undo/redo

src/edit_action.rs

@@ -3,6 +3,12 @@ use crate::{app::App, cursor::Cursor};
 
 #[derive(Debug)]
 pub enum EditAction {
+	// this is a hacky workaround to allow disjoint borrows for
+	// undoing/redoing edits. because the undo/redo operations need
+	// to borrow an EditAction from edit_history, but should never touch
+	// edit_history themselves, we can swap out the action in question,
+	// then swap it back in once the undo/redo is done
+	Placeholder,
 	Delete {
 		cursor: Cursor,
 		old_data: Vec<u8>
@@ -11,17 +17,31 @@ pub enum EditAction {
 		cursor: Cursor,
 		old_data: Vec<u8>,
 		new_byte: u8
-	}
+	},
+	// Insert {
+	// 	cursor: Cursor,
+	//  which side of cursor? append/insert
+	// 	new_data: Vec<u8>
+	// }
 }
 
 impl App {
 	pub fn execute_and_add(&mut self, edit_action: EditAction) {
+		assert!(!matches!(edit_action, EditAction::Placeholder));
+		
 		self.execute_edit(&edit_action);
+		
+		if let Some(date) = self.time_traveling {
+			self.edit_history.truncate(date);
+			self.time_traveling = None;
+		}
+		
 		self.edit_history.push(edit_action);
 	}
 	
-	fn execute_edit(&mut self, edit_action: &EditAction) {
+	pub fn execute_edit(&mut self, edit_action: &EditAction) {
 		match edit_action {
+			EditAction::Placeholder => unreachable!(),
 			EditAction::Delete { cursor, .. } => self.delete_at(*cursor),
 			EditAction::Replace {
 				cursor, old_data: _, new_byte
@@ -29,6 +49,16 @@ impl App {
 		}
 	}
 	
+	pub fn undo_edit(&mut self, edit_action: &EditAction) {
+		match edit_action {
+			EditAction::Placeholder => unreachable!(),
+			EditAction::Delete { cursor, old_data } => self.undo_delete_at(*cursor, old_data),
+			EditAction::Replace {
+				cursor, old_data, ..
+			} => self.undo_replace_at_with(*cursor, old_data),
+		}
+	}
+	
 	fn delete_at(&mut self, cursor: Cursor) {
 		self.contents.drain(cursor.range());
 		
@@ -36,8 +66,28 @@ impl App {
 		self.cursor.collapse();
 	}
 	
+	fn undo_delete_at(&mut self, cursor: Cursor, old_data: &[u8]) {
+		let cursor_start = min(cursor.head, cursor.tail);
+		
+		self.contents.splice(
+			cursor_start..cursor_start,
+			old_data.iter().copied()
+		);
+		
+		self.cursor = cursor;
+	}
+	
 	fn replace_at_with(&mut self, cursor: Cursor, new_byte: u8) {
-		self.contents[self.cursor.range()].fill(new_byte);
+		self.contents[cursor.range()].fill(new_byte);
+		
+		self.cursor = cursor;
+	}
+	
+	fn undo_replace_at_with(&mut self, cursor: Cursor, old_data: &[u8]) {
+		self.contents.splice(
+			cursor.range(),
+			old_data.iter().copied()
+		);
 		
 		self.cursor = cursor;
 	}