Creating a todo CLI with Rust

In this article, we’ll build a to-do CLI application with Rust. Local JSON files are used to store the data. Here’s a preview of the app:

Contents

• Getting started
• Creating the folder structure
• Creating the structs
• Creating the utility functions
• Creating the todo functions
• Integrating the functions
• Conclusion

Getting started

First, we create a new project with Cargo:

cargo new todo

Then, we add the following dependencies to the Cargo.toml file:

chrono = "0.4.22"
colorize = "0.1.0"
rand = "0.8.5"
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0.85"

Here’s what each dependency does:

• chrono is used to get the current date and time.
• colorize is used to color the output.
• rand is used to generate random IDs.
• serde and serde_json are used to get the data from the JSON file.

Creating the folder structure

Our src folder will look like this:

src
 ┣ app
 ┃ ┗ mod.rs # The app module
 ┣ structs
 ┃ ┗ mod.rs # The structs
 ┣ todo
 ┃ ┗ mod.rs # Todo related functions
 ┣ utils
 ┃ ┗ mod.rs # Utility functions
 ┗ main.rs # The main file

Now, in the main.rs file, I’ll import all modules:

mod utils;
mod structs;
mod todo;
mod app;

fn main() {
    // ...
}

Creating the structs

Before we start, let’s create the structs that we’ll use to store the data. In the structs/mod.rs file, we’ll create the following structs:

use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize, Debug, Clone)]
pub struct Todo {
    pub created_at: String,
    pub title: String,
    pub done: bool,
    pub id: u32,
    pub updated_at: String,
}

#[derive(Serialize, Deserialize, Debug)]
pub struct ConfigFile {
    pub data: Vec<Todo>,
}

Creating the utility functions

In the utils/mod.rs file, we’ll import the dependencies and create the utility functions:

use crate::structs;
use chrono;
use colorize::*;
use rand::prelude::*;
use serde_json::from_str;
use serde_json::Result;
use std::{fs, io::Write};

The first function is to create the global data file if it doesn’t exist:

pub fn init() {
    // Check if folder exists
    if !fs::metadata("C:\\.todobook").is_ok() {
        fs::create_dir("C:\\.todobook").unwrap(); // Create folder

        // Create file
        let mut file = fs::File::create(DATA_FILE).unwrap();

        // Write to file
        file.write_all(b"{\"data\":[]}").unwrap();

        println!("{} {}", "Created folder and file".green(), DATA_FILE);
    }

    // Check if file exists
    else if !fs::metadata(DATA_FILE).is_ok() {
        // Create file
        let mut file = fs::File::create(DATA_FILE).unwrap();

        // Write to file
        file.write_all(b"{\"data\":[]}").unwrap();

        println!("{} {}", "Created file".green(), DATA_FILE);
    }
}

The next function is to read the arguments from the command line. Before creating a function, we define a struct called Command in the structs module:

pub struct Command {
    pub command: String,
    pub arguments: String,
}

Now, we can create the get_args function.

pub fn get_args() -> structs::Command {
    let args = std::env::args().collect::<Vec<String>>(); // Get arguments and collect them into a vector

    let command = args.get(1).unwrap_or(&"".to_string()).to_string(); // Get command or set it to an empty string
    let arguments = args.get(2).unwrap_or(&"".to_string()).to_string(); // "" arguments or ""

    structs::Command { command, arguments } // Return the command and arguments
}

The next function returns a timestamp.

pub fn get_timestamp() -> String {
    let now = chrono::Local::now();
    let timestamp = now.format("%m-%d %H:%M").to_string();

    timestamp
}

After that, we create a function to generate a random ID:

pub fn get_id() -> u32 {
    // Genrate number between 1 and 1000
    let mut rng = rand::thread_rng();
    let id: u32 = rng.gen_range(1..1000);

    id + rng.gen_range(1..1000)
}

The next function is to read the data from the JSON file:

pub fn get_todos() -> Result<Vec<structs::Todo>> {
    let data = fs::read_to_string(DATA_FILE).unwrap();
    let todos: structs::ConfigFile = from_str(&data)?;

    Ok(todos.data)
}

The last function is to write the data to the JSON file:

pub fn save_todos(todos: Vec<structs::Todo>) {
    let config_file = structs::ConfigFile { data: todos };
    let json = serde_json::to_string(&config_file).unwrap();

    let mut file = fs::File::create(DATA_FILE).unwrap();
    file.write_all(json.as_bytes()).unwrap();
}

And, that’s it for the utility functions.

Creating the todo functions

Now, we create the functions that will be used to add, remove, and list todos. In the todo/mod.rs file, import the dependencies.

use crate::structs::Todo;
use crate::utils;
use colorize::*;

The first function is to add a todo:

pub fn add(title: String) {
    if title.len() < 1 { // Check if title is empty
        println!("{}", "No title provided".red());

        return;
    }

    let mut todos = utils::get_todos().unwrap(); // Get todos

    let todo = Todo {
        created_at: utils::get_timestamp(),
        title,
        done: false,
        id: utils::get_id(),
        updated_at: utils::get_timestamp(),
    };

    todos.push(todo); // Push todo to todos

    utils::save_todos(todos); // Save todos

    println!("{}", "Added todo".green());
}

The next function is to list todos:

pub fn list() {
    let todos = utils::get_todos().unwrap();

    if todos.len() == 0 {
        println!("{}", "No todos".red());
        return;
    }

    println!(
        "{0: <5} | {1: <20} | {2: <20} | {3: <20} | {4: <20}",
        "ID", "Title", "Created at", "Updated at", "Done"
    );

    println!();

    for todo in todos {
        println!(
            "{0: <5} | {1: <20} | {2: <20} | {3: <20} | {4: <20}",
            todo.id,
            todo.title,
            todo.created_at,
            todo.updated_at,
            if todo.done { "Completed ?".green() } else { "No ?".red() }
        );
    }
}

We then create a function to mark a todo as done:

pub fn done(id: String) {
    let mut todos = utils::get_todos().unwrap();
    let id = id.parse::<u32>().unwrap_or(0);

    let exists = todos.iter().any(|todo| todo.id == id);

    if !exists {
        println!("{}", "Todo not found".red());
        return;
    }

    for todo in &mut todos {
        if todo.id == id {
            todo.done = true;
            todo.updated_at = utils::get_timestamp();
        }
    }

    utils::save_todos(todos);

    println!("{}", "Marked todo as done".green());
}

The next function is to remove a todo:

pub fn remove(id: String) {
    let mut todos = utils::get_todos().unwrap();
    let id = id.parse::<u32>().unwrap_or(0);

    let exists = todos.iter().any(|todo| todo.id == id);

    if !exists {
        println!("{}", "Todo not found".red());
        return;
    }

    todos.retain(|todo| todo.id != id);

    utils::save_todos(todos);

    println!("{}", "Removed todo".green());
}

Now, we have all the functions we need to create a todo app. We should integrate and make it work.

Integrating the functions

In the app/mod.rs file, import the dependencies.

use crate::todo::*;
use crate::utils;
use colorize::*;

We export a start function that will be called in the main.rs file.

pub fn start() {
    // ...
}

We first check and create the data file if it doesn’t exist:

utils::init();

We then get the command and arguments:

let args = utils::get_args();

We then match the command and call the appropriate function:

match args.command.as_str() {
    "a" => add(args.arguments),
    "l" => list(),
    "d" => done(args.arguments),
    "r" => remove(args.arguments),
    "q" => std::process::exit(0),
    _ => {
        /// SHOW HELP
    }
}

As for the help, we do this.

println!("{}", "            No command found - Showing help".black());

let help = format!(
    "
    {} {}
    {}
    -----

    Help:

    Command   | Arguments | Description
    {}           text        Add a new todo
    {}                       List all todos
    {}           id          Mark a todo as done
    {}           id          Delete a todo
    ",
    "Welcome to".grey(),
    "TodoBook".cyan(),
    "Simple todo app written in Rust".black(),
    "a".cyan(),
    "l".blue(),
    "d".green(),
    "r".red()
);

println!("{help}");

Now, in the main.rs file, add this function call:

fn main() {
    app::start();
}

Now, we can run the app using cargo run. You should see something like this:

Conclusion

Thanks for reading. I hope you enjoyed this tutorial. If you have any questions, feel free to ask in the comments. You can also check out the source code here.