Added change_case command (#441)

* Added change_case command

* Added switch_to_uppercase and switch_to_lowercase

Renamed change_case to switch_case.

* Updated the Keymap section of the Book

* Use flat_map instead of map + flatten

* Fix switch_to_uppercase using to_lowercase

* Switched 'Alt-`' to uppercase and '`' to lowercase

Co-authored-by: Cor <prive@corpeters.nl>

book/src/keymap.md

@@ -45,6 +45,9 @@
 | -----    | -----------                                     |
 | `r`      | Replace with a character                        |
 | `R`      | Replace with yanked text                        |
+| `~`      | Switch case of the selected text                |
+| `\``     | Set the selected text to upper case             |
+| `Alt-\`` | Set the selected text to lower case             |
 | `i`      | Insert before selection                         |
 | `a`      | Insert after selection (append)                 |
 | `I`      | Insert at the start of the line                 |

helix-term/src/commands.rs

@@ -186,6 +186,9 @@ impl Command {
         extend_till_prev_char,
         extend_prev_char,
         replace,
+        switch_case,
+        switch_to_uppercase,
+        switch_to_lowercase,
         page_up,
         page_down,
         half_page_up,
@@ -780,6 +783,57 @@ fn replace(cx: &mut Context) {
     })
 }
 
+fn switch_case(cx: &mut Context) {
+    let (view, doc) = current!(cx.editor);
+    let transaction =
+        Transaction::change_by_selection(doc.text(), doc.selection(view.id), |range| {
+            let text: Tendril = range
+                .fragment(doc.text().slice(..))
+                .chars()
+                .flat_map(|ch| {
+                    if ch.is_lowercase() {
+                        ch.to_uppercase().collect()
+                    } else if ch.is_uppercase() {
+                        ch.to_lowercase().collect()
+                    } else {
+                        vec![ch]
+                    }
+                })
+                .collect();
+
+            (range.from(), range.to() + 1, Some(text))
+        });
+
+    doc.apply(&transaction, view.id);
+    doc.append_changes_to_history(view.id);
+}
+
+fn switch_to_uppercase(cx: &mut Context) {
+    let (view, doc) = current!(cx.editor);
+    let transaction =
+        Transaction::change_by_selection(doc.text(), doc.selection(view.id), |range| {
+            let text: Tendril = range.fragment(doc.text().slice(..)).to_uppercase().into();
+
+            (range.from(), range.to() + 1, Some(text))
+        });
+
+    doc.apply(&transaction, view.id);
+    doc.append_changes_to_history(view.id);
+}
+
+fn switch_to_lowercase(cx: &mut Context) {
+    let (view, doc) = current!(cx.editor);
+    let transaction =
+        Transaction::change_by_selection(doc.text(), doc.selection(view.id), |range| {
+            let text: Tendril = range.fragment(doc.text().slice(..)).to_lowercase().into();
+
+            (range.from(), range.to() + 1, Some(text))
+        });
+
+    doc.apply(&transaction, view.id);
+    doc.append_changes_to_history(view.id);
+}
+
 fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
     use Direction::*;
     let (view, doc) = current!(cx.editor);

helix-term/src/keymap.rs

@@ -82,6 +82,10 @@ impl Default for Keymaps {
             key!('r') => Command::replace,
             key!('R') => Command::replace_with_yanked,
 
+            key!('~') => Command::switch_case,
+            alt!('`') => Command::switch_to_uppercase,
+            key!('`') => Command::switch_to_lowercase,
+
             key!(Home) => Command::goto_line_start,
             key!(End) => Command::goto_line_end,