Support MEVM context (#46)

* Enable context?

* Update README

* Remove comment

* Remove dead code

README.md

@@ -60,6 +60,28 @@ contract Example {
 }
 ```
 
+### Context.sol
+
+Helper library to interact with the Suave context in the MEVM.
+
+Available functions:
+
+- `confidentialInputs()`: Returns the confidential inputs of the offchain request.
+- `kettleAddress()`: Address of the kettle that is executing the offchain request.
+
+#### Example usage
+
+```solidity
+import "suave-std/Context.sol";
+
+contract Example {
+    function example() {
+        bytes memory inputs = Context.confidentialInputs();
+        address kettle = Context.kettleAddress();
+    }
+}
+```
+
 ### protocols/MevShare.sol
 
 Helper library to send bundle requests with the Mev-Share protocol.

src/Context.sol

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: Unlicense
+pragma solidity ^0.8.13;
+
+import "./suavelib/Suave.sol";
+
+library Context {
+    function confidentialInputs() internal returns (bytes memory) {
+        return Suave.contextGet("confidentialInputs");
+    }
+
+    function kettleAddress() internal returns (address) {
+        bytes memory addr = Suave.contextGet("kettleAddress");
+        return abi.decode(addr, (address));
+    }
+}

src/Test.sol

@@ -4,6 +4,7 @@ pragma solidity ^0.8.8;
 import "./forge/Registry.sol";
 import "./suavelib/Suave.sol";
 import "forge-std/Test.sol";
+import "./forge/ContextConnector.sol";
 
 interface ConfidentialInputsWrapperI {
     function setConfidentialInputs(bytes memory) external;
@@ -15,8 +16,8 @@ interface ConfidentialStoreI {
 }
 
 contract SuaveEnabled is Test {
-    ConfidentialInputsWrapperI constant confInputsWrapper = ConfidentialInputsWrapperI(Suave.CONFIDENTIAL_INPUTS);
     ConfidentialStoreI constant confStoreWrapper = ConfidentialStoreI(Registry.confidentialStoreAddr);
+    ContextConnector constant ctx = ContextConnector(Suave.CONTEXT_GET);
 
     function setUp() public {
         string[] memory inputs = new string[](2);
@@ -33,11 +34,6 @@ contract SuaveEnabled is Test {
 
         // reset the confidential store before each test
         resetConfidentialStore();
-        confInputsWrapper.resetConfidentialInputs();
-    }
-
-    function setConfidentialInputs(bytes memory data) internal {
-        confInputsWrapper.setConfidentialInputs(data);
     }
 
     function detectErrorMessage(bytes memory reason) internal pure returns (string memory) {

src/forge/ContextConnector.sol

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.8;
+
+contract ContextConnector {
+    bytes confidentialInputs;
+    address kettleAddress;
+
+    function setConfidentialInputs(bytes memory _confidentialInputs) public {
+        confidentialInputs = _confidentialInputs;
+    }
+
+    function resetConfidentialInputs() public {
+        confidentialInputs = "";
+    }
+
+    function setKettleAddress(address _kettleAddress) public {
+        kettleAddress = _kettleAddress;
+    }
+
+    function resetKettleAddress() public {
+        setKettleAddress(address(0));
+    }
+
+    fallback() external {
+        (string memory key) = abi.decode(msg.data, (string));
+        bytes32 keyHash = keccak256(abi.encodePacked(key));
+
+        bytes memory msgContent;
+        if (keyHash == keccak256(abi.encodePacked("confidentialInputs"))) {
+            msgContent = confidentialInputs;
+        } else if (keyHash == keccak256(abi.encodePacked("kettleAddress"))) {
+            msgContent = abi.encode(kettleAddress);
+        } else {
+            revert("Invalid context key");
+        }
+
+        bytes memory msgdata = abi.encode(msgContent);
+        assembly {
+            let location := msgdata
+            let length := mload(msgdata)
+            return(add(location, 0x20), length)
+        }
+    }
+}

src/forge/Registry.sol

@@ -4,7 +4,7 @@ pragma solidity ^0.8.8;
 
 import "../suavelib/Suave.sol";
 import "./Connector.sol";
-import "./ConfidentialInputs.sol";
+import "./ContextConnector.sol";
 import "./SuaveAddrs.sol";
 import "./ConfidentialStore.sol";
 import "./ConfidentialStoreConnector.sol";
@@ -35,7 +35,7 @@ library Registry {
         vm.etch(Suave.FETCH_DATA_RECORDS, type(ConfidentialStoreConnector).runtimeCode);
 
         // enable is confidential wrapper
-        vm.etch(Suave.CONFIDENTIAL_INPUTS, type(ConfidentialInputsWrapper).runtimeCode);
+        vm.etch(Suave.CONTEXT_GET, type(ContextConnector).runtimeCode);
     }
 
     function deployCodeTo(bytes memory creationCode, address where) internal {

test/Forge.t.sol

@@ -4,6 +4,7 @@ pragma solidity ^0.8.13;
 import "forge-std/Test.sol";
 import "src/Test.sol";
 import "src/suavelib/Suave.sol";
+import "src/Context.sol";
 
 contract TestForge is Test, SuaveEnabled {
     address[] public addressList = [0xC8df3686b4Afb2BB53e60EAe97EF043FE03Fb829];
@@ -36,15 +37,34 @@ contract TestForge is Test, SuaveEnabled {
         assertEq(keccak256(found), keccak256(value));
     }
 
-    function testForgeConfidentialInputs() public {
-        // ensure that the confidential inputs are empty
-        bytes memory found = Suave.confidentialInputs();
-        assertEq(found.length, 0);
+    function testForgeContextConfidentialInputs() public {
+        bytes memory found1 = Context.confidentialInputs();
+        assertEq(found1.length, 0);
 
         bytes memory input = hex"abcd";
-        setConfidentialInputs(input);
+        ctx.setConfidentialInputs(input);
 
-        bytes memory found2 = Suave.confidentialInputs();
+        bytes memory found2 = Context.confidentialInputs();
         assertEq0(input, found2);
+
+        ctx.resetConfidentialInputs();
+
+        bytes memory found3 = Context.confidentialInputs();
+        assertEq(found3.length, 0);
+    }
+
+    function testForgeContextKettleAddress() public {
+        address found1 = Context.kettleAddress();
+        assertEq(found1, address(0));
+
+        ctx.setKettleAddress(address(this));
+
+        address found2 = Context.kettleAddress();
+        assertEq(found2, address(this));
+
+        ctx.resetKettleAddress();
+
+        address found3 = Context.kettleAddress();
+        assertEq(found3, address(0));
     }
 }