logViewer/crates/tui/src/ui.rs

use crate::app::App;

pub fn render(frame: &mut ratatui::Frame, app: &mut App) {
    use ratatui::layout::{Constraint, Layout};
    use ratatui::style::Style;
    use ratatui::widgets::Paragraph;

    let outer = Layout::vertical([
        Constraint::Length(1),
        Constraint::Min(1),
        Constraint::Length(1),
    ])
    .split(frame.area());

    // ── Title bar ──────────────────────────────────────────────────
    let title_text = if app.is_loaded() {
        let name = app.file_name().unwrap_or("unknown");
        let cursor_display = if app.total_lines() == 0 {
            0
        } else {
            app.cursor_line + 1
        };
        format!(" {} [{}/{}]", name, cursor_display, app.total_lines())
    } else {
        " Log Viewer".to_string()
    };
    frame.render_widget(
        Paragraph::new(title_text).style(Style::default().bold()),
        outer[0],
    );

    // ── Content area ───────────────────────────────────────────────
    if !app.is_loaded() {
        frame.render_widget(Paragraph::new(" No file loaded"), outer[1]);
    } else {
        render_content(frame, app, outer[1]);
    }

    // ── Status bar ─────────────────────────────────────────────────
    frame.render_widget(
        Paragraph::new(" j/k:scroll d/u:half-page f/b:page G/gg:jump Tab:format q:quit"),
        outer[2],
    );
}

fn render_content(frame: &mut ratatui::Frame, app: &mut App, area: ratatui::layout::Rect) {
    use ratatui::style::{Color, Style};
    use ratatui::text::Line;
    use ratatui::widgets::Paragraph;

    let content_width = area.width as usize;
    let content_height = area.height as usize;

    app.content_height = area.height;
    app.content_width = area.width;

    let total_lines = app.total_lines();
    let line_num_width = if total_lines > 0 {
        total_lines.to_string().len()
    } else {
        0
    };
    let gutter_width = if total_lines > 0 {
        line_num_width + 1 + 1
    } else {
        0
    };

    let actual_content_width = content_width.saturating_sub(gutter_width);

    if content_height == 0 || actual_content_width == 0 {
        return;
    }

    app.recompute_wrap_cache(actual_content_width);
    let mut visual_acc: usize = 0;
    let mut start_logical: usize = 0;
    let mut offset_in_line: usize = 0;
    let v_offset = app.v_offset;

    for (i, &h) in app.visual_heights.iter().enumerate() {
        if visual_acc.saturating_add(h) > v_offset {
            start_logical = i;
            offset_in_line = v_offset.saturating_sub(visual_acc);
            break;
        }
        visual_acc += h;
        if i == app.visual_heights.len() - 1 {
            start_logical = i;
            offset_in_line = 0;
        }
    }

    let mut lines: Vec<Line> = Vec::new();
    let mut current_visual_offset: usize = 0;
    let available_rows = content_height;

    for logical_line in start_logical..total_lines {
        let wrapped = &app.wrap_cache[logical_line];
        let start_row = if logical_line == start_logical {
            offset_in_line
        } else {
            0
        };

        for (visual_row, text) in wrapped.iter().enumerate().skip(start_row) {
            if current_visual_offset >= available_rows {
                break;
            }

            let is_cursor = logical_line == app.cursor_line;
            let style = if is_cursor {
                Style::default().bg(Color::DarkGray)
            } else {
                Style::default()
            };

            let gutter_text = if visual_row == 0 {
                format!(
                    "{:>width$} \u{2502}",
                    logical_line + 1,
                    width = line_num_width
                )
            } else {
                format!("{:width$} \u{2502}", "", width = line_num_width)
            };

            let full_line = format!("{}{}", gutter_text, text);
            lines.push(Line::styled(full_line, style));

            current_visual_offset += 1;
        }

        if current_visual_offset >= available_rows {
            break;
        }
    }

    while lines.len() < available_rows {
        lines.push(Line::styled(String::new(), Style::default()));
    }

    frame.render_widget(Paragraph::new(lines), area);
}