ratatui/examples/apps/weather/src/main.rs

//! A Ratatui example that demonstrates how to render weather data using [`BarChart`] widget.
//!
//! Generates random temperature data for each hour of the day and renders it as a vertical bar.
//!
//! This example runs with the Ratatui library code in the branch that you are currently reading.
//! See the [`latest`] branch for the code which works with the most recent Ratatui release.
//!
//! [`latest`]: https://github.com/ratatui/ratatui/tree/latest
//! [`BarChart`]: https://docs.rs/ratatui/latest/ratatui/widgets/struct.BarChart.html

use color_eyre::Result;
use rand::{rng, Rng};
use ratatui::{
    crossterm::event::{self, Event, KeyCode, KeyEventKind},
    layout::{Constraint, Layout},
    style::{Color, Style, Stylize},
    text::Line,
    widgets::{Bar, BarChart, BarGroup},
    DefaultTerminal, Frame,
};

fn main() -> Result<()> {
    color_eyre::install()?;
    let terminal = ratatui::init();
    let app_result = App::new().run(terminal);
    ratatui::restore();
    app_result
}

struct App {
    should_exit: bool,
    temperatures: Vec<u8>,
}

impl App {
    fn new() -> Self {
        let mut rng = rng();
        let temperatures = (0..24).map(|_| rng.random_range(50..90)).collect();
        Self {
            should_exit: false,
            temperatures,
        }
    }

    fn run(mut self, mut terminal: DefaultTerminal) -> Result<()> {
        while !self.should_exit {
            terminal.draw(|frame| self.draw(frame))?;
            self.handle_events()?;
        }
        Ok(())
    }

    fn handle_events(&mut self) -> Result<()> {
        if let Event::Key(key) = event::read()? {
            if key.kind == KeyEventKind::Press && key.code == KeyCode::Char('q') {
                self.should_exit = true;
            }
        }
        Ok(())
    }

    fn draw(&self, frame: &mut Frame) {
        let [title, main] = Layout::vertical([Constraint::Length(1), Constraint::Fill(1)])
            .spacing(1)
            .areas(frame.area());

        frame.render_widget("Weather demo".bold().into_centered_line(), title);
        frame.render_widget(vertical_barchart(&self.temperatures), main);
    }
}

/// Create a vertical bar chart from the temperatures data.
fn vertical_barchart(temperatures: &[u8]) -> BarChart {
    let bars: Vec<Bar> = temperatures
        .iter()
        .enumerate()
        .map(|(hour, value)| vertical_bar(hour, value))
        .collect();
    BarChart::default()
        .data(BarGroup::default().bars(&bars))
        .bar_width(5)
}

fn vertical_bar(hour: usize, temperature: &u8) -> Bar {
    Bar::default()
        .value(u64::from(*temperature))
        .label(Line::from(format!("{hour:>02}:00")))
        .text_value(format!("{temperature:>3}°"))
        .style(temperature_style(*temperature))
        .value_style(temperature_style(*temperature).reversed())
}

/// create a yellow to red value based on the value (50-90)
fn temperature_style(value: u8) -> Style {
    let green = (255.0 * (1.0 - f64::from(value - 50) / 40.0)) as u8;
    let color = Color::Rgb(255, green, 0);
    Style::new().fg(color)
}