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use std::cmp::Ordering::{Equal, Greater, Less};
use crate::{stc::Node, KEY_ARRAY, POINTER_ARRAY};
impl<K: Ord, V> Node<K, V> {
pub fn remove(&mut self, key: &K) -> Option<(K, V)> {
if self.leaf {
'search: for index in 0..KEY_ARRAY {
if let Some(item) = self.keys[index].as_mut() {
match key.cmp(&item.key) {
Less => return None,
Equal => return self.leaf_remove_key(index),
Greater => continue 'search,
}
}
}
None
} else {
'search: for index in 0..KEY_ARRAY {
match self.keys[index].as_mut() {
Some(item) => match key.cmp(&item.key) {
Less => {
if let Some(pointer) = self.pointers[index].as_mut() {
let output = pointer.child.remove(key);
if output.is_some() {
pointer.counter -= 1;
}
return output;
} else {
return None;
}
}
Equal => return self.node_remove_key(index),
Greater => {
if index >= KEY_ARRAY - 1 {
if let Some(pointer) = self.pointers[index + 1].as_mut() {
let output = pointer.child.remove(key);
if output.is_some() {
pointer.counter -= 1;
}
return output;
} else {
return None;
}
} else {
continue 'search;
}
}
},
None => {
if let Some(pointer) = self.pointers[index].as_mut() {
let output = pointer.child.remove(key);
if output.is_some() {
pointer.counter -= 1;
}
return output;
} else {
return None;
}
}
}
}
None
}
}
pub fn remove_index(&mut self, mut index: usize) -> Option<(K, V)> {
if self.leaf {
self.leaf_remove_key(index)
} else {
for loc in 0..KEY_ARRAY {
if let Some(pointer) = self.pointers[loc].as_mut() {
if index < pointer.counter {
let output = pointer.child.remove_index(index);
if output.is_some() {
pointer.counter -= 1;
}
return output;
} else {
index -= pointer.counter
};
if index == 0 {
return self.node_remove_key(loc);
} else {
index -= 1;
continue;
}
} else {
continue;
}
}
None
}
}
}
impl<K: Ord, V> Node<K, V> {
pub fn node_remove_key(&mut self, index: usize) -> Option<(K, V)> {
// if both pointer children pointers[index] + pointers[index+1] are less than KEY_ARRAY, then we can merge the right pointer to the left pointer
let output = self.keys[index].take().map(|item| (item.key, item.value));
if output.is_some() {
self.n -= 1;
}
if let [Some(left_pointer), Some(right_pointer)] = self.pointers[index..index + 2].as_mut()
{
if left_pointer.child.n + right_pointer.child.n < KEY_ARRAY {
self.merge_pointers_from_removed_node(index);
} else {
self.replace_removed_key(index);
}
} else {
self.replace_removed_key(index);
}
output
}
pub fn merge_pointers_from_removed_node(&mut self, index: usize) {
if let [Some(left_pointer), Some(right_pointer)] = self.pointers[index..index + 2].as_mut()
{
left_pointer.counter += right_pointer.counter;
left_pointer.child.n += right_pointer.child.n;
let mut count = 0;
for loc in 0..KEY_ARRAY {
match &left_pointer.child.keys[loc] {
Some(_) => continue,
None => {
left_pointer.child.keys[loc] = right_pointer.child.keys[count].take();
count += 1;
continue;
}
}
}
count = 0;
for loc in 0..POINTER_ARRAY {
match &left_pointer.child.pointers[loc] {
Some(_) => continue,
None => {
left_pointer.child.pointers[loc] =
right_pointer.child.pointers[count].take();
count += 1;
continue;
}
}
}
self.pointers[index + 1] = None;
for i in 0..(KEY_ARRAY - 1) {
if i >= index {
self.keys[i] = self.keys[i + 1].take();
self.pointers[i + 1] = self.pointers[i + 2].take();
}
}
}
if self.is_empty() {
if let Some(pointer) = self.pointers[index].as_mut() {
self.keys = pointer.child.take_keys();
self.n = pointer.child.n;
self.leaf = pointer.child.leaf;
self.pointers = pointer.child.take_pointers();
}
}
}
pub fn replace_removed_key(&mut self, index: usize) {
match self.pointers[index].as_mut() {
Some(p) => {
self.keys[index] = {
let output = p.child.take_last_key();
if output.is_some() {
p.counter -= 1;
}
output
}
}
None => {
for i in 0..(KEY_ARRAY - 1) {
if i >= index {
self.keys[i] = self.keys[i + 1].take();
self.pointers[i] = self.pointers[i + 1].take()
}
}
self.pointers[KEY_ARRAY - 1] = self.pointers[KEY_ARRAY].take()
}
};
}
pub fn leaf_remove_key(&mut self, index: usize) -> Option<(K, V)> {
let output = self.keys[index].take().map(|item| (item.key, item.value));
if output.is_some() {
self.n -= 1;
}
for i in 0..(KEY_ARRAY - 1) {
if i >= index {
self.keys[i] = self.keys[i + 1].take();
}
}
output
}
}