Add surround keybinds

5 files changed, 180 insertions, 2 deletions

diff --git a/helix-core/src/lib.rs b/helix-core/src/lib.rs
index f697bc7f..7d51f88c 100644
--- a/helix-core/src/lib.rs
+++ b/helix-core/src/lib.rs
@@ -16,6 +16,7 @@ pub mod register;
 pub mod search;
 pub mod selection;
 mod state;
+pub mod surround;
 pub mod syntax;
 mod transaction;
 
diff --git a/helix-core/src/surround.rs b/helix-core/src/surround.rs
new file mode 100644
index 00000000..a629d2d3
--- /dev/null
+++ b/helix-core/src/surround.rs
@@ -0,0 +1,58 @@
+use crate::{search, Selection};
+use ropey::RopeSlice;
+
+pub const PAIRS: &[(char, char)] = &[('(', ')'), ('[', ']'), ('{', '}'), ('<', '>')];
+
+/// Given any char in [PAIRS], return the open and closing chars. If not found in
+/// [PAIRS] return (ch, ch).
+pub fn get_pair(ch: char) -> (char, char) {
+    PAIRS
+        .iter()
+        .find(|(open, close)| *open == ch || *close == ch)
+        .copied()
+        .unwrap_or((ch, ch))
+}
+
+/// Find the position of surround pairs of `ch` which can be either a closing
+/// or opening pair. `n` will skip n - 1 pairs (eg. n=2 will discard (only)
+/// the first pair found and keep looking)
+pub fn find_nth_pairs_pos(
+    text: RopeSlice,
+    ch: char,
+    pos: usize,
+    n: usize,
+) -> Option<(usize, usize)> {
+    let (open, close) = get_pair(ch);
+    let open_pos = search::find_nth_prev(text, open, pos, n, true)?;
+    let close_pos = search::find_nth_next(text, close, pos, n, true)?;
+
+    Some((open_pos, close_pos))
+}
+
+/// Find position of surround characters around every cursor. Returns None
+/// if any positions overlap. Note that the positions are in a flat Vec.
+/// Use get_surround_pos().chunks(2) to get matching pairs of surround positions.
+/// `ch` can be either closing or opening pair.
+pub fn get_surround_pos(
+    text: RopeSlice,
+    selection: &Selection,
+    ch: char,
+    skip: usize,
+) -> Option<Vec<usize>> {
+    let mut change_pos = Vec::new();
+
+    for range in selection {
+        let head = range.head;
+
+        match find_nth_pairs_pos(text, ch, head, skip) {
+            Some((open_pos, close_pos)) => {
+                if change_pos.contains(&open_pos) || change_pos.contains(&close_pos) {
+                    return None;
+                }
+                change_pos.extend_from_slice(&[open_pos, close_pos]);
+            }
+            None => return None,
+        }
+    }
+    Some(change_pos)
+}
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 8866b79b..b530e30b 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -255,7 +255,8 @@ impl Command {
         space_mode,
         view_mode,
         left_bracket_mode,
-        right_bracket_mode
+        right_bracket_mode,
+        surround
     );
 }
 
@@ -1906,6 +1907,7 @@ fn goto_mode(cx: &mut Context) {
             match (doc.mode, ch) {
                 (_, 'g') => move_file_start(cx),
                 (_, 'e') => move_file_end(cx),
+                (_, 'm') => match_brackets(cx),
                 (_, 'a') => switch_to_last_accessed_file(cx),
                 (Mode::Normal, 'h') => move_line_start(cx),
                 (Mode::Normal, 'l') => move_line_end(cx),
@@ -3311,6 +3313,122 @@ fn right_bracket_mode(cx: &mut Context) {
     })
 }
 
+fn surround(cx: &mut Context) {
+    let count = cx.count;
+    cx.on_next_key(move |cx, event| {
+        if let KeyEvent {
+            code: KeyCode::Char(ch),
+            ..
+        } = event
+        {
+            // FIXME: count gets reset because of cx.on_next_key()
+            cx.count = count;
+            match ch {
+                'a' => surround_add(cx),
+                'r' => surround_replace(cx),
+                'd' => {
+                    surround_delete(cx);
+                    let (view, doc) = current!(cx.editor);
+                }
+                _ => (),
+            }
+        }
+    })
+}
+
+use helix_core::surround;
+
+fn surround_add(cx: &mut Context) {
+    cx.on_next_key(move |cx, event| {
+        if let KeyEvent {
+            code: KeyCode::Char(ch),
+            ..
+        } = event
+        {
+            let (view, doc) = current!(cx.editor);
+            let text = doc.text().slice(..);
+            let selection = doc.selection(view.id);
+            let (open, close) = surround::get_pair(ch);
+
+            let mut changes = Vec::new();
+            for (i, range) in selection.iter().enumerate() {
+                let (from, to) = (range.from(), range.to() + 1);
+                changes.push((from, from, Some(Tendril::from_char(open))));
+                changes.push((to, to, Some(Tendril::from_char(close))));
+            }
+
+            let transaction = Transaction::change(doc.text(), changes.into_iter());
+            doc.apply(&transaction, view.id);
+            doc.append_changes_to_history(view.id);
+        }
+    })
+}
+
+fn surround_replace(cx: &mut Context) {
+    let count = cx.count();
+    cx.on_next_key(move |cx, event| {
+        if let KeyEvent {
+            code: KeyCode::Char(from),
+            ..
+        } = event
+        {
+            cx.on_next_key(move |cx, event| {
+                if let KeyEvent {
+                    code: KeyCode::Char(to),
+                    ..
+                } = event
+                {
+                    let (view, doc) = current!(cx.editor);
+                    let text = doc.text().slice(..);
+                    let selection = doc.selection(view.id);
+
+                    let change_pos = match surround::get_surround_pos(text, selection, from, count)
+                    {
+                        Some(c) => c,
+                        None => return,
+                    };
+
+                    let (open, close) = surround::get_pair(to);
+                    let transaction = Transaction::change(
+                        doc.text(),
+                        change_pos.iter().enumerate().map(|(i, &pos)| {
+                            let ch = if i % 2 == 0 { open } else { close };
+                            (pos, pos + 1, Some(Tendril::from_char(ch)))
+                        }),
+                    );
+                    doc.apply(&transaction, view.id);
+                    doc.append_changes_to_history(view.id);
+                }
+            });
+        }
+    })
+}
+
+fn surround_delete(cx: &mut Context) {
+    let count = cx.count();
+    cx.on_next_key(move |cx, event| {
+        if let KeyEvent {
+            code: KeyCode::Char(ch),
+            ..
+        } = event
+        {
+            let (view, doc) = current!(cx.editor);
+            let text = doc.text().slice(..);
+            let selection = doc.selection(view.id);
+
+            let change_pos = match surround::get_surround_pos(text, selection, ch, count) {
+                Some(c) => c,
+                None => return,
+            };
+
+            let transaction =
+                Transaction::change(doc.text(), change_pos.into_iter().map(|p| (p, p + 1, None)));
+            doc.apply(&transaction, view.id);
+            doc.append_changes_to_history(view.id);
+        }
+    })
+}
+
 impl fmt::Display for Command {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let Command(name, _) = self;
diff --git a/helix-term/src/keymap.rs b/helix-term/src/keymap.rs
index 46d495c3..cce3d31f 100644
--- a/helix-term/src/keymap.rs
+++ b/helix-term/src/keymap.rs
@@ -200,7 +200,7 @@ impl Default for Keymaps {
             // extend_to_whole_line, crop_to_whole_line
 
 
-            key!('m') => Command::match_brackets,
+            key!('m') => Command::surround,
             // TODO: refactor into
             // key!('m') => commands::select_to_matching,
             // key!('M') => commands::back_select_to_matching,
diff --git a/helix-view/src/document.rs b/helix-view/src/document.rs
index bd45db5a..f0d7b55a 100644
--- a/helix-view/src/document.rs
+++ b/helix-view/src/document.rs
@@ -649,6 +649,7 @@ impl Document {
         }
     }
 
+    /// Commit pending changes to history
     pub fn append_changes_to_history(&mut self, view_id: ViewId) {
         if self.changes.is_empty() {
             return;