feat: add Visual selection and clipboard editing

src/editor.rs

@@ -36,6 +36,7 @@ pub enum Mode {
     Insert,
     Command,
     Search,
+    Visual,
 }
 
 impl fmt::Display for Mode {
@@ -45,6 +46,7 @@ impl fmt::Display for Mode {
             Self::Insert => "INSERT",
             Self::Command => "COMMAND",
             Self::Search => "SEARCH",
+            Self::Visual => "VISUAL",
         })
     }
 }
@@ -63,6 +65,14 @@ pub struct SearchMatch {
     pub end_column: usize,
 }
 
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct Selection {
+    /// Inclusive start of the ordered range, in grapheme coordinates.
+    pub start: Cursor,
+    /// Exclusive end in grapheme coordinates; may be the next row's column 0.
+    pub end: Cursor,
+}
+
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct Feature {
     pub name: String,
@@ -133,6 +143,11 @@ enum Action {
     BigWordNext,
     BigWordPrevious,
     BigWordEnd,
+    Select,
+    Copy,
+    Cut,
+    PasteBefore,
+    PasteAfter,
 }
 
 impl Action {
@@ -150,22 +165,29 @@ impl Action {
             (Mode::Normal, "core.redo") => Redo,
             (Mode::Normal, "core.command") => Command,
             (Mode::Normal, "core.search") => Search,
-            (Mode::Normal, "core.search_next") => SearchNext,
-            (Mode::Normal, "core.search_previous") => SearchPrevious,
-            (Mode::Normal | Mode::Insert, "core.left") => Left,
-            (Mode::Normal | Mode::Insert, "core.right") => Right,
-            (Mode::Normal | Mode::Insert, "core.down") => Down,
-            (Mode::Normal | Mode::Insert, "core.up") => Up,
-            (Mode::Normal | Mode::Insert, "core.line_start") => LineStart,
-            (Mode::Normal | Mode::Insert, "core.line_end") => LineEnd,
-            (Mode::Normal | Mode::Insert, "core.word_next") => WordNext,
-            (Mode::Normal | Mode::Insert, "core.word_previous") => WordPrevious,
-            (Mode::Normal | Mode::Insert, "core.word_end") => WordEnd,
-            (Mode::Normal | Mode::Insert, "core.big_word_next") => BigWordNext,
-            (Mode::Normal | Mode::Insert, "core.big_word_previous") => BigWordPrevious,
-            (Mode::Normal | Mode::Insert, "core.big_word_end") => BigWordEnd,
+            (Mode::Normal | Mode::Visual, "core.search_next") => SearchNext,
+            (Mode::Normal | Mode::Visual, "core.search_previous") => SearchPrevious,
+            (Mode::Normal | Mode::Visual, "core.select") => Select,
+            (Mode::Visual, "core.copy") => Copy,
+            (Mode::Visual, "core.cut") => Cut,
+            (Mode::Normal, "core.paste_before") => PasteBefore,
+            (Mode::Normal, "core.paste_after") => PasteAfter,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.left") => Left,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.right") => Right,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.down") => Down,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.up") => Up,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.line_start") => LineStart,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.line_end") => LineEnd,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.word_next") => WordNext,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.word_previous") => WordPrevious,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.word_end") => WordEnd,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.big_word_next") => BigWordNext,
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.big_word_previous") => {
+                BigWordPrevious
+            }
+            (Mode::Normal | Mode::Insert | Mode::Visual, "core.big_word_end") => BigWordEnd,
             (Mode::Normal | Mode::Insert, "core.delete") => Delete,
-            (Mode::Insert | Mode::Command | Mode::Search, "core.normal") => Normal,
+            (Mode::Insert | Mode::Command | Mode::Search | Mode::Visual, "core.normal") => Normal,
             (Mode::Insert, "core.newline") => Newline,
             (Mode::Insert | Mode::Command | Mode::Search, "core.backspace") => Backspace,
             (Mode::Command | Mode::Search, "core.submit") => Submit,
@@ -257,33 +279,45 @@ fn default_bindings() -> HashMap<Mode, HashMap<Input, Binding>> {
         ('A', AppendLineEnd),
         ('o', OpenBelow),
         ('O', OpenAbove),
-        ('h', Left),
-        ('j', Down),
-        ('k', Up),
-        ('l', Right),
         ('J', JoinLines),
-        ('0', LineStart),
-        ('$', LineEnd),
         ('x', Delete),
         ('u', Undo),
         ('U', Redo),
         (':', Command),
         ('/', Search),
-        ('n', SearchNext),
-        ('N', SearchPrevious),
-        ('w', WordNext),
-        ('b', WordPrevious),
-        ('e', WordEnd),
-        ('W', BigWordNext),
-        ('B', BigWordPrevious),
-        ('E', BigWordEnd),
+        ('p', PasteAfter),
+        ('P', PasteBefore),
     ] {
         bindings
             .entry(Mode::Normal)
             .or_default()
             .insert(Input::Char(key), Binding::Action(action));
     }
-    for mode in [Mode::Normal, Mode::Insert] {
+    for mode in [Mode::Normal, Mode::Visual] {
+        for (key, action) in [
+            ('h', Left),
+            ('j', Down),
+            ('k', Up),
+            ('l', Right),
+            ('0', LineStart),
+            ('$', LineEnd),
+            ('w', WordNext),
+            ('b', WordPrevious),
+            ('e', WordEnd),
+            ('W', BigWordNext),
+            ('B', BigWordPrevious),
+            ('E', BigWordEnd),
+            ('n', SearchNext),
+            ('N', SearchPrevious),
+            ('v', Select),
+        ] {
+            bindings
+                .entry(mode)
+                .or_default()
+                .insert(Input::Char(key), Binding::Action(action));
+        }
+    }
+    for mode in [Mode::Normal, Mode::Insert, Mode::Visual] {
         for (key, action) in [
             (Input::Left, Left),
             (Input::Right, Right),
@@ -291,7 +325,6 @@ fn default_bindings() -> HashMap<Mode, HashMap<Input, Binding>> {
             (Input::Up, Up),
             (Input::Home, LineStart),
             (Input::End, LineEnd),
-            (Input::Delete, Delete),
         ] {
             bindings
                 .entry(mode)
@@ -299,6 +332,27 @@ fn default_bindings() -> HashMap<Mode, HashMap<Input, Binding>> {
                 .insert(key, Binding::Action(action));
         }
     }
+    for mode in [Mode::Normal, Mode::Insert] {
+        bindings
+            .entry(mode)
+            .or_default()
+            .insert(Input::Delete, Binding::Action(Delete));
+    }
+    bindings
+        .entry(Mode::Visual)
+        .or_default()
+        .insert(Input::Escape, Binding::Action(Normal));
+    for (key, action) in [
+        (Input::Char('y'), Copy),
+        (Input::Char('d'), Cut),
+        (Input::Char('x'), Cut),
+        (Input::Delete, Cut),
+    ] {
+        bindings
+            .entry(Mode::Visual)
+            .or_default()
+            .insert(key, Binding::Action(action));
+    }
     for mode in [Mode::Insert, Mode::Command, Mode::Search] {
         for (key, action) in [
             (Input::Escape, Normal),
@@ -329,6 +383,8 @@ pub struct Editor {
     command_line: String,
     search_query: String,
     search_match: Option<SearchMatch>,
+    selection_anchor: Option<Cursor>,
+    clipboard: String,
     message: String,
     path: Option<PathBuf>,
     quit: bool,
@@ -361,6 +417,8 @@ impl Editor {
             command_line: String::new(),
             search_query: String::new(),
             search_match: None,
+            selection_anchor: None,
+            clipboard: String::new(),
             message: String::new(),
             path,
             quit: false,
@@ -404,6 +462,28 @@ impl Editor {
     pub fn search_match(&self) -> Option<SearchMatch> {
         self.search_match
     }
+    /// Ordered, end-exclusive range in Visual mode; None in other modes.
+    /// An empty final row produces an empty range, not a synthetic character.
+    pub fn selection(&self) -> Option<Selection> {
+        if self.mode != Mode::Visual {
+            return None;
+        }
+        let anchor = self.selection_anchor?;
+        let (start, mut end) =
+            if (anchor.row, anchor.column) <= (self.cursor.row, self.cursor.column) {
+                (anchor, self.cursor)
+            } else {
+                (self.cursor, anchor)
+            };
+        let line = &self.lines[end.row];
+        if grapheme_byte(line, end.column) < line.len() {
+            end.column += 1;
+        } else if end.row + 1 < self.lines.len() {
+            end.row += 1;
+            end.column = 0;
+        }
+        Some(Selection { start, end })
+    }
     pub fn message(&self) -> &str {
         &self.message
     }
@@ -506,6 +586,7 @@ impl Editor {
             "insert" => Mode::Insert,
             "command" => Mode::Command,
             "search" => Mode::Search,
+            "visual" => Mode::Visual,
             _ => return Err(format!("Unknown binding mode: {mode}")),
         };
         let key = parse_key(key)?;
@@ -633,6 +714,19 @@ impl Editor {
             }
             Action::SearchNext => self.seek_search(true),
             Action::SearchPrevious => self.seek_search(false),
+            Action::Select => {
+                if self.mode == Mode::Visual {
+                    self.clear_selection();
+                } else {
+                    self.selection_anchor = Some(self.cursor);
+                    self.mode = Mode::Visual;
+                    self.message.clear();
+                }
+            }
+            Action::Copy => self.copy_selection(false),
+            Action::Cut => self.copy_selection(true),
+            Action::PasteBefore => self.paste_clipboard(false),
+            Action::PasteAfter => self.paste_clipboard(true),
             Action::Normal => {
                 if self.mode == Mode::Insert {
                     self.finish_insert();
@@ -642,6 +736,8 @@ impl Editor {
                 } else {
                     self.command_line.clear();
                     self.mode = Mode::Normal;
+                    self.selection_anchor = None;
+                    self.clamp_cursor();
                 }
             }
             Action::Newline => self.insert_text("\n"),
@@ -716,6 +812,7 @@ impl Editor {
             self.finish_insert();
         }
         self.mode = Mode::Normal;
+        self.selection_anchor = None;
         self.clamp_cursor();
         let command = command.trim().strip_prefix(':').unwrap_or(command.trim());
         let (name, args) = command
@@ -801,6 +898,9 @@ impl Editor {
                     || matches!(effect, Effect::Replace(_))
             })
             .then(|| self.snapshot());
+        if before.is_some() {
+            self.clear_selection();
+        }
         for effect in effects {
             match effect {
                 Effect::Insert(text) => self.insert_text(&normalize_newlines(&text)),
@@ -851,11 +951,100 @@ impl Editor {
     fn record(&mut self, before: Snapshot) {
         if before.lines != self.lines {
             self.search_match = None;
+            self.clear_selection();
             self.undo.push(before);
             self.redo.clear();
         }
     }
 
+    fn copy_selection(&mut self, cut: bool) {
+        let Some(selection) = self.selection() else {
+            return;
+        };
+        if selection.start == selection.end {
+            self.clear_selection();
+            self.set_message("Nothing selected");
+            return;
+        }
+        let start = selection.start;
+        let end = selection.end;
+        let start_byte = grapheme_byte(&self.lines[start.row], start.column);
+        let end_byte = grapheme_byte(&self.lines[end.row], end.column);
+        self.clipboard = if start.row == end.row {
+            self.lines[start.row][start_byte..end_byte].to_owned()
+        } else {
+            let capacity = self.lines[start.row..end.row]
+                .iter()
+                .map(String::len)
+                .sum::<usize>()
+                - start_byte
+                + end_byte
+                + end.row
+                - start.row;
+            let mut text = String::with_capacity(capacity);
+            text.push_str(&self.lines[start.row][start_byte..]);
+            for line in &self.lines[start.row + 1..end.row] {
+                text.push('\n');
+                text.push_str(line);
+            }
+            text.push('\n');
+            text.push_str(&self.lines[end.row][..end_byte]);
+            text
+        };
+        let before = cut.then(|| self.snapshot());
+        self.clear_selection();
+        self.cursor = start;
+        if cut {
+            if start.row == end.row {
+                self.lines[start.row].replace_range(start_byte..end_byte, "");
+            } else {
+                let mut tail = self
+                    .lines
+                    .drain(start.row + 1..=end.row)
+                    .next_back()
+                    .expect("cross-line selection includes an end row");
+                tail.replace_range(..end_byte, &self.lines[start.row][..start_byte]);
+                self.lines[start.row] = tail;
+            }
+        }
+        self.clamp_cursor();
+        if let Some(before) = before {
+            self.record(before);
+        }
+        self.set_message(if cut {
+            "Cut selection"
+        } else {
+            "Copied selection"
+        });
+    }
+
+    fn paste_clipboard(&mut self, after: bool) {
+        if self.clipboard.is_empty() {
+            self.set_message("Clipboard is empty");
+            return;
+        }
+        let before = self.snapshot();
+        if after {
+            self.cursor.column =
+                (self.cursor.column + 1).min(grapheme_count(&self.lines[self.cursor.row]));
+        }
+        let text = std::mem::take(&mut self.clipboard);
+        self.insert_text(&text);
+        self.clipboard = text;
+        self.cursor.column = self.cursor.column.saturating_sub(1);
+        self.clamp_cursor();
+        self.record(before);
+        self.message.clear();
+    }
+
+    fn clear_selection(&mut self) {
+        self.selection_anchor = None;
+        if self.mode == Mode::Visual {
+            self.mode = Mode::Normal;
+            self.clamp_cursor();
+        }
+    }
+
     fn begin_insert(&mut self) {
         self.insert_start = Some(self.snapshot());
         self.mode = Mode::Insert;
@@ -916,7 +1105,9 @@ impl Editor {
 
     fn max_column(&self) -> usize {
         let count = grapheme_count(&self.lines[self.cursor.row]);
-        if self.mode == Mode::Insert {
+        if self.mode == Mode::Insert
+            || (self.mode == Mode::Visual && self.cursor.row + 1 < self.lines.len())
+        {
             count
         } else {
             count.saturating_sub(1)
@@ -1336,6 +1527,207 @@ mod tests {
         }
     }
 
+    #[test]
+    fn visual_ranges_copy_both_directions_and_cut_and_paste_multiline_graphemes() {
+        let mut editor = editor();
+        let text = "a界e\u{301}z\n\n👩‍🚀tail\n";
+        editor.apply(vec![Effect::Replace(text.into())]).unwrap();
+        editor.handle(Input::Right);
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Right);
+        assert_eq!(
+            editor.selection(),
+            Some(Selection {
+                start: Cursor { row: 0, column: 1 },
+                end: Cursor { row: 0, column: 3 },
+            })
+        );
+        editor.handle(Input::Left);
+        editor.handle(Input::Left);
+        assert_eq!(
+            editor.selection().unwrap().start,
+            Cursor { row: 0, column: 0 }
+        );
+        assert_eq!(
+            editor.selection().unwrap().end,
+            Cursor { row: 0, column: 2 }
+        );
+        editor.handle(Input::Down);
+        assert_eq!(
+            editor.selection().unwrap().end,
+            Cursor { row: 2, column: 0 }
+        );
+        let selected = editor.selection();
+        editor.handle(Input::Paste(":q!\n".into()));
+        assert_eq!(editor.selection(), selected);
+        assert_eq!(editor.context().text, text);
+        assert!(!editor.should_quit());
+        editor.handle(Input::Down);
+        assert_eq!(
+            editor.selection().unwrap().end,
+            Cursor { row: 2, column: 1 }
+        );
+        editor.handle(Input::Char('d'));
+        assert_eq!(editor.mode(), Mode::Normal);
+        assert_eq!(editor.selection(), None);
+        assert_eq!(editor.context().text, "atail\n");
+        editor.handle(Input::Char('P'));
+        assert_eq!(editor.context().text, text);
+        editor.handle(Input::Char('u'));
+        assert_eq!(editor.context().text, "atail\n");
+        editor.handle(Input::Char('u'));
+        assert_eq!(editor.context().text, text);
+        editor.handle(Input::Char('U'));
+        assert_eq!(editor.context().text, "atail\n");
+        editor.handle(Input::Char('U'));
+        assert_eq!(editor.context().text, text);
+
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Up);
+        editor.handle(Input::Up);
+        editor.handle(Input::Char('y'));
+        assert_eq!(editor.context().text, text);
+        editor.handle(Input::Char('P'));
+        assert_eq!(
+            editor.context().text,
+            "a界e\u{301}z\n\n👩‍🚀a界e\u{301}z\n\n👩‍🚀tail\n"
+        );
+        editor.handle(Input::Char('u'));
+        assert_eq!(editor.context().text, text);
+    }
+
+    #[test]
+    fn clipboard_copy_preserves_redo_and_pastes_are_independent_of_clipboard_history() {
+        let mut editor = editor();
+        editor.apply(vec![Effect::Replace("x界".into())]).unwrap();
+        editor.handle(Input::Char('u'));
+        editor.handle(Input::Char('p'));
+        editor.handle(Input::Char('P'));
+        assert_eq!(editor.context().text, "");
+        editor.handle(Input::Char('U'));
+        assert_eq!(editor.context().text, "x界");
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Right);
+        editor.handle(Input::Char('y'));
+        assert_eq!(editor.mode(), Mode::Normal);
+        assert_eq!(editor.context().text, "x界");
+        editor.handle(Input::Char('u'));
+        assert_eq!(editor.context().text, "");
+        editor.handle(Input::Char('P'));
+        assert_eq!(editor.context().text, "x界");
+        editor.handle(Input::Char('u'));
+        assert_eq!(editor.context().text, "");
+        editor.handle(Input::Char('U'));
+        editor.handle(Input::Char('p'));
+        assert_eq!(editor.context().text, "x界x界");
+        editor.handle(Input::Char('u'));
+        editor.handle(Input::Char('P'));
+        assert_eq!(editor.context().text, "xx界界");
+        editor.handle(Input::Char('u'));
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Char('y'));
+        editor.handle(Input::Char('U'));
+        assert_eq!(editor.context().text, "xx界界");
+        editor.handle(Input::Char('u'));
+        editor.handle(Input::Char('P'));
+        assert_eq!(editor.context().text, "x界界");
+
+        editor.apply(vec![Effect::Replace("".into())]).unwrap();
+        editor.handle(Input::Char('v'));
+        let empty = editor.selection().unwrap();
+        assert_eq!(empty.start, empty.end);
+        editor.handle(Input::Char('d'));
+        editor.handle(Input::Char('p'));
+        assert_eq!(editor.context().text, "界");
+        editor.handle(Input::Char('u'));
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Escape);
+        editor.handle(Input::Char('U'));
+        assert_eq!(editor.context().text, "界");
+    }
+
+    #[test]
+    fn visual_empty_lines_and_line_end_include_real_newlines_and_cancel_clamps_cursor() {
+        let mut editor = editor();
+        let text = "ab\n\ncd\n";
+        editor.apply(vec![Effect::Replace(text.into())]).unwrap();
+        editor.handle(Input::Down);
+        editor.handle(Input::Char('v'));
+        assert_eq!(
+            editor.selection(),
+            Some(Selection {
+                start: Cursor { row: 1, column: 0 },
+                end: Cursor { row: 2, column: 0 },
+            })
+        );
+        editor.handle(Input::Char('y'));
+        editor.handle(Input::Down);
+        editor.handle(Input::Char('p'));
+        assert_eq!(editor.context().text, "ab\n\nc\nd\n");
+        editor.handle(Input::Char('u'));
+        assert_eq!(editor.context().text, text);
+        editor.handle(Input::Up);
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Delete);
+        assert_eq!(editor.context().text, "ab\ncd\n");
+        editor.handle(Input::Char('u'));
+        assert_eq!(editor.context().text, text);
+        editor.handle(Input::Up);
+        editor.handle(Input::End);
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::End);
+        assert_eq!(editor.cursor(), Cursor { row: 0, column: 2 });
+        assert_eq!(
+            editor.selection().unwrap().end,
+            Cursor { row: 1, column: 0 }
+        );
+        editor.handle(Input::Char('y'));
+        editor.handle(Input::Char('P'));
+        assert_eq!(editor.context().text, "ab\nb\n\ncd\n");
+        editor.handle(Input::Char('u'));
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::End);
+        editor.handle(Input::Escape);
+        assert_eq!(editor.mode(), Mode::Normal);
+        assert_eq!(editor.cursor(), Cursor { row: 0, column: 1 });
+        assert_eq!(editor.selection(), None);
+    }
+
+    #[test]
+    fn selected_effects_validate_before_mode_changes_and_clipboard_graphemes_can_merge() {
+        let mut editor = editor();
+        editor
+            .apply(vec![Effect::Replace("abcd\n👩‍🚀x".into())])
+            .unwrap();
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Down);
+        editor.handle(Input::End);
+        let selected = editor.selection();
+        assert!(editor.apply(vec![Effect::Replace("\0".into())]).is_err());
+        assert_eq!(editor.mode(), Mode::Visual);
+        assert_eq!(editor.selection(), selected);
+        editor.apply(vec![Effect::Replace("z".into())]).unwrap();
+        assert_eq!(editor.mode(), Mode::Normal);
+        assert_eq!(editor.selection(), None);
+        assert_eq!(editor.cursor(), Cursor::default());
+        editor.handle(Input::Char('v'));
+        editor.execute("plugins");
+        assert_eq!(editor.selection(), None);
+        assert_eq!(editor.mode(), Mode::Normal);
+
+        editor
+            .apply(vec![Effect::Replace("\u{301}".into())])
+            .unwrap();
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Char('y'));
+        editor.apply(vec![Effect::Replace("a".into())]).unwrap();
+        editor.handle(Input::Char('p'));
+        assert_eq!(editor.context().text, "a\u{301}");
+        assert_eq!(editor.cursor(), Cursor::default());
+        editor.handle(Input::Char('u'));
+        assert_eq!(editor.context().text, "a");
+    }
+
     #[test]
     fn word_motions_distinguish_punctuation_cross_empty_lines_and_preserve_history() {
         let mut editor = editor();