tuika 0.4.0

A composable terminal UI toolkit — flexbox layout, overlays, focus, and safe ratatui interoperability.
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//! Loader — spinner + message + optional cancel hint on one row.
//!
//! Pi's `BorderedLoader` analog. Kept borderless so callers compose it with
//! [`Boxed`](super::Boxed) when they want a frame; on its own it fits inline in
//! a status row or overlay.

use ratatui_core::layout::Rect;

use crate::geometry::Size;
use crate::surface::Surface;
use crate::view::{RenderCtx, View};

use super::spinner::{Spinner, SpinnerStyle};

/// An animated loading row.
///
/// ![loader demo](https://raw.githubusercontent.com/everruns/yolop/main/crates/tuika/docs/demos/loader.gif)
pub struct Loader {
    frame: u64,
    message: String,
    hint: Option<String>,
    spinner_style: SpinnerStyle,
}

impl Loader {
    /// A loader for the given frame counter showing `message` next to the spinner.
    pub fn new(frame: u64, message: impl Into<String>) -> Self {
        Self {
            frame,
            message: message.into(),
            hint: None,
            spinner_style: SpinnerStyle::default(),
        }
    }

    /// A trailing dim hint, e.g. "esc to cancel".
    pub fn hint(mut self, hint: impl Into<String>) -> Self {
        self.hint = Some(hint.into());
        self
    }

    /// Set the spinner glyph set.
    pub fn spinner_style(mut self, style: SpinnerStyle) -> Self {
        self.spinner_style = style;
        self
    }
}

impl View for Loader {
    fn measure(&self, available: Size) -> Size {
        Size::new(available.width, 1)
    }

    fn render(&self, area: Rect, surface: &mut Surface, ctx: &RenderCtx) {
        if area.width == 0 || area.height == 0 {
            return;
        }
        // Spinner in the first cell.
        Spinner::new(self.frame).style(self.spinner_style).render(
            Rect::new(area.x, area.y, 1, 1),
            surface,
            ctx,
        );

        let mut x = area.x.saturating_add(2);
        x = surface.set_string(x, area.y, &self.message, ctx.theme.text_style());

        if let Some(hint) = &self.hint {
            let hint = format!("  {hint}");
            let hint_w = hint.len() as u16;
            // Right-align the hint if it fits past the message.
            let hx = area.right().saturating_sub(hint_w);
            if hx > x {
                surface.set_string(hx, area.y, &hint, ctx.theme.muted_style());
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::Surface;
    use crate::style::Theme;
    use crate::test_support::{buffer, row};
    use crate::view::{RenderCtx, View};

    #[test]
    fn loader_renders_spinner_and_message() {
        let loader = Loader::new(0, "thinking").hint("esc to cancel");
        let mut buf = buffer(30, 1);
        let theme = Theme::default();
        let ctx = RenderCtx::new(&theme);
        let area = buf.area;
        let mut surface = Surface::new(&mut buf, area);
        loader.render(area, &mut surface, &ctx);
        let line = row(&buf, 0);
        assert!(line.contains("thinking"), "{line}");
        assert!(line.contains("esc to cancel"), "{line}");
    }
}