Show preview of selected command (#643)

* Only show help if terminal strictly has more than one line

* There is no border around the input line in compact mode

* Add command preview

* Dynamic preview height

* Avoid extra allocations

Co-authored-by: Conrad Ludgate <oon@conradludgate.com>

* Address clippy error

* Merge normal and compact views code

* Add show_preview setting, disabled by default

* Convert `bool` to `int` with `if` for legibility

---------

Co-authored-by: Conrad Ludgate <oon@conradludgate.com>

2 files changed, 139 insertions, 117 deletions

diff --git a/atuin-client/src/settings.rs b/atuin-client/src/settings.rs
index 2975edba..95b01c86 100644
--- a/atuin-client/src/settings.rs
+++ b/atuin-client/src/settings.rs
@@ -112,6 +112,7 @@ pub struct Settings {
     pub filter_mode: FilterMode,
     pub filter_mode_shell_up_key_binding: FilterMode,
     pub shell_up_key_binding: bool,
+    pub show_preview: bool,
     pub exit_mode: ExitMode,
     #[serde(with = "serde_regex", default = "RegexSet::empty")]
     pub history_filter: RegexSet,
@@ -296,6 +297,7 @@ impl Settings {
             .set_default("filter_mode", "global")?
             .set_default("filter_mode_shell_up_key_binding", "global")?
             .set_default("shell_up_key_binding", false)?
+            .set_default("show_preview", false)?
             .set_default("exit_mode", "return-original")?
             .set_default("session_token", "")?
             .set_default("style", "auto")?
diff --git a/src/command/client/search/interactive.rs b/src/command/client/search/interactive.rs
index 903c3362..9e7d3409 100644
--- a/src/command/client/search/interactive.rs
+++ b/src/command/client/search/interactive.rs
@@ -175,107 +175,43 @@ impl State {
     }
 
     #[allow(clippy::cast_possible_truncation)]
-    fn draw<T: Backend>(&mut self, f: &mut Frame<'_, T>, results: &[History]) {
-        let chunks = Layout::default()
-            .direction(Direction::Vertical)
-            .margin(0)
-            .constraints([
-                Constraint::Length(3),
-                Constraint::Min(1),
-                Constraint::Length(3),
-            ])
-            .split(f.size());
-
-        let top_chunks = Layout::default()
-            .direction(Direction::Horizontal)
-            .constraints([Constraint::Percentage(50); 2])
-            .split(chunks[0]);
-
-        let top_left_chunks = Layout::default()
-            .direction(Direction::Vertical)
-            .constraints([Constraint::Length(1); 3])
-            .split(top_chunks[0]);
-
-        let top_right_chunks = Layout::default()
-            .direction(Direction::Vertical)
-            .constraints([Constraint::Length(1); 3])
-            .split(top_chunks[1]);
-
-        let title = if self.update_needed.is_some() {
-            let version = self.update_needed.clone().unwrap();
-
-            Paragraph::new(Text::from(Span::styled(
-                format!(" Atuin v{VERSION} - UPDATE AVAILABLE {version}"),
-                Style::default().add_modifier(Modifier::BOLD).fg(Color::Red),
-            )))
+    #[allow(clippy::bool_to_int_with_if)]
+    fn draw<T: Backend>(
+        &mut self,
+        f: &mut Frame<'_, T>,
+        results: &[History],
+        compact: bool,
+        show_preview: bool,
+    ) {
+        let border_size = if compact { 0 } else { 1 };
+        let preview_width = f.size().width - 2;
+        let preview_height = if show_preview {
+            let longest_command = results
+                .iter()
+                .max_by(|h1, h2| h1.command.len().cmp(&h2.command.len()));
+            longest_command.map_or(0, |v| {
+                std::cmp::min(
+                    4,
+                    (v.command.len() as u16 + preview_width - 1 - border_size)
+                        / (preview_width - border_size),
+                )
+            }) + border_size * 2
+        } else if compact {
+            0
         } else {
-            Paragraph::new(Text::from(Span::styled(
-                format!(" Atuin v{VERSION}"),
-                Style::default().add_modifier(Modifier::BOLD),
-            )))
+            1
         };
-
-        let help = vec![
-            Span::raw(" Press "),
-            Span::styled("Esc", Style::default().add_modifier(Modifier::BOLD)),
-            Span::raw(" to exit."),
-        ];
-
-        let help = Paragraph::new(Text::from(Spans::from(help)));
-        let stats = Paragraph::new(Text::from(Span::raw(format!(
-            "history count: {} ",
-            self.history_count
-        ))));
-
-        f.render_widget(title, top_left_chunks[1]);
-        f.render_widget(help, top_left_chunks[2]);
-        f.render_widget(stats.alignment(Alignment::Right), top_right_chunks[1]);
-
-        let results = HistoryList::new(results).block(
-            Block::default()
-                .borders(Borders::TOP | Borders::LEFT | Borders::RIGHT)
-                .border_type(BorderType::Rounded),
-        );
-
-        f.render_stateful_widget(results, chunks[1], &mut self.results_state);
-
-        let input = format!(
-            "[{:^14}] {}",
-            self.filter_mode.as_str(),
-            self.input.as_str(),
-        );
-        let input = Paragraph::new(input).block(
-            Block::default()
-                .borders(Borders::BOTTOM | Borders::LEFT | Borders::RIGHT)
-                .border_type(BorderType::Rounded)
-                .title(format!(
-                    "{:─>width$}",
-                    "",
-                    width = chunks[2].width as usize - 2
-                )),
-        );
-        f.render_widget(input, chunks[2]);
-
-        let width = UnicodeWidthStr::width(self.input.substring());
-        f.set_cursor(
-            // Put cursor past the end of the input text
-            chunks[2].x + width as u16 + PREFIX_LENGTH + 2,
-            // Move one line down, from the border to the input line
-            chunks[2].y + 1,
-        );
-    }
-
-    #[allow(clippy::cast_possible_truncation)]
-    fn draw_compact<T: Backend>(&mut self, f: &mut Frame<'_, T>, results: &[History]) {
+        let show_help = !compact || f.size().height > 1;
         let chunks = Layout::default()
             .direction(Direction::Vertical)
             .margin(0)
             .horizontal_margin(1)
             .constraints(
                 [
-                    Constraint::Length(1),
+                    Constraint::Length(if show_help { 1 } else { 0 }),
                     Constraint::Min(1),
-                    Constraint::Length(1),
+                    Constraint::Length(1 + border_size),
+                    Constraint::Length(preview_height),
                 ]
                 .as_ref(),
             )
@@ -293,48 +229,136 @@ impl State {
             )
             .split(chunks[0]);
 
-        let title = Paragraph::new(Text::from(Span::styled(
-            format!("Atuin v{VERSION}"),
-            Style::default().fg(Color::DarkGray),
-        )));
+        let title = self.build_title();
+        f.render_widget(title, header_chunks[0]);
+
+        let help = self.build_help();
+        f.render_widget(help, header_chunks[1]);
+
+        let stats = self.build_stats();
+        f.render_widget(stats, header_chunks[2]);
+
+        let results_list = Self::build_results_list(compact, results);
+        f.render_stateful_widget(results_list, chunks[1], &mut self.results_state);
+
+        let input = self.build_input(compact, chunks[2].width.into());
+        f.render_widget(input, chunks[2]);
+
+        let preview = self.build_preview(results, compact, preview_width, chunks[3].width.into());
+        f.render_widget(preview, chunks[3]);
+
+        let extra_width = UnicodeWidthStr::width(self.input.substring());
+
+        let cursor_offset = if compact { 0 } else { 1 };
+        f.set_cursor(
+            // Put cursor past the end of the input text
+            chunks[2].x + extra_width as u16 + PREFIX_LENGTH + 1 + cursor_offset,
+            chunks[2].y + cursor_offset,
+        );
+    }
+
+    fn build_title(&mut self) -> Paragraph {
+        let title = if self.update_needed.is_some() {
+            let version = self.update_needed.clone().unwrap();
+
+            Paragraph::new(Text::from(Span::styled(
+                format!(" Atuin v{VERSION} - UPDATE AVAILABLE {version}"),
+                Style::default().add_modifier(Modifier::BOLD).fg(Color::Red),
+            )))
+        } else {
+            Paragraph::new(Text::from(Span::styled(
+                format!(" Atuin v{VERSION}"),
+                Style::default().add_modifier(Modifier::BOLD),
+            )))
+        };
+        title
+    }
 
+    #[allow(clippy::unused_self)]
+    fn build_help(&mut self) -> Paragraph {
         let help = Paragraph::new(Text::from(Spans::from(vec![
             Span::styled("Esc", Style::default().add_modifier(Modifier::BOLD)),
             Span::raw(" to exit"),
         ])))
         .style(Style::default().fg(Color::DarkGray))
         .alignment(Alignment::Center);
+        help
+    }
 
+    fn build_stats(&mut self) -> Paragraph {
         let stats = Paragraph::new(Text::from(Span::raw(format!(
             "history count: {}",
             self.history_count,
         ))))
         .style(Style::default().fg(Color::DarkGray))
         .alignment(Alignment::Right);
+        stats
+    }
 
-        f.render_widget(title, header_chunks[0]);
-        f.render_widget(help, header_chunks[1]);
-        f.render_widget(stats, header_chunks[2]);
-
-        let results = HistoryList::new(results);
-        f.render_stateful_widget(results, chunks[1], &mut self.results_state);
+    fn build_results_list(compact: bool, results: &[History]) -> HistoryList {
+        let results_list = if compact {
+            HistoryList::new(results)
+        } else {
+            HistoryList::new(results).block(
+                Block::default()
+                    .borders(Borders::TOP | Borders::LEFT | Borders::RIGHT)
+                    .border_type(BorderType::Rounded),
+            )
+        };
+        results_list
+    }
 
+    fn build_input(&mut self, compact: bool, chunk_width: usize) -> Paragraph {
         let input = format!(
             "[{:^14}] {}",
             self.filter_mode.as_str(),
             self.input.as_str(),
         );
-        let input = Paragraph::new(input);
-        f.render_widget(input, chunks[2]);
-
-        let extra_width = UnicodeWidthStr::width(self.input.substring());
+        let input = if compact {
+            Paragraph::new(input)
+        } else {
+            Paragraph::new(input).block(
+                Block::default()
+                    .borders(Borders::LEFT | Borders::RIGHT)
+                    .border_type(BorderType::Rounded)
+                    .title(format!("{:─>width$}", "", width = chunk_width - 2)),
+            )
+        };
+        input
+    }
 
-        f.set_cursor(
-            // Put cursor past the end of the input text
-            chunks[2].x + extra_width as u16 + PREFIX_LENGTH + 1,
-            // Move one line down, from the border to the input line
-            chunks[2].y + 1,
-        );
+    fn build_preview(
+        &mut self,
+        results: &[History],
+        compact: bool,
+        preview_width: u16,
+        chunk_width: usize,
+    ) -> Paragraph {
+        let selected = self.results_state.selected();
+        let command = if results.is_empty() {
+            String::new()
+        } else {
+            use itertools::Itertools as _;
+            let s = &results[selected].command;
+            s.char_indices()
+                .step_by(preview_width.into())
+                .map(|(i, _)| i)
+                .chain(Some(s.len()))
+                .tuple_windows()
+                .map(|(a, b)| &s[a..b])
+                .join("\n")
+        };
+        let preview = if compact {
+            Paragraph::new(command).style(Style::default().fg(Color::DarkGray))
+        } else {
+            Paragraph::new(command).block(
+                Block::default()
+                    .borders(Borders::BOTTOM | Borders::LEFT | Borders::RIGHT)
+                    .border_type(BorderType::Rounded)
+                    .title(format!("{:─>width$}", "", width = chunk_width - 2)),
+            )
+        };
+        preview
     }
 }
 
@@ -420,11 +444,7 @@ pub async fn history(
             atuin_client::settings::Style::Compact => true,
             atuin_client::settings::Style::Full => false,
         };
-        if compact {
-            terminal.draw(|f| app.draw_compact(f, &results))?;
-        } else {
-            terminal.draw(|f| app.draw(f, &results))?;
-        }
+        terminal.draw(|f| app.draw(f, &results, compact, settings.show_preview))?;
 
         let initial_input = app.input.as_str().to_owned();
         let initial_filter_mode = app.filter_mode;