discover-dapps/contracts/token/MiniMeToken.sol

pragma solidity ^0.5.2;

/*
    Copyright 2016, Jordi Baylina
    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 <http://www.gnu.org/licenses/>.
 */
/**
 * @title MiniMeToken Contract
 * @author Jordi Baylina
 * @dev This token contract's goal is to make it easy for anyone to clone this
 *  token using the token distribution at a given block, this will allow DAO's
 *  and DApps to upgrade their features in a decentralized manner without
 *  affecting the original token
 * @dev It is ERC20 compliant, but still needs to under go further testing.
 */

import "./Controlled.sol";
import "./TokenController.sol";
import "./ApproveAndCallFallBack.sol";
import "./MiniMeTokenInterface.sol";
import "./TokenFactory.sol";

/**
 * @dev The actual token contract, the default controller is the msg.sender
 *  that deploys the contract, so usually this token will be deployed by a
 *  token controller contract, which Giveth will call a "Campaign"
 */


contract MiniMeToken is MiniMeTokenInterface, Controlled {

    string public name;                //The Token's name: e.g. DigixDAO Tokens
    uint8 public decimals;             //Number of decimals of the smallest unit
    string public symbol;              //An identifier: e.g. REP
    string public constant VERSION = "MMT_0.1"; //An arbitrary versioning scheme

    /**
     * @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
    MiniMeToken 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;

    // The factory used to create new clone tokens
    TokenFactory public tokenFactory;

////////////////
// Constructor
////////////////

    /** 
     * @notice Constructor to create a MiniMeToken
     * @param _tokenFactory The address of the MiniMeTokenFactory contract that
     *  will create the Clone token contracts, the token factory needs to be
     *  deployed first
     * @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(
        address _tokenFactory,
        address _parentToken,
        uint _parentSnapShotBlock,
        string memory _tokenName,
        uint8 _decimalUnits,
        string memory _tokenSymbol,
        bool _transfersEnabled
    ) 
        public
    {
        tokenFactory = TokenFactory(_tokenFactory);
        name = _tokenName;                                 // Set the name
        decimals = _decimalUnits;                          // Set the decimals
        symbol = _tokenSymbol;                             // Set the symbol
        parentToken = MiniMeToken(address(uint160(_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) external 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
    ) 
        external 
        returns (bool success)
    {

        // The controller of this contract can move tokens around at will,
        //  this is important to recognize! Confirm that you trust the
        //  controller of this contract, which in most situations should be
        //  another open source smart contract or 0x0
        if (msg.sender != controller) {
            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;
        }

        // Alerts the token controller of the transfer
        if (isContract(controller)) {
            require(TokenController(controller).onTransfer(_from, _to, _amount));
        }

        // 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;
    }

    function doApprove(
        address _from,
        address _spender,
        uint256 _amount
    )
        internal 
        returns (bool)
    {
        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[_from][_spender] == 0));

        // Alerts the token controller of the approve function call
        if (isContract(controller)) {
            require(TokenController(controller).onApprove(_from, _spender, _amount));
        }

        allowed[_from][_spender] = _amount;
        emit Approval(_from, _spender, _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) external 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) external returns (bool success) {
        doApprove(msg.sender, _spender, _amount);
    }

    /**
     * @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
    ) 
        external
        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(
        address _spender,
        uint256 _amount,
        bytes calldata _extraData
    ) 
        external
        returns (bool success)
    {
        require(doApprove(msg.sender, _spender, _amount));

        ApproveAndCallFallBack(_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() external 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);
        }
    }

////////////////
// Clone Token Method
////////////////

    /**
     * @notice Creates a new clone token with the initial distribution being
     *  this token at `snapshotBlock`
     * @param _cloneTokenName Name of the clone token
     * @param _cloneDecimalUnits Number of decimals of the smallest unit
     * @param _cloneTokenSymbol Symbol of the clone token
     * @param _snapshotBlock Block when the distribution of the parent token is
     *  copied to set the initial distribution of the new clone token;
     *  if the block is zero than the actual block, the current block is used
     * @param _transfersEnabled True if transfers are allowed in the clone
     * @return The address of the new MiniMeToken Contract
     */
    function createCloneToken(
        string calldata _cloneTokenName,
        uint8 _cloneDecimalUnits,
        string calldata _cloneTokenSymbol,
        uint _snapshotBlock,
        bool _transfersEnabled
        ) 
            external
            returns(address)
        {
        uint snapshotBlock = _snapshotBlock;
        if (snapshotBlock == 0) {
            snapshotBlock = block.number;
        }
        MiniMeToken cloneToken = MiniMeToken(
            tokenFactory.createCloneToken(
            address(this),
            snapshotBlock,
            _cloneTokenName,
            _cloneDecimalUnits,
            _cloneTokenSymbol,
            _transfersEnabled
            ));

        cloneToken.changeController(msg.sender);

        // An event to make the token easy to find on the blockchain
        emit NewCloneToken(address(cloneToken), snapshotBlock);
        return address(cloneToken);
    }

////////////////
// 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
    )
        external
        onlyController
        returns (bool)
    {
        uint curTotalSupply = totalSupplyAt(block.number);
        require(curTotalSupply + _amount >= curTotalSupply); // Check for overflow
        uint previousBalanceTo = balanceOfAt(_owner, block.number);
        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
    ) 
        external
        onlyController
        returns (bool)
    {
        uint curTotalSupply = totalSupplyAt(block.number);
        require(curTotalSupply >= _amount);
        uint previousBalanceFrom = balanceOfAt(_owner, block.number);
        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) external onlyController {
        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 Internal function to determine if an address is a contract
     * @param _addr The address being queried
     * @return True if `_addr` is a contract
     */
    function isContract(address _addr) internal returns(bool) {
        uint size;
        if (_addr == address(0)) {
            return false;
        }    
        assembly {
            size := extcodesize(_addr)
        }
        return size>0;
    }

    /**
     * @dev Helper function to return a min betwen the two uints
     */
    function min(uint a, uint b) internal pure returns (uint) {
        return a < b ? a : b;
    }

    /**
     * @notice The fallback function: If the contract's controller has not been
     *  set to 0, then the `proxyPayment` method is called which relays the
     *  ether and creates tokens as described in the token controller contract
     */
    function () external payable {
        require(isContract(controller));
        require(TokenController(controller).proxyPayment.value(msg.value)(msg.sender));
    }

//////////
// Safety Methods
//////////

    /**
     * @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 claimTokens(address _token) external onlyController {
        if (_token == address(0)) {
            controller.transfer(address(this).balance);
            return;
        }

        MiniMeToken token = MiniMeToken(address(uint160(_token)));
        uint balance = token.balanceOf(address(this));
        token.transfer(controller, balance);
        emit ClaimedTokens(_token, controller, balance);
    }

////////////////
// Events
////////////////
    event ClaimedTokens(address indexed _token, address indexed _controller, uint _amount);
    event Transfer(address indexed _from, address indexed _to, uint256 _amount);
    event NewCloneToken(address indexed _cloneToken, uint snapshotBlock);
    event Approval(
        address indexed _owner,
        address indexed _spender,
        uint256 _amount
    );

}