use core::cmp::Ordering;
use core::marker::PhantomData;
use core::mem::{self, MaybeUninit};
use core::ptr::{self, NonNull, Unique};
use core::slice;
use crate::alloc::{AllocRef, Global, Layout};
use crate::boxed::Box;
const B: usize = 6;
pub const MIN_LEN: usize = B - 1;
pub const CAPACITY: usize = 2 * B - 1;
#[repr(C)]
struct LeafNode<K, V> {
    
    
    parent: *const InternalNode<K, V>,
    
    
    
    parent_idx: MaybeUninit<u16>,
    
    
    
    
    len: u16,
    
    
    keys: [MaybeUninit<K>; CAPACITY],
    vals: [MaybeUninit<V>; CAPACITY],
}
impl<K, V> LeafNode<K, V> {
    
    
    unsafe fn new() -> Self {
        LeafNode {
            
            
            keys: [MaybeUninit::UNINIT; CAPACITY],
            vals: [MaybeUninit::UNINIT; CAPACITY],
            parent: ptr::null(),
            parent_idx: MaybeUninit::uninit(),
            len: 0,
        }
    }
}
#[repr(C)]
struct InternalNode<K, V> {
    data: LeafNode<K, V>,
    
    
    edges: [MaybeUninit<BoxedNode<K, V>>; 2 * B],
}
impl<K, V> InternalNode<K, V> {
    
    
    
    
    
    
    
    unsafe fn new() -> Self {
        InternalNode { data: LeafNode::new(), edges: [MaybeUninit::UNINIT; 2 * B] }
    }
}
struct BoxedNode<K, V> {
    ptr: Unique<LeafNode<K, V>>,
}
impl<K, V> BoxedNode<K, V> {
    fn from_leaf(node: Box<LeafNode<K, V>>) -> Self {
        BoxedNode { ptr: Box::into_unique(node) }
    }
    fn from_internal(node: Box<InternalNode<K, V>>) -> Self {
        BoxedNode { ptr: Box::into_unique(node).cast() }
    }
    unsafe fn from_ptr(ptr: NonNull<LeafNode<K, V>>) -> Self {
        BoxedNode { ptr: Unique::from(ptr) }
    }
    fn as_ptr(&self) -> NonNull<LeafNode<K, V>> {
        NonNull::from(self.ptr)
    }
}
pub struct Root<K, V> {
    node: BoxedNode<K, V>,
    
    height: usize,
}
unsafe impl<K: Sync, V: Sync> Sync for Root<K, V> {}
unsafe impl<K: Send, V: Send> Send for Root<K, V> {}
impl<K, V> Root<K, V> {
    
    pub fn new_leaf() -> Self {
        Root { node: BoxedNode::from_leaf(Box::new(unsafe { LeafNode::new() })), height: 0 }
    }
    pub fn as_ref(&self) -> NodeRef<marker::Immut<'_>, K, V, marker::LeafOrInternal> {
        NodeRef {
            height: self.height,
            node: self.node.as_ptr(),
            root: ptr::null(),
            _marker: PhantomData,
        }
    }
    pub fn as_mut(&mut self) -> NodeRef<marker::Mut<'_>, K, V, marker::LeafOrInternal> {
        NodeRef {
            height: self.height,
            node: self.node.as_ptr(),
            root: self as *mut _,
            _marker: PhantomData,
        }
    }
    pub fn into_ref(self) -> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
        NodeRef {
            height: self.height,
            node: self.node.as_ptr(),
            root: ptr::null(),
            _marker: PhantomData,
        }
    }
    
    
    pub fn push_level(&mut self) -> NodeRef<marker::Mut<'_>, K, V, marker::Internal> {
        let mut new_node = Box::new(unsafe { InternalNode::new() });
        new_node.edges[0].write(unsafe { BoxedNode::from_ptr(self.node.as_ptr()) });
        self.node = BoxedNode::from_internal(new_node);
        self.height += 1;
        let mut ret = NodeRef {
            height: self.height,
            node: self.node.as_ptr(),
            root: self as *mut _,
            _marker: PhantomData,
        };
        unsafe {
            ret.reborrow_mut().first_edge().correct_parent_link();
        }
        ret
    }
    
    
    
    
    pub fn pop_level(&mut self) {
        assert!(self.height > 0);
        let top = self.node.ptr;
        self.node = unsafe {
            BoxedNode::from_ptr(
                self.as_mut().cast_unchecked::<marker::Internal>().first_edge().descend().node,
            )
        };
        self.height -= 1;
        unsafe {
            (*self.as_mut().as_leaf_mut()).parent = ptr::null();
        }
        unsafe {
            Global.dealloc(NonNull::from(top).cast(), Layout::new::<InternalNode<K, V>>());
        }
    }
}
pub struct NodeRef<BorrowType, K, V, Type> {
    
    height: usize,
    node: NonNull<LeafNode<K, V>>,
    
    root: *const Root<K, V>,
    _marker: PhantomData<(BorrowType, Type)>,
}
impl<'a, K: 'a, V: 'a, Type> Copy for NodeRef<marker::Immut<'a>, K, V, Type> {}
impl<'a, K: 'a, V: 'a, Type> Clone for NodeRef<marker::Immut<'a>, K, V, Type> {
    fn clone(&self) -> Self {
        *self
    }
}
unsafe impl<BorrowType, K: Sync, V: Sync, Type> Sync for NodeRef<BorrowType, K, V, Type> {}
unsafe impl<'a, K: Sync + 'a, V: Sync + 'a, Type> Send for NodeRef<marker::Immut<'a>, K, V, Type> {}
unsafe impl<'a, K: Send + 'a, V: Send + 'a, Type> Send for NodeRef<marker::Mut<'a>, K, V, Type> {}
unsafe impl<K: Send, V: Send, Type> Send for NodeRef<marker::Owned, K, V, Type> {}
impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::Internal> {
    fn as_internal(&self) -> &InternalNode<K, V> {
        unsafe { &*(self.node.as_ptr() as *mut InternalNode<K, V>) }
    }
}
impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
    fn as_internal_mut(&mut self) -> &mut InternalNode<K, V> {
        unsafe { &mut *(self.node.as_ptr() as *mut InternalNode<K, V>) }
    }
}
impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
    
    
    
    
    
    pub fn len(&self) -> usize {
        self.as_leaf().len as usize
    }
    
    
    pub fn height(&self) -> usize {
        self.height
    }
    
    
    pub fn forget_type(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
        NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
    }
    
    fn reborrow(&self) -> NodeRef<marker::Immut<'_>, K, V, Type> {
        NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
    }
    
    
    
    
    fn as_leaf(&self) -> &LeafNode<K, V> {
        
        
        
        unsafe { self.node.as_ref() }
    }
    
    pub fn keys(&self) -> &[K] {
        self.reborrow().into_key_slice()
    }
    
    fn vals(&self) -> &[V] {
        self.reborrow().into_val_slice()
    }
    
    
    
    
    
    
    
    pub fn ascend(
        self,
    ) -> Result<Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge>, Self> {
        let parent_as_leaf = self.as_leaf().parent as *const LeafNode<K, V>;
        if let Some(non_zero) = NonNull::new(parent_as_leaf as *mut _) {
            Ok(Handle {
                node: NodeRef {
                    height: self.height + 1,
                    node: non_zero,
                    root: self.root,
                    _marker: PhantomData,
                },
                idx: unsafe { usize::from(*self.as_leaf().parent_idx.as_ptr()) },
                _marker: PhantomData,
            })
        } else {
            Err(self)
        }
    }
    pub fn first_edge(self) -> Handle<Self, marker::Edge> {
        unsafe { Handle::new_edge(self, 0) }
    }
    pub fn last_edge(self) -> Handle<Self, marker::Edge> {
        let len = self.len();
        unsafe { Handle::new_edge(self, len) }
    }
    
    pub fn first_kv(self) -> Handle<Self, marker::KV> {
        let len = self.len();
        assert!(len > 0);
        unsafe { Handle::new_kv(self, 0) }
    }
    
    pub fn last_kv(self) -> Handle<Self, marker::KV> {
        let len = self.len();
        assert!(len > 0);
        unsafe { Handle::new_kv(self, len - 1) }
    }
}
impl<K, V> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
    
    
    
    pub unsafe fn deallocate_and_ascend(
        self,
    ) -> Option<Handle<NodeRef<marker::Owned, K, V, marker::Internal>, marker::Edge>> {
        let height = self.height;
        let node = self.node;
        let ret = self.ascend().ok();
        Global.dealloc(
            node.cast(),
            if height > 0 {
                Layout::new::<InternalNode<K, V>>()
            } else {
                Layout::new::<LeafNode<K, V>>()
            },
        );
        ret
    }
}
impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
    
    
    unsafe fn cast_unchecked<NewType>(&mut self) -> NodeRef<marker::Mut<'_>, K, V, NewType> {
        NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
    }
    
    
    
    
    
    
    
    
    
    
    unsafe fn reborrow_mut(&mut self) -> NodeRef<marker::Mut<'_>, K, V, Type> {
        NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
    }
    
    
    
    
    
    
    fn as_leaf_mut(&mut self) -> *mut LeafNode<K, V> {
        self.node.as_ptr()
    }
    fn keys_mut(&mut self) -> &mut [K] {
        
        
        
        unsafe { self.reborrow_mut().into_key_slice_mut() }
    }
    fn vals_mut(&mut self) -> &mut [V] {
        
        
        
        unsafe { self.reborrow_mut().into_val_slice_mut() }
    }
}
impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
    fn into_key_slice(self) -> &'a [K] {
        unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().keys), self.len()) }
    }
    fn into_val_slice(self) -> &'a [V] {
        unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().vals), self.len()) }
    }
    fn into_slices(self) -> (&'a [K], &'a [V]) {
        
        let k = unsafe { ptr::read(&self) };
        (k.into_key_slice(), self.into_val_slice())
    }
}
impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
    
    
    pub fn into_root_mut(self) -> &'a mut Root<K, V> {
        unsafe { &mut *(self.root as *mut Root<K, V>) }
    }
    fn into_key_slice_mut(mut self) -> &'a mut [K] {
        
        unsafe {
            slice::from_raw_parts_mut(
                MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).keys),
                self.len(),
            )
        }
    }
    fn into_val_slice_mut(mut self) -> &'a mut [V] {
        
        unsafe {
            slice::from_raw_parts_mut(
                MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).vals),
                self.len(),
            )
        }
    }
    fn into_slices_mut(mut self) -> (&'a mut [K], &'a mut [V]) {
        
        
        
        
        
        let len = self.len();
        let leaf = self.as_leaf_mut();
        
        let keys = unsafe {
            slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).keys), len)
        };
        let vals = unsafe {
            slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).vals), len)
        };
        (keys, vals)
    }
}
impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
    
    pub fn push(&mut self, key: K, val: V) {
        assert!(self.len() < CAPACITY);
        let idx = self.len();
        unsafe {
            ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
            ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
            (*self.as_leaf_mut()).len += 1;
        }
    }
    
    pub fn push_front(&mut self, key: K, val: V) {
        assert!(self.len() < CAPACITY);
        unsafe {
            slice_insert(self.keys_mut(), 0, key);
            slice_insert(self.vals_mut(), 0, val);
            (*self.as_leaf_mut()).len += 1;
        }
    }
}
impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
    
    
    pub fn push(&mut self, key: K, val: V, edge: Root<K, V>) {
        assert!(edge.height == self.height - 1);
        assert!(self.len() < CAPACITY);
        let idx = self.len();
        unsafe {
            ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
            ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
            self.as_internal_mut().edges.get_unchecked_mut(idx + 1).write(edge.node);
            (*self.as_leaf_mut()).len += 1;
            Handle::new_edge(self.reborrow_mut(), idx + 1).correct_parent_link();
        }
    }
    
    unsafe fn correct_childrens_parent_links(&mut self, first: usize, after_last: usize) {
        debug_assert!(first <= self.len());
        debug_assert!(after_last <= self.len() + 1);
        for i in first..after_last {
            Handle::new_edge(self.reborrow_mut(), i).correct_parent_link();
        }
    }
    fn correct_all_childrens_parent_links(&mut self) {
        let len = self.len();
        unsafe { self.correct_childrens_parent_links(0, len + 1) };
    }
    
    
    pub fn push_front(&mut self, key: K, val: V, edge: Root<K, V>) {
        assert!(edge.height == self.height - 1);
        assert!(self.len() < CAPACITY);
        unsafe {
            slice_insert(self.keys_mut(), 0, key);
            slice_insert(self.vals_mut(), 0, val);
            slice_insert(
                slice::from_raw_parts_mut(
                    MaybeUninit::first_ptr_mut(&mut self.as_internal_mut().edges),
                    self.len() + 1,
                ),
                0,
                edge.node,
            );
            (*self.as_leaf_mut()).len += 1;
            self.correct_all_childrens_parent_links();
        }
    }
}
impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
    
    
    pub fn pop(&mut self) -> (K, V, Option<Root<K, V>>) {
        assert!(self.len() > 0);
        let idx = self.len() - 1;
        unsafe {
            let key = ptr::read(self.keys().get_unchecked(idx));
            let val = ptr::read(self.vals().get_unchecked(idx));
            let edge = match self.reborrow_mut().force() {
                ForceResult::Leaf(_) => None,
                ForceResult::Internal(internal) => {
                    let edge =
                        ptr::read(internal.as_internal().edges.get_unchecked(idx + 1).as_ptr());
                    let mut new_root = Root { node: edge, height: internal.height - 1 };
                    (*new_root.as_mut().as_leaf_mut()).parent = ptr::null();
                    Some(new_root)
                }
            };
            (*self.as_leaf_mut()).len -= 1;
            (key, val, edge)
        }
    }
    
    
    pub fn pop_front(&mut self) -> (K, V, Option<Root<K, V>>) {
        assert!(self.len() > 0);
        let old_len = self.len();
        unsafe {
            let key = slice_remove(self.keys_mut(), 0);
            let val = slice_remove(self.vals_mut(), 0);
            let edge = match self.reborrow_mut().force() {
                ForceResult::Leaf(_) => None,
                ForceResult::Internal(mut internal) => {
                    let edge = slice_remove(
                        slice::from_raw_parts_mut(
                            MaybeUninit::first_ptr_mut(&mut internal.as_internal_mut().edges),
                            old_len + 1,
                        ),
                        0,
                    );
                    let mut new_root = Root { node: edge, height: internal.height - 1 };
                    (*new_root.as_mut().as_leaf_mut()).parent = ptr::null();
                    for i in 0..old_len {
                        Handle::new_edge(internal.reborrow_mut(), i).correct_parent_link();
                    }
                    Some(new_root)
                }
            };
            (*self.as_leaf_mut()).len -= 1;
            (key, val, edge)
        }
    }
    fn into_kv_pointers_mut(mut self) -> (*mut K, *mut V) {
        (self.keys_mut().as_mut_ptr(), self.vals_mut().as_mut_ptr())
    }
}
impl<BorrowType, K, V> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
    
    pub fn force(
        self,
    ) -> ForceResult<
        NodeRef<BorrowType, K, V, marker::Leaf>,
        NodeRef<BorrowType, K, V, marker::Internal>,
    > {
        if self.height == 0 {
            ForceResult::Leaf(NodeRef {
                height: self.height,
                node: self.node,
                root: self.root,
                _marker: PhantomData,
            })
        } else {
            ForceResult::Internal(NodeRef {
                height: self.height,
                node: self.node,
                root: self.root,
                _marker: PhantomData,
            })
        }
    }
}
pub struct Handle<Node, Type> {
    node: Node,
    idx: usize,
    _marker: PhantomData<Type>,
}
impl<Node: Copy, Type> Copy for Handle<Node, Type> {}
impl<Node: Copy, Type> Clone for Handle<Node, Type> {
    fn clone(&self) -> Self {
        *self
    }
}
impl<Node, Type> Handle<Node, Type> {
    
    pub fn into_node(self) -> Node {
        self.node
    }
    
    pub fn idx(&self) -> usize {
        self.idx
    }
}
impl<BorrowType, K, V, NodeType> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV> {
    
    
    pub unsafe fn new_kv(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
        debug_assert!(idx < node.len());
        Handle { node, idx, _marker: PhantomData }
    }
    pub fn left_edge(self) -> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
        unsafe { Handle::new_edge(self.node, self.idx) }
    }
    pub fn right_edge(self) -> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
        unsafe { Handle::new_edge(self.node, self.idx + 1) }
    }
}
impl<BorrowType, K, V, NodeType, HandleType> PartialEq
    for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
{
    fn eq(&self, other: &Self) -> bool {
        self.node.node == other.node.node && self.idx == other.idx
    }
}
impl<BorrowType, K, V, NodeType, HandleType> PartialOrd
    for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
{
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        if self.node.node == other.node.node { Some(self.idx.cmp(&other.idx)) } else { None }
    }
}
impl<BorrowType, K, V, NodeType, HandleType>
    Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
{
    
    pub fn reborrow(&self) -> Handle<NodeRef<marker::Immut<'_>, K, V, NodeType>, HandleType> {
        
        Handle { node: self.node.reborrow(), idx: self.idx, _marker: PhantomData }
    }
}
impl<'a, K, V, NodeType, HandleType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, HandleType> {
    
    
    
    
    
    
    
    
    
    
    pub unsafe fn reborrow_mut(
        &mut self,
    ) -> Handle<NodeRef<marker::Mut<'_>, K, V, NodeType>, HandleType> {
        
        Handle { node: self.node.reborrow_mut(), idx: self.idx, _marker: PhantomData }
    }
}
impl<BorrowType, K, V, NodeType> Handle<NodeRef<BorrowType, K, V, NodeType>, marker::Edge> {
    
    
    pub unsafe fn new_edge(node: NodeRef<BorrowType, K, V, NodeType>, idx: usize) -> Self {
        debug_assert!(idx <= node.len());
        Handle { node, idx, _marker: PhantomData }
    }
    pub fn left_kv(self) -> Result<Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV>, Self> {
        if self.idx > 0 {
            Ok(unsafe { Handle::new_kv(self.node, self.idx - 1) })
        } else {
            Err(self)
        }
    }
    pub fn right_kv(self) -> Result<Handle<NodeRef<BorrowType, K, V, NodeType>, marker::KV>, Self> {
        if self.idx < self.node.len() {
            Ok(unsafe { Handle::new_kv(self.node, self.idx) })
        } else {
            Err(self)
        }
    }
}
impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge> {
    
    
    
    
    
    fn insert_fit(&mut self, key: K, val: V) -> *mut V {
        
        debug_assert!(self.node.len() < CAPACITY);
        unsafe {
            slice_insert(self.node.keys_mut(), self.idx, key);
            slice_insert(self.node.vals_mut(), self.idx, val);
            (*self.node.as_leaf_mut()).len += 1;
            self.node.vals_mut().get_unchecked_mut(self.idx)
        }
    }
    
    
    
    
    pub fn insert(mut self, key: K, val: V) -> (InsertResult<'a, K, V, marker::Leaf>, *mut V) {
        if self.node.len() < CAPACITY {
            let ptr = self.insert_fit(key, val);
            let kv = unsafe { Handle::new_kv(self.node, self.idx) };
            (InsertResult::Fit(kv), ptr)
        } else {
            let middle = unsafe { Handle::new_kv(self.node, B) };
            let (mut left, k, v, mut right) = middle.split();
            let ptr = if self.idx <= B {
                unsafe { Handle::new_edge(left.reborrow_mut(), self.idx).insert_fit(key, val) }
            } else {
                unsafe {
                    Handle::new_edge(
                        right.as_mut().cast_unchecked::<marker::Leaf>(),
                        self.idx - (B + 1),
                    )
                    .insert_fit(key, val)
                }
            };
            (InsertResult::Split(left, k, v, right), ptr)
        }
    }
}
impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
    
    
    fn correct_parent_link(mut self) {
        let idx = self.idx as u16;
        let ptr = self.node.as_internal_mut() as *mut _;
        let mut child = self.descend();
        unsafe {
            (*child.as_leaf_mut()).parent = ptr;
            (*child.as_leaf_mut()).parent_idx.write(idx);
        }
    }
    
    
    unsafe fn cast_unchecked<NewType>(
        &mut self,
    ) -> Handle<NodeRef<marker::Mut<'_>, K, V, NewType>, marker::Edge> {
        Handle::new_edge(self.node.cast_unchecked(), self.idx)
    }
    
    
    
    fn insert_fit(&mut self, key: K, val: V, edge: Root<K, V>) {
        
        debug_assert!(self.node.len() < CAPACITY);
        debug_assert!(edge.height == self.node.height - 1);
        unsafe {
            
            self.cast_unchecked::<marker::Leaf>().insert_fit(key, val);
            slice_insert(
                slice::from_raw_parts_mut(
                    MaybeUninit::first_ptr_mut(&mut self.node.as_internal_mut().edges),
                    self.node.len(),
                ),
                self.idx + 1,
                edge.node,
            );
            for i in (self.idx + 1)..(self.node.len() + 1) {
                Handle::new_edge(self.node.reborrow_mut(), i).correct_parent_link();
            }
        }
    }
    
    
    
    pub fn insert(
        mut self,
        key: K,
        val: V,
        edge: Root<K, V>,
    ) -> InsertResult<'a, K, V, marker::Internal> {
        assert!(edge.height == self.node.height - 1);
        if self.node.len() < CAPACITY {
            self.insert_fit(key, val, edge);
            let kv = unsafe { Handle::new_kv(self.node, self.idx) };
            InsertResult::Fit(kv)
        } else {
            let middle = unsafe { Handle::new_kv(self.node, B) };
            let (mut left, k, v, mut right) = middle.split();
            if self.idx <= B {
                unsafe {
                    Handle::new_edge(left.reborrow_mut(), self.idx).insert_fit(key, val, edge);
                }
            } else {
                unsafe {
                    Handle::new_edge(
                        right.as_mut().cast_unchecked::<marker::Internal>(),
                        self.idx - (B + 1),
                    )
                    .insert_fit(key, val, edge);
                }
            }
            InsertResult::Split(left, k, v, right)
        }
    }
}
impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge> {
    
    
    
    
    pub fn descend(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
        NodeRef {
            height: self.node.height - 1,
            node: unsafe {
                (&*self.node.as_internal().edges.get_unchecked(self.idx).as_ptr()).as_ptr()
            },
            root: self.node.root,
            _marker: PhantomData,
        }
    }
}
impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Immut<'a>, K, V, NodeType>, marker::KV> {
    pub fn into_kv(self) -> (&'a K, &'a V) {
        unsafe {
            let (keys, vals) = self.node.into_slices();
            (keys.get_unchecked(self.idx), vals.get_unchecked(self.idx))
        }
    }
}
impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
    pub fn into_kv_mut(self) -> (&'a mut K, &'a mut V) {
        unsafe {
            let (keys, vals) = self.node.into_slices_mut();
            (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
        }
    }
}
impl<'a, K, V, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
    pub fn kv_mut(&mut self) -> (&mut K, &mut V) {
        unsafe {
            let (keys, vals) = self.node.reborrow_mut().into_slices_mut();
            (keys.get_unchecked_mut(self.idx), vals.get_unchecked_mut(self.idx))
        }
    }
}
impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::KV> {
    
    
    
    
    
    
    
    pub fn split(mut self) -> (NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, K, V, Root<K, V>) {
        unsafe {
            let mut new_node = Box::new(LeafNode::new());
            let k = ptr::read(self.node.keys().get_unchecked(self.idx));
            let v = ptr::read(self.node.vals().get_unchecked(self.idx));
            let new_len = self.node.len() - self.idx - 1;
            ptr::copy_nonoverlapping(
                self.node.keys().as_ptr().add(self.idx + 1),
                new_node.keys.as_mut_ptr() as *mut K,
                new_len,
            );
            ptr::copy_nonoverlapping(
                self.node.vals().as_ptr().add(self.idx + 1),
                new_node.vals.as_mut_ptr() as *mut V,
                new_len,
            );
            (*self.node.as_leaf_mut()).len = self.idx as u16;
            new_node.len = new_len as u16;
            (self.node, k, v, Root { node: BoxedNode::from_leaf(new_node), height: 0 })
        }
    }
    
    
    pub fn remove(
        mut self,
    ) -> (Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>, K, V) {
        unsafe {
            let k = slice_remove(self.node.keys_mut(), self.idx);
            let v = slice_remove(self.node.vals_mut(), self.idx);
            (*self.node.as_leaf_mut()).len -= 1;
            (self.left_edge(), k, v)
        }
    }
}
impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::KV> {
    
    
    
    
    
    
    
    pub fn split(mut self) -> (NodeRef<marker::Mut<'a>, K, V, marker::Internal>, K, V, Root<K, V>) {
        unsafe {
            let mut new_node = Box::new(InternalNode::new());
            let k = ptr::read(self.node.keys().get_unchecked(self.idx));
            let v = ptr::read(self.node.vals().get_unchecked(self.idx));
            let height = self.node.height;
            let new_len = self.node.len() - self.idx - 1;
            ptr::copy_nonoverlapping(
                self.node.keys().as_ptr().add(self.idx + 1),
                new_node.data.keys.as_mut_ptr() as *mut K,
                new_len,
            );
            ptr::copy_nonoverlapping(
                self.node.vals().as_ptr().add(self.idx + 1),
                new_node.data.vals.as_mut_ptr() as *mut V,
                new_len,
            );
            ptr::copy_nonoverlapping(
                self.node.as_internal().edges.as_ptr().add(self.idx + 1),
                new_node.edges.as_mut_ptr(),
                new_len + 1,
            );
            (*self.node.as_leaf_mut()).len = self.idx as u16;
            new_node.data.len = new_len as u16;
            let mut new_root = Root { node: BoxedNode::from_internal(new_node), height };
            for i in 0..(new_len + 1) {
                Handle::new_edge(new_root.as_mut().cast_unchecked(), i).correct_parent_link();
            }
            (self.node, k, v, new_root)
        }
    }
    
    
    
    pub fn can_merge(&self) -> bool {
        (self.reborrow().left_edge().descend().len()
            + self.reborrow().right_edge().descend().len()
            + 1)
            <= CAPACITY
    }
    
    
    
    
    
    pub fn merge(
        mut self,
    ) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
        let self1 = unsafe { ptr::read(&self) };
        let self2 = unsafe { ptr::read(&self) };
        let mut left_node = self1.left_edge().descend();
        let left_len = left_node.len();
        let mut right_node = self2.right_edge().descend();
        let right_len = right_node.len();
        
        assert!(left_len + right_len < CAPACITY);
        unsafe {
            ptr::write(
                left_node.keys_mut().get_unchecked_mut(left_len),
                slice_remove(self.node.keys_mut(), self.idx),
            );
            ptr::copy_nonoverlapping(
                right_node.keys().as_ptr(),
                left_node.keys_mut().as_mut_ptr().add(left_len + 1),
                right_len,
            );
            ptr::write(
                left_node.vals_mut().get_unchecked_mut(left_len),
                slice_remove(self.node.vals_mut(), self.idx),
            );
            ptr::copy_nonoverlapping(
                right_node.vals().as_ptr(),
                left_node.vals_mut().as_mut_ptr().add(left_len + 1),
                right_len,
            );
            slice_remove(&mut self.node.as_internal_mut().edges, self.idx + 1);
            for i in self.idx + 1..self.node.len() {
                Handle::new_edge(self.node.reborrow_mut(), i).correct_parent_link();
            }
            (*self.node.as_leaf_mut()).len -= 1;
            (*left_node.as_leaf_mut()).len += right_len as u16 + 1;
            let layout = if self.node.height > 1 {
                ptr::copy_nonoverlapping(
                    right_node.cast_unchecked().as_internal().edges.as_ptr(),
                    left_node
                        .cast_unchecked()
                        .as_internal_mut()
                        .edges
                        .as_mut_ptr()
                        .add(left_len + 1),
                    right_len + 1,
                );
                for i in left_len + 1..left_len + right_len + 2 {
                    Handle::new_edge(left_node.cast_unchecked().reborrow_mut(), i)
                        .correct_parent_link();
                }
                Layout::new::<InternalNode<K, V>>()
            } else {
                Layout::new::<LeafNode<K, V>>()
            };
            Global.dealloc(right_node.node.cast(), layout);
            Handle::new_edge(self.node, self.idx)
        }
    }
    
    
    
    pub fn steal_left(&mut self) {
        unsafe {
            let (k, v, edge) = self.reborrow_mut().left_edge().descend().pop();
            let k = mem::replace(self.reborrow_mut().into_kv_mut().0, k);
            let v = mem::replace(self.reborrow_mut().into_kv_mut().1, v);
            match self.reborrow_mut().right_edge().descend().force() {
                ForceResult::Leaf(mut leaf) => leaf.push_front(k, v),
                ForceResult::Internal(mut internal) => internal.push_front(k, v, edge.unwrap()),
            }
        }
    }
    
    
    
    pub fn steal_right(&mut self) {
        unsafe {
            let (k, v, edge) = self.reborrow_mut().right_edge().descend().pop_front();
            let k = mem::replace(self.reborrow_mut().into_kv_mut().0, k);
            let v = mem::replace(self.reborrow_mut().into_kv_mut().1, v);
            match self.reborrow_mut().left_edge().descend().force() {
                ForceResult::Leaf(mut leaf) => leaf.push(k, v),
                ForceResult::Internal(mut internal) => internal.push(k, v, edge.unwrap()),
            }
        }
    }
    
    pub fn bulk_steal_left(&mut self, count: usize) {
        unsafe {
            let mut left_node = ptr::read(self).left_edge().descend();
            let left_len = left_node.len();
            let mut right_node = ptr::read(self).right_edge().descend();
            let right_len = right_node.len();
            
            assert!(right_len + count <= CAPACITY);
            assert!(left_len >= count);
            let new_left_len = left_len - count;
            
            {
                let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
                let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
                let parent_kv = {
                    let kv = self.reborrow_mut().into_kv_mut();
                    (kv.0 as *mut K, kv.1 as *mut V)
                };
                
                ptr::copy(right_kv.0, right_kv.0.add(count), right_len);
                ptr::copy(right_kv.1, right_kv.1.add(count), right_len);
                
                move_kv(left_kv, new_left_len + 1, right_kv, 0, count - 1);
                
                move_kv(parent_kv, 0, right_kv, count - 1, 1);
                
                move_kv(left_kv, new_left_len, parent_kv, 0, 1);
            }
            (*left_node.reborrow_mut().as_leaf_mut()).len -= count as u16;
            (*right_node.reborrow_mut().as_leaf_mut()).len += count as u16;
            match (left_node.force(), right_node.force()) {
                (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
                    
                    let right_edges = right.reborrow_mut().as_internal_mut().edges.as_mut_ptr();
                    ptr::copy(right_edges, right_edges.add(count), right_len + 1);
                    right.correct_childrens_parent_links(count, count + right_len + 1);
                    move_edges(left, new_left_len + 1, right, 0, count);
                }
                (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
                _ => {
                    unreachable!();
                }
            }
        }
    }
    
    pub fn bulk_steal_right(&mut self, count: usize) {
        unsafe {
            let mut left_node = ptr::read(self).left_edge().descend();
            let left_len = left_node.len();
            let mut right_node = ptr::read(self).right_edge().descend();
            let right_len = right_node.len();
            
            assert!(left_len + count <= CAPACITY);
            assert!(right_len >= count);
            let new_right_len = right_len - count;
            
            {
                let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
                let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
                let parent_kv = {
                    let kv = self.reborrow_mut().into_kv_mut();
                    (kv.0 as *mut K, kv.1 as *mut V)
                };
                
                move_kv(parent_kv, 0, left_kv, left_len, 1);
                
                move_kv(right_kv, 0, left_kv, left_len + 1, count - 1);
                
                move_kv(right_kv, count - 1, parent_kv, 0, 1);
                
                ptr::copy(right_kv.0.add(count), right_kv.0, new_right_len);
                ptr::copy(right_kv.1.add(count), right_kv.1, new_right_len);
            }
            (*left_node.reborrow_mut().as_leaf_mut()).len += count as u16;
            (*right_node.reborrow_mut().as_leaf_mut()).len -= count as u16;
            match (left_node.force(), right_node.force()) {
                (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
                    move_edges(right.reborrow_mut(), 0, left, left_len + 1, count);
                    
                    let right_edges = right.reborrow_mut().as_internal_mut().edges.as_mut_ptr();
                    ptr::copy(right_edges.add(count), right_edges, new_right_len + 1);
                    right.correct_childrens_parent_links(0, new_right_len + 1);
                }
                (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
                _ => {
                    unreachable!();
                }
            }
        }
    }
}
unsafe fn move_kv<K, V>(
    source: (*mut K, *mut V),
    source_offset: usize,
    dest: (*mut K, *mut V),
    dest_offset: usize,
    count: usize,
) {
    ptr::copy_nonoverlapping(source.0.add(source_offset), dest.0.add(dest_offset), count);
    ptr::copy_nonoverlapping(source.1.add(source_offset), dest.1.add(dest_offset), count);
}
unsafe fn move_edges<K, V>(
    mut source: NodeRef<marker::Mut<'_>, K, V, marker::Internal>,
    source_offset: usize,
    mut dest: NodeRef<marker::Mut<'_>, K, V, marker::Internal>,
    dest_offset: usize,
    count: usize,
) {
    let source_ptr = source.as_internal_mut().edges.as_mut_ptr();
    let dest_ptr = dest.as_internal_mut().edges.as_mut_ptr();
    ptr::copy_nonoverlapping(source_ptr.add(source_offset), dest_ptr.add(dest_offset), count);
    dest.correct_childrens_parent_links(dest_offset, dest_offset + count);
}
impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::Edge> {
    pub fn forget_node_type(
        self,
    ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::Edge> {
        unsafe { Handle::new_edge(self.node.forget_type(), self.idx) }
    }
}
impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge> {
    pub fn forget_node_type(
        self,
    ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::Edge> {
        unsafe { Handle::new_edge(self.node.forget_type(), self.idx) }
    }
}
impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::KV> {
    pub fn forget_node_type(
        self,
    ) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> {
        unsafe { Handle::new_kv(self.node.forget_type(), self.idx) }
    }
}
impl<BorrowType, K, V, HandleType>
    Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, HandleType>
{
    
    pub fn force(
        self,
    ) -> ForceResult<
        Handle<NodeRef<BorrowType, K, V, marker::Leaf>, HandleType>,
        Handle<NodeRef<BorrowType, K, V, marker::Internal>, HandleType>,
    > {
        match self.node.force() {
            ForceResult::Leaf(node) => {
                ForceResult::Leaf(Handle { node, idx: self.idx, _marker: PhantomData })
            }
            ForceResult::Internal(node) => {
                ForceResult::Internal(Handle { node, idx: self.idx, _marker: PhantomData })
            }
        }
    }
}
impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, marker::Edge> {
    
    
    pub fn move_suffix(
        &mut self,
        right: &mut NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>,
    ) {
        unsafe {
            let left_new_len = self.idx;
            let mut left_node = self.reborrow_mut().into_node();
            let right_new_len = left_node.len() - left_new_len;
            let mut right_node = right.reborrow_mut();
            assert!(right_node.len() == 0);
            assert!(left_node.height == right_node.height);
            if right_new_len > 0 {
                let left_kv = left_node.reborrow_mut().into_kv_pointers_mut();
                let right_kv = right_node.reborrow_mut().into_kv_pointers_mut();
                move_kv(left_kv, left_new_len, right_kv, 0, right_new_len);
                (*left_node.reborrow_mut().as_leaf_mut()).len = left_new_len as u16;
                (*right_node.reborrow_mut().as_leaf_mut()).len = right_new_len as u16;
                match (left_node.force(), right_node.force()) {
                    (ForceResult::Internal(left), ForceResult::Internal(right)) => {
                        move_edges(left, left_new_len + 1, right, 1, right_new_len);
                    }
                    (ForceResult::Leaf(_), ForceResult::Leaf(_)) => {}
                    _ => {
                        unreachable!();
                    }
                }
            }
        }
    }
}
pub enum ForceResult<Leaf, Internal> {
    Leaf(Leaf),
    Internal(Internal),
}
pub enum InsertResult<'a, K, V, Type> {
    Fit(Handle<NodeRef<marker::Mut<'a>, K, V, Type>, marker::KV>),
    Split(NodeRef<marker::Mut<'a>, K, V, Type>, K, V, Root<K, V>),
}
pub mod marker {
    use core::marker::PhantomData;
    pub enum Leaf {}
    pub enum Internal {}
    pub enum LeafOrInternal {}
    pub enum Owned {}
    pub struct Immut<'a>(PhantomData<&'a ()>);
    pub struct Mut<'a>(PhantomData<&'a mut ()>);
    pub enum KV {}
    pub enum Edge {}
}
unsafe fn slice_insert<T>(slice: &mut [T], idx: usize, val: T) {
    ptr::copy(slice.as_ptr().add(idx), slice.as_mut_ptr().add(idx + 1), slice.len() - idx);
    ptr::write(slice.get_unchecked_mut(idx), val);
}
unsafe fn slice_remove<T>(slice: &mut [T], idx: usize) -> T {
    let ret = ptr::read(slice.get_unchecked(idx));
    ptr::copy(slice.as_ptr().add(idx + 1), slice.as_mut_ptr().add(idx), slice.len() - idx - 1);
    ret
}