Do breaking changes on nft template to fit with the new library

Point to the new template changing the first import line to

#import "@ligo/fa/lib/fa2/asset/single_asset.mligo" "SINGLEASSET"

It means you will change the namespace from NFT to SINGLEASSET everywhere (like this you are sure to use the correct library)

Change the offer and storage definitions

type offer = {
  quantity : nat,
  price : nat
};

type storage =
  {
    administrators: set<address>,
    totalSupply: nat,
    offers: map<address,offer>,  //user sells an offer
    ledger: SINGLEASSET.Ledger.t,
    metadata: SINGLEASSET.Metadata.t,
    token_metadata: SINGLEASSET.TokenMetadata.t,
    operators: SINGLEASSET.Operators.t,
    owners: set<SINGLEASSET.Storage.owner>
  };

Explanations:

• offers is now a map<address,offer>, because you don't have to store token_id as key, now the key is the owner address. Each owner can sell a part of the unique collection
• offer requires a quantity, each owner will sell a part of the unique collection
• totalSupply is set at mint time in order to track the global quantity of minted items on the collection. It avoids to recalculate all the time the quantity from each owner holdings (this value is constant)
• Because the ledger is made of big_map of key owners, we cache the keys to be able to loop on it
• Since we have a unique collection, we remove token_ids. token_id will be set to 0

We don't change parameter type because the signature is the same, but you can edit the comments because it is no more same parameter and also change to the new namespace SINGLEASSET

type parameter =
  | ["Mint", nat,bytes,bytes,bytes,bytes] // quantity, name , description ,symbol , bytesipfsUrl
  | ["Buy", nat, address]  //buy quantity at a seller offer price
  | ["Sell", nat, nat]  //sell quantity at a price
  | ["AddAdministrator" , address]
  | ["Transfer", SINGLEASSET.transfer]
  | ["Balance_of", SINGLEASSET.balance_of]
  | ["Update_operators", SINGLEASSET.update_operators];

Edit the mint function to add the quantity extra param, and finally change the return

const mint = (quantity : nat, name : bytes, description : bytes ,symbol : bytes , ipfsUrl : bytes, s : storage) : ret => {

   if(quantity <= (0 as nat)) return failwith("0");

   if(! Set.mem(Tezos.get_sender(), s.administrators)) return failwith("1");

   const token_info: map<string, bytes> =
     Map.literal(list([
      ["name", name],
      ["description",description],
      ["interfaces", (bytes `["TZIP-12"]`)],
      ["thumbnailUri", ipfsUrl],
      ["symbol",symbol],
      ["decimals", (bytes `0`)]
     ])) as map<string, bytes>;


    const metadata : bytes = bytes
  `{
      "name":"FA2 NFT Marketplace",
      "description":"Example of FA2 implementation",
      "version":"0.0.1",
      "license":{"name":"MIT"},
      "authors":["Marigold<contact@marigold.dev>"],
      "homepage":"https://marigold.dev",
      "source":{
        "tools":["Ligo"],
        "location":"https://github.com/ligolang/contract-catalogue/tree/main/lib/fa2"},
      "interfaces":["TZIP-012"],
      "errors": [],
      "views": []
      }` ;

     return [list([]) as list<operation>,
          {...s,
     totalSupply: quantity,
     ledger: Big_map.literal(list([[Tezos.get_sender(),quantity as nat]])) as SINGLEASSET.Ledger.t,
     metadata : Big_map.literal(list([["",  bytes `tezos-storage:data`],["data", metadata]])),
     token_metadata: Big_map.add(0 as nat, {token_id: 0 as nat,token_info:token_info},s.token_metadata),
     operators: Big_map.empty as SINGLEASSET.Operators.t,
     owners: Set.add(Tezos.get_sender(),s.owners)}];
     };

Edit the sell function to replace token_id by quantity, we add/override an offer for the user

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

  //check balance of seller
  const sellerBalance = SINGLEASSET.Storage.get_amount_for_owner({ledger:s.ledger,metadata:s.metadata,operators:s.operators,token_metadata:s.token_metadata,owners:s.owners})(Tezos.get_source());
  if(quantity > sellerBalance) return failwith("2");

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

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

Also edit the buy function to replace token_id by quantity, check quantities, check final price is enough and update the current offer

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

  //search for the offer
  return match( Map.find_opt(seller,s.offers) , {
    None : () => failwith("3"),
    Some : (offer : offer) => {
      //check if quantity is enough
      if(quantity > offer.quantity) return failwith("4");
      //check if amount have been paid enough
      if(Tezos.get_amount() < (offer.price * quantity) * (1 as mutez)) return failwith("5");

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

      //transfer tokens from seller to buyer
      let ledger = SINGLEASSET.Ledger.decrease_token_amount_for_user(s.ledger)(seller)(quantity);
      ledger = SINGLEASSET.Ledger.increase_token_amount_for_user(ledger)(Tezos.get_source())(quantity);

      //update new offer
      const newOffer = {...offer,quantity : abs(offer.quantity - quantity)};

      return [list([op]) as list<operation>, {...s, offers : Map.update(seller,Some(newOffer),s.offers), ledger : ledger, owners : Set.add(Tezos.get_source(),s.owners)}];
    }
  });
};

Finally, update the namespaces and replace token_ids by owners on the main function

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: SINGLEASSET.transfer) => {
      const ret2 : [list<operation>, SINGLEASSET.storage] = SINGLEASSET.transfer(p)({ledger:s.ledger,metadata:s.metadata,token_metadata:s.token_metadata,operators:s.operators,owners:s.owners});
      return [ret2[0],{...s,ledger:ret2[1].ledger,metadata:ret2[1].metadata,token_metadata:ret2[1].token_metadata,operators:ret2[1].operators,owners:ret2[1].owners}];
     },
     Balance_of: (p: SINGLEASSET.balance_of) => {
      const ret2 : [list<operation>, SINGLEASSET.storage] = SINGLEASSET.balance_of(p)({ledger:s.ledger,metadata:s.metadata,token_metadata:s.token_metadata,operators:s.operators,owners:s.owners});
      return [ret2[0],{...s,ledger:ret2[1].ledger,metadata:ret2[1].metadata,token_metadata:ret2[1].token_metadata,operators:ret2[1].operators,owners:ret2[1].owners}];
      },
     Update_operators: (p: SINGLEASSET.update_operator) => {
      const ret2 : [list<operation>, SINGLEASSET.storage] = SINGLEASSET.update_ops(p)({ledger:s.ledger,metadata:s.metadata,token_metadata:s.token_metadata,operators:s.operators,owners:s.owners});
      return [ret2[0],{...s,ledger:ret2[1].ledger,metadata:ret2[1].metadata,token_metadata:ret2[1].token_metadata,operators:ret2[1].operators,owners:ret2[1].owners}];
      }
     });

Edit the storage file nft.storageList.jsligo as it. (⚠️ you can change the administrator address to your own address or keep alice)

#include "nft.jsligo"
const default_storage =
{
    administrators: Set.literal(list(["tz1VSUr8wwNhLAzempoch5d6hLRiTh8Cjcjb" as address])) as set<address>,
    totalSupply: 0 as nat,
    offers: Map.empty as map<address,offer>,
    ledger: Big_map.empty as SINGLEASSET.Ledger.t,
    metadata: Big_map.empty as SINGLEASSET.Metadata.t,
    token_metadata: Big_map.empty as SINGLEASSET.TokenMetadata.t,
    operators: Big_map.empty as SINGLEASSET.Operators.t,
    owners: Set.empty as set<SINGLEASSET.Storage.owner>,
  }
;

Compile again and 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   │ KT1HAxs2RuoxWni1WqabGJjBvnkGtyNwVFSX │ nft   │ 0                │ https://ghostnet.ecadinfra.com │
└──────────┴──────────────────────────────────────┴───────┴──────────────────┴────────────────────────────────┘

🎉 Hooray! We finished the smart contract (backend) 🎉

Update in App.tsx

We just need to fetch the token_id == 0. Replace the function refreshUserContextOnPageReload by

const refreshUserContextOnPageReload = async () => {
  console.log("refreshUserContext");
  //CONTRACT
  try {
    let c = await Tezos.contract.at(nftContractAddress, tzip12);
    console.log("nftContractAddress", nftContractAddress);

    let nftContrat: NftWalletType = await Tezos.wallet.at<NftWalletType>(
      nftContractAddress
    );
    const storage = (await nftContrat.storage()) as Storage;

    try {
      let tokenMetadata: TZIP21TokenMetadata = (await c
        .tzip12()
        .getTokenMetadata(0)) as TZIP21TokenMetadata;
      nftContratTokenMetadataMap.set(0, tokenMetadata);

      setNftContratTokenMetadataMap(new Map(nftContratTokenMetadataMap)); //new Map to force refresh
    } catch (error) {
      console.log("error refreshing nftContratTokenMetadataMap: ");
    }

    setNftContrat(nftContrat);
    setStorage(storage);
  } catch (error) {
    console.log("error refreshing nft contract: ", error);
  }

  //USER
  const activeAccount = await wallet.client.getActiveAccount();
  if (activeAccount) {
    setUserAddress(activeAccount.address);
    const balance = await Tezos.tz.getBalance(activeAccount.address);
    setUserBalance(balance.toNumber());
  }

  console.log("refreshUserContext ended.");
};

Update in MintPage.tsx

We introduce the quantity and remove the token_id variable. Replace the full file by the following content:

import OpenWithIcon from "@mui/icons-material/OpenWith";
import {
  Button,
  CardHeader,
  CardMedia,
  MobileStepper,
  Stack,
  SwipeableDrawer,
  TextField,
  Toolbar,
  useMediaQuery,
} from "@mui/material";
import Box from "@mui/material/Box";
import Card from "@mui/material/Card";
import CardContent from "@mui/material/CardContent";
import Paper from "@mui/material/Paper";
import Typography from "@mui/material/Typography";
import { BigNumber } from "bignumber.js";
import { useSnackbar } from "notistack";
import React, { useEffect, useState } from "react";
import { TZIP21TokenMetadata, UserContext, UserContextType } from "./App";
import { TransactionInvalidBeaconError } from "./TransactionInvalidBeaconError";

import {
  AddCircleOutlined,
  Close,
  KeyboardArrowLeft,
  KeyboardArrowRight,
} from "@mui/icons-material";
import { char2Bytes } from "@taquito/utils";
import { useFormik } from "formik";
import SwipeableViews from "react-swipeable-views";
import * as yup from "yup";
import { address, bytes, nat } from "./type-aliases";
export default function MintPage() {
  const {
    userAddress,
    storage,
    nftContrat,
    refreshUserContextOnPageReload,
    nftContratTokenMetadataMap,
  } = React.useContext(UserContext) as UserContextType;
  const { enqueueSnackbar } = useSnackbar();
  const [pictureUrl, setPictureUrl] = useState<string>("");
  const [file, setFile] = useState<File | null>(null);

  const [activeStep, setActiveStep] = React.useState(0);

  const handleNext = () => {
    setActiveStep((prevActiveStep) => prevActiveStep + 1);
  };

  const handleBack = () => {
    setActiveStep((prevActiveStep) => prevActiveStep - 1);
  };

  const handleStepChange = (step: number) => {
    setActiveStep(step);
  };
  const validationSchema = yup.object({
    name: yup.string().required("Name is required"),
    description: yup.string().required("Description is required"),
    symbol: yup.string().required("Symbol is required"),
    quantity: yup
      .number()
      .required("Quantity is required")
      .positive("ERROR: The number must be greater than 0!"),
  });

  const formik = useFormik({
    initialValues: {
      name: "",
      description: "",
      token_id: 0,
      symbol: "WINE",
      quantity: 1,
    } as TZIP21TokenMetadata & { quantity: number },
    validationSchema: validationSchema,
    onSubmit: (values) => {
      mint(values);
    },
  });

  //open mint drawer if admin
  useEffect(() => {
    if (storage && storage!.administrators.indexOf(userAddress! as address) < 0)
      setFormOpen(false);
    else setFormOpen(true);
  }, [userAddress]);

  const mint = async (
    newTokenDefinition: TZIP21TokenMetadata & { quantity: number }
  ) => {
    try {
      //IPFS
      if (file) {
        const formData = new FormData();
        formData.append("file", file);

        const requestHeaders: HeadersInit = new Headers();
        requestHeaders.set(
          "pinata_api_key",
          `${process.env.REACT_APP_PINATA_API_KEY}`
        );
        requestHeaders.set(
          "pinata_secret_api_key",
          `${process.env.REACT_APP_PINATA_API_SECRET}`
        );

        const resFile = await fetch(
          "https://api.pinata.cloud/pinning/pinFileToIPFS",
          {
            method: "post",
            body: formData,
            headers: requestHeaders,
          }
        );

        const responseJson = await resFile.json();
        console.log("responseJson", responseJson);

        const thumbnailUri = `ipfs://${responseJson.IpfsHash}`;
        setPictureUrl(
          `https://gateway.pinata.cloud/ipfs/${responseJson.IpfsHash}`
        );

        const op = await nftContrat!.methods
          .mint(
            new BigNumber(newTokenDefinition.quantity) as nat,
            char2Bytes(newTokenDefinition.name!) as bytes,
            char2Bytes(newTokenDefinition.description!) as bytes,
            char2Bytes(newTokenDefinition.symbol!) as bytes,
            char2Bytes(thumbnailUri) as bytes
          )
          .send();

        //close directly the form
        setFormOpen(false);
        enqueueSnackbar(
          "Wine collection is minting ... it will be ready on next block, wait for the confirmation message before minting another collection",
          { variant: "info" }
        );

        await op.confirmation(2);

        enqueueSnackbar("Wine collection minted", { 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 [formOpen, setFormOpen] = useState<boolean>(false);

  const toggleDrawer =
    (open: boolean) => (event: React.KeyboardEvent | React.MouseEvent) => {
      if (
        event.type === "keydown" &&
        ((event as React.KeyboardEvent).key === "Tab" ||
          (event as React.KeyboardEvent).key === "Shift")
      ) {
        return;
      }
      setFormOpen(open);
    };

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

  return (
    <Paper>
      {storage ? (
        <Button
          disabled={storage.administrators.indexOf(userAddress! as address) < 0}
          sx={{
            p: 1,
            position: "absolute",
            right: "0",
            display: formOpen ? "none" : "block",
            zIndex: 1,
          }}
          onClick={toggleDrawer(!formOpen)}
        >
          {" Mint Form " +
            (storage!.administrators.indexOf(userAddress! as address) < 0
              ? " (You are not admin)"
              : "")}
          <OpenWithIcon />
        </Button>
      ) : (
        ""
      )}

      <SwipeableDrawer
        onClose={toggleDrawer(false)}
        onOpen={toggleDrawer(true)}
        anchor="right"
        open={formOpen}
        variant="temporary"
      >
        <Toolbar
          sx={
            isTablet
              ? { marginTop: "0", marginRight: "0" }
              : { marginTop: "35px", marginRight: "125px" }
          }
        />
        <Box
          sx={{
            width: isTablet ? "40vw" : "60vw",
            borderColor: "text.secondary",
            borderStyle: "solid",
            borderWidth: "1px",

            height: "calc(100vh - 64px)",
          }}
        >
          <Button
            sx={{
              position: "absolute",
              right: "0",
              display: !formOpen ? "none" : "block",
            }}
            onClick={toggleDrawer(!formOpen)}
          >
            <Close />
          </Button>
          <form onSubmit={formik.handleSubmit}>
            <Stack spacing={2} margin={2} alignContent={"center"}>
              <Typography variant="h5">Mint a new collection</Typography>

              <TextField
                id="standard-basic"
                name="token_id"
                label="token_id"
                value={formik.values.token_id}
                disabled
                variant="filled"
              />
              <TextField
                id="standard-basic"
                name="name"
                label="name"
                required
                value={formik.values.name}
                onChange={formik.handleChange}
                error={formik.touched.name && Boolean(formik.errors.name)}
                helperText={formik.touched.name && formik.errors.name}
                variant="filled"
              />
              <TextField
                id="standard-basic"
                name="symbol"
                label="symbol"
                required
                value={formik.values.symbol}
                onChange={formik.handleChange}
                error={formik.touched.symbol && Boolean(formik.errors.symbol)}
                helperText={formik.touched.symbol && formik.errors.symbol}
                variant="filled"
              />
              <TextField
                id="standard-basic"
                name="description"
                label="description"
                required
                multiline
                minRows={2}
                value={formik.values.description}
                onChange={formik.handleChange}
                error={
                  formik.touched.description &&
                  Boolean(formik.errors.description)
                }
                helperText={
                  formik.touched.description && formik.errors.description
                }
                variant="filled"
              />

              <TextField
                type="number"
                id="standard-basic"
                name="quantity"
                label="quantity"
                required
                value={formik.values.quantity}
                onChange={formik.handleChange}
                error={
                  formik.touched.quantity && Boolean(formik.errors.quantity)
                }
                helperText={formik.touched.quantity && formik.errors.quantity}
                variant="filled"
              />

              {pictureUrl ? (
                <img height={100} width={100} src={pictureUrl} />
              ) : (
                ""
              )}
              <Button variant="contained" component="label" color="primary">
                <AddCircleOutlined />
                Upload an image
                <input
                  type="file"
                  hidden
                  name="data"
                  onChange={(e: React.ChangeEvent<HTMLInputElement>) => {
                    const data = e.target.files ? e.target.files[0] : null;
                    if (data) {
                      setFile(data);
                    }
                    e.preventDefault();
                  }}
                />
              </Button>

              <Button variant="contained" type="submit">
                Mint
              </Button>
            </Stack>
          </form>
        </Box>
      </SwipeableDrawer>

      <Typography variant="h5">Mint your wine collection</Typography>

      {nftContratTokenMetadataMap.size != 0 ? (
        <Box sx={{ width: "70vw" }}>
          <SwipeableViews
            axis="x"
            index={activeStep}
            onChangeIndex={handleStepChange}
            enableMouseEvents
          >
            {Array.from(nftContratTokenMetadataMap!.entries()).map(
              ([token_id, token]) => (
                <Card
                  sx={{
                    display: "block",
                    maxWidth: "80vw",
                    overflow: "hidden",
                  }}
                  key={token_id.toString()}
                >
                  <CardHeader
                    titleTypographyProps={
                      isTablet ? { fontSize: "1.5em" } : { fontSize: "1em" }
                    }
                    title={token.name}
                  />

                  <CardMedia
                    sx={
                      isTablet
                        ? {
                            width: "auto",
                            marginLeft: "33%",
                            maxHeight: "50vh",
                          }
                        : { width: "100%", maxHeight: "40vh" }
                    }
                    component="img"
                    image={token.thumbnailUri?.replace(
                      "ipfs://",
                      "https://gateway.pinata.cloud/ipfs/"
                    )}
                  />

                  <CardContent>
                    <Box>
                      <Typography>{"ID : " + token_id}</Typography>
                      <Typography>{"Symbol : " + token.symbol}</Typography>
                      <Typography>
                        {"Description : " + token.description}
                      </Typography>
                    </Box>
                  </CardContent>
                </Card>
              )
            )}
          </SwipeableViews>
          <MobileStepper
            variant="text"
            steps={Array.from(nftContratTokenMetadataMap!.entries()).length}
            position="static"
            activeStep={activeStep}
            nextButton={
              <Button
                size="small"
                onClick={handleNext}
                disabled={
                  activeStep ===
                  Array.from(nftContratTokenMetadataMap!.entries()).length - 1
                }
              >
                Next
                <KeyboardArrowRight />
              </Button>
            }
            backButton={
              <Button
                size="small"
                onClick={handleBack}
                disabled={activeStep === 0}
              >
                <KeyboardArrowLeft />
                Back
              </Button>
            }
          />
        </Box>
      ) : (
        <Typography sx={{ py: "2em" }} variant="h4">
          Sorry, there is not NFT yet, you need to mint bottles first
        </Typography>
      )}
    </Paper>
  );
}

Update in OffersPage.tsx

We introduce the quantity and remove the token_id variable. Replace the full file by the following content:

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!"),
  quantity: yup
    .number()
    .required("Quantity is required")
    .positive("ERROR: The number must be greater than 0!"),
});

type Offer = {
  price: nat;
  quantity: nat;
};

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

  let [ownerOffers, setOwnerOffers] = React.useState<Offer | null>(null);
  let [ownerBalance, setOwnerBalance] = React.useState<number>(0);

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

  const { enqueueSnackbar } = useSnackbar();

  const formik = useFormik({
    initialValues: {
      price: 0,
      quantity: 1,
    },
    validationSchema: validationSchema,
    onSubmit: (values) => {
      console.log("onSubmit: (values)", values, selectedTokenId);
      sell(selectedTokenId, values.quantity, values.price);
    },
  });

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

      await Promise.all(
        storage.owners.map(async (owner) => {
          if (owner === userAddress) {
            const ownerBalance = await storage.ledger.get(
              userAddress as address
            );
            setOwnerBalance(ownerBalance.toNumber());
            const ownerOffers = await storage.offers.get(
              userAddress as address
            );
            if (ownerOffers && ownerOffers.quantity != BigNumber(0))
              setOwnerOffers(ownerOffers!);

            console.log(
              "found for " +
                owner +
                " on token_id " +
                0 +
                " with balance " +
                ownerBalance
            );
          } else {
            console.log("skip to next owner");
          }
        })
      );
    } 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, quantity: number, price: number) => {
    try {
      const op = await nftContrat?.methods
        .sell(
          BigNumber(quantity) as nat,
          BigNumber(price * 1000000) as nat //to mutez
        )
        .send();

      await op?.confirmation(2);

      enqueueSnackbar(
        "Wine collection (token_id=" +
          token_id +
          ") offer for " +
          quantity +
          " 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>
      {ownerBalance != 0 ? (
        <Fragment>
          <Pagination
            page={currentPageIndex}
            onChange={(_, value) => setCurrentPageIndex(value)}
            count={Math.ceil(1 / itemPerPage)}
            showFirstButton
            showLastButton
          />

          <ImageList
            cols={isDesktop ? itemPerPage / 2 : isTablet ? itemPerPage / 3 : 1}
          >
            <Card key={userAddress + "-" + 0}>
              <CardHeader
                avatar={
                  <Tooltip
                    title={
                      <Box>
                        <Typography>{"ID : " + 0}</Typography>
                        <Typography>
                          {"Description : " +
                            nftContratTokenMetadataMap.get(0)?.description}
                        </Typography>
                      </Box>
                    }
                  >
                    <InfoOutlined />
                  </Tooltip>
                }
                title={nftContratTokenMetadataMap.get(0)?.name}
              />
              <CardMedia
                sx={{ width: "auto", marginLeft: "33%" }}
                component="img"
                height="100px"
                image={nftContratTokenMetadataMap
                  .get(0)
                  ?.thumbnailUri?.replace(
                    "ipfs://",
                    "https://gateway.pinata.cloud/ipfs/"
                  )}
              />

              <CardContent>
                <Box>
                  <Typography variant="body2">
                    {"Owned : " + ownerBalance}
                  </Typography>
                  <Typography variant="body2">
                    {ownerOffers
                      ? "Traded : " +
                        ownerOffers?.quantity +
                        " (price : " +
                        ownerOffers?.price.dividedBy(1000000) +
                        " Tz/b)"
                      : ""}
                  </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(0);
                      formik.handleSubmit(values);
                    }}
                  >
                    <span>
                      <TextField
                        type="number"
                        sx={{ width: "40%" }}
                        name="price"
                        label="price/bottle"
                        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}
                      />
                      <TextField
                        sx={{
                          width: "60%",
                          bottom: 0,
                          position: "relative",
                        }}
                        type="number"
                        label="quantity"
                        name="quantity"
                        placeholder="Enter a quantity"
                        variant="filled"
                        value={formik.values.quantity}
                        onChange={formik.handleChange}
                        error={
                          formik.touched.quantity &&
                          Boolean(formik.errors.quantity)
                        }
                        helperText={
                          formik.touched.quantity && formik.errors.quantity
                        }
                        InputProps={{
                          inputProps: { min: 0, max: ownerBalance },
                          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>
  );
}

Update in WineCataloguePage.tsx

We introduce the quantity and remove the token_id variable. Replace the full file by the following content:

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

type Offer = {
  price: nat;
  quantity: nat;
};

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

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(values.quantity, selectedOfferEntry!);
    },
  });
  const { enqueueSnackbar } = useSnackbar();
  const [currentPageIndex, setCurrentPageIndex] = useState<number>(1);

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

      await op?.confirmation(2);

      enqueueSnackbar(
        "Bought " +
          quantity +
          " unit of Wine collection (token_id:" +
          selectedOfferEntry[0][1] +
          ")",
        {
          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()).filter(([key, offer]) =>
                offer.quantity.isGreaterThan(0)
              ).length / itemPerPage
            )}
            showFirstButton
            showLastButton
          />
          <ImageList
            cols={isDesktop ? itemPerPage / 2 : isTablet ? itemPerPage / 3 : 1}
          >
            {Array.from(storage?.offers.entries())
              .filter(([_, offer]) => offer.quantity.isGreaterThan(0))
              .filter((owner, index) =>
                index >= currentPageIndex * itemPerPage - itemPerPage &&
                index < currentPageIndex * itemPerPage
                  ? true
                  : false
              )
              .map(([owner, offer]) => (
                <Card key={owner}>
                  <CardHeader
                    avatar={
                      <Tooltip
                        title={
                          <Box>
                            <Typography>{"ID : " + 0}</Typography>
                            <Typography>
                              {"Description : " +
                                nftContratTokenMetadataMap.get(0)?.description}
                            </Typography>
                            <Typography>{"Seller : " + owner} </Typography>
                          </Box>
                        }
                      >
                        <InfoOutlined />
                      </Tooltip>
                    }
                    title={nftContratTokenMetadataMap.get(0)?.name}
                  />
                  <CardMedia
                    sx={{ width: "auto", marginLeft: "33%" }}
                    component="img"
                    height="100px"
                    image={nftContratTokenMetadataMap
                      .get(0)
                      ?.thumbnailUri?.replace(
                        "ipfs://",
                        "https://gateway.pinata.cloud/ipfs/"
                      )}
                  />

                  <CardContent>
                    <Box>
                      <Typography variant="body2">
                        {"Price : " +
                          offer.price.dividedBy(1000000) +
                          " XTZ/bottle"}
                      </Typography>
                      <Typography variant="body2">
                        {"Available units : " + offer.quantity}
                      </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([owner, offer]);
                          formik.handleSubmit(values);
                        }}
                      >
                        <TextField
                          type="number"
                          sx={{ bottom: 0, position: "relative" }}
                          fullWidth
                          name="quantity"
                          label="quantity"
                          placeholder="Enter a quantity"
                          variant="filled"
                          value={formik.values.quantity}
                          onChange={formik.handleChange}
                          error={
                            formik.touched.quantity &&
                            Boolean(formik.errors.quantity)
                          }
                          helperText={
                            formik.touched.quantity && formik.errors.quantity
                          }
                          InputProps={{
                            inputProps: { min: 0, max: offer.quantity },
                            endAdornment: (
                              <InputAdornment position="end">
                                <Button
                                  type="submit"
                                  aria-label="add to favorites"
                                >
                                  <ShoppingCartIcon /> BUY
                                </Button>
                              </InputAdornment>
                            ),
                          }}
                        />
                      </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

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 minted NFT yet
2. Create an asset, for example:

• name: Saint Emilion - Franc la Rose
• symbol: SEMIL
• description: Grand cru 2007
• quantity: 1000

3. Click on Upload an image and 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 will ask you to sign the mint operation.

• Confirm operation
• Wait less than 1 minute to get the confirmation notification, the page will be automatically refreshed.

Now you can see the Trading menu and the Bottle offers sub menu

Click on the sub-menu entry

You are owner of this bottle so you can make an offer on it

• Enter a quantity
• Enter a price offer
• Click on SELL button
• Wait a bit for the confirmation, then once automatically refreshed you have an offer attached to your NFT

For buying,

• Disconnect from your user and connect with another account (who has enough XTZ to buy at least 1 bottle)
• The buyer will see that alice is selling some bottles from the unique collection
• Buy some bottles while clicking on BUY button
• Wait for the confirmation, then the offer is updated on the market (depending how many bottle you bought)
• Click on bottle offers sub menu
• You are now the owner of some bottles, you can resell a part of it at your own price, etc ...