/**
 * CSE 373, Spring 2011, Jessica Miller
 * A set for Strings backed by a hash table.  The hash table is using separate 
 * chaining as its collision resolution strategy.
 */
public class StringHashSet implements StringSet {
    private static final int DEFAULT_SIZE = 11;
    private StringHashEntry[] table;
    private int size;
    
    public StringHashSet() {
        this(DEFAULT_SIZE);
    }
    
    public StringHashSet(int tableSize) {
        table = new StringHashEntry[tableSize];
        size = 0;
    }
    
    /** 
     * Adds the specified String to the Set if it is not already present.
     * @return true if this set did not already contain the String 
     */
    public boolean add(String value) {
    	// does the set already contain the value?
        if (contains(value)) {
        	return false;
        }    	
    	
        // figure out where value should go...
        int bucket = hash(value);
        
        // insert the new value
        StringHashEntry newEntry = new StringHashEntry(value, table[bucket]);
        table[bucket] = newEntry;
        size++;
        
        return true;
    }

    /**
     * Returns true if the set contains the specified String.
     */
    public boolean contains(String value) {
        // figure out where value should be...
        int bucket = hash(value);
        
        // check to see if the value is in the set
        StringHashEntry temp = table[bucket];
        while (temp != null) {
            if (temp.data.equals(value)) {
                return true;
            }
            temp = temp.next;
        }
        
        // otherwise, the value was not found
        return false;
    }
    
    /**
     * Prints the set in a hash table-like format.
     */
    public void print() {
        for (int i = 0; i < table.length; i++) {
            System.out.printf("%d: ", i);
            
            StringHashEntry temp = table[i];
            while (temp != null) {
                System.out.print(temp.data);
                if (temp.next != null) {
                    System.out.print(" --> ");
                }
                temp = temp.next;
            }
            
            System.out.println();
        }
    }

    /**
     * Removes the specified String from this set if it is present.
     * @return true if this set contained the specified element 
     */
    public boolean remove(String value) {
        return false;
    }
    
    /**
     * Returns the number of elements in this set (its cardinality)
     */
    public int size() {
        return size;
    }
    
    /**
     * Calculating a String's hash value via polynomial accumulation and 
     * Horner's rule.
     * @param data
     * @return
     */
    private int hash(String data) {
        int hashVal = 0;
        
        for (int i = 0; i < data.length(); i++) {
            hashVal = 37 * hashVal + data.charAt(i);
        }
        
        hashVal %= table.length;
        if (hashVal < 0) {
            hashVal += table.length;
        }
        
        return hashVal;
    }
}