/*
	Data structure to hold a frequency List of words (e.g., from a text)
	Written 2/98, revised 2/04 by Kim Bruce
*/

import structure.*;

public class FreqList {

	// vector of associations holding words and their frequencies
	Vector flist;			
	
	int totalOccurrences;	// total # of instances of words held in list
	
	// Create empty list of word frequencies
	public FreqList(){
		totalOccurrences = 0;
		flist = new Vector();
	}
	
	// post:  if word was not in frequency list it is added w/ frequency of 1,
	//		if already in, then increase frequency by 1
	public void add(String word){
		// Association w/ word
		Association assoc = new Association(word);  
		
		int wordNo = flist.indexOf(assoc);	// location of word in list
		
		if (wordNo == -1){				// word was not in list, insert it
			assoc.setValue(new Integer(1));
			flist.add(assoc);
		} else {								// word was in list, bump frequency
			Association element = (Association)flist.get(wordNo);
			int newValue = ((Integer)(element.getValue())).intValue() + 1;
			element.setValue(new Integer(newValue));
		}
		totalOccurrences++;
	}
	
	// pre: 0 <= prob <= 1
	// post:  Returns a word chosen randomly from the words in the list.  
	//    The probability of a word being chosen is proportional to its
	//		frequency stored in the list.
	public String get(double prob){
		int count = 0;						// sum of frequencies seen so far
		
			// number between 0 and size of list - 1 (inclusive)
		int target = (int)Math.round(prob * (totalOccurrences-1));	

		Association element=null;		// word, frequency pairs from list

			// search until count exceeds random target
		for(int wordNo = 0; count <= target && wordNo < flist.size(); wordNo++) {
			element = (Association)flist.get(wordNo);
			
				// # of occurrences of elt
			int numOccurrences = ((Integer)element.getValue()).intValue();	
			count = count + numOccurrences;
		}
		return (String)element.getKey();
	}
	
	// return string describing all words and frequencies in the list
	public String toString() {
		String answer = "";		// string to accumulate description
		
		for (int wordNo=0; wordNo < flist.size(); wordNo++) {
			Association temp = (Association)flist.get(wordNo);
			answer = answer + "The word \"" + temp.getKey()
								+"\" occurs "+temp.getValue()+" times.\n";
		}
		
		return answer;
	}
		
		
	public static void main(String args[]) {
		FreqList list = new FreqList();
		String testString = "The quick brown fox jumped over the lazy dog "
			+"the fox was too quick for the dog";
		String[] substring = testString.toLowerCase().split(" ");
		
		// Add words to frequency list
		for (int wordNo = 0; wordNo < substring.length; wordNo++){
			list.add(substring[wordNo]);
		}
		System.out.println(list);

		// Pick some words w/ carefully chosen "random" numbers to make sure "get"
		// works properly.  Note advantage of passing in parameter in testing!
		System.out.println(list.get(0.1));
		System.out.println(list.get(1.0));
		System.out.println(list.get(0.5));
	}
}