Method insert

rust/src/node.rs:307–350

Insert a key-value pair and handle splitting if necessary.

(&mut self, key: K, value: V)

    /// Insert a key-value pair and handle splitting if necessary.
    pub fn insert(&mut self, key: K, value: V) -> InsertResult<K, V> {
        // Do binary search once and use the result throughout
        match self.binary_search_keys(&key) {
            Ok(index) => {
                // Key already exists, update the value
                if let Some(old_val) = self.get_value_mut(index) {
                    let old_value = std::mem::replace(old_val, value);
                    InsertResult::Updated(Some(old_value))
                } else {
                    InsertResult::Updated(None)
                }
            }
            Err(index) => {
                // Key doesn't exist, need to insert
                // Check if split is needed BEFORE inserting
                if !self.is_full() {
                    // Room to insert without splitting
                    self.insert_at_index(index, key, value);
                    // Simple insertion - no split needed
                    return InsertResult::Updated(None);
                }

                // Node is full, need to split
                // Don't insert first. That causes the Vecs to overflow.
                // Split the full node
                let mut new_right = self.split();
                // Insert into the correct node
                if index <= self.keys.len() {
                    self.insert_at_index(index, key, value);
                } else {
                    new_right.insert_at_index(index - self.keys.len(), key, value);
                }

                // Determine the separator key (first key of right node)
                let separator_key = new_right.first_key().unwrap().clone();

                InsertResult::Split {
                    old_value: None,
                    new_node_data: SplitNodeData::Leaf(new_right),
                    separator_key,
                }
            }
        }
    }

    /// Insert a key-value pair at the specified index.
    pub fn insert_at_index(&mut self, index: usize, key: K, value: V) {