mkdir todolistcd todolistnpm init -ynpm install --save-dev hardhat

npx hardhat init

code .

npm i dotenv

require("@nomicfoundation/hardhat-toolbox");require("dotenv").config();module.exports = {  solidity: "0.8.19",  networks: {    sepolia: {      url: process.env.ALCHEMY_API_KEY_URL,      accounts: [process.env.PRIVATE_KEY],    },  },};

// SPDX-License-Identifier: MIT// Solidity Versionpragma solidity 0.8.19;contract TodoList {    // Struct to represent a task    struct Task {        uint id; // Unique task identifier        uint date; // Timestamp of task creation        string name; // Task name        string description; // Task description        bool isCompleted; // Flag indicating task completion status        address owner; // Address of the task owner    }    // Array to store all tasks    Task[] public tasks;    // Mapping to associate user addresses with their task IDs    mapping(address => uint[]) private userTasks;    // Constructor function    constructor() {}    // Event emitted when a task is created    event TaskCreated(        uint id,        uint date,        string name,        string description,        bool isCompleted,        address owner    );    // Event emitted when a task is marked as completed    event TaskCompleted(uint id, address owner);    // Event emitted when a task is deleted    event TaskDeleted(uint id, address owner);    // Function to create a new task    function createTask(string memory name, string memory description) public {        uint taskId = tasks.length; // Calculate the new task ID        tasks.push(            Task(taskId, block.timestamp, name, description, false, msg.sender)        ); // Create and add the new task to the array        userTasks[msg.sender].push(taskId); // Update the userTasks mapping        emit TaskCreated(            taskId,            block.timestamp,            name,            description,            false,            msg.sender        ); // Emit a TaskCreated event    }    // Function to retrieve task details by ID    function getTask(        uint id    )        public        view        returns (uint, uint, string memory, string memory, bool, address)    {        // Ensure the task ID is valid        require(id < tasks.length, "Task ID does not exist");         Task storage task = tasks[id]; // Retrieve the task from storage        return (            task.id,            task.date,            task.name,            task.description,            task.isCompleted,            task.owner        ); // Return task details    }    // Function to mark a task as completed    function markTaskCompleted(uint id) public {        // Ensure the task ID is valid        require(id < tasks.length, "Task ID does not exist");         Task storage task = tasks[id]; // Retrieve the task from storage        require(            task.owner == msg.sender,            "Only the owner can complete the task"        );        // Ensure the task is not already completed        require(!task.isCompleted, "Task is already completed");         task.isCompleted = true; // Mark the task as completed        emit TaskCompleted(id, msg.sender); // Emit a TaskCompleted event    }    // Function to delete a task    function deleteTask(uint id) public {        // Ensure the task ID is valid        require(id < tasks.length, "Task ID does not exist");         Task storage task = tasks[id]; // Retrieve the task from storage        // Ensure only the owner can delete the task        require(task.owner == msg.sender, "Only the owner can delete the task");         emit TaskDeleted(id, msg.sender); // Emit a TaskDeleted event        // Delete the task by replacing it with the last task in the array         // and reducing the array size        uint lastIndex = tasks.length - 1;        if (id != lastIndex) {            Task storage lastTask = tasks[lastIndex];            tasks[id] = lastTask;            userTasks[msg.sender][id] = lastIndex;        }        tasks.pop();        userTasks[msg.sender].pop();    }    // Function to retrieve all task IDs belonging to the caller    function getUserTasks() public view returns (uint[] memory) {        // Return the task IDs associated with the caller's address        return userTasks[msg.sender];     }}

const { expect } = require("chai");const { ethers } = require("hardhat");describe("TodoList contract", function () {  let TodoList;  let todolist;  let owner;  before(async function () {    [owner] = await ethers.getSigners();    // Deploy the TodoList contract    todolist = await ethers.deployContract("TodoList");    // await TodoList.waitForDeployment();  });  it("should create a new task", async function () {    const taskName = "Sample Task";    const taskDescription = "This is a sample task description";    // Create a new task    await todolist.createTask(taskName, taskDescription);    // Retrieve the task details    const [id, date, name, description, isCompleted, taskOwner] =      await todolist.getTask(0);    expect(id).to.equal(0);    expect(name).to.equal(taskName);    expect(description).to.equal(taskDescription);    expect(isCompleted).to.equal(false);    expect(taskOwner).to.equal(owner.address);  });  it("should mark a task as completed", async function () {    // Mark the task at index 0 as completed    await todolist.markTaskCompleted(0);    // Retrieve the task details    const [, , , , isCompleted] = await todolist.getTask(0);    expect(isCompleted).to.equal(true);  });  it("should delete a task", async function () {    // Create a new task    await todolist.createTask(      "Task to be deleted",      "This task will be deleted"    );    // Delete the task at index 1    await todolist.deleteTask(1);    // Attempt to retrieve the deleted task (should throw an error)    let errorOccurred = false;    try {      await todolist.getTask(1);    } catch (error) {      errorOccurred = true;    }    expect(errorOccurred).to.equal(true);  });  it("should retrieve the user's tasks", async function () {    // Create a new task    await todolist.createTask("User's Task", "This is the user's task");    // Retrieve the user's tasks    const userTasks = await todolist.getUserTasks();    // Expect that there is at least one task    expect(userTasks.length).to.be.at.least(1);  });});

npx hardhat test

// Import the ethers library from the Hardhat frameworkconst { ethers } = require("hardhat");// Define an asynchronous main function for contract deploymentasync function main() {  // Deploy the contract  const TodoList = await ethers.deployContract("TodoList");  // Log message to show deployment in progress  console.log("Deploying contract.....");  // Wait for the deployment of the contract to complete  await TodoList.waitForDeployment();  // Log the deployment target (contract address) to the console  console.log(`TodoList deployed to ${TodoList.target}`);}// Execute the main function, and handle any errors that may occurmain().catch((error) => {  console.error(error);  process.exitCode = 1;});

npx hardhat run scripts/deploy.js --network sepolia