Add WalletProxyHook (#191)

contracts/hooks/WalletProxyHook.sol

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+// SPDX-License-Identifier: Apache-2.0
+pragma solidity 0.8.18;
+
+import {IWalletProxy} from './interfaces/IWalletProxy.sol';
+import {Implementation} from '../modules/commons/Implementation.sol';
+
+contract WalletProxyHook is IWalletProxy, Implementation {
+  /// @inheritdoc IWalletProxy
+  function PROXY_getImplementation() public view returns (address) {
+    return _getImplementation();
+  }
+}

contracts/hooks/interfaces/IWalletProxy.sol

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+// Copyright Immutable Pty Ltd 2018 - 2023
+// SPDX-License-Identifier: Apache 2.0
+// https://github.com/immutable/contracts/blob/a04f7ecb8a79ad8f1b67f73f770e0545deb6cba2/contracts/allowlist/IWalletProxy.sol
+pragma solidity 0.8.18;
+
+// Interface to retrieve the implemention stored inside the Proxy contract
+/// Interface for Passport Wallet's proxy contract.
+interface IWalletProxy {
+    // Returns the current implementation address used by the proxy contract
+    // solhint-disable-next-line func-name-mixedcase
+    function PROXY_getImplementation() external view returns (address);
+}

foundry_test/hooks/WalletProxyHook.t.sol

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+// SPDX-License-Identifier: Apache-2.0
+pragma solidity 0.8.18;
+
+import 'contracts/hooks/WalletProxyHook.sol';
+import 'contracts/hooks/interfaces/IWalletProxy.sol';
+import 'contracts/modules/commons/ModuleHooks.sol';
+import 'contracts/Factory.sol';
+
+import 'foundry_test/base/AdvTest.sol';
+
+contract WalletProxyHookTest is AdvTest {
+  ModuleHooks private template;
+  ModuleHooks private walletMod;
+  WalletProxyHook private wallet;
+
+  function setUp() external {
+    Factory factory = new Factory();
+    template = new ModuleHooks();
+    walletMod = ModuleHooks(payable(factory.deploy(address(template), bytes32(0))));
+    WalletProxyHook hook = new WalletProxyHook();
+
+    // Add hook
+    vm.prank(address(walletMod));
+    walletMod.addHook(IWalletProxy.PROXY_getImplementation.selector, address(hook));
+
+    wallet = WalletProxyHook(address(walletMod));
+    vm.label(address(wallet), 'wallet');
+  }
+
+  //
+  // Get Implementation
+  //
+
+  function test_PROXY_getImplementation() external {
+    assertEq(wallet.PROXY_getImplementation(), address(template));
+  }
+}