Implementing undo / redo functionality

README.md

@@ -201,6 +201,8 @@ kibi --version    # Print version information and exit
 | Ctrl-C            | Copies the entire line                                        |
 | Ctrl-X            | Cuts the entire line                                          |
 | Ctrl-V            | Will paste the copied line                                    |
+| Ctrl-Z            | Will undo the last remove line, cut or paste                  |
+| Ctrl-Y            | Will redo the last undo                                       |
 
 ### Configuration
 

src/editor.rs

@@ -21,10 +21,12 @@ const PASTE: u8 = ctrl_key(b'V');
 const DUPLICATE: u8 = ctrl_key(b'D');
 const EXECUTE: u8 = ctrl_key(b'E');
 const REMOVE_LINE: u8 = ctrl_key(b'R');
+const UNDO: u8 = ctrl_key(b'Z');
+const REDO: u8 = ctrl_key(b'Y');
 const BACKSPACE: u8 = 127;
 
 const HELP_MESSAGE: &str =
-    "^S save | ^Q quit | ^F find | ^G go to | ^D duplicate | ^E execute | ^C copy | ^X cut | ^V paste";
+    "^S save | ^Q quit | ^F find | ^G go to | ^D duplicate | ^E execute | ^C copy | ^X cut | ^V paste | ^Z undo | ^Y redo";
 
 /// `set_status!` sets a formatted status message for the editor.
 /// Example usage: `set_status!(editor, "{} written to {}", file_size, file_name)`
@@ -122,6 +124,15 @@ pub struct Editor {
     orig_term_mode: Option<sys::TermMode>,
     /// The copied buffer of a row
     copied_row: Vec<u8>,
+    /// The history buffer of latest deleted row
+    history_row: Vec<u8>,
+    /// The history buffer position of latest deleted tow
+    history_row_y: usize,
+    /// If undo/redo have to delete or restore line
+    /// true if restores line | false if deletes line
+    history_restore: bool,
+    /// If redo is available (when exists a previous undo)
+    redo_availability: bool,
 }
 
 /// Describes a status message, shown at the bottom at the screen.
@@ -433,6 +444,41 @@ impl Editor {
         self.update_screen_cols();
     }
 
+    fn undo(&mut self) {
+        if !self.redo_availability {
+            if self.history_restore == true {
+                self.n_bytes += self.history_row.len() as u64;
+                self.rows.insert(self.history_row_y, Row::new(self.history_row.clone()));
+                self.update_row(self.history_row_y, false);
+                (self.cursor.y, self.dirty) = (self.history_row_y, true);
+                // The line number has changed
+                self.update_screen_cols();
+            } else {
+                self.history_row = self.rows[self.history_row_y].chars.clone();
+                self.cursor.y = self.history_row_y;
+                self.delete_current_row();
+            }
+            self.redo_availability = true;
+        }
+    }
+
+    fn redo(&mut self) {
+        if self.redo_availability {
+            if self.history_restore {
+                self.cursor.y = self.history_row_y;
+                self.delete_current_row();
+            } else {
+                self.n_bytes += self.history_row.len() as u64;
+                self.rows.insert(self.history_row_y, Row::new(self.history_row.clone()));
+                self.update_row(self.history_row_y, false);
+                (self.cursor.y, self.dirty) = (self.history_row_y, true);
+                // The line number has changed
+                self.update_screen_cols();
+            }
+        }
+        self.redo_availability = false;
+    }
+
     /// Try to load a file. If found, load the rows and update the render and syntax highlighting.
     /// If not found, do not return an error.
     fn load(&mut self, path: &Path) -> Result<(), Error> {
@@ -613,7 +659,13 @@ impl Editor {
             Key::End => self.cursor.x = self.current_row().map_or(0, |row| row.chars.len()),
             Key::Char(b'\r' | b'\n') => self.insert_new_line(), // Enter
             Key::Char(BACKSPACE | DELETE_BIS) => self.delete_char(), // Backspace or Ctrl + H
-            Key::Char(REMOVE_LINE) => self.delete_current_row(),
+            Key::Char(REMOVE_LINE) => {
+                self.history_row_y = self.cursor.y;
+                self.history_row = self.rows[self.cursor.y].chars.clone();
+                self.history_restore = true;
+                self.redo_availability = false;
+                self.delete_current_row();
+            }
             Key::Delete => {
                 self.move_cursor(&AKey::Right);
                 self.delete_char();
@@ -640,12 +692,23 @@ impl Editor {
             Key::Char(GOTO) => prompt_mode = Some(PromptMode::GoTo(String::new())),
             Key::Char(DUPLICATE) => self.duplicate_current_row(),
             Key::Char(CUT) => {
+                self.history_row_y = self.cursor.y;
+                self.history_row = self.rows[self.cursor.y].chars.clone();
+                self.history_restore = true;
+                self.redo_availability = false;
                 self.copy_current_row();
                 self.delete_current_row();
             }
             Key::Char(COPY) => self.copy_current_row(),
-            Key::Char(PASTE) => self.paste_current_row(),
+            Key::Char(PASTE) => {
+                self.history_row_y = self.cursor.y + 1;
+                self.history_restore = false;
+                self.redo_availability = false;
+                self.paste_current_row();
+            }
             Key::Char(EXECUTE) => prompt_mode = Some(PromptMode::Execute(String::new())),
+            Key::Char(UNDO) => self.undo(),
+            Key::Char(REDO) => self.redo(),
             Key::Char(c) => self.insert_byte(*c),
         }
         self.quit_times = quit_times;