Merge pull request #70 from maticnetwork/batch-withdraw-and-metadata-…

…transfer

Batch deposit/ withdraw MintableERC721 & transfer arbitrary metadata for ERC721

artifacts/DummyERC721.json

@@ -1 +1 @@
-{"abi":[{"inputs":[{"internalType":"string","name":"name_","type":"string"},{"internalType":"string","name":"symbol_","type":"string"}],"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"owner","type":"address"},{"indexed":true,"internalType":"address","name":"approved","type":"address"},{"indexed":true,"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"owner","type":"address"},{"indexed":true,"internalType":"address","name":"operator","type":"address"},{"indexed":false,"internalType":"bool","name":"approved","type":"bool"}],"name":"ApprovalForAll","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"userAddress","type":"address"},{"indexed":false,"internalType":"address payable","name":"relayerAddress","type":"address"},{"indexed":false,"internalType":"bytes","name":"functionSignature","type":"bytes"}],"name":"MetaTransactionExecuted","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":true,"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"Transfer","type":"event"},{"inputs":[],"name":"ERC712_VERSION","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"approve","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"owner","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"baseURI","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"userAddress","type":"address"},{"internalType":"bytes","name":"functionSignature","type":"bytes"},{"internalType":"bytes32","name":"sigR","type":"bytes32"},{"internalType":"bytes32","name":"sigS","type":"bytes32"},{"internalType":"uint8","name":"sigV","type":"uint8"}],"name":"executeMetaTransaction","outputs":[{"internalType":"bytes","name":"","type":"bytes"}],"stateMutability":"payable","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"getApproved","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getChainId","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"pure","type":"function"},{"inputs":[],"name":"getDomainSeperator","outputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"user","type":"address"}],"name":"getNonce","outputs":[{"internalType":"uint256","name":"nonce","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"operator","type":"address"}],"name":"isApprovedForAll","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"ownerOf","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"from","type":"address"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"safeTransferFrom","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"from","type":"address"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"tokenId","type":"uint256"},{"internalType":"bytes","name":"_data","type":"bytes"}],"name":"safeTransferFrom","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"operator","type":"address"},{"internalType":"bool","name":"approved","type":"bool"}],"name":"setApprovalForAll","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"bytes4","name":"interfaceId","type":"bytes4"}],"name":"supportsInterface","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"index","type":"uint256"}],"name":"tokenByIndex","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"uint256","name":"index","type":"uint256"}],"name":"tokenOfOwnerByIndex","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"tokenURI","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"from","type":"address"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"transferFrom","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"mint","outputs":[],"stateMutability":"nonpayable","type":"function"}]}
+{"abi":[{"inputs":[{"internalType":"string","name":"name_","type":"string"},{"internalType":"string","name":"symbol_","type":"string"}],"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"owner","type":"address"},{"indexed":true,"internalType":"address","name":"approved","type":"address"},{"indexed":true,"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"owner","type":"address"},{"indexed":true,"internalType":"address","name":"operator","type":"address"},{"indexed":false,"internalType":"bool","name":"approved","type":"bool"}],"name":"ApprovalForAll","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"userAddress","type":"address"},{"indexed":false,"internalType":"address payable","name":"relayerAddress","type":"address"},{"indexed":false,"internalType":"bytes","name":"functionSignature","type":"bytes"}],"name":"MetaTransactionExecuted","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":true,"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"Transfer","type":"event"},{"inputs":[],"name":"ERC712_VERSION","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"approve","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"owner","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"baseURI","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"userAddress","type":"address"},{"internalType":"bytes","name":"functionSignature","type":"bytes"},{"internalType":"bytes32","name":"sigR","type":"bytes32"},{"internalType":"bytes32","name":"sigS","type":"bytes32"},{"internalType":"uint8","name":"sigV","type":"uint8"}],"name":"executeMetaTransaction","outputs":[{"internalType":"bytes","name":"","type":"bytes"}],"stateMutability":"payable","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"getApproved","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getChainId","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"pure","type":"function"},{"inputs":[],"name":"getDomainSeperator","outputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"user","type":"address"}],"name":"getNonce","outputs":[{"internalType":"uint256","name":"nonce","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"operator","type":"address"}],"name":"isApprovedForAll","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"ownerOf","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"from","type":"address"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"safeTransferFrom","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"from","type":"address"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"tokenId","type":"uint256"},{"internalType":"bytes","name":"_data","type":"bytes"}],"name":"safeTransferFrom","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"operator","type":"address"},{"internalType":"bool","name":"approved","type":"bool"}],"name":"setApprovalForAll","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"bytes4","name":"interfaceId","type":"bytes4"}],"name":"supportsInterface","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"index","type":"uint256"}],"name":"tokenByIndex","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"uint256","name":"index","type":"uint256"}],"name":"tokenOfOwnerByIndex","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"tokenURI","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"from","type":"address"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"transferFrom","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"}],"name":"mint","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"tokenId","type":"uint256"},{"internalType":"bytes","name":"data","type":"bytes"}],"name":"setTokenMetadata","outputs":[],"stateMutability":"nonpayable","type":"function"}]}

contracts/child/ChildToken/ChildERC721.sol

@@ -18,10 +18,8 @@ contract ChildERC721 is
     // limit batching of tokens due to gas limit restrictions
     uint256 public constant BATCH_LIMIT = 20;
 
-    event WithdrawnBatch(
-        address indexed user,
-        uint256[] tokenIds
-    );
+    event WithdrawnBatch(address indexed user, uint256[] tokenIds);
+    event TransferWithMetadata(address indexed from, address indexed to, uint256 indexed tokenId, bytes metaData);
 
     constructor(
         string memory name_,
@@ -98,4 +96,41 @@ contract ChildERC721 is
         }
         emit WithdrawnBatch(_msgSender(), tokenIds);
     }
+
+    /**
+     * @notice called when user wants to withdraw token back to root chain with arbitrary metadata
+     * @dev Should handle withraw by burning user's token.
+     * 
+     * This transaction will be verified when exiting on root chain
+     *
+     * @param tokenId tokenId to withdraw
+     */
+    function withdrawWithMetadata(uint256 tokenId) external {
+
+        require(_msgSender() == ownerOf(tokenId), "ChildERC721: INVALID_TOKEN_OWNER");
+
+        // Encoding metadata associated with tokenId & emitting event
+        emit TransferWithMetadata(_msgSender(), address(0), tokenId, this.encodeTokenMetadata(tokenId));
+
+        _burn(tokenId);
+
+    }
+
+    /**
+     * @notice This method is supposed to be called by client when withdrawing token with metadata
+     * and pass return value of this function as second paramter of `withdrawWithMetadata` method
+     *
+     * It can be overridden by clients to encode data in a different form, which needs to
+     * be decoded back by them correctly during exiting
+     *
+     * @param tokenId Token for which URI to be fetched
+     */
+    function encodeTokenMetadata(uint256 tokenId) external view virtual returns (bytes memory) {
+
+        // You're always free to change this default implementation
+        // and pack more data in byte array which can be decoded back
+        // in L1
+        return abi.encode(tokenURI(tokenId));
+
+    }
 }

contracts/child/ChildToken/ChildMintableERC721.sol

@@ -17,6 +17,10 @@ contract ChildMintableERC721 is
     bytes32 public constant DEPOSITOR_ROLE = keccak256("DEPOSITOR_ROLE");
     mapping (uint256 => bool) public withdrawnTokens;
 
+    // limit batching of tokens due to gas limit restrictions
+    uint256 public constant BATCH_LIMIT = 20;
+
+    event WithdrawnBatch(address indexed user, uint256[] tokenIds);
     event TransferWithMetadata(address indexed from, address indexed to, uint256 indexed tokenId, bytes metaData);
 
     constructor(
@@ -44,20 +48,34 @@ contract ChildMintableERC721 is
     /**
      * @notice called when token is deposited on root chain
      * @dev Should be callable only by ChildChainManager
-     * Should handle deposit by minting the required tokenId for user
+     * Should handle deposit by minting the required tokenId(s) for user
      * Should set `withdrawnTokens` mapping to `false` for the tokenId being deposited
      * Minting can also be done by other functions
      * @param user user address for whom deposit is being done
-     * @param depositData abi encoded tokenId
+     * @param depositData abi encoded tokenIds. Batch deposit also supported.
      */
     function deposit(address user, bytes calldata depositData)
         external
         override
         only(DEPOSITOR_ROLE)
     {
-        uint256 tokenId = abi.decode(depositData, (uint256));
-        withdrawnTokens[tokenId] = false;
-        _mint(user, tokenId);
+
+        // deposit single
+        if (depositData.length == 32) {
+            uint256 tokenId = abi.decode(depositData, (uint256));
+            withdrawnTokens[tokenId] = false;
+            _mint(user, tokenId);
+
+        // deposit batch
+        } else {
+            uint256[] memory tokenIds = abi.decode(depositData, (uint256[]));
+            uint256 length = tokenIds.length;
+            for (uint256 i; i < length; i++) {
+                withdrawnTokens[tokenIds[i]] = false;
+                _mint(user, tokenIds[i]);
+            }
+        }
+
     }
 
     /**
@@ -73,15 +91,41 @@ contract ChildMintableERC721 is
         _burn(tokenId);
     }
 
+    /**
+     * @notice called when user wants to withdraw multiple tokens back to root chain
+     * @dev Should burn user's tokens. This transaction will be verified when exiting on root chain
+     * @param tokenIds tokenId list to withdraw
+     */
+    function withdrawBatch(uint256[] calldata tokenIds) external {
+
+        uint256 length = tokenIds.length;
+        require(length <= BATCH_LIMIT, "ChildMintableERC721: EXCEEDS_BATCH_LIMIT");
+
+        // Iteratively burn ERC721 tokens, for performing
+        // batch withdraw
+        for (uint256 i; i < length; i++) {
+
+            uint256 tokenId = tokenIds[i];
+
+            require(_msgSender() == ownerOf(tokenId), string(abi.encodePacked("ChildMintableERC721: INVALID_TOKEN_OWNER ", tokenId)));
+            withdrawnTokens[tokenId] = true;
+            _burn(tokenId);
+
+        }
+
+        // At last emit this event, which will be used
+        // in MintableERC721 predicate contract on L1
+        // while verifying burn proof
+        emit WithdrawnBatch(_msgSender(), tokenIds);
+
+    }
+
     /**
      * @notice called when user wants to withdraw token back to root chain with token URI
      * @dev Should handle withraw by burning user's token.
      * Should set `withdrawnTokens` mapping to `true` for the tokenId being withdrawn
      * This transaction will be verified when exiting on root chain
      *
-     * Before calling this function, you may want calling `encodeTokenMetadata`
-     * and get metadata to be transferred from L2 to L1 during exit
-     *
      * @param tokenId tokenId to withdraw
      */
     function withdrawWithMetadata(uint256 tokenId) external {

contracts/root/RootToken/DummyERC721.sol

@@ -2,11 +2,13 @@ pragma solidity 0.6.6;
 
 import {ERC721} from "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 import {NativeMetaTransaction} from "../../common/NativeMetaTransaction.sol";
+import {IRootERC721} from "./IRootERC721.sol";
 import {ContextMixin} from "../../common/ContextMixin.sol";
 
 contract DummyERC721 is
     ERC721,
     NativeMetaTransaction,
+    IRootERC721,
     ContextMixin
 {
     constructor(string memory name_, string memory symbol_)
@@ -20,6 +22,30 @@ contract DummyERC721 is
         _mint(_msgSender(), tokenId);
     }
 
+    /**
+     * If you're attempting to bring metadata associated with token
+     * from L2 to L1, you must implement this method
+     *
+     * To be invoked when attempting to exit ERC721 with metadata from L2
+     *
+     * `data` is nothing but arbitrary byte array which
+     * is brought in L1, by event emitted in L2, during withdraw
+     *
+     * Make sure this method is always callable by Predicate contract
+     * who will invoke it when attempting to exit with metadata
+     */
+    function setTokenMetadata(uint256 tokenId, bytes calldata data) external override {
+        // This function should decode metadata obtained from L2
+        // and attempt to set it for this `tokenId`
+        //
+        // Following is just a default implementation, feel
+        // free to define your own encoding/ decoding scheme
+        // for L2 -> L1 token metadata transfer
+        string memory uri = abi.decode(data, (string));
+
+        _setTokenURI(tokenId, uri);
+    }
+
     function _msgSender()
         internal
         override