package algs34;
import stdlib.*;
import algs13.Queue;
/* ***********************************************************************
 *  Compilation:  javac LinearProbingHashST.java
 *  Execution:    java LinearProbingHashST
 *
 *  Symbol table implementation with linear probing hash table.
 *
 *  % java LinearProbingHashST
 *  128.112.136.11
 *  208.216.181.15
 *  null
 *
 *
 *************************************************************************/


public class LinearProbingHashST<K, V> {
  private static final int INIT_CAPACITY = 4;

  private int N;       // number of key-value pairs in the symbol table
  private int M;       // size of linear probing table
  private K[] keys;    // the keys
  private V[] vals;    // the values


  // create an empty hash table - use 16 as default size
  public LinearProbingHashST() {
    this(INIT_CAPACITY);
  }

  // create linear proving hash table of given capacity
  @SuppressWarnings("unchecked")
  public LinearProbingHashST(int capacity) {
    M = capacity;
    keys = (K[]) new Object[M];
    vals = (V[]) new Object[M];
  }

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

  // is the symbol table empty?
  public boolean isEmpty() { return size() == 0; }

  // does a key-value pair with the given key exist in the symbol table?
  public boolean contains(K key) { return get(key) != null; }

  // hash function for keys - returns value between 0 and M-1
  private int hash(K key) {
    return (key.hashCode() & 0x7fffffff) % M;
  }

  // resize the hash table to the given capacity by re-hashing all of the keys
  private void resize(int capacity) {
    LinearProbingHashST<K, V> temp = new LinearProbingHashST<>(capacity);
    for (int i = 0; i < M; i++) {
      if (keys[i] != null) {
        temp.put(keys[i], vals[i]);
      }
    }
    keys = temp.keys;
    vals = temp.vals;
    M    = temp.M;
  }

  // insert the key-value pair into the symbol table
  public void put(K key, V val) {
    if (val == null) delete(key);

    // double table size if 50% full
    if (N >= M/2) resize(2*M);

    int i;
    for (i = hash(key); keys[i] != null; i = (i + 1) % M) {
      if (keys[i].equals(key)) { vals[i] = val; return; }
    }
    keys[i] = key;
    vals[i] = val;
    N++;
  }

  // return the value associated with the given key, null if no such value
  public V get(K key) {
    for (int i = hash(key); keys[i] != null; i = (i + 1) % M)
      if (keys[i].equals(key))
        return vals[i];
    return null;
  }

  // delete the key (and associated value) from the symbol table
  public void delete(K key) {
    if (!contains(key)) return;

    // find position i of key
    int i = hash(key);
    while (!key.equals(keys[i])) {
      i = (i + 1) % M;
    }

    // delete key and associated value
    keys[i] = null;
    vals[i] = null;

    // rehash all keys in same cluster
    i = (i + 1) % M;
    while (keys[i] != null) {
      // delete keys[i] an vals[i] and reinsert
      K keyToRehash = keys[i];
      V valToRehash = vals[i];
      keys[i] = null;
      vals[i] = null;
      N--;
      put(keyToRehash, valToRehash);
      i = (i + 1) % M;
    }

    N--;

    // halves size of array if it's 12.5% full or less
    if (N > 0 && N <= M/8) resize(M/2);

    assert check();
  }

  // return all of the keys as in Iterable
  public Iterable<K> keys() {
    Queue<K> queue = new Queue<>();
    for (int i = 0; i < M; i++)
      if (keys[i] != null) queue.enqueue(keys[i]);
    return queue;
  }

  // integrity check - don't check after each put() because
  // integrity not maintained during a delete()
  private boolean check() {

    // check that hash table is at most 50% full
    if (M < 2*N) {
      System.err.println("Hash table size M = " + M + "; array size N = " + N);
      return false;
    }

    // check that each key in table can be found by get()
    for (int i = 0; i < M; i++) {
      if (keys[i] == null) continue;
      else if (get(keys[i]) != vals[i]) {
        System.err.println("get[" + keys[i] + "] = " + get(keys[i]) + "; vals[i] = " + vals[i]);
        return false;
      }
    }
    return true;
  }


  /* *********************************************************************
   *  Unit test client.
   ***********************************************************************/
  public static void main(String[] args) {
    StdIn.fromFile("data/tiny.txt");

    LinearProbingHashST<String, Integer> st = new LinearProbingHashST<>();
    for (int i = 0; !StdIn.isEmpty(); i++) {
      String key = StdIn.readString();
      st.put(key, i);
    }

    // print keys
    for (String s : st.keys())
      StdOut.println(s + " " + st.get(s));
  }
}