add interface

src/JUSDRepayHelper.sol

@@ -63,7 +63,9 @@ contract JUSDRepayHelper is Ownable {
         // add buffer JUSD
         require(balance <= borrowed + buffer, "repayed jusd too much");
         IJUSDBank(JusdBank).repay(balance, to);
-        IERC20(JUSD).safeTransfer(JusdBank.insurance(), balance - borrowed);
+        if (balance > borrowed) {
+            IERC20(JUSD).safeTransfer(JusdBank.insurance(), balance - borrowed);
+        }
         emit HelpToTransfer(from, to, balance);
     }
 }

src/support/FlattenHelper.sol

@@ -25,6 +25,9 @@ import "../support/TestMarkPriceSource.sol";
 import "../support/MockSwap.sol";
 import "../support/TestVolatilePriceSource.sol";
 import "./TestERC20.sol";
+import "./help/IMessageHandler.sol";
+import "./help/IMessageTransmitter.sol";
+import "./help/ITokenMinter.sol";
 
 // DO NOT REMOVE
 abstract contract ContractForCodeGeneration {

src/support/help/IMessageHandler.sol

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2022, Circle Internet Financial Limited.
+ *
+ * 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.
+ */
+// SPDX-License-Identifier: GPL-2.0-or-later
+pragma solidity ^0.8.19;
+/**
+ * @title IMessageHandler
+ * @notice Handles messages on destination domain forwarded from
+ * an IReceiver
+ */
+interface IMessageHandler {
+    /**
+     * @notice handles an incoming message from a Receiver
+     * @param sourceDomain the source domain of the message
+     * @param sender the sender of the message
+     * @param messageBody The message raw bytes
+     * @return success bool, true if successful
+     */
+    function handleReceiveMessage(
+        uint32 sourceDomain,
+        bytes32 sender,
+        bytes calldata messageBody
+    ) external returns (bool);
+}

src/support/help/IMessageTransmitter.sol

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2022, Circle Internet Financial Limited.
+ *
+ * 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.
+ */
+// SPDX-License-Identifier: GPL-2.0-or-later
+pragma solidity ^0.8.19;
+
+import "./IRelayer.sol";
+import "./IReceiver.sol";
+
+/**
+ * @title IMessageTransmitter
+ * @notice Interface for message transmitters, which both relay and receive messages.
+ */
+interface IMessageTransmitter is IRelayer, IReceiver { }

src/support/help/IReceiver.sol

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2022, Circle Internet Financial Limited.
+ *
+ * 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.
+ */
+// SPDX-License-Identifier: GPL-2.0-or-later
+pragma solidity ^0.8.19;
+/**
+ * @title IReceiver
+ * @notice Receives messages on destination chain and forwards them to IMessageDestinationHandler
+ */
+interface IReceiver {
+    /**
+     * @notice Receives an incoming message, validating the header and passing
+     * the body to application-specific handler.
+     * @param message The message raw bytes
+     * @param signature The message signature
+     * @return success bool, true if successful
+     */
+    function receiveMessage(bytes calldata message, bytes calldata signature)
+        external
+        returns (bool success);
+}

src/support/help/IRelayer.sol

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2022, Circle Internet Financial Limited.
+ *
+ * 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.
+ */
+
+// SPDX-License-Identifier: GPL-2.0-or-later
+pragma solidity ^0.8.19;
+/**
+ * @title IRelayer
+ * @notice Sends messages from source domain to destination domain
+ */
+interface IRelayer {
+    /**
+     * @notice Sends an outgoing message from the source domain.
+     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
+     * @param destinationDomain Domain of destination chain
+     * @param recipient Address of message recipient on destination domain as bytes32
+     * @param messageBody Raw bytes content of message
+     * @return nonce reserved by message
+     */
+    function sendMessage(
+        uint32 destinationDomain,
+        bytes32 recipient,
+        bytes calldata messageBody
+    ) external returns (uint64);
+
+    /**
+     * @notice Sends an outgoing message from the source domain, with a specified caller on the
+     * destination domain.
+     * @dev Increment nonce, format the message, and emit `MessageSent` event with message information.
+     * WARNING: if the `destinationCaller` does not represent a valid address as bytes32, then it will not be possible
+     * to broadcast the message on the destination domain. This is an advanced feature, and the standard
+     * sendMessage() should be preferred for use cases where a specific destination caller is not required.
+     * @param destinationDomain Domain of destination chain
+     * @param recipient Address of message recipient on destination domain as bytes32
+     * @param destinationCaller caller on the destination domain, as bytes32
+     * @param messageBody Raw bytes content of message
+     * @return nonce reserved by message
+     */
+    function sendMessageWithCaller(
+        uint32 destinationDomain,
+        bytes32 recipient,
+        bytes32 destinationCaller,
+        bytes calldata messageBody
+    ) external returns (uint64);
+
+    /**
+     * @notice Replace a message with a new message body and/or destination caller.
+     * @dev The `originalAttestation` must be a valid attestation of `originalMessage`.
+     * @param originalMessage original message to replace
+     * @param originalAttestation attestation of `originalMessage`
+     * @param newMessageBody new message body of replaced message
+     * @param newDestinationCaller the new destination caller
+     */
+    function replaceMessage(
+        bytes calldata originalMessage,
+        bytes calldata originalAttestation,
+        bytes calldata newMessageBody,
+        bytes32 newDestinationCaller
+    ) external;
+}

src/support/help/ITokenMinter.sol

@@ -0,0 +1,56 @@
+/**
+ * @title ITokenMinter
+ * @notice interface for minter of tokens that are mintable, burnable, and interchangeable
+ * across domains.
+ */
+ // SPDX-License-Identifier: GPL-2.0-or-later
+pragma solidity ^0.8.19;
+interface ITokenMinter {
+    /**
+     * @notice Mints `amount` of local tokens corresponding to the
+     * given (`sourceDomain`, `burnToken`) pair, to `to` address.
+     * @dev reverts if the (`sourceDomain`, `burnToken`) pair does not
+     * map to a nonzero local token address. This mapping can be queried using
+     * getLocalToken().
+     * @param sourceDomain Source domain where `burnToken` was burned.
+     * @param burnToken Burned token address as bytes32.
+     * @param to Address to receive minted tokens, corresponding to `burnToken`,
+     * on this domain.
+     * @param amount Amount of tokens to mint. Must be less than or equal
+     * to the minterAllowance of this TokenMinter for given `_mintToken`.
+     * @return mintToken token minted.
+     */
+    function mint(
+        uint32 sourceDomain,
+        bytes32 burnToken,
+        address to,
+        uint256 amount
+    ) external returns (address mintToken);
+
+    /**
+     * @notice Burn tokens owned by this ITokenMinter.
+     * @param burnToken burnable token.
+     * @param amount amount of tokens to burn. Must be less than or equal to this ITokenMinter's
+     * account balance of the given `_burnToken`.
+     */
+    function burn(address burnToken, uint256 amount) external;
+
+    /**
+     * @notice Get the local token associated with the given remote domain and token.
+     * @param remoteDomain Remote domain
+     * @param remoteToken Remote token
+     * @return local token address
+     */
+    function getLocalToken(uint32 remoteDomain, bytes32 remoteToken)
+        external
+        view
+        returns (address);
+
+    /**
+     * @notice Set the token controller of this ITokenMinter. Token controller
+     * is responsible for mapping local tokens to remote tokens, and managing
+     * token-specific limits
+     * @param newTokenController new token controller address
+     */
+    function setTokenController(address newTokenController) external;
+}