handler.rs

Finally we have the handler.rs file. Here, the handle_key_events function takes in two arguments:

• key_event: This is an event provided by the crossterm crate, representing a key press from the user.
• app: A mutable reference to our application’s state, represented by the App struct.

use anyhow::Result;
use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};

use crate::app::App;

/// Handles the key events and updates the state of [`App`].
pub fn handle_key_events(key_event: KeyEvent, app: &mut App) -> Result<()> {
  match key_event.code {
    // Exit application on `ESC` or `q`
    KeyCode::Esc | KeyCode::Char('q') => {
      app.quit();
    },
    // Exit application on `Ctrl-C`
    KeyCode::Char('c') | KeyCode::Char('C') => {
      if key_event.modifiers == KeyModifiers::CONTROL {
        app.quit();
      }
    },
    // Counter handlers
    KeyCode::Right | KeyCode::Char('j') => {
      app.increment_counter();
    },
    KeyCode::Left | KeyCode::Char('k') => {
      app.decrement_counter();
    },
    _ => {},
  }
  Ok(())
}