This smart contract will allow users to purchase tokens that represent parking spots, and they can redeem these tokens for parking time.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract ParkingToken {
string public name = "ParkingToken";
string public symbol = "PARK";
uint256 public totalSupply;
address public owner;
mapping(address => uint256) public balanceOf;
event TokenPurchased(address indexed buyer, uint256 amount);
event TokenRedeemed(address indexed user, uint256 amount);
constructor(uint256 _initialSupply) {
totalSupply = _initialSupply;
balanceOf[msg.sender] = _initialSupply;
owner = msg.sender;
}
modifier onlyOwner() {
require(msg.sender == owner, "Not contract owner");
_;
}
function purchaseTokens() public payable {
uint256 tokensToBuy = msg.value;
require(balanceOf[owner] >= tokensToBuy, "Not enough tokens available");
balanceOf[msg.sender] += tokensToBuy;
balanceOf[owner] -= tokensToBuy;
emit TokenPurchased(msg.sender, tokensToBuy);
}
function redeemTokens(uint256 _amount) public {
Let's implement the requested changes to your Solidity contract. Here's an overview of the tasks:
- Token Purchase (10 tokens per Ether): Modify the
purchaseTokens
function to allow users to buy 10 tokens per Ether. - Redeem Tokens as NFT for Parking: The
redeemTokens
function should allow the user to scan a parking spot and redeem hours of parking based on the value of the token. The user can also sell the NFT at a higher exchange rate for future parking. - Parking Price Calculation: Parking price should be determined based on the value of Ether at $5,000 per parking spot, divided by 13 passengers.
- Transfer Tokens at a Higher Exchange Rate: Users should be able to transfer tokens at a higher exchange rate, driving up the price of parking or gifting in the form of an NFT.
- Contract Owner Ether Withdrawal: Add the ability for the contract owner to withdraw the Ether that has been paid by users for tokens.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract ParkingToken {
string public name = "ParkingToken";
string public symbol = "PARK";
uint256 public totalSupply;
uint256 public tokenPrice = 1 ether / 10; // 10 tokens per 1 Ether
uint256 public parkingPriceInEther = 5000 ether / 13; // $5,000 per spot divided by 13 passengers
address public owner;
mapping(address => uint256) public balanceOf;
// For tracking NFTs (Non-Fungible Value)
struct ParkingSpotNFT {
address owner;
uint256 valueInTokens; // The value of the NFT in tokens
bool isActive;
}
mapping(uint256 => ParkingSpotNFT) public parkingNFTs; // Mapping of NFT ID to ParkingSpotNFT details
uint256 public nextNFTId = 1; // ID tracker for NFTs
event TokenPurchased(address indexed buyer, uint256 amount);
event TokenRedeemed(address indexed user, uint256 amount, uint256 parkingHours);
event NFTCreated(address indexed owner, uint256 nftId, uint256 tokenValue);
event NFTSold(address indexed seller, address indexed buyer, uint256 nftId, uint256 salePrice);
event TokensTransferred(address indexed from, address indexed to, uint256 amount);
event OwnerWithdrawal(uint256 amount);
constructor(uint256 _initialSupply) {
totalSupply = _initialSupply;
balanceOf[msg.sender] = _initialSupply;
owner = msg.sender;
}
modifier onlyOwner() {
require(msg.sender == owner, "Not contract owner");
_;
}
// Purchase tokens at 10 tokens per Ether
function purchaseTokens() public payable {
uint256 tokensToBuy = (msg.value / tokenPrice) * 10; // 10 tokens per Ether
require(balanceOf[owner] >= tokensToBuy, "Not enough tokens available");
balanceOf[msg.sender] += tokensToBuy;
balanceOf[owner] -= tokensToBuy;
emit TokenPurchased(msg.sender, tokensToBuy);
}
// Redeem tokens as an NFT to scan a parking spot or sell at a higher exchange rate
function redeemTokensForNFT(uint256 _amount) public {
require(balanceOf[msg.sender] >= _amount, "Not enough tokens to redeem");
// Create a new NFT for the user
ParkingSpotNFT memory newNFT = ParkingSpotNFT({
owner: msg.sender,
valueInTokens: _amount,
isActive: true
});
parkingNFTs[nextNFTId] = newNFT;
emit NFTCreated(msg.sender, nextNFTId, _amount);
nextNFTId++; // Increment the NFT ID for the next creation
// Deduct tokens from the user
balanceOf[msg.sender] -= _amount;
}
// Calculate parking hours based on token redemption
function scanParkingSpot(uint256 nftId) public {
require(parkingNFTs[nftId].owner == msg.sender, "You do not own this NFT");
require(parkingNFTs[nftId].isActive, "This NFT has already been used");
// Calculate hours of parking based on the token value
uint256 parkingHours = parkingNFTs[nftId].valueInTokens / (parkingPriceInEther / 1 ether);
parkingNFTs[nftId].isActive = false; // Mark the NFT as redeemed
emit TokenRedeemed(msg.sender, parkingNFTs[nftId].valueInTokens, parkingHours);
}
// Sell an NFT at a higher exchange rate
function sellNFT(uint256 nftId, address to, uint256 salePrice) public {
require(parkingNFTs[nftId].owner == msg.sender, "You do not own this NFT");
// Transfer ownership of the NFT
parkingNFTs[nftId].owner = to;
// Transfer tokens based on sale price
require(balanceOf[to] >= salePrice, "Buyer does not have enough tokens");
balanceOf[to] -= salePrice;
balanceOf[msg.sender] += salePrice;
emit NFTSold(msg.sender, to, nftId, salePrice);
}
// Transfer tokens at a higher exchange rate (optional: for gifting or selling tokens)
function transferTokens(address to, uint256 amount, uint256 exchangeRate) public {
uint256 finalAmount = amount * exchangeRate; // Adjust amount based on exchange rate
require(balanceOf[msg.sender] >= finalAmount, "Not enough tokens to transfer");
balanceOf[msg.sender] -= finalAmount;
balanceOf[to] += finalAmount;
emit TokensTransferred(msg.sender, to, finalAmount);
}
// Contract owner can withdraw Ether
function withdrawFunds() public onlyOwner {
uint256 amount = address(this).balance;
payable(owner).transfer(amount);
emit OwnerWithdrawal(amount);
}
// Fallback function for receiving Ether and purchasing tokens
receive() external payable {
purchaseTokens(); // Automatically trigger token purchase if Ether is sent
}
}
-
Token Purchase (10 tokens per Ether):
- The
purchaseTokens
function is modified to allow users to buy 10 tokens per Ether. - Each Ether gets divided by
tokenPrice = 1 ether / 10;
to determine how many tokens a user gets.
- The
-
Redeem Tokens as NFT for Parking:
- The
redeemTokensForNFT
function allows users to redeem tokens to create an NFT for a parking spot. - NFTs are represented by the
ParkingSpotNFT
struct, which stores the owner, token value, and whether the NFT is active. - Users can then "scan" their parking spot by calling
scanParkingSpot
, which calculates parking hours based on token value and marks the NFT as redeemed.
- The
-
Parking Price Calculation:
- The parking price is determined by the value of Ether at $5,000 divided by 13 passengers:
uint256 parkingPriceInEther = 5000 ether / 13;
- This is used in the
scanParkingSpot
function to determine how many hours of parking the user gets for their redeemed tokens.
- The parking price is determined by the value of Ether at $5,000 divided by 13 passengers:
-
Sell or Gift NFTs at a Higher Exchange Rate:
- The
sellNFT
function allows users to sell an NFT at a higher exchange rate (i.e., more tokens than it was originally worth) and transfer ownership. - The
transferTokens
function allows for gifting or transferring tokens at a higher exchange rate, which could drive up the price of parking or be used for rewards.
- The
-
Owner Withdrawal of Ether:
- The
withdrawFunds
function allows the contract owner to withdraw any Ether that users have paid to purchase tokens. The owner can transfer this Ether to their address.
- The
This contract allows the sale of parking tokens, the creation of parking spot NFTs, the ability to redeem them for parking hours, sell NFTs at a higher exchange rate, and lets the contract owner withdraw Ether. This forms the basis of an interactive NFT-based parking solution!
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract ParkingToken {
// Basic information about the token
string public name = "ParkingToken"; // Name of the token
string public symbol = "PARK"; // Symbol of the token
uint256 public totalSupply; // Total supply of tokens
uint256 public tokenPrice = 1 ether; // Price for each token (you can modify this rate)
address public owner; // Owner of the contract
mapping(address => uint256) public balanceOf; // Mapping to store balances of each user
event TokenPurchased(address indexed buyer, uint256 amount); // Event for token purchase
event TokenRedeemed(address indexed user, uint256 amount); // Event for token redemption
constructor(uint256 _initialSupply) {
totalSupply = _initialSupply; // Initialize total token supply
balanceOf[msg.sender] = _initialSupply; // Give all initial tokens to contract owner
owner = msg.sender; // Set contract deployer as owner
}
modifier onlyOwner() {
require(msg.sender == owner, "Not contract owner");
_;
}
// Function to allow users to purchase tokens
function purchaseTokens() public payable {
uint256 tokensToBuy = msg.value / tokenPrice; // Adjust this for token pricing
require(balanceOf[owner] >= tokensToBuy, "Not enough tokens available"); // Ensure owner has enough tokens
balanceOf[msg.sender] += tokensToBuy; // Increase buyer's balance
balanceOf[owner] -= tokensToBuy; // Decrease owner's balance
emit TokenPurchased(msg.sender, tokensToBuy); // Emit purchase event
}
// Function for users to redeem tokens (e.g., pay for parking)
function redeemTokens(uint256 _amount) public {
require(balanceOf[msg.sender] >= _amount, "Not enough tokens"); // Ensure user has enough tokens to redeem
balanceOf[msg.sender] -= _amount; // Deduct the redeemed tokens from user balance
balanceOf[owner] += _amount; // Return tokens to owner (optional)
emit TokenRedeemed(msg.sender, _amount); // Emit redeem event
// You can add logic here for parking time assignment, etc.
// e.g., uint256 parkingTime = _amount * 1 hour;
}
// (Optional) Transfer function for users to transfer tokens to others
function transfer(address _to, uint256 _amount) public {
require(balanceOf[msg.sender] >= _amount, "Not enough tokens");
balanceOf[msg.sender] -= _amount;
balanceOf[_to] += _amount;
}
// (Optional) Function for the owner to withdraw Ether collected from token sales
function withdrawFunds() public onlyOwner {
payable(owner).transfer(address(this).balance); // Transfer contract balance to the owner
}
// Fallback function to handle any Ether sent directly to the contract
receive() external payable {
purchaseTokens(); // Automatically trigger token purchase if Ether is sent
}
}
Key Points to Fill In or Modify: Token Price (tokenPrice):
Right now, each token is priced at 1 Ether (uint256 public tokenPrice = 1 ether;). You can modify the tokenPrice to a different value if needed. redeemTokens Logic:
The redeemTokens function is mostly complete but you need to define how users redeem tokens for parking. For example: How many tokens equal an hour of parking? What happens when they redeem tokens (maybe triggering parking rights)?
uint256 parkingTime = _amount * 1 hours;
-
Fallback Function:
- The
receive()
function allows the contract to automatically sell tokens when someone sends Ether directly to the contract. You don't need to change this unless you have specific requirements.
- The
-
Transfer Logic (Optional):
- The
transfer()
function allows users to transfer tokens to other users. If your project doesn't need token transfers, you can remove this.
- The
-
Withdraw Funds (Optional):
- The
withdrawFunds()
function allows the contract owner to withdraw Ether collected from token purchases. This is useful if you want to withdraw the funds for operational purposes.
- The
-
JavaScript (Web3.js or Ethers.js): Once this contract is deployed, the front-end (HTML/CSS) will need JavaScript (using Web3.js or Ethers.js) to interact with the contract.
- Use Web3.js to call the contract functions (
purchaseTokens
,redeemTokens
) from your frontend. - You'll link the smart contract ABI and address to the frontend in JavaScript.
- Use Web3.js to call the contract functions (
-
Deployment: You'll need to deploy this smart contract on a test network (e.g., Rinkeby) or the main Ethereum network using tools like Remix or Truffle/Hardhat.
Let's implement the requested changes to your Solidity contract. Here's an overview of the tasks:
- Token Purchase (10 tokens per Ether): Modify the
purchaseTokens
function to allow users to buy 10 tokens per Ether. - Redeem Tokens as NFT for Parking: The
redeemTokens
function should allow the user to scan a parking spot and redeem hours of parking based on the value of the token. The user can also sell the NFT at a higher exchange rate for future parking. - Parking Price Calculation: Parking price should be determined based on the value of Ether at $5,000 per parking spot, divided by 13 passengers.
- Transfer Tokens at a Higher Exchange Rate: Users should be able to transfer tokens at a higher exchange rate, driving up the price of parking or gifting in the form of an NFT.
- Contract Owner Ether Withdrawal: Add the ability for the contract owner to withdraw the Ether that has been paid by users for tokens.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract ParkingToken {
string public name = "ParkingToken";
string public symbol = "PARK";
uint256 public totalSupply;
uint256 public tokenPrice = 1 ether / 10; // 10 tokens per 1 Ether
uint256 public parkingPriceInEther = 5000 ether / 13; // $5,000 per spot divided by 13 passengers
address public owner;
mapping(address => uint256) public balanceOf;
// For tracking NFTs (Non-Fungible Value)
struct ParkingSpotNFT {
address owner;
uint256 valueInTokens; // The value of the NFT in tokens
bool isActive;
}
mapping(uint256 => ParkingSpotNFT) public parkingNFTs; // Mapping of NFT ID to ParkingSpotNFT details
uint256 public nextNFTId = 1; // ID tracker for NFTs
event TokenPurchased(address indexed buyer, uint256 amount);
event TokenRedeemed(address indexed user, uint256 amount, uint256 parkingHours);
event NFTCreated(address indexed owner, uint256 nftId, uint256 tokenValue);
event NFTSold(address indexed seller, address indexed buyer, uint256 nftId, uint256 salePrice);
event TokensTransferred(address indexed from, address indexed to, uint256 amount);
event OwnerWithdrawal(uint256 amount);
constructor(uint256 _initialSupply) {
totalSupply = _initialSupply;
balanceOf[msg.sender] = _initialSupply;
owner = msg.sender;
}
modifier onlyOwner() {
require(msg.sender == owner, "Not contract owner");
_;
}
// Purchase tokens at 10 tokens per Ether
function purchaseTokens() public payable {
uint256 tokensToBuy = (msg.value / tokenPrice) * 10; // 10 tokens per Ether
require(balanceOf[owner] >= tokensToBuy, "Not enough tokens available");
balanceOf[msg.sender] += tokensToBuy;
balanceOf[owner] -= tokensToBuy;
emit TokenPurchased(msg.sender, tokensToBuy);
}
// Redeem tokens as an NFT to scan a parking spot or sell at a higher exchange rate
function redeemTokensForNFT(uint256 _amount) public {
require(balanceOf[msg.sender] >= _amount, "Not enough tokens to redeem");
// Create a new NFT for the user
ParkingSpotNFT memory newNFT = ParkingSpotNFT({
owner: msg.sender,
valueInTokens: _amount,
isActive: true
});
parkingNFTs[nextNFTId] = newNFT;
emit NFTCreated(msg.sender, nextNFTId, _amount);
nextNFTId++; // Increment the NFT ID for the next creation
// Deduct tokens from the user
balanceOf[msg.sender] -= _amount;
}
// Calculate parking hours based on token redemption
function scanParkingSpot(uint256 nftId) public {
require(parkingNFTs[nftId].owner == msg.sender, "You do not own this NFT");
require(parkingNFTs[nftId].isActive, "This NFT has already been used");
// Calculate hours of parking based on the token value
uint256 parkingHours = parkingNFTs[nftId].valueInTokens / (parkingPriceInEther / 1 ether);
parkingNFTs[nftId].isActive = false; // Mark the NFT as redeemed
emit TokenRedeemed(msg.sender, parkingNFTs[nftId].valueInTokens, parkingHours);
}
// Sell an NFT at a higher exchange rate
function sellNFT(uint256 nftId, address to, uint256 salePrice) public {
require(parkingNFTs[nftId].owner == msg.sender, "You do not own this NFT");
// Transfer ownership of the NFT
parkingNFTs[nftId].owner = to;
// Transfer tokens based on sale price
require(balanceOf[to] >= salePrice, "Buyer does not have enough tokens");
balanceOf[to] -= salePrice;
balanceOf[msg.sender] += salePrice;
emit NFTSold(msg.sender, to, nftId, salePrice);
}
// Transfer tokens at a higher exchange rate (optional: for gifting or selling tokens)
function transferTokens(address to, uint256 amount, uint256 exchangeRate) public {
uint256 finalAmount = amount * exchangeRate; // Adjust amount based on exchange rate
require(balanceOf[msg.sender] >= finalAmount, "Not enough tokens to transfer");
balanceOf[msg.sender] -= finalAmount;
balanceOf[to] += finalAmount;
emit TokensTransferred(msg.sender, to, finalAmount);
}
// Contract owner can withdraw Ether
function withdrawFunds() public onlyOwner {
uint256 amount = address(this).balance;
payable(owner).transfer(amount);
emit OwnerWithdrawal(amount);
}
// Fallback function for receiving Ether and purchasing tokens
receive() external payable {
purchaseTokens(); // Automatically trigger token purchase if Ether is sent
}
}
-
Token Purchase (10 tokens per Ether):
- The
purchaseTokens
function is modified to allow users to buy 10 tokens per Ether. - Each Ether gets divided by
tokenPrice = 1 ether / 10;
to determine how many tokens a user gets.
- The
-
Redeem Tokens as NFT for Parking:
- The
redeemTokensForNFT
function allows users to redeem tokens to create an NFT for a parking spot. - NFTs are represented by the
ParkingSpotNFT
struct, which stores the owner, token value, and whether the NFT is active. - Users can then "scan" their parking spot by calling
scanParkingSpot
, which calculates parking hours based on token value and marks the NFT as redeemed.
- The
-
Parking Price Calculation:
- The parking price is determined by the value of Ether at $5,000 divided by 13 passengers:
uint256 parkingPriceInEther = 5000 ether / 13;
-
- This is used in the
scanParkingSpot
function to determine how many hours of parking the user gets for their redeemed tokens.
- This is used in the
-
Sell or Gift NFTs at a Higher Exchange Rate:
- The
sellNFT
function allows users to sell an NFT at a higher exchange rate (i.e., more tokens than it was originally worth) and transfer ownership. - The
transferTokens
function allows for gifting or transferring tokens at a higher exchange rate, which could drive up the price of parking or be used for rewards.
- The
-
Owner Withdrawal of Ether:
- The
withdrawFunds
function allows the contract owner to withdraw any Ether that users have paid to purchase tokens. The owner can transfer this Ether to their address.
- The
This contract allows the sale of parking tokens, the creation of parking spot NFTs, the ability to redeem them for parking hours, sell NFTs at a higher exchange rate, and lets the contract owner withdraw Ether. This forms the basis of an interactive NFT-based parking solution!