ced/src/ui/central_panel/line_numbers.rs

use eframe::egui;

fn format_line_number(line_number: usize, line_side: bool, line_count_width: usize) -> String {
    if line_side {
        // Right side: left-align with trailing space for scrollbar clearance
        format!("{:<width$} ", line_number, width = line_count_width)
    } else {
        // Left side: right-align, no trailing space (separator provides gap)
        format!("{:>width$}", line_number, width = line_count_width)
    }
}

pub(super) fn calculate_visual_line_mapping(
    ui: &egui::Ui,
    content: &str,
    available_width: f32,
    font_id: egui::FontId,
) -> Vec<Option<usize>> {
    let mut visual_lines = Vec::new();

    for (line_num, line) in content.lines().enumerate() {
        if line.is_empty() {
            visual_lines.push(Some(line_num + 1));
            continue;
        }

        let galley = ui.fonts_mut(|fonts| {
            fonts.layout(
                line.to_string(),
                font_id.to_owned(),
                egui::Color32::WHITE,
                available_width,
            )
        });

        let wrapped_line_count = galley.rows.len().max(1);
        visual_lines.push(Some(line_num + 1));

        for _ in 1..wrapped_line_count {
            visual_lines.push(None);
        }
    }

    if content.ends_with('\n') && !content.is_empty() {
        let line_num = content.lines().count();
        visual_lines.push(Some(line_num + 1));
    }

    visual_lines
}

pub(super) fn render_line_numbers(
    ui: &mut egui::Ui,
    line_count: usize,
    visual_line_mapping: &[Option<usize>],
    line_number_width: f32,
    word_wrap: bool,
    line_side: bool,
    font_size: f32,
) {
    ui.vertical(|ui| {
        ui.disable();
        ui.set_width(line_number_width);
        ui.spacing_mut().item_spacing.y = 0.0;
        ui.add_space(1.0); // Text Editor default top margin
        let text_color = ui.visuals().weak_text_color();
        let bg_color = ui.visuals().extreme_bg_color;

        let line_numbers_rect = ui.available_rect_before_wrap();
        ui.painter().rect_filled(line_numbers_rect, 0.0, bg_color);

        let font_id = egui::FontId::monospace(font_size);
        let line_count_width = line_count.to_string().len();

        let line_texts = if word_wrap {
            visual_line_mapping
                .into_iter()
                .map(|line_number_opt| {
                    line_number_opt.map_or_else(
                        || " ".repeat(line_count_width),
                        |line_number| format_line_number(line_number, line_side, line_count_width),
                    )
                })
                .collect::<Vec<_>>()
        } else {
            (1..=line_count)
                .map(|i| format_line_number(i, line_side, line_count_width))
                .collect::<Vec<_>>()
        };

        for text in line_texts {
            ui.label(
                egui::RichText::new(text)
                    .font(font_id.to_owned())
                    .color(text_color),
            );
        }
    });
}