    ///  determine the initial distribution of the clone token, set to 0 if it
    ///  is a new token
    /// @param _tokenName Name of the new token
    /// @param _decimalUnits Number of decimals of the new token
    /// @param _tokenSymbol Token Symbol for the new token
    /// @param _transfersEnabled If true, tokens will be able to be transferred
    constructor(
        ERC20Base _parentToken,
        uint _parentSnapShotBlock,
        string memory _tokenName,
        uint8 _decimalUnits,
        string memory _tokenSymbol,
        bool _transfersEnabled
    )  public
    {
        name = _tokenName;                                 // Set the name
        decimals = _decimalUnits;                          // Set the decimals
        symbol = _tokenSymbol;                             // Set the symbol
        parentToken = _parentToken;
        parentSnapShotBlock = _parentSnapShotBlock;
        transfersEnabled = _transfersEnabled;
        creationBlock = block.number;
    }


///////////////////
// ERC20 Methods
///////////////////

    /// @notice Send `_amount` tokens to `_to` from `msg.sender`
    /// @param _to The address of the recipient
    /// @param _amount The amount of tokens to be transferred
    /// @return Whether the transfer was successful or not
    function transfer(address _to, uint256 _amount) public returns (bool success) {
        require(transfersEnabled);
        return doTransfer(msg.sender, _to, _amount);
    }

    /// @notice Send `_amount` tokens to `_to` from `_from` on the condition it
    ///  is approved by `_from`
    /// @param _from The address holding the tokens being transferred
    /// @param _to The address of the recipient
    /// @param _amount The amount of tokens to be transferred
    /// @return True if the transfer was successful
    function transferFrom(address _from, address _to, uint256 _amount) public returns (bool success) {
        require(transfersEnabled);

        // The standard ERC 20 transferFrom functionality
        if (allowed[_from][msg.sender] < _amount)
            return false;
        allowed[_from][msg.sender] -= _amount;
        return doTransfer(_from, _to, _amount);
    }

    /// @dev This is the actual transfer function in the token contract, it can
    ///  only be called by other functions in this contract.
    /// @param _from The address holding the tokens being transferred
    /// @param _to The address of the recipient
    /// @param _amount The amount of tokens to be transferred
    /// @return True if the transfer was successful
    function doTransfer(address _from, address _to, uint _amount) internal returns(bool) {
        if (_amount == 0) {
            return true;
        }
        require(parentSnapShotBlock < block.number);
        // Do not allow transfer to 0x0 or the token contract itself
        require((_to != address(0)) && (_to != address(this)));
        // If the amount being transfered is more than the balance of the
        //  account the transfer returns false
        uint256 previousBalanceFrom = balanceOfAt(_from, block.number);
        if (previousBalanceFrom < _amount) {
            return false;
        }
        // First update the balance array with the new value for the address
        //  sending the tokens
        updateValueAtNow(balances[_from], previousBalanceFrom - _amount);
        // Then update the balance array with the new value for the address
        //  receiving the tokens
        uint256 previousBalanceTo = balanceOfAt(_to, block.number);
        require(previousBalanceTo + _amount >= previousBalanceTo); // Check for overflow
        updateValueAtNow(balances[_to], previousBalanceTo + _amount);
        // An event to make the transfer easy to find on the blockchain
        emit Transfer(_from, _to, _amount);
        return true;
    }

    /// @param _owner The address that's balance is being requested
    /// @return The balance of `_owner` at the current block
    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balanceOfAt(_owner, block.number);
    }

    /// @notice `msg.sender` approves `_spender` to spend `_amount` tokens on
    ///  its behalf. This is a modified version of the ERC20 approve function
    ///  to be a little bit safer
    /// @param _spender The address of the account able to transfer the tokens
    /// @param _amount The amount of tokens to be approved for transfer
    /// @return True if the approval was successful
    function approve(address _spender, uint256 _amount) public returns (bool success) {
        require(transfersEnabled);

        // To change the approve amount you first have to reduce the addresses`
        //  allowance to zero by calling `approve(_spender,0)` if it is not
        //  already 0 to mitigate the race condition described here:
        //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
        require((_amount == 0) || (allowed[msg.sender][_spender] == 0));

        allowed[msg.sender][_spender] = _amount;
        emit Approval(msg.sender, _spender, _amount);
        return true;
    }

    /// @dev This function makes it easy to read the `allowed[]` map
    /// @param _owner The address of the account that owns the token
    /// @param _spender The address of the account able to transfer the tokens
    /// @return Amount of remaining tokens of _owner that _spender is allowed
    ///  to spend
    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }

    /// @notice `msg.sender` approves `_spender` to send `_amount` tokens on
    ///  its behalf, and then a function is triggered in the contract that is
    ///  being approved, `_spender`. This allows users to use their tokens to
    ///  interact with contracts in one function call instead of two
    /// @param _spender The address of the contract able to transfer the tokens
    /// @param _amount The amount of tokens to be approved for transfer
    /// @return True if the function call was successful
    function approveAndCall(ApproveAndCallFallBack _spender, uint256 _amount, bytes memory _extraData) public returns (bool success) {
        require(approve(address(_spender), _amount));

        _spender.receiveApproval(
            msg.sender,
            _amount,
            address(this),
            _extraData
        );

        return true;
    }

    /// @dev This function makes it easy to get the total number of tokens
    /// @return The total number of tokens
    function totalSupply() public view returns (uint) {
        return totalSupplyAt(block.number);
    }


////////////////
// Query balance and totalSupply in History
////////////////

    /// @dev Queries the balance of `_owner` at a specific `_blockNumber`
    /// @param _owner The address from which the balance will be retrieved
    /// @param _blockNumber The block number when the balance is queried
    /// @return The balance at `_blockNumber`
    function balanceOfAt(address _owner, uint _blockNumber) public view returns (uint) {

        // These next few lines are used when the balance of the token is
        //  requested before a check point was ever created for this token, it
        //  requires that the `parentToken.balanceOfAt` be queried at the
        //  genesis block for that token as this contains initial balance of
        //  this token
        if ((balances[_owner].length == 0) || (balances[_owner][0].fromBlock > _blockNumber)) {
            if (address(parentToken) != address(0)) {
                return parentToken.balanceOfAt(_owner, min(_blockNumber, parentSnapShotBlock));
            } else {
                // Has no parent
                return 0;
            }

        // This will return the expected balance during normal situations
        } else {
            return getValueAt(balances[_owner], _blockNumber);
        }
    }

    /// @notice Total amount of tokens at a specific `_blockNumber`.
    /// @param _blockNumber The block number when the totalSupply is queried
    /// @return The total amount of tokens at `_blockNumber`
    function totalSupplyAt(uint _blockNumber) public view returns(uint) {

        // These next few lines are used when the totalSupply of the token is
        //  requested before a check point was ever created for this token, it
        //  requires that the `parentToken.totalSupplyAt` be queried at the
        //  genesis block for this token as that contains totalSupply of this
        //  token at this block number.
        if ((totalSupplyHistory.length == 0) || (totalSupplyHistory[0].fromBlock > _blockNumber)) {
            if (address(parentToken) != address(0)) {
                return parentToken.totalSupplyAt(min(_blockNumber, parentSnapShotBlock));
            } else {
                return 0;
            }

        // This will return the expected totalSupply during normal situations
        } else {
            return getValueAt(totalSupplyHistory, _blockNumber);
        }
    }

////////////////
// Generate and destroy tokens
////////////////

    /// @notice Generates `_amount` tokens that are assigned to `_owner`
    /// @param _owner The address that will be assigned the new tokens
    /// @param _amount The quantity of tokens generated
    /// @return True if the tokens are generated correctly
    function _generateTokens(address _owner, uint _amount) internal returns (bool) {
        uint curTotalSupply = totalSupply();
        require(curTotalSupply + _amount >= curTotalSupply); // Check for overflow
        uint previousBalanceTo = balanceOf(_owner);
        require(previousBalanceTo + _amount >= previousBalanceTo); // Check for overflow
        updateValueAtNow(totalSupplyHistory, curTotalSupply + _amount);
        updateValueAtNow(balances[_owner], previousBalanceTo + _amount);
        emit Transfer(address(0), _owner, _amount);
        return true;
    }


    /// @notice Burns `_amount` tokens from `_owner`
    /// @param _owner The address that will lose the tokens
    /// @param _amount The quantity of tokens to burn
    /// @return True if the tokens are burned correctly
    function _destroyTokens(address _owner, uint _amount) internal returns (bool) {
        uint curTotalSupply = totalSupply();
        require(curTotalSupply >= _amount);
        uint previousBalanceFrom = balanceOf(_owner);
        require(previousBalanceFrom >= _amount);
        updateValueAtNow(totalSupplyHistory, curTotalSupply - _amount);
        updateValueAtNow(balances[_owner], previousBalanceFrom - _amount);
        emit Transfer(_owner, address(0), _amount);
        return true;
    }

////////////////
// Enable tokens transfers
////////////////


    /// @notice Enables token holders to transfer their tokens freely if true
    /// @param _transfersEnabled True if transfers are allowed in the clone
    function _enableTransfers(bool _transfersEnabled) internal {
        transfersEnabled = _transfersEnabled;
    }

////////////////
// Internal helper functions to query and set a value in a snapshot array
////////////////

    /// @dev `getValueAt` retrieves the number of tokens at a given block number
    /// @param checkpoints The history of values being queried
    /// @param _block The block number to retrieve the value at
    /// @return The number of tokens being queried
    function getValueAt(Checkpoint[] storage checkpoints, uint _block) internal view returns (uint) {
        if (checkpoints.length == 0)
            return 0;

        // Shortcut for the actual value
        if (_block >= checkpoints[checkpoints.length-1].fromBlock)
            return checkpoints[checkpoints.length-1].value;
        if (_block < checkpoints[0].fromBlock)
            return 0;

        // Binary search of the value in the array
        uint min = 0;
        uint max = checkpoints.length-1;
        while (max > min) {
            uint mid = (max + min + 1) / 2;
            if (checkpoints[mid].fromBlock<=_block) {
                min = mid;
            } else {
                max = mid-1;
            }
        }
        return checkpoints[min].value;
    }

    /// @dev `updateValueAtNow` used to update the `balances` map and the
    ///  `totalSupplyHistory`
    /// @param checkpoints The history of data being updated
    /// @param _value The new number of tokens
    function updateValueAtNow(Checkpoint[] storage checkpoints, uint _value) internal {
        if ((checkpoints.length == 0) || (checkpoints[checkpoints.length - 1].fromBlock < block.number)) {
            Checkpoint storage newCheckPoint = checkpoints[checkpoints.length++];
            newCheckPoint.fromBlock = uint128(block.number);
            newCheckPoint.value = uint128(_value);
        } else {
            Checkpoint storage oldCheckPoint = checkpoints[checkpoints.length - 1];
            oldCheckPoint.value = uint128(_value);
        }
    }

    /// @dev Helper function to return a min betwen the two uints
    function min(uint a, uint b) pure internal returns (uint) {
        return a < b ? a : b;
    }

    function () external payable {
        require(false, "cannot transfer ether to this contract");
    }
}


pragma solidity >=0.4.21 <0.6.0;

contract TransferableToken{
    function balanceOf(address _owner) public returns (uint256 balance) ;
    function transfer(address _to, uint256 _amount) public returns (bool success) ;
    function transferFrom(address _from, address _to, uint256 _amount) public returns (bool success) ;
}


contract TokenClaimer{

    event ClaimedTokens(address indexed _token, address indexed _to, uint _amount);
    /// @notice This method can be used by the controller to extract mistakenly
    ///  sent tokens to this contract.
    /// @param _token The address of the token contract that you want to recover
    ///  set to 0 in case you want to extract ether.
  function _claimStdTokens(address _token, address payable to) internal {
        if (_token == address(0x0)) {
            to.transfer(address(this).balance);
            return;
        }
        TransferableToken token = TransferableToken(_token);
        uint balance = token.balanceOf(address(this));

        (bool status,) = _token.call(abi.encodeWithSignature("transfer(address,uint256)", to, balance));
        require(status, "call failed");
        emit ClaimedTokens(_token, to, balance);
  }
}


pragma solidity >=0.4.21 <0.6.0;

contract TrustListInterface{
  function is_trusted(address addr) public returns(bool);
}
contract TrustListTools{
  TrustListInterface public list;
  constructor(address _list) public {
    require(_list != address(0x0));
    list = TrustListInterface(_list);
  }

  modifier is_trusted(address addr){
    require(list.is_trusted(addr), "not a trusted issuer");
    _;
  }

}


pragma solidity >=0.4.21 <0.6.0;

contract MultiSigInterface{
  function update_and_check_reach_majority(uint64 id, string memory name, bytes32 hash, address sender) public returns (bool);
  function is_signer(address addr) public view returns(bool);
}

contract MultiSigTools{
  MultiSigInterface public multisig_contract;
  constructor(address _contract) public{
    require(_contract!= address(0x0));
    multisig_contract = MultiSigInterface(_contract);
  }

  modifier only_signer{
    require(multisig_contract.is_signer(msg.sender), "only a signer can call in MultiSigTools");
    _;
  }

  modifier is_majority_sig(uint64 id, string memory name) {
    bytes32 hash = keccak256(abi.encodePacked(msg.sig, msg.data));
    if(multisig_contract.update_and_check_reach_majority(id, name, hash, msg.sender)){
      _;
    }
  }

  event TransferMultiSig(address _old, address _new);

  function transfer_multisig(uint64 id, address _contract) public only_signer
  is_majority_sig(id, "transfer_multisig"){
    require(_contract != address(0x0));
    address old = address(multisig_contract);
    multisig_contract = MultiSigInterface(_contract);
    emit TransferMultiSig(old, _contract);
  }
}


pragma solidity >=0.4.21 <0.6.0;





contract GTToken is ERC20Base, MultiSigTools, TrustListTools, TokenClaimer{

  GTTokenFactory public tokenFactory;

  event NewCloneToken(address indexed _cloneToken, uint _snapshotBlock);

  constructor(
        GTTokenFactory _tokenFactory,
        ERC20Base _parentToken,
        uint _parentSnapShotBlock,
        string memory _tokenName,
        uint8 _decimalUnits,
        string memory _tokenSymbol,
        bool _transfersEnabled,
        address multisig,
        address _tlist)
    ERC20Base(_parentToken,
    _parentSnapShotBlock,
    _tokenName,
    _decimalUnits,
    _tokenSymbol,
    _transfersEnabled) MultiSigTools(multisig) TrustListTools(_tlist) public{
      tokenFactory = _tokenFactory;
    }

    function claimStdTokens(uint64 id, address _token, address payable to) public only_signer is_majority_sig(id, "claimStdTokens"){
      _claimStdTokens(_token, to);
    }

    function createCloneToken(
        string memory _cloneTokenName,
        uint8 _cloneDecimalUnits,
        string memory _cloneTokenSymbol,
        uint _snapshotBlock,
        bool _transfersEnabled,
        address _multisig,
        address _tlist
    )public returns(GTToken){

        uint256 snapshot = _snapshotBlock == 0 ? block.number - 1 : _snapshotBlock;
        GTToken cloneToken = tokenFactory.createCloneToken(this, snapshot,
            _cloneTokenName,
            _cloneDecimalUnits,
            _cloneTokenSymbol,
            _transfersEnabled,
            _multisig,
            _tlist
          );
        emit NewCloneToken(address(cloneToken), snapshot);
        return cloneToken;
    }

    function generateTokens(address _owner, uint _amount)
    public
    is_trusted(msg.sender)
    returns (bool){
      return _generateTokens(_owner, _amount);
    }

    function destroyTokens(address _owner, uint _amount)
    public
    is_trusted(msg.sender)
    returns (bool) {
      return _destroyTokens(_owner, _amount);
    }

    function enableTransfers(uint64 id, bool _transfersEnabled)
    public only_signer
    is_majority_sig(id, "enableTransfers"){
      _enableTransfers(_transfersEnabled);
    }
}

/// @dev This contract is used to generate clone contracts from a contract.
///  In solidity this is the way to create a contract from a contract of the
///  same class
contract GTTokenFactory {
  event NewToken(address indexed _cloneToken, uint _snapshotBlock);

    /// @notice Update the DApp by creating a new token with new functionalities
    ///  the msg.sender becomes the controller of this clone token
    /// @param _parentToken Address of the token being cloned
    /// @param _snapshotBlock Block of the parent token that will
    ///  determine the initial distribution of the clone token
    /// @param _tokenName Name of the new token
    /// @param _decimalUnits Number of decimals of the new token
    /// @param _tokenSymbol Token Symbol for the new token
    /// @param _transfersEnabled If true, tokens will be able to be transferred
    /// @return The address of the new token contract
    function createCloneToken(
        GTToken _parentToken,
        uint _snapshotBlock,
        string memory _tokenName,
        uint8 _decimalUnits,
        string memory _tokenSymbol,
        bool _transfersEnabled,
        address _multisig,
        address _tlist
    ) public returns (GTToken)
    {
        GTToken newToken = new GTToken(
            this,
            _parentToken,
            _snapshotBlock,
            _tokenName,
            _decimalUnits,
            _tokenSymbol,
            _transfersEnabled,
            _multisig,
            _tlist
        );
        emit NewToken(address(newToken), _snapshotBlock);

        return newToken;
    }
}