feat(UniswapV3ExchangeAdapterV2): Add UniswapV3ExchangeAdapterV2 exchange adapter (#240)

* Add uniswapV3ExchangeAdapterV2 contract

* Fix compilation bug

* Add unit tests

* Fix exactOutput bug; Make toBool public and add unit tests for it

* Add integration tests with TradeModule

* Fix coverage: Remove .only from tests

* Improve javadocs and comments; Add suggested changes

Author: Sachin

contracts/protocol/integration/exchange/UniswapV3ExchangeAdapterV2.sol

@@ -0,0 +1,188 @@
+/*
+    Copyright 2022 Set Labs Inc.
+
+    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: Apache License, Version 2.0
+*/
+
+pragma solidity 0.6.10;
+pragma experimental "ABIEncoderV2";
+
+import { BytesLib } from "../../../../external/contracts/uniswap/v3/lib/BytesLib.sol";
+import { ISwapRouter } from "../../../interfaces/external/ISwapRouter.sol";
+
+/**
+ * @title UniswapV3ExchangeAdapterV2
+ * @author Set Protocol
+ *
+ * Exchange adapter for Uniswap V3 SwapRouter that encodes trade data. Supports multi-hop trades.
+ *
+ * CHANGE LOG:
+ * - Generalized ability to choose whether to swap an exact amount of source token for a min amount of
+ * receive token or swap a max amount of source token for an exact amount of receive token.
+ */
+contract UniswapV3ExchangeAdapterV2 {
+
+    using BytesLib for bytes;
+
+    /* ============ State Variables ============ */
+
+    // Address of Uniswap V3 SwapRouter contract
+    address public immutable swapRouter;
+
+    /* ============ Constructor ============ */
+
+    /**
+     * Set state variables
+     *
+     * @param _swapRouter    Address of Uniswap V3 SwapRouter
+     */
+    constructor(address _swapRouter) public {
+        swapRouter = _swapRouter;
+    }
+
+    /* ============ External Getter Functions ============ */
+
+    /**
+     * Return calldata for Uniswap V3 SwapRouter
+     *
+     * @param  _sourceToken              Address of source token to be sold
+     * @param  _destinationToken         Address of destination token to buy
+     * @param  _destinationAddress       Address that assets should be transferred to
+     * @param  _sourceQuantity           Fixed/Max amount of source token to sell
+     * @param  _destinationQuantity      Min/Fixed amount of destination token to buy
+     * @param  _data                     Bytes containing trade path and bool to determine function string.
+     *                                   Equals the output of the generateDataParam function
+     *                                   NOTE: Path for `exactOutput` swaps are reversed
+     *
+     * @return address                   Target contract address
+     * @return uint256                   Call value
+     * @return bytes                     Trade calldata
+     */
+    function getTradeCalldata(
+        address _sourceToken,
+        address _destinationToken,
+        address _destinationAddress,
+        uint256 _sourceQuantity,
+        uint256 _destinationQuantity,
+        bytes calldata _data
+    )
+        external
+        view
+        returns (address, uint256, bytes memory)
+    {
+        // For a single hop trade, `_data.length` is 44. 20 source/destination token address + 3 fees +
+        // 20 source/destination token address + 1 fixInput bool.
+        // For multi-hop trades, `_data.length` is greater than 44.
+        require(_data.length >= 44, "Invalid data");
+
+        bool fixInput = toBool(_data, _data.length - 1);        // `fixInput` bool is stored at last byte
+
+        address sourceFromPath;
+        address destinationFromPath;
+
+        if (fixInput) {
+            sourceFromPath = _data.toAddress(0);
+            destinationFromPath = _data.toAddress(_data.length - 21);
+        } else {
+            // Path for exactOutput swaps are reversed
+            sourceFromPath = _data.toAddress(_data.length - 21);
+            destinationFromPath = _data.toAddress(0);
+        }
+
+        require(_sourceToken == sourceFromPath, "Source token path mismatch");
+        require(_destinationToken == destinationFromPath, "Destination token path mismatch");
+
+        bytes memory pathData = _data.slice(0, _data.length - 1);       // Extract path data from `_data`
+
+        bytes memory callData = fixInput
+            ? abi.encodeWithSelector(
+                ISwapRouter.exactInput.selector,
+                ISwapRouter.ExactInputParams(
+                    pathData,
+                    _destinationAddress,
+                    block.timestamp,
+                    _sourceQuantity,
+                    _destinationQuantity
+                )
+            )
+            : abi.encodeWithSelector(
+                ISwapRouter.exactOutput.selector,
+                ISwapRouter.ExactOutputParams(
+                    pathData,
+                    _destinationAddress,
+                    block.timestamp,
+                    _destinationQuantity,       // swapped vs exactInputParams
+                    _sourceQuantity
+                )
+            );
+
+        return (swapRouter, 0, callData);
+    }
+
+    /**
+     * Returns the address to approve source tokens to for trading. This is the Uniswap SwapRouter address
+     *
+     * @return address             Address of the contract to approve tokens to
+     */
+    function getSpender() external view returns (address) {
+        return swapRouter;
+    }
+
+    /**
+     * Returns the appropriate _data argument for getTradeCalldata. Equal to the encodePacked path with the
+     * fee of each hop between it and fixInput bool at the very end., e.g [token1, fee1, token2, fee2, token3, fixIn].
+     * Note: _fees.length == _path.length - 1
+     *
+     * @param _path array of addresses to use as the path for the trade
+     * @param _fees array of uint24 representing the pool fee to use for each hop
+     * @param _fixIn Boolean indicating if input amount is fixed
+     *
+     * @return bytes  Bytes containing trade path and bool to determine function string.
+     */
+    function generateDataParam(
+        address[] calldata _path,
+        uint24[] calldata _fees,
+        bool _fixIn
+    ) external pure returns (bytes memory) {
+        bytes memory data = "";
+        for (uint256 i = 0; i < _path.length - 1; i++) {
+            data = abi.encodePacked(data, _path[i], _fees[i]);
+        }
+
+        // Last encode has no fee associated with it since _fees.length == _path.length - 1
+        data = abi.encodePacked(data, _path[_path.length - 1]);
+
+        // Encode fixIn
+        return abi.encodePacked(data, _fixIn);
+    }
+
+    /**
+     * Helper function to decode bytes to boolean. Similar to functions found in BytesLib.
+     * Note: Access modifier is set to public to enable complete testing.
+     */
+    function toBool(bytes memory _bytes, uint256 _start) public pure returns (bool) {
+        require(_start + 1 >= _start, "toBool_overflow");
+        require(_bytes.length >= _start + 1, "toBool_outOfBounds");
+        uint8 tempUint;
+
+        assembly {
+            tempUint := mload(add(add(_bytes, 0x1), _start))
+        }
+
+        require(tempUint <= 1, "Invalid bool data");     // Should be either 0 or 1
+
+        return (tempUint == 0) ? false : true;
+    }
+}