/*************************************************************************
 *
 * Copyright (C) 2018-2025 Ruilin Peng (Nick) <pymumu@gmail.com>.
 *
 * smartdns is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * smartdns is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef _GENERIC_RBTREE_H
#define _GENERIC_RBTREE_H

#include <stddef.h>

struct rb_node {
	unsigned long __rb_parent_color;
	struct rb_node *rb_right;
	struct rb_node *rb_left;
} __attribute__((aligned(sizeof(long))));
/* The alignment might seem pointless, but allegedly CRIS needs it */

struct rb_root {
	struct rb_node *rb_node;
};

#define rb_parent(r) ((struct rb_node *)((r)->__rb_parent_color & ~3))

#define RB_ROOT                                                                                                                                                \
	(struct rb_root)                                                                                                                                           \
	{                                                                                                                                                          \
		NULL,                                                                                                                                                  \
	}
#define rb_entry(ptr, type, member) container_of(ptr, type, member)

#define RB_EMPTY_ROOT(root) ((root)->rb_node == NULL)

/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
#define RB_EMPTY_NODE(node) ((node)->__rb_parent_color == (unsigned long)(node))
#define RB_CLEAR_NODE(node) ((node)->__rb_parent_color = (unsigned long)(node))

extern void rb_insert_color(struct rb_node *, struct rb_root *);
extern void rb_erase(struct rb_node *, struct rb_root *);

/* Find logical next and previous nodes in a tree */
extern struct rb_node *rb_next(const struct rb_node *);
extern struct rb_node *rb_prev(const struct rb_node *);
extern struct rb_node *rb_first(const struct rb_root *);
extern struct rb_node *rb_last(const struct rb_root *);

/* Postorder iteration - always visit the parent after its children */
extern struct rb_node *rb_first_postorder(const struct rb_root *);
extern struct rb_node *rb_next_postorder(const struct rb_node *);

/* Fast replacement of a single node without remove/rebalance/add/rebalance */
extern void rb_replace_node(struct rb_node *victim, struct rb_node *new_node, struct rb_root *root);

static inline void rb_link_node(struct rb_node *node, struct rb_node *parent, struct rb_node **rb_link)
{
	node->__rb_parent_color = (unsigned long)parent;
	node->rb_left = node->rb_right = NULL;

	*rb_link = node;
}

#define rb_entry_safe(ptr, type, member)                                                                                                                       \
	({                                                                                                                                                         \
		typeof(ptr) ____ptr = (ptr);                                                                                                                           \
		____ptr ? rb_entry(____ptr, type, member) : NULL;                                                                                                      \
	})

/*
 * Handy for checking that we are not deleting an entry that is
 * already in a list, found in block/{blk-throttle,cfq-iosched}.c,
 * probably should be moved to lib/rbtree.c...
 */
static inline void rb_erase_init(struct rb_node *n, struct rb_root *root)
{
	rb_erase(n, root);
	RB_CLEAR_NODE(n);
}


/*
 * Please note - only struct rb_augment_callbacks and the prototypes for
 * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
 * The rest are implementation details you are not expected to depend on.
 *
 * See Documentation/rbtree.txt for documentation and samples.
 */

struct rb_augment_callbacks {
	void (*propagate)(struct rb_node *node, struct rb_node *stop);
	void (*copy)(struct rb_node *old_node, struct rb_node *new_node);
	void (*rotate)(struct rb_node *old_node, struct rb_node *new_node);
};

extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
	void (*augment_rotate)(struct rb_node *old_node, struct rb_node *new_node));
/*
 * Fixup the rbtree and update the augmented information when rebalancing.
 *
 * On insertion, the user must update the augmented information on the path
 * leading to the inserted node, then call rb_link_node() as usual and
 * rb_augment_inserted() instead of the usual rb_insert_color() call.
 * If rb_augment_inserted() rebalances the rbtree, it will callback into
 * a user provided function to update the augmented information on the
 * affected subtrees.
 */
static inline void
rb_insert_augmented(struct rb_node *node, struct rb_root *root,
		    const struct rb_augment_callbacks *augment)
{
	__rb_insert_augmented(node, root, augment->rotate);
}

#define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,	\
			     rbtype, rbaugmented, rbcompute)		\
static inline void							\
rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)		\
{									\
	while (rb != stop) {						\
		rbstruct *node = rb_entry(rb, rbstruct, rbfield);	\
		rbtype augmented = rbcompute(node);			\
		if (node->rbaugmented == augmented)			\
			break;						\
		node->rbaugmented = augmented;				\
		rb = rb_parent(&node->rbfield);				\
	}								\
}									\
static inline void							\
rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)		\
{									\
	rbstruct *old_node = rb_entry(rb_old, rbstruct, rbfield);		\
	rbstruct *new_node = rb_entry(rb_new, rbstruct, rbfield);		\
	new_node->rbaugmented = old_node->rbaugmented;				\
}									\
static void								\
rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)	\
{									\
	rbstruct *old_node = rb_entry(rb_old, rbstruct, rbfield);		\
	rbstruct *new_node = rb_entry(rb_new, rbstruct, rbfield);		\
	new_node->rbaugmented = old_node->rbaugmented;				\
	old_node->rbaugmented = rbcompute(old_node);				\
}									\
rbstatic const struct rb_augment_callbacks rbname = {			\
	rbname ## _propagate, rbname ## _copy, rbname ## _rotate	\
};


#define	RB_RED		0
#define	RB_BLACK	1

#define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))

#define __rb_color(pc)     ((pc) & 1)
#define __rb_is_black(pc)  __rb_color(pc)
#define __rb_is_red(pc)    (!__rb_color(pc))
#define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
#define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
#define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)

static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
	rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
}

static inline void rb_set_parent_color(struct rb_node *rb,
				       struct rb_node *p, int color)
{
	rb->__rb_parent_color = (unsigned long)p | color;
}

static inline void
__rb_change_child(struct rb_node *old_node, struct rb_node *new_node,
		  struct rb_node *parent, struct rb_root *root)
{
	if (parent) {
		if (parent->rb_left == old_node)
			parent->rb_left = new_node;
		else
			parent->rb_right = new_node;
	} else
		root->rb_node = new_node;
}

extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
	void (*augment_rotate)(struct rb_node *old_node, struct rb_node *new_node));

static inline struct rb_node *
__rb_erase_augmented(struct rb_node *node, struct rb_root *root,
		     const struct rb_augment_callbacks *augment)
{
	struct rb_node *child = node->rb_right, *tmp = node->rb_left;
	struct rb_node *parent, *rebalance;
	unsigned long pc;

	if (!tmp) {
		/*
		 * Case 1: node to erase has no more than 1 child (easy!)
		 *
		 * Note that if there is one child it must be red due to 5)
		 * and node must be black due to 4). We adjust colors locally
		 * so as to bypass __rb_erase_color() later on.
		 */
		pc = node->__rb_parent_color;
		parent = __rb_parent(pc);
		__rb_change_child(node, child, parent, root);
		if (child) {
			child->__rb_parent_color = pc;
			rebalance = NULL;
		} else
			rebalance = __rb_is_black(pc) ? parent : NULL;
		tmp = parent;
	} else if (!child) {
		/* Still case 1, but this time the child is node->rb_left */
		tmp->__rb_parent_color = pc = node->__rb_parent_color;
		parent = __rb_parent(pc);
		__rb_change_child(node, tmp, parent, root);
		rebalance = NULL;
		tmp = parent;
	} else {
		struct rb_node *successor = child, *child2;
		tmp = child->rb_left;
		if (!tmp) {
			/*
			 * Case 2: node's successor is its right child
			 *
			 *    (n)          (s)
			 *    / \          / \
			 *  (x) (s)  ->  (x) (c)
			 *        \
			 *        (c)
			 */
			parent = successor;
			child2 = successor->rb_right;
			augment->copy(node, successor);
		} else {
			/*
			 * Case 3: node's successor is leftmost under
			 * node's right child subtree
			 *
			 *    (n)          (s)
			 *    / \          / \
			 *  (x) (y)  ->  (x) (y)
			 *      /            /
			 *    (p)          (p)
			 *    /            /
			 *  (s)          (c)
			 *    \
			 *    (c)
			 */
			do {
				parent = successor;
				successor = tmp;
				tmp = tmp->rb_left;
			} while (tmp);
			parent->rb_left = child2 = successor->rb_right;
			successor->rb_right = child;
			rb_set_parent(child, successor);
			augment->copy(node, successor);
			augment->propagate(parent, successor);
		}

		successor->rb_left = tmp = node->rb_left;
		rb_set_parent(tmp, successor);

		pc = node->__rb_parent_color;
		tmp = __rb_parent(pc);
		__rb_change_child(node, successor, tmp, root);
		if (child2) {
			successor->__rb_parent_color = pc;
			rb_set_parent_color(child2, parent, RB_BLACK);
			rebalance = NULL;
		} else {
			unsigned long pc2 = successor->__rb_parent_color;
			successor->__rb_parent_color = pc;
			rebalance = __rb_is_black(pc2) ? parent : NULL;
		}
		tmp = successor;
	}

	augment->propagate(tmp, NULL);
	return rebalance;
}

static inline void
rb_erase_augmented(struct rb_node *node, struct rb_root *root,
		   const struct rb_augment_callbacks *augment)
{
	struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
	if (rebalance)
		__rb_erase_color(rebalance, root, augment->rotate);
}

#endif /* _GENERIC_RBTREE_H */

