package algs62; // section 6.2
import stdlib.*;
/* ***********************************************************************
 *  Compilation:  javac BTree.java
 *  Execution:    java BTree
 *
 *  B-tree.
 *
 *  Limitations
 *  -----------
 *   -  Assumes M is even and M >= 4
 *   -  should b be an array of children or list (it would help with
 *      casting to make it a list)
 *
 *************************************************************************/

public class BTree<K extends Comparable<? super K>, V>  {
  private static final int M = 4;    // max children per B-tree node = M-1

  private Node<K,V> root;        // root of the B-tree
  private int HT;           // height of the B-tree
  private int N;            // number of key-value pairs in the B-tree

  // helper B-tree node data type
  private static class Node<K extends Comparable<? super K>, V> {
    public int m;                                // number of children
    @SuppressWarnings("unchecked")
    public final Entry<K,V>[] children = new Entry[M];
    public Node(int k) { m = k; }                      // create a node with k children
  }

  // internal nodes: only use key and next
  // external nodes: only use key and value
  private static class Entry<K extends Comparable<? super K>, V> {
    K key;
    V value;
    Node<K,V> next;     // helper field to iterate over array entries
    public Entry(K key, V value, Node<K,V> next) {
      this.key   = key;
      this.value = value;
      this.next  = next;
    }
  }

  // constructor
  public BTree() { root = new Node<>(0); }

  // return number of key-value pairs in the B-tree
  public int size() { return N; }

  // return height of B-tree
  public int height() { return HT; }


  // search for given key, return associated value; return null if no such key
  public V get(K key) { return search(root, key, HT); }
  private V search(Node<K,V> x, K key, int ht) {
    Entry<K,V>[] children = x.children;

    // external node
    if (ht == 0) {
      for (int j = 0; j < x.m; j++) {
        if (eq(key, children[j].key)) return children[j].value;
      }
    }

    // internal node
    else {
      for (int j = 0; j < x.m; j++) {
        if (j+1 == x.m || less(key, children[j+1].key))
          return search(children[j].next, key, ht-1);
      }
    }
    return null;
  }


  // insert key-value pair
  // add code to check for duplicate keys
  public void put(K key, V value) {
    Node<K,V> u = insert(root, key, value, HT);
    N++;
    if (u == null) return;

    // need to split root
    Node<K,V> t = new Node<>(2);
    t.children[0] = new Entry<>(root.children[0].key, null, root);
    t.children[1] = new Entry<>(u.children[0].key, null, u);
    root = t;
    HT++;
  }


  private Node<K,V> insert(Node<K,V> h, K key, V value, int ht) {
    int j;
    Entry<K,V> t = new Entry<>(key, value, null);

    // external node
    if (ht == 0) {
      for (j = 0; j < h.m; j++) {
        if (less(key, h.children[j].key)) break;
      }
    }

    // internal node
    else {
      for (j = 0; j < h.m; j++) {
        if ((j+1 == h.m) || less(key, h.children[j+1].key)) {
          Node<K,V> u = insert(h.children[j++].next, key, value, ht-1);
          if (u == null) return null;
          t.key = u.children[0].key;
          t.next = u;
          break;
        }
      }
    }

    for (int i = h.m; i > j; i--) h.children[i] = h.children[i-1];
    h.children[j] = t;
    h.m++;
    if (h.m < M) return null;
    else         return split(h);
  }

  // split node in half
  private Node<K,V> split(Node<K,V> h) {
    Node<K,V> t = new Node<>(M/2);
    h.m = M/2;
    for (int j = 0; j < M/2; j++)
      t.children[j] = h.children[M/2+j];
    return t;
  }

  // for debugging
  public String toString() {
    return toString(root, HT, "") + "\n";
  }
  private String toString(Node<K,V> h, int ht, String indent) {
    String s = "";
    Entry<K,V>[] children = h.children;

    if (ht == 0) {
      for (int j = 0; j < h.m; j++) {
        s += indent + children[j].key + " " + children[j].value + "\n";
      }
    }
    else {
      for (int j = 0; j < h.m; j++) {
        if (j > 0) s += indent + "(" + children[j].key + ")\n";
        s += toString(children[j].next, ht-1, indent + "     ");
      }
    }
    return s;
  }


  private boolean less(K k1, K k2) {
    return k1.compareTo(k2) < 0;
  }

  private boolean eq(K k1, K k2) {
    return k1.compareTo(k2) == 0;
  }


  /* ***********************************************************************
   *  test client
   *************************************************************************/
  public static void main(String[] args) {
    BTree<String, String> st = new BTree<>();

    //      st.put("www.cs.princeton.edu", "128.112.136.12");
    st.put("www.cs.princeton.edu", "128.112.136.11");
    st.put("www.princeton.edu",    "128.112.128.15");
    st.put("www.yale.edu",         "130.132.143.21");
    st.put("www.simpsons.com",     "209.052.165.60");
    st.put("www.apple.com",        "17.112.152.32");
    st.put("www.amazon.com",       "207.171.182.16");
    st.put("www.ebay.com",         "66.135.192.87");
    st.put("www.cnn.com",          "64.236.16.20");
    st.put("www.google.com",       "216.239.41.99");
    st.put("www.nytimes.com",      "199.239.136.200");
    st.put("www.microsoft.com",    "207.126.99.140");
    st.put("www.dell.com",         "143.166.224.230");
    st.put("www.slashdot.org",     "66.35.250.151");
    st.put("www.espn.com",         "199.181.135.201");
    st.put("www.weather.com",      "63.111.66.11");
    st.put("www.yahoo.com",        "216.109.118.65");


    StdOut.println("cs.princeton.edu:  " + st.get("www.cs.princeton.edu"));
    StdOut.println("hardvardsucks.com: " + st.get("www.harvardsucks.com"));
    StdOut.println("simpsons.com:      " + st.get("www.simpsons.com"));
    StdOut.println("apple.com:         " + st.get("www.apple.com"));
    StdOut.println("ebay.com:          " + st.get("www.ebay.com"));
    StdOut.println("dell.com:          " + st.get("www.dell.com"));
    StdOut.println();

    StdOut.println("size:    " + st.size());
    StdOut.println("height:  " + st.height());
    StdOut.println(st);
    StdOut.println();
  }

}