// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/delete-a-node-with-one-child-in-a-binary-search-tree

var displayTree = (tree) => console.log(JSON.stringify(tree, null, 2));
function Node(value) {
  this.value = value;
  this.left = null;
  this.right = null;
}

function BinarySearchTree() {
  this.root = null;
  // Only change code below this line
  this.remove = (value) => {
    let parent = null;
    let node = this.root;
    while (node !== null && node.value !== value) {
      parent = node;
      if (node.value < value) {
        node = node.right;
      } else {
        node = node.left;
      }
    }
    if (node === null) return null;
    let child = null;
    if (node.left !== null && node.right === null) child = node.left;
    else if (node.left === null && node.right !== null) child = node.right;
    else if (node.left !== null && node.right !== null) {
      let smallestRightNodeParent = node;
      let smallestRightNode = node.right;
      while (smallestRightNode.left !== null) {
        smallestRightNodeParent = smallestRightNode;
        smallestRightNode = smallestRightNode.left;
      }
      node.value = smallestRightNode.value;
      if (smallestRightNodeParent !== node)
        smallestRightNodeParent.left = smallestRightNode.right;
      else node.right = null;
      return;
    }
    if (parent === null) this.root = child;
    else if (parent.value < value) {
      parent.right = child;
    } else {
      parent.left = child;
    }
  };
}