💳 Sell at an offer price

Define the sell function as below:

const sell = (token_id : nat,price : nat, s : storage) : ret => {

  //check balance of seller
  const sellerBalance = NFT.Storage.get_balance({ledger:s.ledger,metadata:s.metadata,operators:s.operators,token_metadata:s.token_metadata,token_ids : s.token_ids},Tezos.get_source(),token_id);
  if(sellerBalance != (1 as nat)) return failwith("2");

  //need to allow the contract itself to be an operator on behalf of the seller
  const newOperators = NFT.Operators.add_operator(s.operators,Tezos.get_source(),Tezos.get_self_address(),token_id);

  //DECISION CHOICE: if offer already exists, we just override it
  return [list([]) as list<operation>,{...s,offers:Map.add(token_id,{owner : Tezos.get_source(), price : price},s.offers),operators:newOperators}];
};

Then call it in the main function to do the right business operations

const main = ([p, s]: [parameter,storage]): ret =>
    match(p, {
     Mint: (p: [nat,bytes,bytes,bytes,bytes]) => mint(p[0],p[1],p[2],p[3],p[4],s),
     Buy: (p : [nat,address]) => [list([]),s],
     Sell: (p : [nat,nat]) => sell(p[0],p[1], s),
     AddAdministrator : (p : address) => {if(Set.mem(Tezos.get_sender(), s.administrators)){ return [list([]),{...s,administrators:Set.add(p, s.administrators)}]} else {return failwith("1");}} ,
     Transfer: (p: NFT.transfer) => [list([]),s],
     Balance_of: (p: NFT.balance_of) => [list([]),s],
     Update_operators: (p: NFT.update_operator) => [list([]),s],
     });

Explanations:

• User must have enough tokens (wine bottles) to place an offer
• the seller will set the NFT marketplace smart contract as an operator. When the buyer send his money to buy the NFT, the smart contract will change the NFT ownership (it is not interactive with the seller, the martketplace will do it on behalf of the seller based on the offer data)
• we update the storage to publish the offer
• finally, do the correct business by calling sell function inside the sell case on main

💳 Buy a bottle on the marketplace

Now that we have offers available on the marketplace, let's buy bottles!

Edit the smart contract to add the buy feature

const buy = (token_id : nat, seller : address, s : storage) : ret => {

  //search for the offer
  return match( Map.find_opt(token_id,s.offers) , {
    None : () => failwith("3"),
    Some : (offer : offer) => {

      //check if amount have been paid enough
      if(Tezos.get_amount() < offer.price  * (1 as mutez)) return failwith("5");

      // prepare transfer of XTZ to seller
      const op = Tezos.transaction(unit,offer.price  * (1 as mutez),Tezos.get_contract_with_error(seller,"6"));

      //transfer tokens from seller to buyer
      const ledger = NFT.Ledger.transfer_token_from_user_to_user(s.ledger,token_id,seller,Tezos.get_source());

      //remove offer
      return [list([op]) as list<operation>, {...s, offers : Map.update(token_id,None(),s.offers), ledger : ledger}];
    }
  });
};

Call buy function on main

const main = ([p, s]: [parameter,storage]): ret =>
    match(p, {
     Mint: (p: [nat,bytes,bytes,bytes,bytes]) => mint(p[0],p[1],p[2],p[3],p[4],s),
     Buy: (p : [nat,address]) => buy(p[0],p[1],s),
     Sell: (p : [nat,nat]) => sell(p[0],p[1], s),
     AddAdministrator : (p : address) => {if(Set.mem(Tezos.get_sender(), s.administrators)){ return [list([]),{...s,administrators:Set.add(p, s.administrators)}]} else {return failwith("1");}} ,
     Transfer: (p: NFT.transfer) => [list([]),s],
     Balance_of: (p: NFT.balance_of) => [list([]),s],
     Update_operators: (p: NFT.update_operator) => [list([]),s],
     });

Explanations:

• search for the offer based on the token_id or return an error if it does not exist
• check that the amount sent by the buyer is greater than the offer price. If it is ok, transfer the offer price to the seller and transfer the NFT to the buyer
• remove the offer as it has been executed
• finally, do the correct business by calling sell function inside the sell case on main

Compile and deploy

We finished the smart contract implementation of this second training, let's deploy to ghostnet.

TAQ_LIGO_IMAGE=ligolang/ligo:0.57.0 taq compile nft.jsligo
taq deploy nft.tz -e "testing"

┌──────────┬──────────────────────────────────────┬───────┬──────────────────┬────────────────────────────────┐
│ Contract │ Address                              │ Alias │ Balance In Mutez │ Destination                    │
├──────────┼──────────────────────────────────────┼───────┼──────────────────┼────────────────────────────────┤
│ nft.tz   │ KT1PLvVGaM4YE1qLSdLZUZ1EhozqzYUQ1xed │ nft   │ 0                │ https://ghostnet.ecadinfra.com │
└──────────┴──────────────────────────────────────┴───────┴──────────────────┴────────────────────────────────┘

🎉 Hooray! We have implemented and deployed the smart contract (backend) 🎉

Sale page

Edit Sale Page on ./src/OffersPage.tsx

Add this code inside the file :

import { InfoOutlined } from "@mui/icons-material";
import SellIcon from "@mui/icons-material/Sell";

import {
  Box,
  Button,
  Card,
  CardActions,
  CardContent,
  CardHeader,
  CardMedia,
  ImageList,
  InputAdornment,
  Pagination,
  TextField,
  Tooltip,
  Typography,
  useMediaQuery,
} from "@mui/material";
import Paper from "@mui/material/Paper";
import BigNumber from "bignumber.js";
import { useFormik } from "formik";
import { useSnackbar } from "notistack";
import React, { Fragment, useEffect, useState } from "react";
import * as yup from "yup";
import { UserContext, UserContextType } from "./App";
import ConnectButton from "./ConnectWallet";
import { TransactionInvalidBeaconError } from "./TransactionInvalidBeaconError";
import { address, nat } from "./type-aliases";

const itemPerPage: number = 6;

const validationSchema = yup.object({
  price: yup
    .number()
    .required("Price is required")
    .positive("ERROR: The number must be greater than 0!"),
});

type Offer = {
  owner: address;
  price: nat;
};

export default function OffersPage() {
  const [selectedTokenId, setSelectedTokenId] = React.useState<number>(0);
  const [currentPageIndex, setCurrentPageIndex] = useState<number>(1);

  let [offersTokenIDMap, setOffersTokenIDMap] = React.useState<Map<nat, Offer>>(
    new Map()
  );
  let [ownerTokenIds, setOwnerTokenIds] = React.useState<Set<nat>>(new Set());

  const {
    nftContrat,
    nftContratTokenMetadataMap,
    userAddress,
    storage,
    refreshUserContextOnPageReload,
    Tezos,
    setUserAddress,
    setUserBalance,
    wallet,
  } = React.useContext(UserContext) as UserContextType;

  const { enqueueSnackbar } = useSnackbar();

  const formik = useFormik({
    initialValues: {
      price: 0,
    },
    validationSchema: validationSchema,
    onSubmit: (values) => {
      console.log("onSubmit: (values)", values, selectedTokenId);
      sell(selectedTokenId, values.price);
    },
  });

  const initPage = async () => {
    if (storage) {
      console.log("context is not empty, init page now");
      ownerTokenIds = new Set();
      offersTokenIDMap = new Map();

      await Promise.all(
        storage.token_ids.map(async (token_id) => {
          let owner = await storage.ledger.get(token_id);
          if (owner === userAddress) {
            ownerTokenIds.add(token_id);

            const ownerOffers = await storage.offers.get(token_id);
            if (ownerOffers) offersTokenIDMap.set(token_id, ownerOffers);

            console.log(
              "found for " +
                owner +
                " on token_id " +
                token_id +
                " with balance " +
                1
            );
          } else {
            console.log("skip to next token id");
          }
        })
      );
      setOwnerTokenIds(new Set(ownerTokenIds)); //force refresh
      setOffersTokenIDMap(new Map(offersTokenIDMap)); //force refresh
    } else {
      console.log("context is empty, wait for parent and retry ...");
    }
  };

  useEffect(() => {
    (async () => {
      console.log("after a storage changed");
      await initPage();
    })();
  }, [storage]);

  useEffect(() => {
    (async () => {
      console.log("on Page init");
      await initPage();
    })();
  }, []);

  const sell = async (token_id: number, price: number) => {
    try {
      const op = await nftContrat?.methods
        .sell(
          BigNumber(token_id) as nat,
          BigNumber(price * 1000000) as nat //to mutez
        )
        .send();

      await op?.confirmation(2);

      enqueueSnackbar(
        "Wine collection (token_id=" +
          token_id +
          ") offer for " +
          1 +
          " units at price of " +
          price +
          " XTZ",
        { variant: "success" }
      );

      refreshUserContextOnPageReload(); //force all app to refresh the context
    } catch (error) {
      console.table(`Error: ${JSON.stringify(error, null, 2)}`);
      let tibe: TransactionInvalidBeaconError =
        new TransactionInvalidBeaconError(error);
      enqueueSnackbar(tibe.data_message, {
        variant: "error",
        autoHideDuration: 10000,
      });
    }
  };

  const isDesktop = useMediaQuery("(min-width:1100px)");
  const isTablet = useMediaQuery("(min-width:600px)");

  return (
    <Paper>
      <Typography style={{ paddingBottom: "10px" }} variant="h5">
        Sell my bottles
      </Typography>
      {ownerTokenIds && ownerTokenIds.size != 0 ? (
        <Fragment>
          <Pagination
            page={currentPageIndex}
            onChange={(_, value) => setCurrentPageIndex(value)}
            count={Math.ceil(
              Array.from(ownerTokenIds.entries()).length / itemPerPage
            )}
            showFirstButton
            showLastButton
          />

          <ImageList
            cols={isDesktop ? itemPerPage / 2 : isTablet ? itemPerPage / 3 : 1}
          >
            {Array.from(ownerTokenIds.entries())
              .filter((_, index) =>
                index >= currentPageIndex * itemPerPage - itemPerPage &&
                index < currentPageIndex * itemPerPage
                  ? true
                  : false
              )
              .map(([token_id]) => (
                <Card key={token_id + "-" + token_id.toString()}>
                  <CardHeader
                    avatar={
                      <Tooltip
                        title={
                          <Box>
                            <Typography>
                              {" "}
                              {"ID : " + token_id.toString()}{" "}
                            </Typography>
                            <Typography>
                              {"Description : " +
                                nftContratTokenMetadataMap.get(
                                  token_id.toNumber()
                                )?.description}
                            </Typography>
                          </Box>
                        }
                      >
                        <InfoOutlined />
                      </Tooltip>
                    }
                    title={
                      nftContratTokenMetadataMap.get(token_id.toNumber())?.name
                    }
                  />
                  <CardMedia
                    sx={{ width: "auto", marginLeft: "33%" }}
                    component="img"
                    height="100px"
                    image={nftContratTokenMetadataMap
                      .get(token_id.toNumber())
                      ?.thumbnailUri?.replace(
                        "ipfs://",
                        "https://gateway.pinata.cloud/ipfs/"
                      )}
                  />

                  <CardContent>
                    <Box>
                      <Typography variant="body2">
                        {offersTokenIDMap.get(token_id)
                          ? "Traded : " +
                            1 +
                            " (price : " +
                            offersTokenIDMap
                              .get(token_id)
                              ?.price.dividedBy(1000000) +
                            " Tz)"
                          : ""}
                      </Typography>
                    </Box>
                  </CardContent>

                  <CardActions>
                    {!userAddress ? (
                      <Box marginLeft="5vw">
                        <ConnectButton
                          Tezos={Tezos}
                          nftContratTokenMetadataMap={
                            nftContratTokenMetadataMap
                          }
                          setUserAddress={setUserAddress}
                          setUserBalance={setUserBalance}
                          wallet={wallet}
                        />
                      </Box>
                    ) : (
                      <form
                        style={{ width: "100%" }}
                        onSubmit={(values) => {
                          setSelectedTokenId(token_id.toNumber());
                          formik.handleSubmit(values);
                        }}
                      >
                        <span>
                          <TextField
                            type="number"
                            name="price"
                            label="price"
                            placeholder="Enter a price"
                            variant="filled"
                            value={formik.values.price}
                            onChange={formik.handleChange}
                            error={
                              formik.touched.price &&
                              Boolean(formik.errors.price)
                            }
                            helperText={
                              formik.touched.price && formik.errors.price
                            }
                            InputProps={{
                              endAdornment: (
                                <InputAdornment position="end">
                                  <Button
                                    type="submit"
                                    aria-label="add to favorites"
                                  >
                                    <SellIcon /> Sell
                                  </Button>
                                </InputAdornment>
                              ),
                            }}
                          />
                        </span>
                      </form>
                    )}
                  </CardActions>
                </Card>
              ))}{" "}
          </ImageList>
        </Fragment>
      ) : (
        <Typography sx={{ py: "2em" }} variant="h4">
          Sorry, you don't own any bottles, buy or mint some first
        </Typography>
      )}
    </Paper>
  );
}

Explanations :

• the template will display all owned NFTs. Only NFTs belonging to the logged user are selected
• for each nft, we have a form to make an offer at a price
• if you do an offer, it calls the sell function and the smart contract entrypoint nftContrat?.methods.sell(BigNumber(token_id) as nat,BigNumber(price * 1000000) as nat).send(). We multiply the XTZ price by 10^6 because the smartcontract manipulates mutez.

Let's play : Sell

1. Connect with your wallet an choose alice account (or one of the administrators you set on the smart contract earlier). You are redirected to the Administration /mint page as there is no nft minted yet

2. Enter these values on the form for example :

• name: Saint Emilion - Franc la Rose
• symbol: SEMIL
• description: Grand cru 2007

3. Click on Upload an image an select a bottle picture on your computer

4. Click on Mint button

Your picture will be pushed to IPFS and be displayed, then your wallet ask you to sign the mint operation.

• Confirm operation

• Wait less than 1 minute until you get the confirmation notification, the page will automatically be refreshed.

5. Now, go to the Trading menu and the Sell bottles sub menu.

6. Click on the sub-menu entry

You are owner of this bottle so you can create an offer to sell it.

• Enter a price offer
• Click on SELL button
• Wait a bit for the confirmation, then after auto refresh you have an offer for this NFT

Wine Catalogue page

Edit the Wine Catalogue page on ./src/WineCataloguePage.tsx

Add the following code inside the file

import { InfoOutlined } from "@mui/icons-material";
import ShoppingCartIcon from "@mui/icons-material/ShoppingCart";
import {
  Box,
  Button,
  Card,
  CardActions,
  CardContent,
  CardHeader,
  CardMedia,
  ImageList,
  Pagination,
  Tooltip,
  useMediaQuery,
} from "@mui/material";
import Paper from "@mui/material/Paper";
import Typography from "@mui/material/Typography";

import BigNumber from "bignumber.js";
import { useFormik } from "formik";
import { useSnackbar } from "notistack";
import React, { Fragment, useState } from "react";
import * as yup from "yup";
import { UserContext, UserContextType } from "./App";
import ConnectButton from "./ConnectWallet";
import { TransactionInvalidBeaconError } from "./TransactionInvalidBeaconError";
import { address, nat } from "./type-aliases";

const itemPerPage: number = 6;

type OfferEntry = [nat, Offer];

type Offer = {
  owner: address;
  price: nat;
};

const validationSchema = yup.object({});

export default function WineCataloguePage() {
  const {
    Tezos,
    nftContratTokenMetadataMap,
    setUserAddress,
    setUserBalance,
    wallet,
    userAddress,
    nftContrat,
    refreshUserContextOnPageReload,
    storage,
  } = React.useContext(UserContext) as UserContextType;
  const [selectedOfferEntry, setSelectedOfferEntry] =
    React.useState<OfferEntry | null>(null);

  const formik = useFormik({
    initialValues: {
      quantity: 1,
    },
    validationSchema: validationSchema,
    onSubmit: (values) => {
      console.log("onSubmit: (values)", values, selectedOfferEntry);
      buy(selectedOfferEntry!);
    },
  });
  const { enqueueSnackbar } = useSnackbar();
  const [currentPageIndex, setCurrentPageIndex] = useState<number>(1);

  const buy = async (selectedOfferEntry: OfferEntry) => {
    try {
      const op = await nftContrat?.methods
        .buy(
          BigNumber(selectedOfferEntry[0]) as nat,
          selectedOfferEntry[1].owner
        )
        .send({
          amount: selectedOfferEntry[1].price.toNumber(),
          mutez: true,
        });

      await op?.confirmation(2);

      enqueueSnackbar(
        "Bought " +
          1 +
          " unit of Wine collection (token_id:" +
          selectedOfferEntry[0] +
          ")",
        {
          variant: "success",
        }
      );

      refreshUserContextOnPageReload(); //force all app to refresh the context
    } catch (error) {
      console.table(`Error: ${JSON.stringify(error, null, 2)}`);
      let tibe: TransactionInvalidBeaconError =
        new TransactionInvalidBeaconError(error);
      enqueueSnackbar(tibe.data_message, {
        variant: "error",
        autoHideDuration: 10000,
      });
    }
  };
  const isDesktop = useMediaQuery("(min-width:1100px)");
  const isTablet = useMediaQuery("(min-width:600px)");
  return (
    <Paper>
      <Typography style={{ paddingBottom: "10px" }} variant="h5">
        Wine catalogue
      </Typography>

      {storage?.offers && storage?.offers.size != 0 ? (
        <Fragment>
          <Pagination
            page={currentPageIndex}
            onChange={(_, value) => setCurrentPageIndex(value)}
            count={Math.ceil(
              Array.from(storage?.offers.entries()).length / itemPerPage
            )}
            showFirstButton
            showLastButton
          />
          <ImageList
            cols={isDesktop ? itemPerPage / 2 : isTablet ? itemPerPage / 3 : 1}
          >
            {Array.from(storage?.offers.entries())

              .filter((_, index) =>
                index >= currentPageIndex * itemPerPage - itemPerPage &&
                index < currentPageIndex * itemPerPage
                  ? true
                  : false
              )
              .map(([token_id, offer]) => (
                <Card key={offer.owner + "-" + token_id.toString()}>
                  <CardHeader
                    avatar={
                      <Tooltip
                        title={
                          <Box>
                            <Typography>
                              {" "}
                              {"ID : " + token_id.toString()}{" "}
                            </Typography>
                            <Typography>
                              {"Description : " +
                                nftContratTokenMetadataMap.get(
                                  token_id.toNumber()
                                )?.description}
                            </Typography>
                            <Typography>
                              {"Seller : " + offer.owner}{" "}
                            </Typography>
                          </Box>
                        }
                      >
                        <InfoOutlined />
                      </Tooltip>
                    }
                    title={
                      nftContratTokenMetadataMap.get(token_id.toNumber())?.name
                    }
                  />
                  <CardMedia
                    sx={{ width: "auto", marginLeft: "33%" }}
                    component="img"
                    height="100px"
                    image={nftContratTokenMetadataMap
                      .get(token_id.toNumber())
                      ?.thumbnailUri?.replace(
                        "ipfs://",
                        "https://gateway.pinata.cloud/ipfs/"
                      )}
                  />

                  <CardContent>
                    <Box>
                      <Typography variant="body2">
                        {" "}
                        {"Price : " + offer.price.dividedBy(1000000) + " XTZ"}
                      </Typography>
                    </Box>
                  </CardContent>

                  <CardActions>
                    {!userAddress ? (
                      <Box marginLeft="5vw">
                        <ConnectButton
                          Tezos={Tezos}
                          nftContratTokenMetadataMap={
                            nftContratTokenMetadataMap
                          }
                          setUserAddress={setUserAddress}
                          setUserBalance={setUserBalance}
                          wallet={wallet}
                        />
                      </Box>
                    ) : (
                      <form
                        style={{ width: "100%" }}
                        onSubmit={(values) => {
                          setSelectedOfferEntry([token_id, offer]);
                          formik.handleSubmit(values);
                        }}
                      >
                        <Button type="submit" aria-label="add to favorites">
                          <ShoppingCartIcon /> BUY
                        </Button>
                      </form>
                    )}
                  </CardActions>
                </Card>
              ))}
          </ImageList>
        </Fragment>
      ) : (
        <Typography sx={{ py: "2em" }} variant="h4">
          Sorry, there is not NFT to buy yet, you need to mint or sell bottles
          first
        </Typography>
      )}
    </Paper>
  );
}

Let's play: Buy some wine!

Now you can see on Trading menu the Wine catalogue sub menu, click on it.

As you are connected with the default administrator you can see your own unique offer on the market

• Disconnect from your user and connect with another account who has enough XTZ to buy the bottle
• The buyer can see that alice is selling a bottle
• Buy the bottle by clicking on BUY button
• Once confirmed, the offer is removed from the market
• Click on bottle offers sub menu
• You are now the owner of this bottle, you can resell it at your own price, etc ...