Implement ChaiBridge

contracts/asset-proxy/contracts/src/bridges/ChaiBridge.sol

@@ -0,0 +1,64 @@
+/*
+
+  Copyright 2019 ZeroEx Intl.
+
+  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.
+
+*/
+
+pragma solidity ^0.5.9;
+pragma experimental ABIEncoderV2;
+
+import "../interfaces/IERC20Bridge.sol";
+import "../interfaces/IChai.sol";
+import "@0x/contracts-utils/contracts/src/DeploymentConstants.sol";
+import "@0x/contracts-erc20/contracts/src/interfaces/IERC20Token.sol";
+
+
+// solhint-disable space-after-comma
+contract ChaiBridge is
+    IERC20Bridge,
+    DeploymentConstants
+{
+    /// @dev Withdraws `amount` of `from` address's Dai from the Chai contract.
+    ///      Transfers `amount` of Dai to `to` address.
+    /// @param from Address to transfer asset from.
+    /// @param to Address to transfer asset to.
+    /// @param amount Amount of asset to transfer.
+    /// @return success The magic bytes `0x37708e9b` if successful.
+    function bridgeTransferFrom(
+        address /* tokenAddress */,
+        address from,
+        address to,
+        uint256 amount,
+        bytes calldata /* bridgeData */
+    )
+        external
+        returns (bytes4 success)
+    {
+        // Ensure that only the `ERC20BridgeProxy` can call this function.
+        require(
+            msg.sender == _getERC20BridgeProxyAddress(),
+            "ChaiBridge/ONLY_CALLABLE_BY_ERC20_BRIDGE_PROXY"
+        );
+
+        // Withdraw `from` address's Dai.
+        // NOTE: This contract must be approved to spend Chai on behalf of `from`.
+        IChai(_getChaiAddress()).draw(from, amount);
+
+        // Transfer Dai to `to`
+        IERC20Token(_getDaiAddress()).transfer(to, amount);
+
+        return BRIDGE_SUCCESS;
+    }
+}

contracts/asset-proxy/contracts/src/interfaces/IChai.sol

@@ -0,0 +1,32 @@
+/*
+
+  Copyright 2019 ZeroEx Intl.
+
+  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.
+
+*/
+
+pragma solidity ^0.5.9;
+
+// The actual Chai contract can be found here: https://github.com/dapphub/chai
+contract IChai {
+
+    /// @dev Withdraws Dai owned by `src`
+    /// @param src Address that owns Dai.
+    /// @param wad Amount of Dai to withdraw.
+    function draw(
+        address src,
+        uint256 wad
+    )
+        external;
+}