improvise/src/ui/category_panel.rs

use ratatui::{
    buffer::Buffer,
    layout::Rect,
    style::{Color, Modifier, Style},
};

use unicode_width::UnicodeWidthStr;

use crate::protocol::{CatTreeEntry, CategoryTreeCache, flatten_cat_tree};
use crate::ui::app::Panel as PanelKind;
use crate::ui::panel::PanelContent;
use crate::view::Axis;

fn axis_display(axis: Axis) -> (String, Color) {
    (axis.to_string(), crate::draw::axis_fg(axis.color()))
}

/// The category panel draws one flattened tree and nothing else: the axis
/// travels on the entry (improvise-edp), so there is no `View` here.
pub struct CategoryContent {
    tree: Vec<CatTreeEntry>,
}

impl CategoryContent {
    pub fn new(
        categories: &CategoryTreeCache,
        expanded: &std::collections::HashSet<String>,
    ) -> Self {
        Self {
            tree: flatten_cat_tree(categories, expanded),
        }
    }
}

impl PanelContent for CategoryContent {
    fn panel(&self) -> PanelKind {
        PanelKind::Category
    }

    fn active_color(&self) -> Color {
        Color::Cyan
    }

    fn title(&self) -> &str {
        " Categories "
    }

    fn item_count(&self) -> usize {
        self.tree.len()
    }

    fn empty_message(&self) -> &str {
        "(no categories — use :add-cat <name>)"
    }

    fn render_item(&self, index: usize, is_selected: bool, inner: Rect, buf: &mut Buffer) {
        let y = inner.y + index as u16;

        let base_style = if is_selected {
            Style::default()
                .fg(Color::Black)
                .bg(Color::Cyan)
                .add_modifier(Modifier::BOLD)
        } else {
            Style::default()
        };

        if is_selected {
            let fill = " ".repeat(inner.width as usize);
            buf.set_string(inner.x, y, &fill, base_style);
        }

        match &self.tree[index] {
            CatTreeEntry::Category {
                name,
                item_count,
                expanded,
                axis,
            } => {
                let indicator = if *expanded { "▼" } else { "▶" };
                let (axis_str, axis_color) = axis_display(*axis);
                let name_part = format!("{indicator} {name} ({item_count})");
                let axis_part = format!(" [{axis_str}]");

                buf.set_string(inner.x, y, &name_part, base_style);
                if name_part.width() + axis_part.width() < inner.width as usize {
                    buf.set_string(
                        inner.x + name_part.width() as u16,
                        y,
                        &axis_part,
                        if is_selected {
                            base_style
                        } else {
                            Style::default().fg(axis_color)
                        },
                    );
                }
            }
            CatTreeEntry::Item { item_name, .. } => {
                let label = format!("  · {item_name}");
                buf.set_string(inner.x, y, &label, base_style);
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::protocol::CategoryRow;
    use crate::ui::app::AppMode;
    use crate::ui::panel::Panel;
    use ratatui::{layout::Rect, widgets::Widget};

    /// improvise-8l0c — `context/test-evidence/tui.md`.
    fn drawn_row(name: &str) -> String {
        let cache = CategoryTreeCache {
            categories: vec![CategoryRow {
                name: name.to_string(),
                axis: Axis::Row,
                items: vec!["x".to_string()],
            }],
        };
        let area = Rect::new(0, 0, 30, 4);
        let mut buf = Buffer::empty(area);
        Panel::new(
            CategoryContent::new(&cache, &Default::default()),
            &AppMode::Normal,
            0,
        )
        .render(area, &mut buf);
        buf.content()[31..59].iter().map(|c| c.symbol()).collect()
    }

    /// improvise-8l0c — `context/test-evidence/tui.md`.
    #[test]
    fn the_axis_tag_sits_beside_a_multibyte_category_name() {
        let ascii = drawn_row("Cafe");
        let wide = drawn_row("Café");
        assert_eq!(
            ascii.replace("Cafe", "Café"),
            wide,
            "the axis tag moved because the name was measured in bytes"
        );
    }
}