[WIP] Credit draft implementation.

contracts/CreditRule.sol

@@ -0,0 +1,170 @@
+pragma solidity ^0.5.0;
+
+// 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 "./SafeMath.sol";
+import "./TokenRules.sol";
+
+contract CreditRule {
+
+    /* Usings */
+
+    using SafeMath for uint256;
+
+
+    /* Struct */
+
+    struct CreditInfo {
+        uint256 amount;
+        bool inProgress;
+    }
+
+
+    /* Storage */
+
+    address public budgetHolder;
+
+    TokenRules public tokenRules;
+
+    mapping(address => CreditInfo) public credits;
+
+
+    /* Modifiers */
+
+    modifier onlyBudgetHolder()
+    {
+        require(
+            msg.sender == budgetHolder,
+            "Only budget holder is allowed to call."
+        );
+
+        _;
+    }
+
+
+    /* Special Functions */
+
+    constructor(
+        address _budgetHolder,
+        address _tokenRules
+    )
+        public
+    {
+        require(
+            _budgetHolder != address(0),
+            "Budget holder's address is null."
+        );
+
+        require(
+            _tokenRules != address(0),
+            "Token rules's address is null."
+        );
+
+        budgetHolder = _budgetHolder;
+
+        tokenRules = TokenRules(_tokenRules);
+    }
+
+
+    /* External Functions */
+
+    function executeRule(
+        uint256 _creditAmount,
+        address _to, // token holder address
+        bytes calldata _data // token holder execute rule data
+    )
+        external
+        payable
+        onlyBudgetHolder
+        returns(bool executionStatus_)
+    {
+        require(_to != address(0));
+
+        CreditInfo storage c = credits[_to];
+
+        require(
+            !c.inProgress,
+            "Re-entrancy occured in crediting process."
+        );
+
+        c.inProgress = true;
+        c.amount = _creditAmount;
+
+        bytes memory returnData;
+        // solium-disable-next-line security/no-call-value
+        (executionStatus_, returnData) = address(_to).call.value(msg.value)(_data);
+
+        c.amount = 0;
+        c.inProgress = false;
+    }
+
+    function executeTransfers(
+        address _from,
+        address[] calldata _transfersTo,
+        uint256[] calldata _transfersAmount
+    )
+        external
+    {
+        if (credits[_from].inProgress) {
+            uint256 sumAmount = 0;
+
+            for(uint256 i = 0; i < _transfersAmount.length; ++i) {
+                sumAmount = sumAmount.add(_transfersAmount[i]);
+            }
+
+            uint256 creditAmount = credits[_from].amount;
+
+            uint256 amountToTransferFromBudgetHolder = (
+                sumAmount > creditAmount ? creditAmount : sumAmount
+            );
+
+            executeTransfer(
+                budgetHolder,
+                _from,
+                amountToTransferFromBudgetHolder
+            );
+        }
+
+        tokenRules.executeTransfers(
+            _from,
+            _transfersTo,
+            _transfersAmount
+        );
+    }
+
+
+    /* Private Functions */
+
+    function executeTransfer(
+        address _from,
+        address _beneficiary,
+        uint256 _amount
+    )
+        private
+    {
+        address[] memory transfersTo = new address[](1);
+        transfersTo[0] = _beneficiary;
+
+        uint256[] memory transfersAmount = new uint256[](1);
+        transfersAmount[0] = _amount;
+
+        tokenRules.executeTransfers(
+            _from,
+            transfersTo,
+            transfersAmount
+        );
+    }
+
+}

contracts/test_doubles/unit_tests/TokenRulesSpy.sol

@@ -1,18 +1,38 @@
 pragma solidity ^0.5.0;
 
+import "../../EIP20TokenInterface.sol";
+
 contract TokenRulesSpy {
 
+    /* Structs */
+
+    struct TransactionEntry {
+        address from;
+        address[] transfersTo;
+        uint256[] transfersAmount;
+    }
+
+
     /* Storage */
 
+    EIP20TokenInterface public token;
+
+    TransactionEntry[] public transactions;
+
+    uint256 public transactionsLength;
+
     mapping (address => bool) public allowedTransfers;
 
-    address public recordedFrom;
 
-    address[] public recordedTransfersTo;
-    uint256 public recordedTransfersToLength;
+    /* Special Functions */
+
+    constructor(EIP20TokenInterface _token)
+        public
+    {
+        require(address(_token) != address(0), "Token address is null.");
 
-    uint256[] public recordedTransfersAmount;
-    uint256 public recordedTransfersAmountLength;
+        token = _token;
+    }
 
 
     /* External Functions */
@@ -29,20 +49,56 @@ contract TokenRulesSpy {
         allowedTransfers[msg.sender] = false;
     }
 
+    function fromTransaction(uint256 index)
+        external
+        view
+        returns (address)
+    {
+        return transactions[index].from;
+    }
+
+    function transfersToTransaction(uint256 index)
+        external
+        view
+        returns (address[] memory)
+    {
+        return transactions[index].transfersTo;
+    }
+
+    function transfersAmountTransaction(uint256 index)
+        external
+        view
+        returns (uint256[] memory)
+    {
+        return transactions[index].transfersAmount;
+    }
+
     function executeTransfers(
         address _from,
         address[] calldata _transfersTo,
         uint256[] calldata _transfersAmount
     )
         external
     {
-        recordedFrom = _from;
+        TransactionEntry memory entry = TransactionEntry({
+            from: _from,
+            transfersTo: new address[](0),
+            transfersAmount: new uint256[](0)
+        });
+
+        transactions.push(entry);
+
+        for (uint256 i = 0; i < _transfersTo.length; ++i) {
+            transactions[transactionsLength].transfersTo.push(_transfersTo[i]);
+        }
 
-        recordedTransfersTo = _transfersTo;
-        recordedTransfersToLength = _transfersTo.length;
+        for (uint256 i = 0; i < _transfersAmount.length; ++i) {
+            transactions[transactionsLength].transfersAmount.push(
+                _transfersAmount[i]
+            );
+        }
 
-        recordedTransfersAmount = _transfersAmount;
-        recordedTransfersAmountLength = _transfersAmount.length;
+        ++transactionsLength;
     }
 
 }

contracts/test_doubles/unit_tests/credit_rule/CustomRuleWithCredit.sol

@@ -0,0 +1,87 @@
+pragma solidity ^0.5.0;
+
+// 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 "../../../SafeMath.sol";
+import "../../../CreditRule.sol";
+
+contract CustomRuleWithCredit {
+
+    /* Usings */
+
+    using SafeMath for uint256;
+
+    event Pay(
+        address _to,
+        uint256 _amount
+    );
+
+    /* Storage */
+
+    CreditRule public creditRule;
+
+    bool public markedToFail;
+
+
+    /* Special Functions */
+
+    constructor(
+        address _creditRule
+    )
+        public
+    {
+        require(
+            address(_creditRule) != address(0),
+            "Credit rule's address is null."
+        );
+
+        creditRule = CreditRule(_creditRule);
+    }
+
+
+    /* External Functions */
+
+    function makeMeFail()
+        external
+    {
+        markedToFail = true;
+    }
+
+    function pay(
+        address _to,
+        uint256 _amount
+    )
+        external
+    {
+        require(
+            !markedToFail,
+            "The function is marked to fail."
+        );
+
+        address[] memory transfersTo = new address[](1);
+        transfersTo[0] = _to;
+
+        uint256[] memory transfersAmount = new uint256[](1);
+        transfersAmount[0] = _amount;
+
+        creditRule.executeTransfers(
+            msg.sender,
+            transfersTo,
+            transfersAmount
+        );
+
+        emit Pay(_to, _amount);
+    }
+}