add documentation for Router and update the MEV section in the docs t…

…o reflect new design

contracts/plugins/trading/DutchTrade.sol

@@ -11,7 +11,6 @@ import "../../interfaces/ITrade.sol";
 
 interface IDutchTradeCallee {
     function dutchTradeCallback(
-        address caller,
         address buyToken,
         // {qBuyTok}
         uint256 buyAmount,
@@ -209,7 +208,7 @@ contract DutchTrade is ITrade {
         // {qBuyTok}
         amountIn = _bidAmount(price);
 
-        // Transfer in buy tokens
+        // Mark bidder
         bidder = msg.sender;
 
         // status must begin OPEN
@@ -219,9 +218,11 @@ contract DutchTrade is ITrade {
         if (price > bestPrice.mul(ONE_POINT_FIVE, CEIL)) {
             broker.reportViolation();
         }
+
+        // Transfer buy tokens from bidder
         sell.safeTransfer(bidder, lot()); // {qSellTok}
         uint256 balanceBefore = buy.balanceOf(address(this)); // {qBuyTok}
-        IDutchTradeCallee(bidder).dutchTradeCallback(bidder, address(buy), amountIn, data);
+        IDutchTradeCallee(bidder).dutchTradeCallback(address(buy), amountIn, data);
         require(
             amountIn <= buy.balanceOf(address(this)) - balanceBefore,
             "insufficient buy tokens"

contracts/plugins/trading/DutchTradeRouter.sol

@@ -6,6 +6,11 @@ import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 import { IDutchTradeCallee, TradeStatus, DutchTrade } from "../trading/DutchTrade.sol";
 import { IMain } from "../../interfaces/IMain.sol";
 
+/** @title DutchTradeRouter
+ * @notice Utility contract for placing bids on DutchTrade auctions
+ * @dev This contract is needed as end user wallets cannot call DutchTrade.bid directly anymore, 
+ tests and UI need to be updated to use this contract
+ */
 contract DutchTradeRouter is IDutchTradeCallee {
     using SafeERC20 for IERC20;
     struct Bid {
@@ -53,17 +58,14 @@ contract DutchTradeRouter is IDutchTradeCallee {
     }
 
     /// @notice Callback for DutchTrade
-    /// @param caller The caller of the callback, should be the router
     /// @param buyToken The token DutchTrade is expecting to receive
     /// @param buyAmount The amt the DutchTrade is expecting to receive {qBuyToken}
     /// @notice Data is not used here
     function dutchTradeCallback(
-        address caller,
         address buyToken,
         uint256 buyAmount,
         bytes calldata
     ) external {
-        require(caller == address(this), "Invalid caller");
         require(msg.sender == address(_currentTrade), "Incorrect callee");
         IERC20(buyToken).safeTransfer(msg.sender, buyAmount); //  {qBuyToken}
     }

docs/mev.md

@@ -27,7 +27,7 @@ Bidding instructions from the `DutchTrade` contract:
 `DutchTrade` (relevant) interface:
 
 ```solidity
-function bid() external; // execute a bid at the current block number
+function bid(bytes memory data) external; // execute a bid at the current block number
 
 function sell() external view returns (IERC20);
 
@@ -43,6 +43,8 @@ function bidAmount(uint256 blockNumber) external view returns (uint256); // {qBu
 
 To participate:
 
+Make sure calling contract implements the `IDutchTradeCallee` interface. It contains a single method function `dutchTradeCallbac(address buyToken,uint256 buyAmount,bytes calldata data) external;`. This method will be called by the `DutchTrade` as a callback after calling `bid` and before the trade has been resolved. The trader is expected to pay for the trade during the callback. See `DutchTradeRouter.sol` for an example.
+
 1. Call `status()` view; the auction is ongoing if return value is 1
 2. Call `lot()` to see the number of tokens being sold
 3. Call `bidAmount()` to see the number of tokens required to buy the lot, at various block numbers