// SPDX-License-Identifier: GPL-2.0-or-later
/*
  Red Black Trees
  (C) 1999  Andrea Arcangeli <andrea@suse.de>
  (C) 2002  David Woodhouse <dwmw2@infradead.org>
  (C) 2012  Michel Lespinasse <walken@google.com>


  linux/lib/rbtree.c
*/
/*
 *              RedBlackTree_linux_userspace
 *    (C) Copyright 2021-2022
 *        Andrea Di Iorio      
 * 
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *    1. Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *    2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions, and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *    3. The name of the RedBlackTree_linux_userspace or the names of its contributors may
 *       not be used to endorse or promote products derived from this
 *       software without specific written permission.
 * 
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 *  TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 *  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE RedBlackTree_linux_userspace GROUP OR ITS CONTRIBUTORS
 *  BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */ 

///#include <linux/rbtree_augmented.h>	//TODO LESS_DEPENDENCIES
#include "linuxK_rbtree_minimalized.h"	///fulfill embedded deps needed //TODO LESS_DEPENDENCIES
//#include <linux/export.h>

/*	MINIMALIZED VERSION WITHOUT THE IMPORT OF rbtree_augmented 
 * red-black trees properties:  https://en.wikipedia.org/wiki/Rbtree
 *
 *  1) A node is either red or black
 *  2) The root is black
 *  3) All leaves (NULL) are black
 *  4) Both children of every red node are black
 *  5) Every simple path from root to leaves contains the same number
 *     of black nodes.
 *
 *  4 and 5 give the O(log n) guarantee, since 4 implies you cannot have two
 *  consecutive red nodes in a path and every red node is therefore followed by
 *  a black. So if B is the number of black nodes on every simple path (as per
 *  5), then the longest possible path due to 4 is 2B.
 *
 *  We shall indicate color with case, where black nodes are uppercase and red
 *  nodes will be lowercase. Unknown color nodes shall be drawn as red within
 *  parentheses and have some accompanying text comment.
 */

/*
 * Notes on lockless lookups:
 *
 * All stores to the tree structure (rb_left and rb_right) must be done using
 * WRITE_ONCE(). And we must not inadvertently cause (temporary) loops in the
 * tree structure as seen in program order.
 *
 * These two requirements will allow lockless iteration of the tree -- not
 * correct iteration mind you, tree rotations are not atomic so a lookup might
 * miss entire subtrees.
 *
 * But they do guarantee that any such traversal will only see valid elements
 * and that it will indeed complete -- does not get stuck in a loop.
 *
 * It also guarantees that if the lookup returns an element it is the 'correct'
 * one. But not returning an element does _NOT_ mean it's not present.
 *
 * NOTE:
 *
 * Stores to __rb_parent_color are not important for simple lookups so those
 * are left undone as of now. Nor did I check for loops involving parent
 * pointers.
 */

///rb_set_black	//TODO ADDONLY_GENERIC

static inline struct rb_node *rb_red_parent(struct rb_node *red)
{
	return (struct rb_node *)red->__rb_parent_color;
}

/*
 * Helper function for rotations:
 * - old's parent and color get assigned to new
 * - old gets assigned new as a parent and 'color' as a color.
 */
static inline void
__rb_rotate_set_parents(struct rb_node *old, struct rb_node *new,
			struct rb_root *root, int color)
{
	struct rb_node *parent = rb_parent(old);
	new->__rb_parent_color = old->__rb_parent_color;
	rb_set_parent_color(old, new, color);
	__rb_change_child(old, new, parent, root);
}

///TODO REMOVE AGUMENT
static __always_inline void
__rb_insert(struct rb_node *node, struct rb_root *root)
{
	struct rb_node *parent = rb_red_parent(node), *gparent, *tmp;

	while (true) {
		/*
		 * Loop invariant: node is red.
		 */
		if (unlikely(!parent)) {
			/*
			 * The inserted node is root. Either this is the
			 * first node, or we recursed at Case 1 below and
			 * are no longer violating 4).
			 */
			rb_set_parent_color(node, NULL, RB_BLACK);
			break;
		}

		/*
		 * If there is a black parent, we are done.
		 * Otherwise, take some corrective action as,
		 * per 4), we don't want a red root or two
		 * consecutive red nodes.
		 */
		if(rb_is_black(parent))
			break;

		gparent = rb_red_parent(parent);

		tmp = gparent->rb_right;
		if (parent != tmp) {	/* parent == gparent->rb_left */
			if (tmp && rb_is_red(tmp)) {
				/*
				 * Case 1 - node's uncle is red (color flips).
				 *
				 *       G            g
				 *      / \          / \
				 *     p   u  -->   P   U
				 *    /            /
				 *   n            n
				 *
				 * However, since g's parent might be red, and
				 * 4) does not allow this, we need to recurse
				 * at g.
				 */
				rb_set_parent_color(tmp, gparent, RB_BLACK);
				rb_set_parent_color(parent, gparent, RB_BLACK);
				node = gparent;
				parent = rb_parent(node);
				rb_set_parent_color(node, parent, RB_RED);
				continue;
			}

			tmp = parent->rb_right;
			if (node == tmp) {
				/*
				 * Case 2 - node's uncle is black and node is
				 * the parent's right child (left rotate at parent).
				 *
				 *      G             G
				 *     / \           / \
				 *    p   U  -->    n   U
				 *     \           /
				 *      n         p
				 *
				 * This still leaves us in violation of 4), the
				 * continuation into Case 3 will fix that.
				 */
				tmp = node->rb_left;
				WRITE_ONCE(parent->rb_right, tmp);
				WRITE_ONCE(node->rb_left, parent);
				if (tmp)
					rb_set_parent_color(tmp, parent,
							    RB_BLACK);
				rb_set_parent_color(parent, node, RB_RED);
				///augment_rotate(parent, node); //TODO DEL AUGMENTED DEP
				parent = node;
				tmp = node->rb_right;
			}

			/*
			 * Case 3 - node's uncle is black and node is
			 * the parent's left child (right rotate at gparent).
			 *
			 *        G           P
			 *       / \         / \
			 *      p   U  -->  n   g
			 *     /                 \
			 *    n                   U
			 */
			WRITE_ONCE(gparent->rb_left, tmp); /* == parent->rb_right */
			WRITE_ONCE(parent->rb_right, gparent);
			if (tmp)
				rb_set_parent_color(tmp, gparent, RB_BLACK);
			__rb_rotate_set_parents(gparent, parent, root, RB_RED);
			///augment_rotate(gparent, parent); //TODO DEL_AUGMENTED_DEP
			break;
		} else {
			tmp = gparent->rb_left;
			if (tmp && rb_is_red(tmp)) {
				/* Case 1 - color flips */
				rb_set_parent_color(tmp, gparent, RB_BLACK);
				rb_set_parent_color(parent, gparent, RB_BLACK);
				node = gparent;
				parent = rb_parent(node);
				rb_set_parent_color(node, parent, RB_RED);
				continue;
			}

			tmp = parent->rb_left;
			if (node == tmp) {
				/* Case 2 - right rotate at parent */
				tmp = node->rb_right;
				WRITE_ONCE(parent->rb_left, tmp);
				WRITE_ONCE(node->rb_right, parent);
				if (tmp)
					rb_set_parent_color(tmp, parent,
							    RB_BLACK);
				rb_set_parent_color(parent, node, RB_RED);
				///augment_rotate(parent, node); //TODO DEL_AUGMENTED_DEP
				parent = node;
				tmp = node->rb_left;
			}

			/* Case 3 - left rotate at gparent */
			WRITE_ONCE(gparent->rb_right, tmp); /* == parent->rb_left */
			WRITE_ONCE(parent->rb_left, gparent);
			if (tmp)
				rb_set_parent_color(tmp, gparent, RB_BLACK);
			__rb_rotate_set_parents(gparent, parent, root, RB_RED);
			///augment_rotate(gparent, parent); //TODO DEL_AUGMENTED_DEP
			break;
		}
	}
}

/*
 * Inline version for rb_erase() use - we want to be able to inline
 * and eliminate the dummy_rotate callback there
 */
///____rb_erase_color	//TODO ADDONLY_GENERIC

/* Non-inline version for rb_erase_augmented() use */
///__rb_erase_color	//TODO ADDONLY_GENERIC

/*	TODO LESS_DEPENDENCIES MINIMALIZED
 * Non-augmented rbtree manipulation functions.
 *
 * We use dummy augmented callbacks here, and have the compiler optimize them
 * out of the rb_insert_color() and rb_erase() function definitions.

static inline void dummy_propagate(struct rb_node *node, struct rb_node *stop) {}
static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {}
static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {}

static const struct rb_augment_callbacks dummy_callbacks = {
	.propagate = dummy_propagate,
	.copy = dummy_copy,
	.rotate = dummy_rotate
};*/
void rb_insert_color(struct rb_node *node, struct rb_root *root)
{
	__rb_insert(node, root);
}

///rb_erase	//TODO ADDONLY_GENERIC

/** TODO LESS_DEPENDENCIES - AUGMENTED REMOVE
 * Augmented rbtree manipulation functions.
 *
 * This instantiates the same __always_inline functions as in the non-augmented
 * case, but this time with user-defined callbacks.
 */
///__rb_insert_augmented todo LESS_DEPENDENCIES - AUGMENTED REMOVE

////// Traversing
/*
 * This function returns the first node (in sort order) of the tree.
 */
struct rb_node *rb_first(const struct rb_root *root)
{
	struct rb_node	*n;

	n = root->rb_node;
	if (!n)
		return NULL;
	while (n->rb_left)
		n = n->rb_left;
	return n;
}

struct rb_node *rb_last(const struct rb_root *root)
{
	struct rb_node	*n;

	n = root->rb_node;
	if (!n)
		return NULL;
	while (n->rb_right)
		n = n->rb_right;
	return n;
}

struct rb_node *rb_next(const struct rb_node *node)
{
	struct rb_node *parent;

	if (RB_EMPTY_NODE(node))
		return NULL;

	/*
	 * If we have a right-hand child, go down and then left as far
	 * as we can.
	 */
	if (node->rb_right) {
		node = node->rb_right;
		while (node->rb_left)
			node = node->rb_left;
		return (struct rb_node *)node;
	}

	/*
	 * No right-hand children. Everything down and left is smaller than us,
	 * so any 'next' node must be in the general direction of our parent.
	 * Go up the tree; any time the ancestor is a right-hand child of its
	 * parent, keep going up. First time it's a left-hand child of its
	 * parent, said parent is our 'next' node.
	 */
	while ((parent = rb_parent(node)) && node == parent->rb_right)
		node = parent;

	return parent;
}

struct rb_node *rb_prev(const struct rb_node *node)
{
	struct rb_node *parent;

	if (RB_EMPTY_NODE(node))
		return NULL;

	/*
	 * If we have a left-hand child, go down and then right as far
	 * as we can.
	 */
	if (node->rb_left) {
		node = node->rb_left;
		while (node->rb_right)
			node = node->rb_right;
		return (struct rb_node *)node;
	}

	/*
	 * No left-hand children. Go up till we find an ancestor which
	 * is a right-hand child of its parent.
	 */
	while ((parent = rb_parent(node)) && node == parent->rb_left)
		node = parent;

	return parent;
}

///rb_replace_node	//TODO ADDONLY_GENERIC
///rb_replace_node_rcu	//TODO LESS_DEPENDENCIES

static struct rb_node *rb_left_deepest_node(const struct rb_node *node)
{
	for (;;) {
		if (node->rb_left)
			node = node->rb_left;
		else if (node->rb_right)
			node = node->rb_right;
		else
			return (struct rb_node *)node;
	}
}

struct rb_node *rb_next_postorder(const struct rb_node *node)
{
	const struct rb_node *parent;
	if (!node)
		return NULL;
	parent = rb_parent(node);

	/* If we're sitting on node, we've already seen our children */
	if (parent && node == parent->rb_left && parent->rb_right) {
		/* If we are the parent's left node, go to the parent's right
		 * node then all the way down to the left */
		return rb_left_deepest_node(parent->rb_right);
	} else
		/* Otherwise we are the parent's right node, and the parent
		 * should be next */
		return (struct rb_node *)parent;
}

struct rb_node *rb_first_postorder(const struct rb_root *root)
{
	if (!root->rb_node)
		return NULL;

	return rb_left_deepest_node(root->rb_node);
}