Car Rent DApp - README

Welcome to the Car Rent DApp! This decentralized application (DApp) is designed for car rental ventures, providing a streamlined process for users to hire cars. Car owners can set their own hire rates, and the admin plays a crucial role in approving suitable cars for hire, ensuring the company's image is protected.

Features

User-Friendly Interface
Car Listing: Car owners can list their vehicles for hire as well end user
Deployed contract wallet address which is the admin approve and reject cars that are not suitable fo the company
Transaction History Users can view their previous transactions with address they have transact with
Real-time Availability-Instant updates on car availability, users can check if a particular car is currently on hire
Payment Handling: Secure payment processing, users can only hire a car if the previous user has completed the payment.

Technologies

CarRent is a project that utilizes the Toastify, RainbowKit, and Smart Contract technologies with Next.js.

Installation

To run the project locally, follow these steps:

Clone the repository: git clone https://github.com/your-username/CarRent.git
Install dependencies: npm install
Start the development server: npm run dev

Usage

Once the project is running, you can access it in your browser at http://localhost:3000. Here are some usage examples:

Connect your wallet
Navigate to Hire cars on your navbar
Rent a car of your choice
Make payment and View rental history

Contributing

If you would like to contribute to CarRent, please follow these guidelines:

Fork the repository
Create a new branch: git checkout -b my-feature
Make your changes and commit them: git commit -m 'Add new feature'
Push to the branch: git push origin my-feature
Submit a pull request

Explaining the smart contract

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

// Importing AccessControl for role management.
import "@openzeppelin/contracts/access/AccessControl.sol";

// Interface for interacting with an ERC-20 token.
interface IERC20Token {
    function transfer(address, uint256) external returns (bool);
    function approve(address, uint256) external returns (bool);
    function transferFrom(address, address, uint256) external returns (bool);
    function totalSupply() external view returns (uint256);
    function balanceOf(address) external view returns (uint256);
    function allowance(address, address) external view returns (uint256);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// CarBooking contract managing car rentals and approvals.
contract CarBooking is AccessControl {
    // Address of the Celo Dollar token.
    address internal cUsdTokenAddress = 0x874069Fa1Eb16D44d622F2e0Ca25eeA172369bC1;

    // Address of the administrator.
    address admin;
    
    // Number of cars and rents for tracking.
    uint256 public carLength;
    uint256 public rentLength;

    // Enum defining car status (not accepted, accepted, out of service).
    enum CarStatus {
        NOTACCEPT,
        ACCEPTED,
        OUT_OF_SERVICE
    }

    // Enum defining order status (open, in progress, cancelled, completed).
    enum OrderStatus {
        OPEN,
        INPROGRESS,
        CANCELLED,
        COMPLETED
    }

Explanation of Imports and Contract Structure:

The contract imports AccessControl for role management.
An interface IERC20Token is defined for interacting with an ERC-20 token.
CarBooking manages car rentals and approvals.

    // Struct representing a car rental.
    struct Rent {
        uint256 carID;
        address carAddress;
        address BookingAcount;
        string name;
        string destination;
        uint256 amount;
        bool paid;
    }

    // Struct representing a car.
    struct Car {
        address payable owner;
        address admin;
        string model;
        string image;
        string plateNumber;
        uint256 bookingPrice;
        uint256 rentCar;
        CarStatus carStatus;
        OrderStatus orderStatus;
        Rent[] carRent; // Store the indices of rents for this car
    }

Explanation of Structs:

Structs Rent and Car define the structure of car rentals and cars.

    // Constructor initializes the contract and grants admin role to the deployer.
    constructor() {
        _grantRole(DEFAULT_ADMIN_ROLE, msg.sender);
        admin = msg.sender;
    }

    // Modifier ensuring only the admin can call a function.
    modifier onlyAdmin() {
        require(hasRole(DEFAULT_ADMIN_ROLE, msg.sender), "Only admin can call this function");
        _;
    }
    
    // Mapping associating car ID with car details.
    mapping (uint256 => Car) public cars;

Explanation of Constructor, Modifier, and Mapping:

The constructor initializes the contract and grants the admin role.
Modifier onlyAdmin restricts certain functions to the admin.
The cars mapping associates a unique ID with each car, storing details about each car.

    // Function to add a new car with specified details.
    function addCar(string memory _model, string memory _imageCar, string memory _plateNumber, uint256 _bookingPrice) public {
        Car storage newCar = cars[carLength];
        newCar.owner = payable(msg.sender);
        newCar.admin = admin;
        newCar.model = _model;
        newCar.image = _imageCar;
        newCar.plateNumber = _plateNumber;
        newCar.bookingPrice = _bookingPrice;
        carLength++;
    }

Explanation of addCar Function:

The addCar function allows the addition of a new car with specified details.
It creates a new car instance with the provided details and increments carLength.

    // Function to approve a car for usage.
    function carApprove(uint256 _carId) public onlyAdmin {
        Car storage car = cars[_carId];
        require(car.carStatus == CarStatus.NOTACCEPT, "Car did not meet the service standards or already accepted");
        car.carStatus = CarStatus.ACCEPTED;
    }

Explanation of carApprove Function:

The carApprove function approves a car for usage.
It checks if the car is not already accepted and meets service standards.
If conditions are met, it updates the car status to "ACCEPTED."

    // Function to reject a previously accepted car.
    function rejectCar(uint256 _carId) public onlyAdmin {
        Car storage car = cars[_carId];
        require(car.carStatus == CarStatus.ACCEPTED, "Car not accepted");
        car.carStatus = CarStatus.NOTACCEPT;
    }

Explanation of rejectCar Function:

The rejectCar function rejects a previously accepted car.
It checks if the car is already accepted before updating the status to "NOTACCEPT."

    // Function to mark an accepted car as out of service.
    function outOfServiceCar(uint256 _carId) public onlyAdmin {
        Car storage car = cars[_carId];
        require(car.carStatus == CarStatus.ACCEPTED, "Car is not approved");
        car.carStatus = CarStatus.OUT_OF_SERVICE;
    }

Explanation of outOfServiceCar Function:

The outOfServiceCar function marks an accepted car as out of service.
It checks if the car is approved before updating the status to "OUT_OF_SERVICE."

    // Function to add a new car rental.
    function addRent(uint256 _carID, string memory _name, string memory _destination) public {
        require(_carID < carLength, "Invalid Car index");
        Car storage car = cars[_carID];
        require(car.carStatus == CarStatus.ACCEPTED, "Car is not approved for usage");
        require(car.orderStatus == OrderStatus.OPEN, "Car is already on hire");
        Rent memory newRent = Rent({
            carID: _carID,
            carAddress: car.owner,
            BookingAcount: msg.sender,
            name: _name,
            destination: _destination,
            amount: car.bookingPrice,
            paid: false
        });
        rentLength++;

        cars[_carID].orderStatus = OrderStatus.INPROGRESS; 
        cars[_carID].carRent.push(newRent);
    }

Explanation of addRent Function:

The addRent function enables a user to rent a car.
It checks if the car is approved for usage and not already on hire.
If conditions are met, a new rent instance is created, and the car's order status is updated to "INPROGRESS."

    // Function to get details of a specific car.
    function getCars(uint256 _index) public view returns (
        address, address, string memory, string memory,
        string memory, uint256,
        uint256,
        CarStatus, 
        OrderStatus
    ) {
        Car storage car = cars[_index];
        return (
            car.owner,
            car.admin,
            car.model,
            car.image,
            car.plateNumber,
            car.bookingPrice,
            car.rentCar,
            car.carStatus,
            car.orderStatus
        );
    }

Explanation of getCars Function:

The getCars function retrieves details of a specific car using its index.
It returns relevant information such as owner, model, image, etc.

    // Function to get details of a specific car rental.
    function getRent(uint256 _index) public view returns (
        uint256,
        address,
        address,
        string memory,
        string memory,
        uint256,
        bool
    ) {
        Car storage car = cars[_index];
        return (
            car.carRent[_index].carID,
            car.carRent[_index].carAddress,
            car.carRent[_index].BookingAcount,
            car.carRent[_index].name,
            car.carRent[_index].destination,
            car.carRent[_index].amount,
            car.carRent[_index].paid
        );
    }

Explanation of getRent Function:

The getRent function retrieves details of a specific car rental using its index.
It returns information such as car ID, customer address, rental amount, etc.

    // Function to get the total number of cars.
    function getCarLength() public view returns(uint256) {
        return carLength;
    }

Explanation of getCarLength Function:

The getCarLength function returns the total number of cars.

    // Function to get the total number of car rentals.
    function getRentLength() public view returns(uint256) {
        return rentLength;
    }

Explanation of getRentLength Function:

The getRentLength function returns the total number of car rentals.

    // Function for processing car rental payment.
    function carRentPayment(uint256 _index) external payable {
        Car storage car = cars[_index];
        require(msg.sender == car.carRent[_index].BookingAcount, "Must be the owner");
        require(IERC20Token(cUsdTokenAddress).transferFrom(
            msg.sender,
            cars[_index].owner,
            car.bookingPrice
         ), "Transfer failed");
        car.carRent[_index].paid = true;
        cars[_index].orderStatus = OrderStatus.OPEN; 
    }
}

Explanation of carRentPayment Function: