feature: current in Common. Event for Message

solidity/contracts/Common.sol

@@ -7,10 +7,11 @@ abstract contract Common {
     enum States {ACTIVE, FAILED}
 
     uint32 public immutable originSLIP44;
-    address public updater;
     bytes32 public immutable DOMAIN_HASH;
 
+    address public updater;
     States public state;
+    bytes32 public current;
 
     event Update(
         bytes32 indexed _oldRoot,
@@ -24,9 +25,14 @@ abstract contract Common {
         bytes _signature2
     );
 
-    constructor(uint32 _originSLIP44, address _updater) {
+    constructor(
+        uint32 _originSLIP44,
+        address _updater,
+        bytes32 _current
+    ) {
         originSLIP44 = _originSLIP44;
         updater = _updater;
+        current = _current;
         DOMAIN_HASH = keccak256(abi.encodePacked(_originSLIP44, "OPTICS"));
         state = States.ACTIVE;
     }

solidity/contracts/Home.sol

@@ -9,20 +9,32 @@ contract Home is MerkleTreeManager, QueueManager, Common {
     using QueueLib for QueueLib.Queue;
     using MerkleLib for MerkleLib.Tree;
 
+    mapping(uint32 => uint32) public sequences;
+
     uint256 constant BOND_SIZE = 50 ether;
 
+    event Message(
+        uint32 indexed destination,
+        uint32 indexed sequence,
+        // the message is after this root. Some future update will contain it.
+        bytes32 indexed current,
+        bytes message
+    );
     event ImproperUpdate();
 
-    constructor(uint32 _originSLIP44, address _updater)
+    constructor(
+        uint32 _originSLIP44,
+        address _updater,
+        bytes32 _current
+    )
         payable
         MerkleTreeManager()
         QueueManager()
-        Common(_originSLIP44, _updater)
+        Common(_originSLIP44, _updater, _current)
     {
         require(msg.value >= BOND_SIZE, "insufficient bond");
     }
 
-    // TODO
     function fail() internal override {
         _setFailed();
         msg.sender.transfer(address(this).balance / 2);
@@ -33,11 +45,15 @@ contract Home is MerkleTreeManager, QueueManager, Common {
         bytes32 recipient,
         bytes memory body
     ) external notFailed {
+        uint32 sequence = sequences[destination] + 1;
+        sequences[destination] = sequence;
+
         bytes32 _digest =
             keccak256(
                 abi.encodePacked(
                     originSLIP44,
                     bytes32(uint256(uint160(msg.sender))),
+                    sequence,
                     destination,
                     recipient,
                     body
@@ -46,6 +62,7 @@ contract Home is MerkleTreeManager, QueueManager, Common {
 
         tree.insert(_digest);
         queue.enqueue(root());
+        emit Message(destination, sequence, current, body);
     }
 
     function update(
@@ -67,6 +84,7 @@ contract Home is MerkleTreeManager, QueueManager, Common {
         bytes memory _signature
     ) public notFailed returns (bool) {
         require(Common.checkSig(_newRoot, _oldRoot, _signature), "bad sig");
+        require(_oldRoot == current, "Not a current update");
         if (!queue.contains(_newRoot)) {
             fail();
             emit ImproperUpdate();

solidity/contracts/Replica.sol

@@ -9,7 +9,6 @@ abstract contract Replica is Common {
     uint32 public immutable ownSLIP44;
     uint256 public optimisticSeconds;
 
-    bytes32 current;
     bytes32 pending;
     uint256 confirmAt;
 
@@ -20,11 +19,11 @@ abstract contract Replica is Common {
         uint32 _ownSLIP44,
         address _updater,
         uint256 _optimisticSeconds,
-        bytes32 _start
-    ) Common(_originSLIP44, _updater) {
+        bytes32 _current
+    ) Common(_originSLIP44, _updater, _current) {
         ownSLIP44 = _ownSLIP44;
         optimisticSeconds = _optimisticSeconds;
-        current = _start;
+        current = _current;
     }
 
     function fail() internal override {
@@ -93,7 +92,10 @@ contract ProcessingReplica is Replica, HasZeroHashes {
 
     function _beforeUpdate() internal override {}
 
-    function process(bytes calldata _message) public {
+    function process(bytes memory _message)
+        public
+        returns (bool, bytes memory)
+    {
         bytes29 _m = _message.ref(0);
 
         uint32 _destination = uint32(_m.indexUint(36, 4));
@@ -113,7 +115,7 @@ contract ProcessingReplica is Replica, HasZeroHashes {
         bytes memory payload = _m.slice(76, _m.len() - 76, 0).clone();
 
         // results intentionally ignored
-        recipient.call(payload);
+        return recipient.call(payload);
     }
 
     function prove(
@@ -134,7 +136,7 @@ contract ProcessingReplica is Replica, HasZeroHashes {
         bytes32 leaf,
         bytes32[32] calldata proof,
         uint256 index,
-        bytes calldata message
+        bytes memory message
     ) external {
         require(prove(leaf, proof, index), "!prove");
         process(message);