#include <blue/ds/tree.h>
#include <stdlib.h>
#include <string.h>

#define ITERATOR_RECURSIVE           0x01u

#define ITERATOR_IS_RECURSIVE(it)    (((it)->_f01 & ITERATOR_RECURSIVE) != 0)
#define ITERATOR_UNSET_RECURSIVE(it) ((it)->_f01 &= ~ITERATOR_RECURSIVE)
#define ITERATOR_SET_RECURSIVE(it)   ((it)->_f01 |= ITERATOR_RECURSIVE)

#define NODE_PARENT(n)               ((n)->__p01)
#define NODE_FIRST_CHILD(n)          ((n)->__p02)
#define NODE_NEXT_SIBLING(n)         ((n)->__p03)

/*** PRIVATE DATA *************************************************************/

struct b_tree_p {
	struct b_tree_node *t_root;
};

/*** PRIVATE FUNCTIONS ********************************************************/

static void tree_set_root(struct b_tree_p *tree, struct b_tree_node *node)
{
	tree->t_root = node;
}

static const struct b_tree_node *next_node(
	const struct b_tree_node *node, bool recursive, int *depth_diff)
{
	if (!node) {
		return NULL;
	}

	if (!recursive) {
		node = NODE_NEXT_SIBLING(node);
		return node;
	}

	int d = 0;
	struct b_tree_node *next = NODE_FIRST_CHILD(node);
	if (next) {
		d = 1;
		*depth_diff = d;
		return next;
	}

	const struct b_tree_node *n = node;
	next = NODE_NEXT_SIBLING(n);
	while (!next) {
		n = NODE_PARENT(n);
		if (!n) {
			break;
		}

		d--;
		next = NODE_NEXT_SIBLING(n);
	}

	*depth_diff = d;
	return next;
}

static void reparent_children(
	struct b_tree_node *old_parent, struct b_tree_node *new_parent)
{
	struct b_tree_node *last = NODE_FIRST_CHILD(new_parent);
	while (last && NODE_NEXT_SIBLING(last)) {
		last = NODE_NEXT_SIBLING(last);
	}

	struct b_tree_node *cur = NODE_FIRST_CHILD(old_parent);
	while (cur) {
		struct b_tree_node *next = NODE_NEXT_SIBLING(cur);
		NODE_PARENT(cur) = new_parent;
		NODE_NEXT_SIBLING(cur) = NULL;

		if (last) {
			NODE_NEXT_SIBLING(last) = cur;
		} else {
			NODE_FIRST_CHILD(new_parent) = cur;
		}

		last = cur;
		cur = next;
	}
}

/*** PUBLIC FUNCTIONS *********************************************************/

void b_tree_set_root(b_tree *tree, struct b_tree_node *node)
{
	B_CLASS_DISPATCH_STATIC(B_TYPE_TREE, tree_set_root, tree, node);
}

void b_tree_node_add_child(struct b_tree_node *parent, struct b_tree_node *child)
{
	if (NODE_PARENT(child)) {
		return;
	}

	NODE_PARENT(child) = parent;
	if (!NODE_FIRST_CHILD(parent)) {
		NODE_FIRST_CHILD(parent) = child;
		return;
	}

	struct b_tree_node *cur = NODE_FIRST_CHILD(parent);
	while (NODE_NEXT_SIBLING(cur)) {
		cur = NODE_NEXT_SIBLING(cur);
	}

	NODE_NEXT_SIBLING(cur) = child;
}

void b_tree_node_add_sibling(struct b_tree_node *node, struct b_tree_node *to_add)
{
	if (NODE_PARENT(to_add) || !NODE_PARENT(node)) {
		return;
	}

	b_tree_node_add_child(NODE_PARENT(node), to_add);
}

struct b_tree_node *b_tree_node_get_child(struct b_tree_node *node, size_t at)
{
	size_t i = 0;
	struct b_tree_node *cur = NODE_FIRST_CHILD(node);

	while (i < at) {
		if (!cur) {
			return NULL;
		}

		cur = NODE_NEXT_SIBLING(cur);
		i++;
	}

	return cur;
}

/*** VIRTUAL FUNCTIONS ********************************************************/

static void tree_init(b_object *obj, void *priv)
{
	struct b_tree_p *tree = priv;
}

static void tree_fini(b_object *obj, void *priv)
{
	struct b_tree_p *tree = priv;
}

/*** CLASS DEFINITION *********************************************************/

B_TYPE_CLASS_DEFINITION_BEGIN(b_tree)
	B_TYPE_CLASS_INTERFACE_BEGIN(b_object, B_TYPE_OBJECT)
		B_INTERFACE_ENTRY(to_string) = NULL;
	B_TYPE_CLASS_INTERFACE_END(b_object, B_TYPE_OBJECT)
B_TYPE_CLASS_DEFINITION_END(b_tree)

B_TYPE_DEFINITION_BEGIN(b_tree)
	B_TYPE_ID(0x8d8fa36b, 0xc515, 0x4803, 0x8124, 0xfd704f01b8ae);
	B_TYPE_CLASS(b_tree_class);
	B_TYPE_INSTANCE_INIT(tree_init);
	B_TYPE_INSTANCE_INIT(tree_fini);
B_TYPE_DEFINITION_END(b_tree)

/*** ITERATOR FUNCTIONS *******************************************************/

static bool tree_iterator_next(struct b_iterator *it)
{
	return b_tree_iterator_next((struct b_tree_iterator *)it);
}

static b_status tree_iterator_erase(struct b_iterator *it)
{
	return b_tree_iterator_erase((struct b_tree_iterator *)it);
}

static bool tree_iterator_is_valid(const struct b_iterator *it)
{
	return b_tree_iterator_is_valid((const struct b_tree_iterator *)it);
}

struct b_tree_node *b_tree_node_get_parent(struct b_tree_node *node)
{
	return NODE_PARENT(node);
}

int b_tree_iterator_begin(b_tree *tree, b_tree_iterator *it)
{
	struct b_tree_p *p = b_object_get_private(tree, B_TYPE_TREE);
	return b_tree_iterator_begin_at_node_recursive(p->t_root, it);
}

static b_iterator_ops it_ops = {
	.it_next = tree_iterator_next,
	.it_erase = tree_iterator_erase,
	.it_close = NULL,
	.it_is_valid = tree_iterator_is_valid,
};

int b_tree_iterator_begin_at_node(struct b_tree_node *node, b_tree_iterator *it)
{
	it->node = NODE_FIRST_CHILD(node);
	it->i = 0;
	it->depth = 0;

	it->_base.it_ops = &it_ops;

	ITERATOR_UNSET_RECURSIVE(it);

	return 0;
}

int b_tree_iterator_begin_at_node_recursive(
	struct b_tree_node *node, b_tree_iterator *it)
{
	it->node = node;
	it->i = 0;
	it->depth = 0;
	it->_base.it_ops = &it_ops;

	ITERATOR_SET_RECURSIVE(it);

	return 0;
}

bool b_tree_iterator_next(struct b_tree_iterator *it)
{
	int depth_diff = 0;
	const struct b_tree_node *next
		= next_node(it->node, ITERATOR_IS_RECURSIVE(it), &depth_diff);

	if (next) {
		it->depth += depth_diff;
		it->i++;
	} else {
		it->depth = 0;
		it->i = 0;
	}

	it->node = (struct b_tree_node *)next;
	return it->node != NULL;
}

static void remove_node(struct b_tree_node *node)
{
	struct b_tree_node *parent = NODE_PARENT(node);
	if (!parent) {
		return;
	}

	struct b_tree_node *n0 = NULL, *n1 = NULL;
	n0 = NODE_FIRST_CHILD(parent);

	while (n0) {
		if (n0 == node) {
			break;
		}

		n1 = n0;
		n0 = NODE_NEXT_SIBLING(n0);
	}

	if (!n0) {
		return;
	}

	if (n1) {
		NODE_NEXT_SIBLING(n1) = NODE_NEXT_SIBLING(n0);
	} else {
		NODE_FIRST_CHILD(parent) = NODE_NEXT_SIBLING(n0);
	}

	NODE_PARENT(n0) = NODE_NEXT_SIBLING(n0) = NULL;
}

b_status b_tree_iterator_erase(struct b_tree_iterator *it)
{
	if (!it->node) {
		return B_ERR_OUT_OF_BOUNDS;
	}

	struct b_tree_node *parent = NODE_PARENT(it->node);
	if (!parent) {
		return B_ERR_NOT_SUPPORTED;
	}

	int d = 0;
	struct b_tree_node *n = it->node;
	struct b_tree_node *next = NODE_NEXT_SIBLING(n);

	if (!next) {
		next = NODE_FIRST_CHILD(n);
	}

	while (!next) {
		n = NODE_PARENT(n);
		if (!n) {
			break;
		}

		d--;
		next = NODE_NEXT_SIBLING(n);
	}

	remove_node(it->node);
	reparent_children(it->node, parent);

	return B_SUCCESS;
}

bool b_tree_iterator_is_valid(const struct b_tree_iterator *it)
{
	return it->node != NULL;
}