added approve and call gas relayed for ERC20

contracts/identity/IdentityGasRelay.sol

@@ -11,6 +11,7 @@ import "../token/ERC20Token.sol";
 contract IdentityGasRelay is Identity {
     
     bytes4 public constant CALL_PREFIX = bytes4(keccak256("callGasRelay(address,uint256,bytes32,uint256,uint256,address)"));
+    bytes4 public constant APPROVEANDCALL_PREFIX = bytes4(keccak256("approveAndCallGasRelay(address,address,uint256,bytes32,uint256,uint256)"));
 
     event ExecutedGasRelayed(bytes32 signHash, bool success);
 
@@ -83,6 +84,82 @@ contract IdentityGasRelay is Identity {
         }        
     }
 
+    /**
+     * @notice include ethereum signed approve ERC20 and call hash 
+     *         (`ERC20Token(baseToken).approve(_to, _value)` + `_to.call(_data)`).
+     *         in return of gas proportional amount multiplied by `_gasPrice` of `_gasToken`
+     *         fixes race condition in double transaction for ERC20.
+     * @param _baseToken token approved for `_to`
+     * @param _to destination of call
+     * @param _value call value (ether)
+     * @param _data call data
+     * @param _nonce current identity nonce
+     * @param _gasPrice price in SNT paid back to msg.sender for each gas unit used
+     * @param _gasMinimal minimal amount of gas needed to complete the execution
+     * @param _gasToken token being used for paying `msg.sender`
+     * @param _messageSignatures rsv concatenated ethereum signed message signatures required
+     */
+    function approveAndCallGasRelayed(
+        address _baseToken, 
+        address _to,
+        uint256 _value,
+        bytes _data,
+        uint _nonce,
+        uint _gasPrice,
+        uint _gasMinimal,
+        address _gasToken,
+        bytes _messageSignatures
+    ) 
+        external 
+    {
+        //verify transaction parameters
+        require(_nonce == nonce);
+        uint startGas = gasleft();
+        require(startGas >= _gasMinimal);
+        require(_baseToken != address(0)); //_baseToken should be something!
+        require(_to != address(this)); //no management with approveAndCall
+        
+        // calculates signHash
+        bytes32 signHash = getSignHash(
+            approveAndCallGasRelayHash(
+                _baseToken,
+                _to,
+                _value,
+                keccak256(_data),
+                _nonce,
+                _gasPrice,
+                _gasMinimal,
+                _gasToken               
+            )
+        );
+        
+        //verify if signatures are valid and came from correct actors;
+        verifySignatures(
+            ACTION_KEY, //no management with approveAndCall
+            signHash, 
+            _messageSignatures
+        );
+        
+        approveAndCall(
+            signHash,
+            _baseToken,
+            _to,
+            _value,
+            _data
+        );
+
+        //refund gas used using contract held ERC20 tokens or ETH
+        if (_gasPrice > 0) {
+            uint256 _amount = 21000 + (startGas - gasleft());
+            _amount = _amount * _gasPrice;
+            if (_gasToken == address(0)) {
+                address(msg.sender).transfer(_amount);
+            } else {
+                ERC20Token(_gasToken).transfer(msg.sender, _amount);
+            }
+        }        
+
+    }
 
     /**
      * @notice reverts if signatures are not valid for the signed hash and required key type. 
@@ -154,6 +231,46 @@ contract IdentityGasRelay is Identity {
         );
     }
 
+    
+    /**
+     * @notice get callHash
+     * @param _to destination of call
+     * @param _value call value (ether)
+     * @param _dataHash call data hash
+     * @param _nonce current identity nonce
+     * @param _gasPrice price in SNT paid back to msg.sender for each gas unit used
+     * @param _gasMinimal minimal amount of gas needed to complete the execution
+     * @param _gasToken token being used for paying `msg.sender` 
+     * @return callGasRelayHash the hash to be signed by wallet
+     */
+    function approveAndCallGasRelayHash(
+        address _baseToken,
+        address _to,
+        uint256 _value,
+        bytes32 _dataHash,
+        uint _nonce,
+        uint256 _gasPrice,
+        uint256 _gasMinimal,
+        address _gasToken
+    )
+        public 
+        view 
+        returns (bytes32 _callGasRelayHash) 
+    {
+        _callGasRelayHash = keccak256(
+            address(this), 
+            APPROVEANDCALL_PREFIX, 
+            _baseToken,
+            _to,
+            _value,
+            _dataHash,
+            _nonce,
+            _gasPrice,
+            _gasMinimal,
+            _gasToken
+        );
+    }
+
     /**
      * @notice Hash a hash with `"\x19Ethereum Signed Message:\n32"`
      * @param _hash Sign to hash.
@@ -226,4 +343,23 @@ contract IdentityGasRelay is Identity {
         require(v == 27 || v == 28);
     }
     
+    function approveAndCall(
+        bytes32 _signHash,
+        address _token,
+        address _to,
+        uint256 _value,
+        bytes _data
+    )
+        private 
+    {
+        //executes transaction
+        nonce++;
+        ERC20Token(_token).approve(_to, _value);
+        emit ExecutedGasRelayed(
+            _signHash, 
+            _to.call(_data)
+        );
+        
+    }
+
 }