From f0e314d0872dc6d8a52fbfdc213bb30385425c98 Mon Sep 17 00:00:00 2001
From: Denis Fadeev <denis@fadeev.org>
Date: Mon, 23 Dec 2024 16:31:19 +0300
Subject: [PATCH] nft: refactor to extract transferCrossChain into an abstract
 contract

---
 contracts/nft/contracts/evm/UniversalNFT.sol  | 58 +++++----------
 .../evm/UniversalNFTTransferrable.sol         | 70 +++++++++++++++++++
 2 files changed, 86 insertions(+), 42 deletions(-)
 create mode 100644 contracts/nft/contracts/evm/UniversalNFTTransferrable.sol

diff --git a/contracts/nft/contracts/evm/UniversalNFT.sol b/contracts/nft/contracts/evm/UniversalNFT.sol
index 9fa8868..19cf834 100644
--- a/contracts/nft/contracts/evm/UniversalNFT.sol
+++ b/contracts/nft/contracts/evm/UniversalNFT.sol
@@ -14,6 +14,7 @@ import {UUPSUpgradeable} from "@openzeppelin/contracts-upgradeable/proxy/utils/U
 import {ERC721PausableUpgradeable} from "@openzeppelin/contracts-upgradeable/token/ERC721/extensions/ERC721PausableUpgradeable.sol";
 
 import "../shared/UniversalNFTEvents.sol";
+import "./UniversalNFTTransferrable.sol";
 
 contract UniversalNFT is
     Initializable,
@@ -24,14 +25,14 @@ contract UniversalNFT is
     OwnableUpgradeable,
     ERC721BurnableUpgradeable,
     UUPSUpgradeable,
-    UniversalNFTEvents
+    UniversalNFTEvents,
+    UniversalNFTTransferrable
 {
-    GatewayEVM public gateway;
     uint256 private _nextTokenId;
+    GatewayEVM public gateway;
     address public universal;
     uint256 public gasLimitAmount;
 
-    error InvalidAddress();
     error Unauthorized();
     error InvalidGasLimit();
     error GasTokenTransferFailed();
@@ -65,6 +66,18 @@ contract UniversalNFT is
         gateway = GatewayEVM(gatewayAddress);
     }
 
+    function getGateway() public view override returns (GatewayEVM) {
+        return gateway;
+    }
+
+    function getUniversal() public view override returns (address) {
+        return universal;
+    }
+
+    function getGasLimitAmount() public view override returns (uint256) {
+        return gasLimitAmount;
+    }
+
     function setGasLimit(uint256 gas) external onlyOwner {
         if (gas == 0) revert InvalidGasLimit();
         gasLimitAmount = gas;
@@ -93,45 +106,6 @@ contract UniversalNFT is
         emit TokenMinted(to, tokenId, uri);
     }
 
-    function transferCrossChain(
-        uint256 tokenId,
-        address receiver,
-        address destination
-    ) external payable whenNotPaused {
-        if (receiver == address(0)) revert InvalidAddress();
-
-        string memory uri = tokenURI(tokenId);
-        _burn(tokenId);
-        bytes memory message = abi.encode(
-            destination,
-            receiver,
-            tokenId,
-            uri,
-            msg.sender
-        );
-        if (destination == address(0)) {
-            gateway.call(
-                universal,
-                message,
-                RevertOptions(address(this), false, address(0), message, 0)
-            );
-        } else {
-            gateway.depositAndCall{value: msg.value}(
-                universal,
-                message,
-                RevertOptions(
-                    address(this),
-                    true,
-                    address(0),
-                    abi.encode(receiver, tokenId, uri, msg.sender),
-                    gasLimitAmount
-                )
-            );
-        }
-
-        emit TokenTransfer(destination, receiver, tokenId, uri);
-    }
-
     function onCall(
         MessageContext calldata context,
         bytes calldata message
diff --git a/contracts/nft/contracts/evm/UniversalNFTTransferrable.sol b/contracts/nft/contracts/evm/UniversalNFTTransferrable.sol
new file mode 100644
index 0000000..1ab523a
--- /dev/null
+++ b/contracts/nft/contracts/evm/UniversalNFTTransferrable.sol
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.26;
+
+import "@zetachain/protocol-contracts/contracts/evm/GatewayEVM.sol";
+import {RevertOptions} from "@zetachain/protocol-contracts/contracts/evm/GatewayEVM.sol";
+import "../shared/UniversalNFTEvents.sol";
+import {ERC721Upgradeable} from "@openzeppelin/contracts-upgradeable/token/ERC721/ERC721Upgradeable.sol";
+
+abstract contract UniversalNFTTransferrable is
+    ERC721Upgradeable,
+    UniversalNFTEvents
+{
+    error InvalidAddress();
+
+    function getGateway() public view virtual returns (GatewayEVM);
+
+    function getUniversal() public view virtual returns (address);
+
+    function getGasLimitAmount() public view virtual returns (uint256);
+
+    /**
+     * @notice Transfers an NFT to another chain.
+     * @dev    Burns the NFT locally, then sends an encoded message to the
+     *         Gateway to recreate it on the destination chain (or revert if needed).
+     * @param  tokenId The ID of the NFT to transfer.
+     * @param  receiver The address on the destination chain that will receive the NFT.
+     * @param  destination The contract address on the destination chain (or address(0) if same chain).
+     */
+    function transferCrossChain(
+        uint256 tokenId,
+        address receiver,
+        address destination
+    ) external payable virtual {
+        if (receiver == address(0)) revert InvalidAddress();
+
+        string memory uri = tokenURI(tokenId);
+
+        _burn(tokenId);
+
+        bytes memory message = abi.encode(
+            destination,
+            receiver,
+            tokenId,
+            uri,
+            msg.sender
+        );
+
+        if (destination == address(0)) {
+            getGateway().call(
+                getUniversal(),
+                message,
+                RevertOptions(address(this), false, address(0), message, 0)
+            );
+        } else {
+            getGateway().depositAndCall{value: msg.value}(
+                getUniversal(),
+                message,
+                RevertOptions(
+                    address(this),
+                    true,
+                    address(0),
+                    abi.encode(receiver, tokenId, uri, msg.sender),
+                    getGasLimitAmount()
+                )
+            );
+        }
+
+        emit TokenTransfer(destination, receiver, tokenId, uri);
+    }
+}