[DO NOT MERGE NOT TESTED] consensusWithdraw proposol

contracts/LedgerChannel.sol

@@ -48,6 +48,19 @@ contract LedgerChannel {
         uint256 updateLCtimeout
     );
 
+    event DidLCWithdrawal(
+        bytes32 indexed lcID,
+        address withdrawalAddress,
+        uint256 sequence,
+        uint256 ethBalanceA,
+        uint256 ethBalanceI,
+        uint256 tokenBalanceA,
+        uint256 tokenBalanceI,
+        uint256 ethWithdrawalAmount,
+        uint256 tokenWithdrawalAmount
+    );
+
+
     event DidLCClose (
         bytes32 indexed channelId,
         uint256 sequence,
@@ -234,6 +247,88 @@ contract LedgerChannel {
         emit DidLCDeposit(_lcID, recipient, _balance, isToken);
     }
 
+    // A consensus withdraw is essentially doing a consensus close for a partial amount and then opening a new channel with the remaining balances
+    // we are doing it while keeping the same channel by changing initialDeposit
+
+    // We may want to change initialDeposit to a different variable name like lastCheckedInBalances
+    // multiple consensusWithdraws can happen offchain before submitting to chain as long as both parties remain smart about what the balances truly are.
+
+    // if multiple consensus withdraws happen off chain before getting submitted to chain some issues happen when trying to batch them.
+    // for example: partyA withdraws, partyI then wishes to batch their own withdraw with patyA.  But now partyI can submit their first withdrawal to chain and invalidate the 2nd one whenever they wish
+    // this would also invalidate all state updates after the first withdrawal.
+    function consensusWithdraw(
+        bytes32 _lcID,
+        uint256[7] withdrawParams, // [sequence, ethBalanceA, ethBalanceI, tokenBalanceA, tokenBalanceI, ethWithdrawal, tokenWithdrawal]
+        address _withdrawalAddress,
+        string _sigA,
+        string _sigI
+    )
+        public
+    {
+        // first we make sure the channel is open and the balances all add up.   This means that the consensusWithdraw must be submitted to chain before trying to closeChannel or
+        // both parties can ignore the consensusWithdraw and submit a consensusClose for the correct balances (batching together the withdraw and the close)
+        require(Channels[_lcID].isOpen == true);
+        require(Channels[_lcID].initialDeposit[0] + Channels[_lcID].ethBalances[2] + Channels[_lcID].ethBalances[3] == withdrawParams[1] + withdrawParams[2] + withdrawParams[5]);
+        require(Channels[_lcID].initialDeposit[1] + Channels[_lcID].erc20Balances[2] + Channels[_lcID].erc20Balances[3] == withdrawParams[3] + withdrawParams[4] + withdrawParams[6]);
+
+        // prevent replay attacks
+        require(withdrawParams[0] > Channels[_lcID].sequence);
+
+        // verify sigs
+        bytes32 _state = keccak256(
+            abi.encodePacked(
+                _lcID,
+                true,
+                withdrawParams[0],
+              // what are these 2?
+                uint256(0),
+                bytes32(0x0),
+                Channels[_lcID].partyAddresses[0],
+                Channels[_lcID].partyAddresses[1],
+                // withdrawParams[1], // commenting this out because it's determinstic still (balances must add up to total) and getting a stack too deep error
+                withdrawParams[2],
+                withdrawParams[3],
+                withdrawParams[4],
+                withdrawParams[5],
+                withdrawParams[6]
+            )
+        );
+
+        require(Channels[_lcID].partyAddresses[0] == ECTools.recoverSigner(_state, _sigA));
+        require(Channels[_lcID].partyAddresses[1] == ECTools.recoverSigner(_state, _sigI));
+
+        // transfer eth
+        if(withdrawParams[5] != 0) {
+            _withdrawalAddress.transfer(withdrawParams[5]);
+        }
+
+        // transfer Tokens
+        if(withdrawParams[6] != 0) {
+            require(Channels[_lcID].token.transfer(_withdrawalAddress, withdrawParams[6]), "happyWithdrawlChannel: token transfer failure");
+        }
+
+        // update the new channel as if it just now got created with the current sequence
+        Channels[_lcID].sequence = withdrawParams[0];
+        Channels[_lcID].initialDeposit = [withdrawParams[1] + withdrawParams[2], withdrawParams[3] + withdrawParams[4]];
+
+
+
+        Channels[_lcID].ethBalances = [withdrawParams[1], withdrawParams[2]];
+        Channels[_lcID].erc20Balances = [withdrawParams[3], withdrawParams[4]];
+
+        emit DidLCWithdrawal(
+            _lcID,
+            _withdrawalAddress,
+            withdrawParams[0],
+            withdrawParams[1],
+            withdrawParams[2],
+            withdrawParams[3],
+            withdrawParams[4],
+            withdrawParams[5],
+            withdrawParams[6]
+        );
+    }
+
     // TODO: Check there are no open virtual channels, the client should have cought this before signing a close LC state update
     function consensusCloseChannel(
         bytes32 _lcID,