Add object selection (textobjects) (#385)

* Add textobjects for word

* Add textobjects for surround characters

* Apply clippy lints

* Remove ThisWordPrevBound in favor of PrevWordEnd

It's the same as PrevWordEnd except for taking the current char
into account, so use a "flag" to capture that usecase

* Add tests for PrevWordEnd movement

* Remove ThisWord* movements

They did not preserve anchor positions and were only used
for textobject boundary search anyway so replace them with
simple position finding functions

* Rewrite tests of word textobject

* Add tests for surround textobject

* Add textobject docs

* Refactor textobject word position functions

* Apply clippy lints on textobject

* Fix overflow error with textobjects

1 files changed, 31 insertions, 1 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 860d8e22..d198b803 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -3502,6 +3502,9 @@ fn right_bracket_mode(cx: &mut Context) {
     })
 }
 
+use helix_core::surround;
+use helix_core::textobject;
+
 fn match_mode(cx: &mut Context) {
     let count = cx.count;
     cx.on_next_key(move |cx, event| {
@@ -3517,13 +3520,40 @@ fn match_mode(cx: &mut Context) {
                 's' => surround_add(cx),
                 'r' => surround_replace(cx),
                 'd' => surround_delete(cx),
+                'a' => select_textobject(cx, textobject::TextObject::Around),
+                'i' => select_textobject(cx, textobject::TextObject::Inside),
                 _ => (),
             }
         }
     })
 }
 
-use helix_core::surround;
+fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
+    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).transform(|range| {
+                match ch {
+                    'w' => textobject::textobject_word(text, range, objtype, count),
+                    // TODO: cancel new ranges if inconsistent surround matches across lines
+                    ch if !ch.is_ascii_alphanumeric() => {
+                        textobject::textobject_surround(text, range, objtype, ch, count)
+                    }
+                    _ => range,
+                }
+            });
+
+            doc.set_selection(view.id, selection);
+        }
+    })
+}
 
 fn surround_add(cx: &mut Context) {
     cx.on_next_key(move |cx, event| {