#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

typedef struct bstree {
  int key;
  char *value;

  struct bstree *left;
  struct bstree *right;
} TREE_NODE;

TREE_NODE *tree_create(int key, char *value) {
  TREE_NODE *node;
  node = malloc(sizeof(TREE_NODE));
  if (node == NULL) {
    fprintf(stderr, "Error allocating node");
    return NULL;
  }
  node->key = key;
  node->value = value;
  node->left = NULL;
  node->right = NULL;
  return node;
}

void add_leaf(int key, char *value, TREE_NODE *tree) {
  TREE_NODE *node;
  node = tree_create(key, value);
  if (tree == NULL) {
    return;
  }

  while (tree != NULL) {
    if (key < tree->key) {
      if (tree->left == NULL) {
        tree->left = node;
        return;
      } else {
        tree = tree->left;
      }
    } else if (key > tree->key) {
      if (tree->right == NULL) {
        tree->right = node;
        return;
      } else {
        tree = tree->right;
      }
    } else
      return;
  }
}

TREE_NODE *tree_lookup(TREE_NODE *tree, int key) {
  while (tree != NULL) {
    if (key == tree->key) {
      return tree;
    } else if (key < tree->key) {
      tree = tree->left;
    } else {
      tree = tree->right;
    }
  }
  return tree;
}

TREE_NODE *parent_lookup(TREE_NODE *tree, int key) {
  while (tree != NULL) {
    if ((tree->left != NULL && (key == (tree->left)->key)) ||
        (tree->right != NULL && (key == (tree->right)->key))) {
      return tree;
    } else if (key < tree->key) {
      tree = tree->left;
    } else {
      tree = tree->right;
    }
  }
  return tree;
}

void delete_node(TREE_NODE *tree, int key) {

  TREE_NODE *node = tree_lookup(tree, key);
  tree = parent_lookup(tree, key);

  if (node->left == NULL && node->right == NULL) {
    if (tree->left == node) {
      free(node);
      tree->left = NULL;
    } else {
      free(node);
      tree->right = NULL;
    }
  } else if (node->left != NULL && node->right == NULL) {
    if (tree->left == node) {
      tree->left = node->left;
      free(node);
    } else {
      tree->right = node->left;
      free(node);
    }
  } else if (node->left == NULL && node->right != NULL) {
    if (tree->left == node) {
      tree->left = node->right;
      free(node);
    } else {
      tree->right = node->right;
      free(node);
    }
  } else {
    if ((node->right)->left == NULL) {
      tree = node->right;
      node->key = tree->key;
      node->value = tree->value;
      node->right = tree->right;
      free(tree);
    } else {
      tree = node;
      while (tree->left != NULL) {
        tree = tree->left;
      }
      node->key = tree->key;
      node->value = tree->value;
      free(tree);
    }
  }
  return;
}

int main(int argc, char const *argv[]) {
  TREE_NODE *tree;
  tree = tree_create(180, "First");
  add_leaf(50, "second", tree);
  add_leaf(250, "third", tree);
  add_leaf(40, "fourth", tree);
  add_leaf(30, "fifth", tree);
  add_leaf(45, "sixth", tree);
  add_leaf(44, "seventh", tree);
  delete_node(tree, 45);
  return 0;
}
/*
                180
              /    \
            50      250
          /
        40
      /    \
    30     45
         /
        44
*/