feat: submitting todo assignment

assignments/Solidity/Todo/.gitignore

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+# Node modules
+/node_modules
+
+# Compilation output
+/dist
+
+# pnpm deploy output
+/bundle
+
+# Hardhat Build Artifacts
+/artifacts
+
+# Hardhat compilation (v2) support directory
+/cache
+
+# Typechain output
+/types
+
+# Hardhat coverage reports
+/coverage

assignments/Solidity/Todo/README.md

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+# Todo Smart Contract
+
+A Solidity smart contract for managing personal TODO tasks with deadlines and status tracking.
+
+---
+
+## Overview
+
+This contract allows users to:
+
+* Create TODO tasks with a text description and deadline
+* Track the status of tasks: Pending, Done, Cancelled, or Defaulted
+* Mark tasks as completed, automatically setting them to Done or Defaulted based on deadline
+
+---
+
+## Contract Details
+
+* **License**: MIT
+* **Solidity Version**: ^0.8.28
+
+---
+
+## State Variables
+
+| Variable      | Type                      | Description                       |
+| ------------- | ------------------------- | --------------------------------- |
+| `todoCounter` | uint256                   | Tracks the total number of TODOs  |
+| `todos`       | mapping(uint => TodoList) | Stores all TODO items by their ID |
+
+### TodoList Struct
+
+| Variable   | Type    | Description                                      |
+| ---------- | ------- | ------------------------------------------------ |
+| `id`       | uint    | Unique ID of the task                            |
+| `owner`    | address | Task creator                                     |
+| `text`     | string  | Task description                                 |
+| `status`   | enum    | Task status: Pending, Done, Cancelled, Defaulted |
+| `deadline` | uint256 | Timestamp when the task is due                   |
+
+---
+
+## Functions
+
+### createTodo(string _text, uint _deadline)
+
+Creates a new TODO task.
+
+**Access:** Public
+
+**Requirements:**
+
+* `_text` cannot be empty
+* `_deadline` must be at least 10 minutes in the future
+* Caller cannot be zero address
+
+**Notes:**
+
+* Increments `todoCounter`
+* Saves the new TODO in `todos` mapping
+* Emits `TodoCreated` event
+
+---
+
+### completedTodo(uint _id)
+
+Marks a TODO as completed.
+
+**Access:** Task owner only
+
+**Requirements:**
+
+* `_id` must exist
+* TODO must be `Pending`
+* Caller must be the task owner
+
+**Notes:**
+
+* If the deadline has passed, sets status to `Defaulted`
+* Otherwise, sets status to `Done`
+
+---
+
+## Events
+
+| Event                                     | Description                        |
+| ----------------------------------------- | ---------------------------------- |
+| `TodoCreated(string text, uint deadline)` | Emitted when a new TODO is created |
+
+---
+
+## Important Notes
+
+1. **Task Ownership**: Only the task creator can mark a TODO as completed.
+2. **Deadline Handling**: If a task is completed after its deadline, its status is automatically set to `Defaulted`.
+3. **Pending Tasks**: Only tasks with `Pending` status can be completed.
+
+---
+
+## Error Messages
+
+| Message               | Meaning                                   |
+| --------------------- | ----------------------------------------- |
+| "Empty text"          | TODO text is empty                        |
+| "Invalid Deadline"    | Deadline is less than 10 minutes from now |
+| "Zero address"        | Caller is the zero address                |
+| "Invalid id"          | TODO ID does not exist                    |
+| "Not pending"         | TODO is not in Pending status             |
+| "Unauthorized Caller" | Caller is not the task owner              |
+
+---
+
+## License
+
+MIT
+
+---

assignments/Solidity/Todo/contracts/Counter.sol

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+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.28;
+
+contract Counter {
+  uint public x;
+
+  event Increment(uint by);
+
+  function inc() public {
+    x++;
+    emit Increment(1);
+  }
+
+  function incBy(uint by) public {
+    require(by > 0, "incBy: increment should be positive");
+    x += by;
+    emit Increment(by);
+  }
+}

assignments/Solidity/Todo/contracts/Counter.t.sol

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+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.28;
+
+import {Counter} from "./Counter.sol";
+import {Test} from "forge-std/Test.sol";
+
+// Solidity tests are compatible with foundry, so they
+// use the same syntax and offer the same functionality.
+
+contract CounterTest is Test {
+  Counter counter;
+
+  function setUp() public {
+    counter = new Counter();
+  }
+
+  function test_InitialValue() public view {
+    require(counter.x() == 0, "Initial value should be 0");
+  }
+
+  function testFuzz_Inc(uint8 x) public {
+    for (uint8 i = 0; i < x; i++) {
+      counter.inc();
+    }
+    require(counter.x() == x, "Value after calling inc x times should be x");
+  }
+
+  function test_IncByZero() public {
+    vm.expectRevert();
+    counter.incBy(0);
+  }
+}

assignments/Solidity/Todo/contracts/Todo.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.28;
+
+contract Todo {
+    uint256 todoCounter;
+
+    enum Status {
+        Pending,
+        Done,
+        Cancelled,
+        Defaulted
+    }
+
+    struct TodoList {
+        uint id;
+        address owner;
+        string text;
+        Status status;
+        uint256 deadline;
+    }
+    mapping(uint => TodoList) public todos;
+    event TodoCreated(string text, uint deadline);
+
+    function createTodo(
+        string memory _text,
+        uint _deadline
+    ) external returns (uint) {
+        require(bytes(_text).length > 0, "Empty text");
+        require(_deadline > (block.timestamp + 600), "Invalid Deadline");
+           require(msg.sender != address(0), "Zero address");
+
+        todoCounter++;
+
+        todos[todoCounter] = TodoList(
+            todoCounter,
+            msg.sender,
+            _text,
+            Status.Pending,
+            _deadline
+        );
+
+        emit TodoCreated(_text, _deadline);
+        return todoCounter;
+    }
+
+    function completedTodo(uint _id) external {
+        //  TodoList memory t = todos[todoCounter]
+        require((_id > 0) && (_id <= todoCounter), "Invalid id");
+
+        TodoList storage todo = todos[_id];
+        require(todo.status == Status.Pending, "Not pending");
+        require(msg.sender == todo.owner, "Unauthorized Caller");
+
+        if (block.timestamp > todo.deadline) {
+            todo.status = Status.Defaulted;
+        } else {
+            todo.status = Status.Done;
+        }
+    }
+}

assignments/Solidity/Todo/hardhat.config.ts

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+import "dotenv/config";
+import hardhatToolboxMochaEthersPlugin from "@nomicfoundation/hardhat-toolbox-mocha-ethers";
+import { configVariable, defineConfig } from "hardhat/config";
+
+export default defineConfig({
+  plugins: [hardhatToolboxMochaEthersPlugin],
+  solidity: {
+    profiles: {
+      default: {
+        version: "0.8.28",
+      },
+      production: {
+        version: "0.8.28",
+        settings: {
+          optimizer: {
+            enabled: true,
+            runs: 200,
+          },
+        },
+      },
+    },
+  },
+  networks: {
+    hardhatMainnet: {
+      type: "edr-simulated",
+      chainType: "l1",
+    },
+    hardhatOp: {
+      type: "edr-simulated",
+      chainType: "op",
+    },
+    sepolia: {
+      type: "http",
+      chainType: "l1",
+      url: configVariable("SEPOLIA_RPC_URL"),
+      accounts: [configVariable("SEPOLIA_PRIVATE_KEY")],
+    },
+  },
+  verify: {
+    etherscan: {
+      apiKey: configVariable("ETHERSCAN_API_KEY"),
+    },
+  },
+});