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));
	}
}