Different preview modes: full, count, none

src/app.rs

@@ -124,6 +124,7 @@ impl App {
         };
 
         let mut viewer = JsonViewer::new(flatjson, opt.mode);
+        viewer.set_preview(opt.preview);
         viewer.scrolloff_setting = opt.scrolloff;
 
         let screen_writer =
@@ -311,12 +312,6 @@ impl App {
                         None
                     }
                 }
-                KeyEvent(Key::Char('p')) => {
-                    self.input_state = InputState::PendingPCommand;
-                    self.input_buffer.clear();
-                    self.buffer_input(b'p');
-                    None
-                }
                 KeyEvent(Key::Char('y')) => {
                     match &self.clipboard_context {
                         Ok(_) => {
@@ -463,6 +458,7 @@ impl App {
                         Key::End => Some(Action::FocusBottom),
                         Key::Char('%') => Some(Action::FocusMatchingPair),
                         Key::Char('m') => Some(Action::ToggleMode),
+                        Key::Char('p') => Some(Action::TogglePreview),
                         Key::Char('<') => {
                             self.screen_writer
                                 .decrease_indentation_level(self.viewer.flatjson.2 as u16);

src/jless.help

@@ -65,6 +65,12 @@
 
   Space        Toggle the collapsed state of the currently focused node.
 
+                                    DISPLAY
+
+  m            Toggle display mode: line (default), data
+
+  p            Cycle preview mode: full (default), count, none
+
                                     SCROLLING
 
   ^e        *  Scroll down one line (or N lines).

src/lineprinter.rs

@@ -12,7 +12,7 @@ use crate::search::MatchRangeIter;
 use crate::terminal;
 use crate::terminal::{Color, Style, Terminal};
 use crate::truncatedstrview::TruncatedStrView;
-use crate::viewer::Mode;
+use crate::viewer::{Mode, Preview};
 
 // This module is responsible for printing single lines of JSON to
 // the screen, complete with syntax highlighting and highlighting
@@ -138,6 +138,7 @@ pub struct LineNumber {
 
 pub struct LinePrinter<'a, 'b> {
     pub mode: Mode,
+    pub preview: Preview,
     pub terminal: &'a mut dyn Terminal,
 
     // The entire FlatJson data structure and the specific line
@@ -796,27 +797,44 @@ impl<'a, 'b> LinePrinter<'a, 'b> {
             available_space -= 1;
         }
 
-        let always_quote_string_object_keys = self.mode == Mode::Line;
-        let is_nested = false;
-        let mut used_space = self.generate_container_preview(
-            row,
-            available_space,
-            is_nested,
-            always_quote_string_object_keys,
-        )?;
+        let mut used_space = 0;
+
+        if self.preview == Preview::Full {
+            let always_quote_string_object_keys = self.mode == Mode::Line;
+            let is_nested = false;
+            let mut used_space = self.generate_container_preview(
+                row,
+                available_space,
+                is_nested,
+                always_quote_string_object_keys,
+            )?;
+            let always_quote_string_object_keys = self.mode == Mode::Line;
 
-        if self.trailing_comma {
-            used_space += 1;
             if self.trailing_comma {
-                self.highlight_str(
-                    ",",
-                    Some(self.row.range.end),
-                    (
-                        &highlighting::DEFAULT_STYLE,
-                        &highlighting::SEARCH_MATCH_HIGHLIGHTED,
-                    ),
-                )?;
+                used_space += 1;
+                if self.trailing_comma {
+                    self.highlight_str(
+                        ",",
+                        Some(self.row.range.end),
+                        (
+                            &highlighting::DEFAULT_STYLE,
+                            &highlighting::SEARCH_MATCH_HIGHLIGHTED,
+                        ),
+                    )?;
+                }
             }
+        } else if self.preview == Preview::None {
+            self.highlight_str(
+                " ",
+                Some(self.row.range.end),
+                (
+                    &highlighting::DEFAULT_STYLE,
+                    &highlighting::SEARCH_MATCH_HIGHLIGHTED,
+                ),
+            )?;
+            used_space = 1;
+        } else {
+            used_space = self.generate_container_count(row, available_space)?;
         }
 
         Ok(used_space)
@@ -944,6 +962,55 @@ impl<'a, 'b> LinePrinter<'a, 'b> {
         Ok(num_printed)
     }
 
+    // Similar to generate_container_preview, except it only prints the count
+    // of the number of children:
+    // - number of key-val pairs in a hash, ie "{ 3 }"
+    // - number of items in an array, ie "[ 2 ]"
+    fn generate_container_count(
+        &mut self,
+        row: &Row,
+        available_space: isize,
+    ) -> Result<isize, fmt::Error> {
+        debug_assert!(row.is_opening_of_container());
+
+        // Minimum amount of space required == 3: […]
+        if available_space < 3 {
+            return Ok(0);
+        }
+
+        let mut next_sibling = row.first_child();
+        let mut count: usize = 0;
+        while let OptionIndex::Index(child) = next_sibling {
+            next_sibling = self.flatjson[child].next_sibling;
+            count += 1;
+        }
+
+        let container_type = row.value.container_type().unwrap();
+        let mut count_str = format!(
+            "{} {} item{} {}",
+            container_type.open_str(),
+            count,
+            if count == 1 { "" } else { "s" },
+            container_type.close_str()
+        );
+
+        if count_str.len() as isize > available_space {
+            count_str = format!(
+                "{}…{}",
+                container_type.open_str(),
+                container_type.close_str()
+            );
+        }
+
+        self.highlight_str(
+            &count_str,
+            Some(self.row.range.start),
+            highlighting::PREVIEW_STYLES,
+        )?;
+        let len = count_str.chars().count() as isize;
+        Ok(len)
+    }
+
     // {a…: …, …}
     //
     // [a, …]
@@ -1214,6 +1281,7 @@ mod tests {
     ) -> LinePrinter<'a, 'a> {
         LinePrinter {
             mode: Mode::Data,
+            preview: Preview::Full,
             terminal,
             flatjson,
             row: &flatjson[index],
@@ -1855,6 +1923,81 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn test_generate_countainer_count() -> std::fmt::Result {
+        let json_arr = r#"[1,2,3]       "#;
+        let json_obj = r#"{"a":1, "b":2}"#;
+        let json_one = r#"{"c":3}"#;
+        //               012345678901234 (14 chars)
+        let fj_arr = parse_top_level_json(json_arr.to_owned()).unwrap();
+        let fj_obj = parse_top_level_json(json_obj.to_owned()).unwrap();
+        let fj_one = parse_top_level_json(json_one.to_owned()).unwrap();
+
+        let mut term = TextOnlyTerminal::new();
+        let mut line: LinePrinter = LinePrinter {
+            preview: Preview::Count,
+            ..default_line_printer(&mut term, &fj_arr, 0)
+        };
+
+        for (available_space, used_space, expected) in
+            vec![(14, 11, r#"[ 3 items ]"#), (4, 3, r#"[…]"#), (2, 0, r#""#)].into_iter()
+        {
+            let used = line.generate_container_count(&fj_arr[0], available_space)?;
+            assert_eq!(
+                expected,
+                line.terminal.output(),
+                "expected preview with {} available columns (used up {} columns)",
+                available_space,
+                UnicodeWidthStr::width(line.terminal.output()),
+            );
+            assert_eq!(used_space, used);
+
+            line.terminal.clear_output();
+        }
+
+        line = LinePrinter {
+            preview: Preview::Count,
+            ..default_line_printer(&mut term, &fj_obj, 0)
+        };
+
+        for (available_space, used_space, expected) in
+            vec![(14, 11, r#"{ 2 items }"#), (4, 3, r#"{…}"#), (2, 0, r#""#)].into_iter()
+        {
+            let used = line.generate_container_count(&fj_obj[0], available_space)?;
+            assert_eq!(
+                expected,
+                line.terminal.output(),
+                "expected preview with {} available columns (used up {} columns)",
+                available_space,
+                UnicodeWidthStr::width(line.terminal.output()),
+            );
+            assert_eq!(used_space, used);
+
+            line.terminal.clear_output();
+        }
+
+        line = LinePrinter {
+            preview: Preview::Count,
+            ..default_line_printer(&mut term, &fj_one, 0)
+        };
+
+        for (available_space, used_space, expected) in vec![(14, 10, r#"{ 1 item }"#)].into_iter() {
+            let used = line.generate_container_count(&fj_one[0], available_space)?;
+            assert_eq!(
+                expected,
+                line.terminal.output(),
+                "expected preview with {} available columns (used up {} columns)",
+                available_space,
+                UnicodeWidthStr::width(line.terminal.output()),
+            );
+            assert_eq!(used_space, used);
+
+            line.terminal.clear_output();
+        }
+
+        Ok(())
+    }
+
     #[test]
     fn test_generate_array_preview() -> fmt::Result {
         let json = r#"[1, {"x": true}, null, "hello", true]"#;

src/options.rs

@@ -2,7 +2,7 @@ use std::path::PathBuf;
 
 use clap::{ArgAction, Parser, ValueEnum};
 
-use crate::viewer::Mode;
+use crate::viewer::{Mode, Preview};
 
 #[derive(PartialEq, Eq, Copy, Clone, Debug, ValueEnum)]
 pub enum DataFormat {
@@ -29,6 +29,15 @@ pub struct Opt {
     #[arg(short, long, value_enum, hide_possible_values = true, default_value_t = Mode::Data)]
     pub mode: Mode,
 
+    /// Initial preview of container nodes. In full mode (--preview full;
+    /// the default), containers will be rendered as much as they can be in
+    /// the width of the terminal. In count mode (--preview count), only
+    /// the child node count will be rendered. In none mode (--preview none),
+    /// no preview will be rendered at all. This can be toggled by pressing
+    /// 'p'.
+    #[arg(short, long, value_enum, hide_possible_values = true, default_value_t = Preview::Count)]
+    pub preview: Preview,
+
     // This godforsaken configuration to get both --line-numbers and --no-line-numbers to
     // work (with --line-numbers as the default) and --relative-line-numbers and
     // --no-relative-line-numbers to work (with --no-relative-line-numbers as the default)

src/screenwriter.rs

@@ -255,6 +255,7 @@ impl ScreenWriter {
 
         let mut line = lp::LinePrinter {
             mode: viewer.mode,
+            preview: viewer.get_preview(),
             terminal: &mut self.terminal,
 
             flatjson: &viewer.flatjson,