Merge pull request #870 from keep-network/relay-request-callback

Relay request callback

Update both Solidity and Go code to provide optional relay request callback.

contracts/solidity/contracts/KeepRandomBeaconImplV1.sol

@@ -41,6 +41,8 @@ contract KeepRandomBeaconImplV1 is Ownable {
         address sender;
         uint256 payment;
         bytes groupPubKey;
+        address callbackContract;
+        string callbackMethod;
     }
 
     mapping(uint256 => Request) internal _requests;
@@ -79,7 +81,7 @@ contract KeepRandomBeaconImplV1 is Ownable {
         // to trigger the creation of the first group. Requests are removed on successful
         // entries so genesis entry can only be called once.
         _requestCounter++;
-        _requests[_requestCounter] = Request(msg.sender, 0, genesisGroupPubKey);
+        _requests[_requestCounter] = Request(msg.sender, 0, genesisGroupPubKey, address(0), "");
     }
 
     /**
@@ -96,6 +98,19 @@ contract KeepRandomBeaconImplV1 is Ownable {
      * @return An uint256 representing uniquely generated relay request ID. It is also returned as part of the event.
      */
     function requestRelayEntry(uint256 seed) public payable returns (uint256) {
+        return requestRelayEntry(seed, address(0), "");
+    }
+
+    /**
+     * @dev Creates a request to generate a new relay entry, which will include a
+     * random number (by signing the previous entry's random number).
+     * @param seed Initial seed random value from the client. It should be a cryptographically generated random value.
+     * @param callbackContract Callback contract address. Callback is called once a new relay entry has been generated.
+     * @param callbackMethod Callback contract method signature. String representation of your method with a single
+     * uint256 input parameter i.e. "relayEntryCallback(uint256)".
+     * @return An uint256 representing uniquely generated relay request ID. It is also returned as part of the event.
+     */
+    function requestRelayEntry(uint256 seed, address callbackContract, string memory callbackMethod) public payable returns (uint256) {
         require(
             msg.value >= _minPayment,
             "Payment is less than required minimum."
@@ -110,7 +125,7 @@ contract KeepRandomBeaconImplV1 is Ownable {
 
         _requestCounter++;
 
-        _requests[_requestCounter] = Request(msg.sender, msg.value, groupPubKey);
+        _requests[_requestCounter] = Request(msg.sender, msg.value, groupPubKey, callbackContract, callbackMethod);
 
         emit RelayEntryRequested(_requestCounter, msg.value, _previousEntry, seed, groupPubKey);
         return _requestCounter;
@@ -161,6 +176,12 @@ contract KeepRandomBeaconImplV1 is Ownable {
         require(_requests[requestID].groupPubKey.equalStorage(groupPubKey), "Provided group was not selected to produce entry for this request.");
         require(BLS.verify(groupPubKey, abi.encodePacked(previousEntry, seed), bytes32(groupSignature)), "Group signature failed to pass BLS verification.");
 
+        address callbackContract = _requests[requestID].callbackContract;
+
+        if (callbackContract != address(0)) {
+            callbackContract.call(abi.encodeWithSignature(_requests[requestID].callbackMethod, groupSignature));
+        }
+
         delete _requests[requestID];
         _previousEntry = groupSignature;
 

contracts/solidity/contracts/examples/CallbackContract.sol

@@ -0,0 +1,29 @@
+pragma solidity ^0.5.4;
+
+
+/**
+ * @title CallbackContract
+ * @dev Example callback contract for Random Beacon.
+ */
+contract CallbackContract {
+
+    uint256 internal _lastEntry;
+
+    /**
+     * @dev Example of a callback method. Method signature can be
+     * calculated as bytes4(keccak256("callback(uint256)")
+    */
+    function callback(uint256 requestResponse)
+        public
+    {
+        _lastEntry = requestResponse;
+    }
+
+    /**
+     * @dev Returns previous entry.
+     */
+    function lastEntry() public view returns (uint256)
+    {
+        return _lastEntry;
+    }
+}

contracts/solidity/scripts/genesis.js

@@ -0,0 +1,32 @@
+const KeepRandomBeaconProxy = artifacts.require('KeepRandomBeacon.sol')
+const KeepRandomBeacon = artifacts.require("KeepRandomBeaconImplV1")
+
+// The data below should match genesis relay request data defined on contract
+// initialization i.e. in 2_deploy_contracts.js. Successful genesis entry will
+// trigger creation of the first group that will be chosen to respond on the
+// next relay request, resulting another relay entry with creation of another
+// group and so on.
+
+// https://www.wolframalpha.com/input/?i=pi+to+78+digits
+const previousEntry = web3.utils.toBN('31415926535897932384626433832795028841971693993751058209749445923078164062862')
+
+// https://www.wolframalpha.com/input/?i=e+to+78+digits
+const seed = web3.utils.toBN('27182818284590452353602874713526624977572470936999595749669676277240766303535')
+
+// Data generated using client keep-core/pkg/bls package signing previous entry using master secret key '123'
+const groupPubKey = "0x1f1954b33144db2b5c90da089e8bde287ec7089d5d6433f3b6becaefdb678b1b2a9de38d14bef2cf9afc3c698a4211fa7ada7b4f036a2dfef0dc122b423259d0"
+const groupSignature = web3.utils.toBN('10920102476789591414949377782104707130412218726336356788412941355500907533021')
+
+module.exports = async function () {
+
+  const keepRandomBeaconProxy = await KeepRandomBeaconProxy.deployed()
+  let contract = await KeepRandomBeacon.at(keepRandomBeaconProxy.address)
+  try {
+    await contract.relayEntry(1, groupSignature, groupPubKey, previousEntry, seed)
+    console.log('Genesis entry successfully submitted.')
+  } catch(error) {
+    console.error('Genesis entry submission failed with', error)
+  }
+
+  process.exit()
+}

contracts/solidity/scripts/request-relay-entry-with-callback.js

@@ -0,0 +1,31 @@
+const crypto = require("crypto")
+const KeepRandomBeacon = artifacts.require("KeepRandomBeaconImplV1")
+const KeepRandomBeaconProxy = artifacts.require('KeepRandomBeacon.sol')
+
+// Example usage:
+// truffle exec ./scripts/request-relay-entry-with-callback.js yourContractAddress "callbackMethodName" payment
+// truffle exec ./scripts/request-relay-entry-with-callback.js 0x9F57C01059057d821c6b4B04A4598322661C934F "callback(uint256)" 100
+
+module.exports = async function() {
+
+  const keepRandomBeaconProxy = await KeepRandomBeaconProxy.deployed()
+  const contractInstance = await KeepRandomBeacon.at(keepRandomBeaconProxy.address)
+
+  try {
+    let tx = await contractInstance.methods['requestRelayEntry(uint256,address,string)'](crypto.randomBytes(32), process.argv[4], process.argv[5], {value: process.argv[6]})
+    console.log('Successfully requested relay entry with a callback. RequestId =', tx.logs[0].args.requestID.toString())
+    console.log(
+      '\n---Transaction Summary---' + '\n' +
+      'From:' + tx.receipt.from + '\n' +
+      'To:' + tx.receipt.to + '\n' +
+      'BlockNumber:' + tx.receipt.blockNumber + '\n' +
+      'TotalGas:' + tx.receipt.cumulativeGasUsed + '\n' +
+      'TransactionHash:' + tx.receipt.transactionHash + '\n' +
+      '--------------------------'
+    )
+  } catch(error) {
+    console.error('Request failed with', error)
+  }
+
+  process.exit()
+}