feat(tui): scroll long result names and page through results

Closes #55.

While [2] Results is focused the Info pane describes the highlighted
result, so a truncated path can be read in full. h/l (or the arrow keys)
scroll the filename column by display cells, 0 and $ jump to either end
of the highlighted name, and Home/End, g/G, PgUp/PgDn and Ctrl-f/b/d/u
move through the list; the same keys work while a filter is being typed.

Ctrl chords are no longer read as their bare letter: outside [2] they do
nothing, where before Ctrl-d deleted a search and Ctrl-c opened rooms.
Space after a filter that matches nothing no longer indexes an empty
list.

soulseek-rs/src/ui/panes/results_pane.rs

@@ -6,14 +6,25 @@ use crate::ui::{
 };
 use ratatui::{
     Frame,
-    layout::Rect,
+    layout::{Constraint, Layout, Rect},
     text::{Line, Span},
     widgets::{Cell, HighlightSpacing, Paragraph, Row, Table, TableState},
 };
 use std::collections::HashSet;
+use unicode_truncate::UnicodeTruncateStr;
 
 const VERSION: &str = env!("CARGO_PKG_VERSION");
 
+const WIDTHS: [Constraint; 7] = [
+    Constraint::Length(3),
+    Constraint::Fill(3),
+    Constraint::Length(12),
+    Constraint::Length(15),
+    Constraint::Length(10),
+    Constraint::Length(12),
+    Constraint::Length(6),
+];
+
 pub struct ResultsPaneParams<'a> {
     pub items: &'a [FileDisplayData],
     pub table_state: &'a mut TableState,
@@ -25,6 +36,38 @@ pub struct ResultsPaneParams<'a> {
     pub is_filtering: bool,
     pub focused: bool,
     pub active_search_query: Option<&'a str>,
+    pub name_offset: usize,
+}
+
+fn name_column_width(area: Rect) -> usize {
+    let inner = pane_block(false).inner(area);
+    let symbol = Line::from(HIGHLIGHT_SYMBOL).width() as u16;
+    let [_, columns] =
+        Layout::horizontal([Constraint::Length(symbol), Constraint::Fill(0)])
+            .areas(inner);
+    usize::from(Layout::horizontal(WIDTHS).spacing(1).split(columns)[1].width)
+}
+
+const fn overflow(cells: usize, width: usize) -> usize {
+    if cells <= width { 0 } else { cells + 1 - width }
+}
+
+#[must_use]
+pub fn name_end_offset(name: &str, area: Rect) -> usize {
+    overflow(Span::raw(name).width(), name_column_width(area))
+}
+
+fn scroll_name(name: &str, offset: usize, width: usize) -> Line<'_> {
+    if offset == 0 {
+        return Line::from(name);
+    }
+    let cells = Span::raw(name).width();
+    let skip = offset.min(overflow(cells, width));
+    if skip == 0 {
+        return Line::from(name);
+    }
+    let (tail, _) = name.unicode_truncate_start(cells - skip);
+    Line::from(vec![Span::raw("…"), Span::raw(tail)])
 }
 
 /// Whether the rendered row `display_idx` is selected. `selected_indices` holds
@@ -59,6 +102,7 @@ pub fn render_results_pane(
         is_filtering,
         focused,
         active_search_query,
+        name_offset,
     } = params;
     if items.is_empty() {
         let title = match active_search_query {
@@ -105,6 +149,7 @@ pub fn render_results_pane(
     ])
     .height(1);
 
+    let name_width = name_column_width(area);
     let rows: Vec<Row> = items
         .iter()
         .enumerate()
@@ -137,7 +182,12 @@ pub fn render_results_pane(
 
             Row::new(vec![
                 Cell::from(checkbox).style(checkbox_style),
-                Cell::from(file.filename.clone()).style(body_style()),
+                Cell::from(scroll_name(
+                    &file.filename,
+                    name_offset,
+                    name_width,
+                ))
+                .style(body_style()),
                 Cell::from(format_bytes(file.size)).style(warning_style()),
                 Cell::from(file.username.clone()).style(info_style()),
                 Cell::from(bitrate_str).style(dimmed_style()),
@@ -147,16 +197,6 @@ pub fn render_results_pane(
         })
         .collect();
 
-    let widths = [
-        ratatui::layout::Constraint::Length(3),
-        ratatui::layout::Constraint::Fill(3),
-        ratatui::layout::Constraint::Length(12),
-        ratatui::layout::Constraint::Length(15),
-        ratatui::layout::Constraint::Length(10),
-        ratatui::layout::Constraint::Length(12),
-        ratatui::layout::Constraint::Length(6),
-    ];
-
     let title = if is_filtering {
         format!("Results · filter: '{filter_query}'")
     } else if let Some(query) = active_search_query {
@@ -165,7 +205,7 @@ pub fn render_results_pane(
         "Results".to_string()
     };
 
-    let table = Table::new(rows, widths)
+    let table = Table::new(rows, WIDTHS)
         .header(header)
         .row_highlight_style(row_highlight_style())
         .highlight_symbol(HIGHLIGHT_SYMBOL)
@@ -177,9 +217,78 @@ pub fn render_results_pane(
 
 #[cfg(test)]
 mod tests {
-    use super::row_is_selected;
+    use super::{ResultsPaneParams, render_results_pane, row_is_selected};
+    use crate::models::FileDisplayData;
+    use ratatui::{Terminal, backend::TestBackend, widgets::TableState};
     use std::collections::HashSet;
 
+    fn render_rows(items: &[FileDisplayData], name_offset: usize) -> String {
+        let mut state = TableState::default();
+        state.select(Some(0));
+        let mut terminal =
+            Terminal::new(TestBackend::new(80, 6)).expect("backend");
+        terminal
+            .draw(|frame| {
+                render_results_pane(
+                    frame,
+                    frame.area(),
+                    ResultsPaneParams {
+                        items,
+                        table_state: &mut state,
+                        selected_indices: &HashSet::new(),
+                        original_indices: None,
+                        filter_query: "",
+                        is_filtering: false,
+                        focused: true,
+                        active_search_query: None,
+                        name_offset,
+                    },
+                );
+            })
+            .expect("draw");
+        terminal.backend().to_string()
+    }
+
+    fn file(filename: &str) -> FileDisplayData {
+        FileDisplayData {
+            filename: filename.to_string(),
+            username: "bob".to_string(),
+            ..Default::default()
+        }
+    }
+
+    #[test]
+    fn a_scrolled_name_shows_its_tail_up_to_the_column_edge() {
+        let items = [
+            file("abcdefghijklmnopqrstuvwxyz0123456789ABCD"),
+            file("short.mp3"),
+        ];
+        let screen = render_rows(&items, usize::MAX);
+        assert!(screen.contains("…456789ABCD"), "{screen}");
+        assert!(!screen.contains("3456789ABCD"), "{screen}");
+        assert!(screen.contains(" short.mp3 "), "{screen}");
+
+        let screen = render_rows(&items, 8);
+        assert!(screen.contains("…ijklmnopqr"), "{screen}");
+        assert!(!screen.contains("hijklmnopqr"), "{screen}");
+    }
+
+    #[test]
+    fn a_wide_glyph_name_scrolls_by_cells_not_chars() {
+        let items = [file("零一二三四五六七八九十百千万亿東西南北中")];
+        let screen = render_rows(&items, usize::MAX);
+        assert!(screen.contains("…東西南北中"), "{screen}");
+        assert!(!screen.contains("亿東"), "{screen}");
+    }
+
+    #[test]
+    fn an_unscrolled_name_starts_at_its_beginning() {
+        let items = [file("abcdefghijklmnopqrstuvwxyz0123456789ABCD")];
+        let screen = render_rows(&items, 0);
+        assert!(screen.contains("abcdefghijk"), "{screen}");
+        assert!(!screen.contains("…"), "{screen}");
+    }
+
     #[test]
     fn identity_mapping_used_when_no_filter() {
         let selected: HashSet<usize> = std::iter::once(1).collect();