/*
   Copyright (c) 2014 Anton Titov.

   Copyright (c) 2014 pCloud Ltd.  All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met: Redistributions of source code must retain the above
   copyright notice, this list of conditions and the following
   disclaimer.  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.  Neither the name of pCloud Ltd nor the
   names of its contributors may be used to endorse or promote
   products derived from this software without specific prior 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 pCloud
   Ltd 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 <assert.h>
#include <string.h>

#include "pdbg.h"
#include "ptree.h"

static inline long int ptree_max(long int a, long int b) {
  return a > b ? a : b;
}

static void ptree_recalc_height(psync_tree *e) {
  e->height =
      ptree_max(ptree_height(e->left), ptree_height(e->right)) +
      1;
}

static psync_tree *ptree_rotate_left(psync_tree *e) {
  psync_tree *e2;
  e2 = e->right;
  e2->parent = e->parent;
  e->right = e2->left;
  if (e->right) {
    e->right->parent = e;
    ptree_recalc_height(e);
  } else
    e->height = ptree_height(e->left) + 1;
  e->parent = e2;
  e2->left = e;
  ptree_recalc_height(e2);
  return e2;
}

static psync_tree *ptree_rotate_right(psync_tree *e) {
  psync_tree *e2;
  e2 = e->left;
  e2->parent = e->parent;
  e->left = e2->right;
  if (e->left) {
    e->left->parent = e;
    ptree_recalc_height(e);
  } else
    e->height = ptree_height(e->right) + 1;
  e->parent = e2;
  e2->right = e;
  ptree_recalc_height(e2);
  return e2;
}

psync_tree *ptree_init_node(psync_tree *node) {
  node->left = NULL;
  node->right = NULL;
  node->parent = NULL;
  node->height = 1;
  return node;
}

static psync_tree *ptree_go_up_rebalance_add(psync_tree *tree,
                                                  psync_tree *e) {
  long int lheight, rheight, dheight;
up:
  lheight = ptree_height(e->left);
  rheight = ptree_height(e->right);
  dheight = lheight - rheight;
  if (dheight == 0)
    return tree;
  else if (dheight == 1 || dheight == -1) {
    e->height = rheight + (dheight + 1) / 2 + 1;
    if (e->parent) {
      e = e->parent;
      goto up;
    } else {
      pdbg_assert(tree == e);
      return tree;
    }
  } else if (dheight == 2) {
    if (ptree_height(e->left->right) > ptree_height(e->left->left))
      e->left = ptree_rotate_left(e->left);
    if (e == tree)
      return ptree_rotate_right(e);
    else {
      psync_tree *e2 = e->parent;
      if (e2->left == e)
        e2->left = ptree_rotate_right(e);
      else {
        pdbg_assert(e2->right == e);
        e2->right = ptree_rotate_right(e);
      }
      return tree;
    }
  } else {
    pdbg_assert(dheight == -2);
    if (ptree_height(e->right->left) > ptree_height(e->right->right))
      e->right = ptree_rotate_right(e->right);
    if (e == tree)
      return ptree_rotate_left(e);
    else {
      psync_tree *e2 = e->parent;
      if (e2->left == e)
        e2->left = ptree_rotate_left(e);
      else {
        pdbg_assert(e2->right == e);
        e2->right = ptree_rotate_left(e);
      }
      return tree;
    }
  }
}

psync_tree *ptree_get_add_after(psync_tree *tree, psync_tree *node,
                                     psync_tree *newnode) {
  if (!tree)
    return ptree_init_node(newnode);
  if (!node)
    return ptree_get_add_before(tree, ptree_get_first(tree), newnode);
  ptree_init_node(newnode);
  if (node->right) {
    node = node->right;
    while (node->left)
      node = node->left;
    node->left = newnode;
  } else
    node->right = newnode;
  newnode->parent = node;
  return ptree_go_up_rebalance_add(tree, node);
}

psync_tree *ptree_get_add_before(psync_tree *tree, psync_tree *node,
                                      psync_tree *newnode) {
  if (!tree)
    return ptree_init_node(newnode);
  if (!node)
    return ptree_get_add_after(tree, ptree_get_last(tree), newnode);
  ptree_init_node(newnode);
  if (node->left) {
    node = node->left;
    while (node->right)
      node = node->right;
    node->right = newnode;
  } else
    node->left = newnode;
  newnode->parent = node;
  return ptree_go_up_rebalance_add(tree, node);
}

psync_tree *ptree_get_added_at(psync_tree *tree, psync_tree *parent,
                                    psync_tree *newnode) {
  ptree_init_node(newnode);
  newnode->parent = parent;
  if (parent)
    return ptree_go_up_rebalance_add(tree, parent);
  else
    return tree;
}

static psync_tree *ptree_go_up_rebalance_del(psync_tree *tree,
                                                  psync_tree *e) {
  long int lheight, rheight, dheight;
up:
  lheight = ptree_height(e->left);
  rheight = ptree_height(e->right);
  dheight = lheight - rheight;
  if (dheight == 0) {
    e->height = rheight + 1;
    if (e->parent) {
      e = e->parent;
      goto up;
    } else {
      pdbg_assert(tree == e);
      return tree;
    }
  } else if (dheight == 1 || dheight == -1)
    return tree;
  else if (dheight == 2) {
    if (ptree_height(e->left->right) > ptree_height(e->left->left))
      e->left = ptree_rotate_left(e->left);
    if (e == tree)
      return ptree_rotate_right(e);
    else {
      psync_tree *e2 = e->parent;
      if (e2->left == e)
        e2->left = ptree_rotate_right(e);
      else {
        pdbg_assert(e2->right == e);
        e2->right = ptree_rotate_right(e);
      }
      e = e2;
      goto up;
    }
  } else {
    pdbg_assert(dheight == -2);
    if (ptree_height(e->right->left) > ptree_height(e->right->right))
      e->right = ptree_rotate_right(e->right);
    if (e == tree)
      return ptree_rotate_left(e);
    else {
      psync_tree *e2 = e->parent;
      if (e2->left == e)
        e2->left = ptree_rotate_left(e);
      else {
        pdbg_assert(e2->right == e);
        e2->right = ptree_rotate_left(e);
      }
      e = e2;
      goto up;
    }
  }
}

static psync_tree *ptree_replace_me_with(psync_tree *tree,
                                              psync_tree *node,
                                              psync_tree *repl) {
  psync_tree *parent;
  parent = node->parent;
  if (!parent) {
    pdbg_assert(tree == node);
    tree = repl;
  } else if (node == parent->left)
    parent->left = repl;
  else {
    pdbg_assert(node == parent->right);
    parent->right = repl;
  }
  if (repl)
    repl->parent = parent;
  if (parent)
    return ptree_go_up_rebalance_del(tree, parent);
  else if (!tree)
    return NULL;
  else
    return ptree_go_up_rebalance_del(tree, tree);
}

psync_tree *ptree_get_del(psync_tree *tree, psync_tree *node) {
  if (!node->left && !node->right)
    return ptree_replace_me_with(tree, node, NULL);
  else if (!node->left)
    return ptree_replace_me_with(tree, node, node->right);
  else if (!node->right)
    return ptree_replace_me_with(tree, node, node->left);
  else {
    psync_tree *el, *parent, **addr;
    if (node->left->height > node->right->height) {
      el = node->left;
      addr = &node->left;
      while (el->right) {
        addr = &el->right;
        el = el->right;
      }
      parent = el->parent;
      *addr = el->left;
      if (el->left)
        el->left->parent = parent;
    } else {
      el = node->right;
      addr = &node->right;
      while (el->left) {
        addr = &el->left;
        el = el->left;
      }
      parent = el->parent;
      *addr = el->right;
      if (el->right)
        el->right->parent = parent;
    }
    memcpy(el, node, sizeof(psync_tree));
    if (parent == node)
      parent = el;
    if (node->left)
      node->left->parent = el;
    if (node->right)
      node->right->parent = el;
    if (node->parent) {
      if (node->parent->left == node)
        node->parent->left = el;
      else {
        pdbg_assert(node->parent->right == node);
        node->parent->right = el;
      }
    } else {
      pdbg_assert(node == tree);
      tree = el;
    }
    return ptree_go_up_rebalance_del(tree, parent);
  }
}