Gas Tokens in Bridges (#2523)

* Gas Tokens in Bridges

* Added freesGasTokensFromCollector.

To handle the case where GST2 is being traded and the balanceOf checks become confusing

* Update CHANGELOGs

contracts/asset-proxy/CHANGELOG.json

@@ -13,6 +13,10 @@
             {
                 "note": "Change names of `ERC20BridgeTransfer` args to be less ambiguous.",
                 "pr": 2524
+            },
+            {
+                "note": "Added `MixinGasToken` allowing Gas Tokens to be freed",
+                "pr": 2523
             }
         ]
     },

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

@@ -26,6 +26,7 @@ import "@0x/contracts-exchange-libs/contracts/src/IWallet.sol";
 import "@0x/contracts-utils/contracts/src/DeploymentConstants.sol";
 import "../interfaces/IERC20Bridge.sol";
 import "../interfaces/ICurve.sol";
+import "./MixinGasToken.sol";
 
 
 // solhint-disable not-rely-on-time
@@ -33,7 +34,8 @@ import "../interfaces/ICurve.sol";
 contract CurveBridge is
     IERC20Bridge,
     IWallet,
-    DeploymentConstants
+    DeploymentConstants,
+    MixinGasToken
 {
     struct CurveBridgeData {
         address curveAddress;
@@ -60,6 +62,7 @@ contract CurveBridge is
         bytes calldata bridgeData
     )
         external
+        freesGasTokensFromCollector
         returns (bytes4 success)
     {
         // Decode the bridge data to get the Curve metadata.

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

@@ -0,0 +1,55 @@
+/*
+
+  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 ^0.5.16;
+
+import "@0x/contracts-utils/contracts/src/DeploymentConstants.sol";
+import "../interfaces/IGasToken.sol";
+
+
+contract MixinGasToken is
+    DeploymentConstants
+{
+
+    /// @dev Frees gas tokens based on the amount of gas consumed in the function
+    modifier freesGasTokens {
+        uint256 gasBefore = gasleft();
+        _;
+        IGasToken gst = IGasToken(_getGstAddress());
+        if (address(gst) != address(0)) {
+            // (gasUsed + FREE_BASE) / (2 * REIMBURSE - FREE_TOKEN)
+            //            14154             24000        6870
+            uint256 value = (gasBefore - gasleft() + 14154) / 41130;
+            gst.freeUpTo(value);
+        }
+    }
+
+    /// @dev Frees gas tokens using the balance of `from`. Amount freed is based
+    ///     on the gas consumed in the function
+    modifier freesGasTokensFromCollector() {
+        uint256 gasBefore = gasleft();
+        _;
+        IGasToken gst = IGasToken(_getGstAddress());
+        if (address(gst) != address(0)) {
+            // (gasUsed + FREE_BASE) / (2 * REIMBURSE - FREE_TOKEN)
+            //            14154             24000        6870
+            uint256 value = (gasBefore - gasleft() + 14154) / 41130;
+            gst.freeFromUpTo(_getGstCollectorAddress(), value);
+        }
+    }
+}

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

@@ -0,0 +1,40 @@
+/*
+
+  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 ^0.5.15;
+
+import "@0x/contracts-erc20/contracts/src/interfaces/IERC20Token.sol";
+
+
+contract IGasToken is IERC20Token {
+
+    /// @dev Frees up to `value` sub-tokens
+    /// @param value The amount of tokens to free
+    /// @return How many tokens were freed
+    function freeUpTo(uint256 value) external returns (uint256 freed);
+
+    /// @dev Frees up to `value` sub-tokens owned by `from`
+    /// @param from The owner of tokens to spend
+    /// @param value The amount of tokens to free
+    /// @return How many tokens were freed
+    function freeFromUpTo(address from, uint256 value) external returns (uint256 freed);
+
+    /// @dev Mints `value` amount of tokens
+    /// @param value The amount of tokens to mint
+    function mint(uint256 value) external;
+}

contracts/asset-proxy/package.json

@@ -38,7 +38,7 @@
         "docs:json": "typedoc --excludePrivate --excludeExternals --excludeProtected --ignoreCompilerErrors --target ES5 --tsconfig typedoc-tsconfig.json --json $JSON_FILE_PATH $PROJECT_FILES"
     },
     "config": {
-        "abis": "./test/generated-artifacts/@(ChaiBridge|CurveBridge|DydxBridge|ERC1155Proxy|ERC20BridgeProxy|ERC20Proxy|ERC721Proxy|Eth2DaiBridge|IAssetData|IAssetProxy|IAssetProxyDispatcher|IAuthorizable|IChai|ICurve|IDydx|IDydxBridge|IERC20Bridge|IEth2Dai|IKyberNetworkProxy|IUniswapExchange|IUniswapExchangeFactory|KyberBridge|MixinAssetProxyDispatcher|MixinAuthorizable|MultiAssetProxy|Ownable|StaticCallProxy|TestChaiBridge|TestDydxBridge|TestERC20Bridge|TestEth2DaiBridge|TestKyberBridge|TestStaticCallTarget|TestUniswapBridge|UniswapBridge).json",
+        "abis": "./test/generated-artifacts/@(ChaiBridge|CurveBridge|DydxBridge|ERC1155Proxy|ERC20BridgeProxy|ERC20Proxy|ERC721Proxy|Eth2DaiBridge|IAssetData|IAssetProxy|IAssetProxyDispatcher|IAuthorizable|IChai|ICurve|IDydx|IDydxBridge|IERC20Bridge|IEth2Dai|IGasToken|IKyberNetworkProxy|IUniswapExchange|IUniswapExchangeFactory|KyberBridge|MixinAssetProxyDispatcher|MixinAuthorizable|MixinGasToken|MultiAssetProxy|Ownable|StaticCallProxy|TestChaiBridge|TestDydxBridge|TestERC20Bridge|TestEth2DaiBridge|TestKyberBridge|TestStaticCallTarget|TestUniswapBridge|UniswapBridge).json",
         "abis:comment": "This list is auto-generated by contracts-gen. Don't edit manually."
     },
     "repository": {

contracts/asset-proxy/src/artifacts.ts

@@ -23,12 +23,14 @@ import * as IDydx from '../generated-artifacts/IDydx.json';
 import * as IDydxBridge from '../generated-artifacts/IDydxBridge.json';
 import * as IERC20Bridge from '../generated-artifacts/IERC20Bridge.json';
 import * as IEth2Dai from '../generated-artifacts/IEth2Dai.json';
+import * as IGasToken from '../generated-artifacts/IGasToken.json';
 import * as IKyberNetworkProxy from '../generated-artifacts/IKyberNetworkProxy.json';
 import * as IUniswapExchange from '../generated-artifacts/IUniswapExchange.json';
 import * as IUniswapExchangeFactory from '../generated-artifacts/IUniswapExchangeFactory.json';
 import * as KyberBridge from '../generated-artifacts/KyberBridge.json';
 import * as MixinAssetProxyDispatcher from '../generated-artifacts/MixinAssetProxyDispatcher.json';
 import * as MixinAuthorizable from '../generated-artifacts/MixinAuthorizable.json';
+import * as MixinGasToken from '../generated-artifacts/MixinGasToken.json';
 import * as MultiAssetProxy from '../generated-artifacts/MultiAssetProxy.json';
 import * as Ownable from '../generated-artifacts/Ownable.json';
 import * as StaticCallProxy from '../generated-artifacts/StaticCallProxy.json';
@@ -55,6 +57,7 @@ export const artifacts = {
     DydxBridge: DydxBridge as ContractArtifact,
     Eth2DaiBridge: Eth2DaiBridge as ContractArtifact,
     KyberBridge: KyberBridge as ContractArtifact,
+    MixinGasToken: MixinGasToken as ContractArtifact,
     UniswapBridge: UniswapBridge as ContractArtifact,
     IAssetData: IAssetData as ContractArtifact,
     IAssetProxy: IAssetProxy as ContractArtifact,
@@ -66,6 +69,7 @@ export const artifacts = {
     IDydxBridge: IDydxBridge as ContractArtifact,
     IERC20Bridge: IERC20Bridge as ContractArtifact,
     IEth2Dai: IEth2Dai as ContractArtifact,
+    IGasToken: IGasToken as ContractArtifact,
     IKyberNetworkProxy: IKyberNetworkProxy as ContractArtifact,
     IUniswapExchange: IUniswapExchange as ContractArtifact,
     IUniswapExchangeFactory: IUniswapExchangeFactory as ContractArtifact,

contracts/asset-proxy/src/wrappers.ts

@@ -21,12 +21,14 @@ export * from '../generated-wrappers/i_dydx';
 export * from '../generated-wrappers/i_dydx_bridge';
 export * from '../generated-wrappers/i_erc20_bridge';
 export * from '../generated-wrappers/i_eth2_dai';
+export * from '../generated-wrappers/i_gas_token';
 export * from '../generated-wrappers/i_kyber_network_proxy';
 export * from '../generated-wrappers/i_uniswap_exchange';
 export * from '../generated-wrappers/i_uniswap_exchange_factory';
 export * from '../generated-wrappers/kyber_bridge';
 export * from '../generated-wrappers/mixin_asset_proxy_dispatcher';
 export * from '../generated-wrappers/mixin_authorizable';
+export * from '../generated-wrappers/mixin_gas_token';
 export * from '../generated-wrappers/multi_asset_proxy';
 export * from '../generated-wrappers/ownable';
 export * from '../generated-wrappers/static_call_proxy';

contracts/asset-proxy/test/artifacts.ts

@@ -23,12 +23,14 @@ import * as IDydx from '../test/generated-artifacts/IDydx.json';
 import * as IDydxBridge from '../test/generated-artifacts/IDydxBridge.json';
 import * as IERC20Bridge from '../test/generated-artifacts/IERC20Bridge.json';
 import * as IEth2Dai from '../test/generated-artifacts/IEth2Dai.json';
+import * as IGasToken from '../test/generated-artifacts/IGasToken.json';
 import * as IKyberNetworkProxy from '../test/generated-artifacts/IKyberNetworkProxy.json';
 import * as IUniswapExchange from '../test/generated-artifacts/IUniswapExchange.json';
 import * as IUniswapExchangeFactory from '../test/generated-artifacts/IUniswapExchangeFactory.json';
 import * as KyberBridge from '../test/generated-artifacts/KyberBridge.json';
 import * as MixinAssetProxyDispatcher from '../test/generated-artifacts/MixinAssetProxyDispatcher.json';
 import * as MixinAuthorizable from '../test/generated-artifacts/MixinAuthorizable.json';
+import * as MixinGasToken from '../test/generated-artifacts/MixinGasToken.json';
 import * as MultiAssetProxy from '../test/generated-artifacts/MultiAssetProxy.json';
 import * as Ownable from '../test/generated-artifacts/Ownable.json';
 import * as StaticCallProxy from '../test/generated-artifacts/StaticCallProxy.json';
@@ -55,6 +57,7 @@ export const artifacts = {
     DydxBridge: DydxBridge as ContractArtifact,
     Eth2DaiBridge: Eth2DaiBridge as ContractArtifact,
     KyberBridge: KyberBridge as ContractArtifact,
+    MixinGasToken: MixinGasToken as ContractArtifact,
     UniswapBridge: UniswapBridge as ContractArtifact,
     IAssetData: IAssetData as ContractArtifact,
     IAssetProxy: IAssetProxy as ContractArtifact,
@@ -66,6 +69,7 @@ export const artifacts = {
     IDydxBridge: IDydxBridge as ContractArtifact,
     IERC20Bridge: IERC20Bridge as ContractArtifact,
     IEth2Dai: IEth2Dai as ContractArtifact,
+    IGasToken: IGasToken as ContractArtifact,
     IKyberNetworkProxy: IKyberNetworkProxy as ContractArtifact,
     IUniswapExchange: IUniswapExchange as ContractArtifact,
     IUniswapExchangeFactory: IUniswapExchangeFactory as ContractArtifact,

contracts/asset-proxy/test/wrappers.ts

@@ -21,12 +21,14 @@ export * from '../test/generated-wrappers/i_dydx';
 export * from '../test/generated-wrappers/i_dydx_bridge';
 export * from '../test/generated-wrappers/i_erc20_bridge';
 export * from '../test/generated-wrappers/i_eth2_dai';
+export * from '../test/generated-wrappers/i_gas_token';
 export * from '../test/generated-wrappers/i_kyber_network_proxy';
 export * from '../test/generated-wrappers/i_uniswap_exchange';
 export * from '../test/generated-wrappers/i_uniswap_exchange_factory';
 export * from '../test/generated-wrappers/kyber_bridge';
 export * from '../test/generated-wrappers/mixin_asset_proxy_dispatcher';
 export * from '../test/generated-wrappers/mixin_authorizable';
+export * from '../test/generated-wrappers/mixin_gas_token';
 export * from '../test/generated-wrappers/multi_asset_proxy';
 export * from '../test/generated-wrappers/ownable';
 export * from '../test/generated-wrappers/static_call_proxy';

contracts/asset-proxy/tsconfig.json

@@ -21,12 +21,14 @@
         "generated-artifacts/IDydxBridge.json",
         "generated-artifacts/IERC20Bridge.json",
         "generated-artifacts/IEth2Dai.json",
+        "generated-artifacts/IGasToken.json",
         "generated-artifacts/IKyberNetworkProxy.json",
         "generated-artifacts/IUniswapExchange.json",
         "generated-artifacts/IUniswapExchangeFactory.json",
         "generated-artifacts/KyberBridge.json",
         "generated-artifacts/MixinAssetProxyDispatcher.json",
         "generated-artifacts/MixinAuthorizable.json",
+        "generated-artifacts/MixinGasToken.json",
         "generated-artifacts/MultiAssetProxy.json",
         "generated-artifacts/Ownable.json",
         "generated-artifacts/StaticCallProxy.json",
@@ -56,12 +58,14 @@
         "test/generated-artifacts/IDydxBridge.json",
         "test/generated-artifacts/IERC20Bridge.json",
         "test/generated-artifacts/IEth2Dai.json",
+        "test/generated-artifacts/IGasToken.json",
         "test/generated-artifacts/IKyberNetworkProxy.json",
         "test/generated-artifacts/IUniswapExchange.json",
         "test/generated-artifacts/IUniswapExchangeFactory.json",
         "test/generated-artifacts/KyberBridge.json",
         "test/generated-artifacts/MixinAssetProxyDispatcher.json",
         "test/generated-artifacts/MixinAuthorizable.json",
+        "test/generated-artifacts/MixinGasToken.json",
         "test/generated-artifacts/MultiAssetProxy.json",
         "test/generated-artifacts/Ownable.json",
         "test/generated-artifacts/StaticCallProxy.json",

contracts/utils/CHANGELOG.json

@@ -1,4 +1,13 @@
 [
+    {
+        "version": "4.5.0",
+        "changes": [
+            {
+                "note": "Added `GST_ADDRESS` and `GST_COLLECTOR_ADDRESS`",
+                "pr": 2523
+            }
+        ]
+    },
     {
         "timestamp": 1583220306,
         "version": "4.4.3",

contracts/utils/contracts/src/DeploymentConstants.sol

@@ -54,6 +54,14 @@ contract DeploymentConstants {
     address constant internal KYBER_ETH_ADDRESS = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
     /// @dev Mainnet address of the dYdX contract.
     address constant private DYDX_ADDRESS = 0x1E0447b19BB6EcFdAe1e4AE1694b0C3659614e4e;
+    /// @dev Mainnet address of the GST2 contract
+    address constant private GST_ADDRESS = 0x0000000000b3F879cb30FE243b4Dfee438691c04;
+    /// @dev Mainnet address of the GST Collector
+    address constant private GST_COLLECTOR_ADDRESS = address(0);
+    // /// @dev Kovan address of the GST2 contract
+    // address constant private GST_ADDRESS = address(0);
+    // /// @dev Kovan address of the GST Collector
+    // address constant private GST_COLLECTOR_ADDRESS = address(0);
 
     /// @dev Overridable way to get the `KyberNetworkProxy` address.
     /// @return kyberAddress The `IKyberNetworkProxy` address.
@@ -144,4 +152,24 @@ contract DeploymentConstants {
     {
         return DYDX_ADDRESS;
     }
+
+    /// @dev An overridable way to retrieve the GST2 contract address.
+    /// @return gst The GST contract.
+    function _getGstAddress()
+        internal
+        view
+        returns (address gst)
+    {
+        return GST_ADDRESS;
+    }
+
+    /// @dev An overridable way to retrieve the GST Collector address.
+    /// @return collector The GST collector address.
+    function _getGstCollectorAddress()
+        internal
+        view
+        returns (address collector)
+    {
+        return GST_COLLECTOR_ADDRESS;
+    }
 }