Initial/draft implementation of token rules.

contracts/BrandedToken.sol

@@ -26,6 +26,7 @@ import "./SafeMath.sol";
 import "./openst-protocol/EIP20Token.sol";
 import "./openst-protocol/UtilityTokenAbstract.sol";
 import "./Internal.sol";
+import "./TokenRulesTokenInterface.sol";
 
 
 /**
@@ -44,7 +45,8 @@ import "./Internal.sol";
  *        on Ethereum (before v1.0).
  *
  */
-contract BrandedToken is EIP20Token, UtilityTokenAbstract, Internal {
+contract BrandedToken
+    is EIP20Token, UtilityTokenAbstract, TokenRulesTokenInterface, Internal {
 
      /* Usings */
 
@@ -178,6 +180,16 @@ contract BrandedToken is EIP20Token, UtilityTokenAbstract, Internal {
         EIP20Token.approve(_spender, _value);
     }
 
+    function clearAllowance(address _approver) public returns (bool)
+    {
+        allowed[_approver][msg.sender] = 0;
+
+        emit Approval(_approver, msg.sender, 0);
+
+        return true;
+
+    }
+
     /**
      * @notice Public function mintEIP20.
      *
@@ -198,7 +210,7 @@ contract BrandedToken is EIP20Token, UtilityTokenAbstract, Internal {
         returns (bool /* success */)
     {
         require(
-            (isInternalActor[_beneficiary] == true),
+            isInternalActor[_beneficiary] == true,
             "beneficiary is invalid economy actor!"
         );
 

contracts/SharedStructs.sol

@@ -0,0 +1,36 @@
+pragma solidity ^0.4.24;
+
+
+// Copyright 2018 OpenST Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+
+library SharedStructs {
+
+    /* Structs */
+
+    struct TokenRule {
+        string ruleName;
+        address ruleAddress;
+    }
+
+    struct TokenRuleConstraint {
+        address constraintAddress;
+    }
+
+    struct TokenRuleTransfer {
+        address to;
+        uint256 amount;
+    }
+}

contracts/TokenRules.sol

@@ -0,0 +1,260 @@
+pragma solidity ^0.4.23;
+pragma experimental ABIEncoderV2;
+
+// Copyright 2018 OpenST Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import "./SharedStructs.sol";
+import "./TokenRulesTokenInterface.sol";
+import "./SafeMath.sol";
+
+
+contract TokenRules {
+
+     /* Usings */
+
+    using SafeMath for uint256;
+
+
+    /* Events */
+
+    event RuleRegistered(
+        address _sender,
+        string _ruleName,
+        address _ruleAddress
+    );
+
+    event ConstraintAdded(address _sender, address _constraintAddress);
+
+    event ConstraintRemoved(address _sender, address _constraintAddress);
+
+
+    /* Variables */
+
+    SharedStructs.TokenRule[] public rules;
+    mapping (string => SharedStructs.TokenRule) public rulesByName;
+    mapping (address => SharedStructs.TokenRule) public rulesByAddress;
+
+    SharedStructs.TokenRuleConstraint[] public constraints;
+
+    address public organization;
+    address public token;
+
+
+    /* Modifiers */
+
+    modifier onlyOrganization {
+        require(
+            organization == msg.sender,
+            "Only organization is allowed to call."
+        );
+        _;
+    }
+
+    modifier onlyRule {
+        require (
+            rulesByAddress[msg.sender].ruleAddress != address(0),
+            "Only registered rule is allowed to call");
+        _;
+    }
+
+
+    /* Functions */
+
+    constructor (
+        address _organization,
+        address _token
+    )
+        public
+    {
+        require(_organization != address(0), "Organization address is null.");
+        require(_token != address(0), "Token address is null.");
+
+        organization = _organization;
+        token = _token;
+    }
+
+    /**
+     * @param _ruleName The name of a rule to register.
+     * @param _ruleAddress The address of a rule to register.
+     *
+     * @return true in case of success, otherwise false.
+     */
+    function registerRule (
+        string _ruleName,
+        address _ruleAddress
+    )
+        external
+        onlyOrganization
+        returns (bool)
+    {
+        require(bytes(_ruleName).length != 0, "Rule name is empty.");
+        require(_ruleAddress != address(0), "Rule address is null.");
+        require (
+            rulesByName[_ruleName].ruleAddress == address(0),
+            "Rule name exists."
+        );
+        require (
+            rulesByAddress[_ruleAddress].ruleAddress == address(0),
+            "Rule address exists."
+        );
+
+        SharedStructs.TokenRule memory rule;
+        rule.ruleName = _ruleName;
+        rule.ruleAddress = _ruleAddress;
+
+        rulesByName[_ruleName] = rule;
+        rulesByAddress[_ruleAddress] = rule;
+        rules.push(rule);
+
+        emit RuleRegistered(msg.sender, _ruleName, _ruleAddress);
+
+        return true;
+    }
+
+    function executeTransfers (
+        address _from,
+        SharedStructs.TokenRuleTransfer[] _transfers
+    )
+        external
+        onlyRule
+        returns (bool)
+    {
+        if (0 == _transfers.length) {
+            return true;
+        }
+
+        require (
+            checkConstraints(_from, _transfers),
+            "Constraints not fullfilled."
+        );
+
+        for (uint256 i = 0; i < _transfers.length; ++i) {
+            TokenRulesTokenInterface(token).transferFrom(
+                _from,
+                _transfers[i].to,
+                _transfers[i].amount
+            );
+        }
+
+        TokenRulesTokenInterface(token).clearAllowance(_from);
+
+        return true;
+    }
+
+    function addConstraint (
+        address _constraintAddress
+    )
+        external
+        onlyOrganization
+        returns (bool)
+    {
+        require(_constraintAddress != address(0), "Constraint to add is null.");
+
+        uint256 index = findConstraintIndex(_constraintAddress);
+
+        require (
+            index == constraints.length,
+            "Constraint to add already exists."
+        );
+
+        constraints.push(
+            SharedStructs.TokenRuleConstraint(
+                {constraintAddress: _constraintAddress}
+            )
+        );
+
+        emit ConstraintAdded(msg.sender, _constraintAddress);
+
+        return true;
+    }
+
+    function removeConstraint (
+        address _constraintAddress
+    )
+        external
+        onlyOrganization
+        returns (bool)
+    {
+        require (
+            _constraintAddress != address(0),
+            "Constraint to remvoe is null."
+        );
+
+        uint256 index = findConstraintIndex(_constraintAddress);
+
+        require (
+            index != constraints.length,
+            "Constraint to remove does not exist."
+        );
+
+        removeConstraintByIndex(index);
+
+        return true;
+    }
+
+    function checkConstraints (
+        address _from,
+        SharedStructs.TokenRuleTransfer[] _transfers
+    )
+        public
+        view
+        returns (bool)
+    {
+        return true;
+    }
+
+    /**
+     * @dev Finds index of constraint.
+     *
+     * @param _constraint Constraint to find in constraints array.
+     *
+     * @return index_ Returns index of the constraint if exists,
+     *                otherwise returns constraints.length.
+     */
+    function findConstraintIndex(address _constraint)
+        private
+        view
+        returns (uint256 index_)
+    {
+        index_ = 0;
+        while (
+            index_ < constraints.length &&
+            constraints[index_].constraintAddress != _constraint
+        )
+        {
+            ++index_;
+        }
+    }
+
+    // solium-disable-next-line security/no-assign-params
+    function removeConstraintByIndex(uint256 _index)
+        private
+        returns (bool)
+    {
+        require (
+            _index < 0 || _index >= constraints.length,
+            "Index is out of range."
+        );
+
+        while ( _index < constraints.length - 1) {
+            constraints[_index] = constraints[_index + 1];
+            _index++;
+        }
+
+        --constraints.length;
+
+        return true;
+    }
+}

contracts/TokenRulesTokenInterface.sol

@@ -0,0 +1,24 @@
+pragma solidity ^0.4.23;
+
+// Copyright 2018 OpenST Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+interface TokenRulesTokenInterface
+{
+    function clearAllowance(address _approver) external returns (bool);
+
+    function transferFrom(
+        address _from, address _to, uint256 _amount
+    ) external returns (bool);
+}