Added 'unSellLand' to allow users to cancel their NFT sales

contracts/Land.sol

@@ -33,7 +33,7 @@ contract LandNFT is ERC721, ERC721Enumerable, ERC721URIStorage, Ownable {
     {
         uint256 tokenId = _tokenIdCounter.current();
         _tokenIdCounter.increment();
-        _mint(msg.sender, tokenId);
+        _safeMint(msg.sender, tokenId);
 
         _setTokenURI(tokenId, uri);
         createLand(tokenId, price);
@@ -45,13 +45,11 @@ contract LandNFT is ERC721, ERC721Enumerable, ERC721URIStorage, Ownable {
         require(price > 0, "Price must be at least 1 wei");
         lands[tokenId] = Land(
             tokenId,
+            payable(address(0)),
             payable(msg.sender),
-            payable(address(this)),
             price,
             false
         );
-
-        _transfer(msg.sender, address(this), tokenId);
     }
 
     function buyLand(uint256 tokenId) public payable {
@@ -81,6 +79,18 @@ contract LandNFT is ERC721, ERC721Enumerable, ERC721URIStorage, Ownable {
         _transfer(msg.sender, address(this), tokenId);
     }
 
+    function unSellLand(uint256 tokenId) public payable {
+        require(
+            lands[tokenId].seller == msg.sender,
+            "Only item owner can perform this operation"
+        );
+        lands[tokenId].owner = payable(msg.sender);
+        lands[tokenId].sold = true;
+        lands[tokenId].seller = payable(address(0));
+
+        _transfer(address(this), msg.sender, tokenId);
+    }
+
     function getLand(uint256 tokenId) public view returns (Land memory) {
         return lands[tokenId];
     }
@@ -89,7 +99,6 @@ contract LandNFT is ERC721, ERC721Enumerable, ERC721URIStorage, Ownable {
         return _tokenIdCounter.current();
     }
 
-
     // The following functions are overrides required by Solidity.
 
     function _beforeTokenTransfer(

src/components/nfts.js

@@ -7,6 +7,7 @@ import {
   buyLand,
   fetchNftContractOwner,
   sellLand,
+  unSellLand
 } from "../utils/minter";
 import { Badge, Card, Stack, Row, Col } from "react-bootstrap";
 import { useContractKit } from "@celo-tools/use-contractkit";
@@ -89,6 +90,20 @@ const Nft = ({ minterContract }) => {
     }
   };
 
+  const unSell = async (index) => {
+    try {
+      setLoading(true);
+      await unSellLand(minterContract, index, performActions);
+      toast(<NotificationSuccess text="Updating NFT list...." />);
+      getAssets();
+    } catch (error) {
+      console.log(error);
+      toast(<NotificationError text="Failed to send NFT." />);
+    } finally {
+      setLoading(false);
+    }
+  };
+
   useEffect(() => {
     try {
       if (address && minterContract) {
@@ -136,6 +151,9 @@ const Nft = ({ minterContract }) => {
                             </Card.Header>
                             <img src={_nft.image} alt="" />
                             <div className="card-body">
+                              {parseInt(_nft.seller.slice(0, 24)) !== 0 ?
+                                <p className="card-text">Seller: { truncateAddress(_nft.seller) }</p> : <></>
+                              }
                               <p className="card-text">{_nft.address}</p>
                               <p className="card-text">{_nft.description}</p>
                               <Row className="mt-2 mb-2">
@@ -154,16 +172,28 @@ const Nft = ({ minterContract }) => {
                               </Row>
                               <div className="d-flex justify-content-between align-items-center">
                                 <div className="btn-group">
-                                  {!_nft.sold ? (
-                                    <button
-                                      type="button"
-                                      className="btn btn-outline-primary"
-                                      onClick={() =>
-                                        buy(_nft.index, _nft.tokenId)
-                                      }
-                                    >
-                                      Buy
-                                    </button>
+                                  {(parseInt(_nft.seller.slice(0, 24)) !== 0) && !_nft.sold ? (
+                                     (_nft.seller === defaultAccount) ? (
+                                      <button
+                                        type="button"
+                                        className="btn btn-outline-primary"
+                                        onClick={() =>
+                                          unSell(_nft.index, _nft.tokenId)
+                                        }
+                                      >
+                                        Cancel Sale
+                                      </button>
+                                    ) : (
+                                      <button
+                                        type="button"
+                                        className="btn btn-outline-primary"
+                                        onClick={() =>
+                                          buy(_nft.index, _nft.tokenId)
+                                        }
+                                      >
+                                        Buy
+                                      </button>
+                                      )
                                   ) : defaultAccount === _nft.owner ? (
                                     <button
                                       type="button"

src/contracts/LandAddress.json

@@ -1,3 +1,3 @@
 {
-  "Land": "0xba51090402c850758e8cB3B5984590379FE972f4"
+  "Land": "0x92E1d77F3282bA513D8411a13541606134cE9Ea0"
 }

src/utils/minter.js

@@ -74,6 +74,7 @@ export const getLands = async (minterContract) => {
           index: i,
           tokenId: i,
           owner,
+          seller: land.seller,
           price: land.price,
           sold: land.sold,
           address: meta.data.address,
@@ -151,3 +152,16 @@ export const sellLand = async (minterContract, tokenId, performActions) => {
     console.log({ error });
   }
 };
+
+export const unSellLand = async (minterContract, tokenId, performActions) => {
+  try {
+    await performActions(async (kit) => {
+      const { defaultAccount } = kit;
+      await minterContract.methods
+        .unSellLand(tokenId)
+        .send({ from: defaultAccount });
+    });
+  } catch (error) {
+    console.log({ error });
+  }
+};