Add initial L0 Hook and test

solidity/contracts/hooks/LayerZeroHook.sol

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: MIT
+pragma solidity >=0.8.0;
+
+/*@@@@@@@       @@@@@@@@@
+ @@@@@@@@@       @@@@@@@@@
+  @@@@@@@@@       @@@@@@@@@
+   @@@@@@@@@       @@@@@@@@@
+    @@@@@@@@@@@@@@@@@@@@@@@@@
+     @@@@@  HYPERLANE  @@@@@@@
+    @@@@@@@@@@@@@@@@@@@@@@@@@
+   @@@@@@@@@       @@@@@@@@@
+  @@@@@@@@@       @@@@@@@@@
+ @@@@@@@@@       @@@@@@@@@
+@@@@@@@@@       @@@@@@@@*/
+
+import {Message} from "../libs/Message.sol";
+import {MailboxClient} from "../client/MailboxClient.sol";
+import {Indexed} from "../libs/Indexed.sol";
+import {IPostDispatchHook} from "../interfaces/hooks/IPostDispatchHook.sol";
+import {AbstractPostDispatchHook} from "./libs/AbstractPostDispatchHook.sol";
+import {StandardHookMetadata} from "./libs/StandardHookMetadata.sol";
+
+contract LayerZeroHook is AbstractPostDispatchHook, MailboxClient, Indexed {
+    constructor(address _mailbox) MailboxClient(_mailbox) {}
+
+    // ============ External Functions ============
+
+    /// @inheritdoc IPostDispatchHook
+    function hookType() external pure override returns (uint8) {
+        return uint8(IPostDispatchHook.Types.LAYER_ZERO);
+    }
+
+    /// @inheritdoc AbstractPostDispatchHook
+    function _postDispatch(
+        bytes calldata metadata,
+        bytes calldata message
+    ) internal virtual override {}
+
+    /// @inheritdoc AbstractPostDispatchHook
+    function _quoteDispatch(
+        bytes calldata metadata,
+        bytes calldata message
+    ) internal view virtual override returns (uint256) {}
+}

solidity/contracts/interfaces/hooks/IPostDispatchHook.sol

@@ -23,7 +23,8 @@ interface IPostDispatchHook {
         FALLBACK_ROUTING,
         ID_AUTH_ISM,
         PAUSABLE,
-        PROTOCOL_FEE
+        PROTOCOL_FEE,
+        LAYER_ZERO
     }
 
     /**

solidity/test/hooks/LayerZeroHook.t.sol

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.13;
+
+import {LZEndpointMock} from "@layerzerolabs/solidity-examples/contracts/lzApp/mocks/LZEndpointMock.sol";
+import {Test} from "forge-std/Test.sol";
+import {TestMailbox} from "../../contracts/test/TestMailbox.sol";
+import {LayerZeroHook} from "../../contracts/hooks/LayerZeroHook.sol";
+import {IPostDispatchHook} from "../../contracts/interfaces/hooks/IPostDispatchHook.sol";
+
+contract LayerZeroHookTest is Test {
+    LZEndpointMock lZEndpointMock;
+    TestMailbox public mailbox;
+    LayerZeroHook hook;
+
+    function setUp() public {
+        lZEndpointMock = new LZEndpointMock(uint16(block.chainid));
+        mailbox = new TestMailbox(0);
+        hook = new LayerZeroHook(address(mailbox));
+    }
+
+    // function testPostDispatch_emit() public {}
+
+    function testQuoteDispatch() public {
+        assertEq(hook.quoteDispatch("", ""), 0);
+    }
+
+    function testHookType() public {
+        assertEq(hook.hookType(), uint8(IPostDispatchHook.Types.LAYER_ZERO));
+    }
+}