feat(document): implement delete support

src/document.rs

@@ -32,6 +32,14 @@ impl Document {
         }
     }
 
+    pub fn delete(&mut self, at: &Position) {
+        if at.y >= self.len() {
+            return;
+        }
+        let row = self.rows.get_mut(at.y).unwrap();
+        row.delete(at.x);
+    }
+
     pub fn open(filename: &str) -> Result<Self, std::io::Error> {
         let contents = fs::read_to_string(filename)?;
         let mut rows = vec![];

src/editor.rs

@@ -89,6 +89,7 @@ impl Editor {
                 self.document.insert(&self.cursor_position, c);
                 self.move_cursor(Key::Right);
             }
+            Key::Delete => self.document.delete(&self.cursor_position),
             Key::Up
             | Key::Left
             | Key::Right

src/row.rs

@@ -61,4 +61,16 @@ impl Row {
         }
         self.update_len();
     }
+
+    pub fn delete(&mut self, at: usize) {
+        if at >= self.len() {
+            return;
+        } else {
+            let mut result: String = self.contents[..].graphemes(true).take(at).collect();
+            let remainder: String = self.contents[..].graphemes(true).skip(at + 1).collect();
+            result.push_str(&remainder);
+            self.contents = result;
+        }
+        self.update_len();
+    }
 }