feat: oracle contract

solidity/contracts/BlockHeaderOracle.sol

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity =0.8.19;
+
+/**
+ * @title BlockHeaderOracle
+ * @notice This contract's purpose is to return the latest stored L1 block header and timestamp
+ * @notice Every X minutes a "magical" off-chain agent provides the latest block header and timestamp
+ */
+contract BlockHeaderOracle {
+  /**
+   * @notice Emits when the block header and timestamp are updated
+   */
+  event BlockHeaderUpdated(bytes _blockHeader, uint256 _blockTimestamp, uint256 _blockNumber);
+
+  /**
+   * @notice The block header
+   */
+  bytes public blockHeader;
+
+  /**
+   * @notice The block timestamp of the latest block header
+   */
+  uint256 public blockTimestamp;
+
+  /**
+   * @notice Updates the block header and timestamp
+   * @param _blockHeader The block header
+   * @param _blockTimestamp The block timestamp
+   * @param _blockNumber The block number
+   */
+  function updateBlockHeader(bytes memory _blockHeader, uint256 _blockTimestamp, uint256 _blockNumber) external {
+    blockHeader = _blockHeader;
+    blockTimestamp = _blockTimestamp;
+
+    emit BlockHeaderUpdated(_blockHeader, _blockTimestamp, _blockNumber);
+  }
+
+  /**
+   * @notice Returns the latest block header and timestamp
+   * @return _blockHeader The block header
+   * @return _blockTimestamp The block timestamp
+   */
+  function getLatestBlockHeader() external view returns (bytes memory _blockHeader, uint256 _blockTimestamp) {
+    return (blockHeader, blockTimestamp);
+  }
+}

solidity/test/e2e/Common.sol

@@ -5,11 +5,15 @@ import {DSTestPlus} from '@defi-wonderland/solidity-utils/solidity/test/DSTestPl
 import {IERC20} from 'isolmate/interfaces/tokens/IERC20.sol';
 import {SafeProxy} from 'safe-contracts/proxies/SafeProxy.sol';
 import {Enum} from 'safe-contracts/common/Enum.sol';
+
 import {StorageMirror} from 'contracts/StorageMirror.sol';
 import {UpdateStorageMirrorGuard} from 'contracts/UpdateStorageMirrorGuard.sol';
 import {GuardCallbackModule} from 'contracts/GuardCallbackModule.sol';
+import {BlockHeaderOracle} from 'contracts/BlockHeaderOracle.sol';
+
 import {IGuardCallbackModule} from 'interfaces/IGuardCallbackModule.sol';
 import {ISafe} from 'interfaces/ISafe.sol';
+
 import {IGnosisSafeProxyFactory} from 'test/e2e/IGnosisSafeProxyFactory.sol';
 import {TestConstants} from 'test/utils/TestConstants.sol';
 import {ContractDeploymentAddress} from 'test/utils/ContractDeploymentAddress.sol';
@@ -25,6 +29,7 @@ contract CommonE2EBase is DSTestPlus, TestConstants {
   StorageMirror public storageMirror;
   UpdateStorageMirrorGuard public updateStorageMirrorGuard;
   GuardCallbackModule public guardCallbackModule;
+  BlockHeaderOracle public oracle;
   ISafe public safe;
   IGnosisSafeProxyFactory public gnosisSafeProxyFactory = IGnosisSafeProxyFactory(GNOSIS_SAFE_PROXY_FACTORY);
 
@@ -52,6 +57,10 @@ contract CommonE2EBase is DSTestPlus, TestConstants {
     updateStorageMirrorGuard = new UpdateStorageMirrorGuard(guardCallbackModule); // deployer nonce 2
     label(address(updateStorageMirrorGuard), 'UpdateStorageMirrorGuard');
 
+    vm.prank(deployer);
+    oracle = new BlockHeaderOracle(); // deployer nonce 3
+    label(address(oracle), 'MockOracle');
+
     // Make sure the theoritical address was calculated correctly
     assert(address(updateStorageMirrorGuard) == _updateStorageMirrorGuardTheoriticalAddress);
 

solidity/test/unit/MockOracle.t.sol

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity >=0.8.4 <0.9.0;
+
+import {Test} from 'forge-std/Test.sol';
+import {BlockHeaderOracle} from 'contracts/BlockHeaderOracle.sol';
+
+abstract contract Base is Test {
+  event BlockHeaderUpdated(bytes _blockHeader, uint256 _blockTimestamp, uint256 _blockNumber);
+
+  BlockHeaderOracle public oracle;
+
+  function setUp() public {
+    oracle = new BlockHeaderOracle();
+  }
+}
+
+contract UnitBlockHeaderOracle is Base {
+  function testUpdateBlockHeader(bytes memory _blockHeader, uint256 _blockTimestamp, uint256 _blockNumber) public {
+    vm.expectEmit(true, true, true, true);
+    emit BlockHeaderUpdated(_blockHeader, _blockTimestamp, _blockNumber);
+    oracle.updateBlockHeader(_blockHeader, _blockTimestamp, _blockNumber);
+
+    assertEq(_blockHeader, oracle.blockHeader(), 'Block header should be saved');
+    assertEq(_blockTimestamp, oracle.blockTimestamp(), 'Block timestamp should be saved');
+  }
+
+  function testGetLatestBlockHeader() public {
+    bytes memory _blockHeader = '0x1234';
+    uint256 _blockTimestamp = 1234;
+    uint256 _blockNumber = 1234;
+
+    oracle.updateBlockHeader(_blockHeader, _blockTimestamp, _blockNumber);
+
+    (bytes memory _savedBlockHeader, uint256 _savedBlockTimestamp) = oracle.getLatestBlockHeader();
+
+    assertEq(_blockHeader, _savedBlockHeader, 'Block header should be saved');
+    assertEq(_blockTimestamp, _savedBlockTimestamp, 'Block timestamp should be saved');
+  }
+}