import java.util.ArrayList;

/**
 * Posting list deals with the operations of a posting list and a
 * term list. <p>
 *
 * @author cs379/csci335 students of 2004/2006
 * @revised Xiannong Meng
 * @date 2013-04-26
 * 
 * <p>Revision notes: simplified the posting list to be just posting node
 * each of which contains a doc name and a term frequency.</p>
 */
public class PostingList {

    /*
     * Data members
     */
    public static boolean DEBUG = false;
    // public static boolean DEBUG = true;

    private ArrayList<PostingHeader> termList;

    /**
     * Default constructor.<p>
     */
    public PostingList() {
	
	this.termList = new ArrayList<PostingHeader>();
    }

    /**
     * <p>Adding a new term to the term list.</p>
     * 
     * <p>Precondition: The term does not exist in the list.</p>
     * <p>Postcondition: The term now is on the list.</p>
     * 
     * @param term The new term to add to the list
     * @param docName The name of the document that contains this
     *        term.
     */
    public void addTerm(String term, String docName) {

	PostingHeader node = new PostingHeader(term, docName, 1);
	this.termList.add(node);
    }

    /**
     * <p>Update the posting list node when a term is already
     * on the term list.</p>
     * <p>Two scenarios:</p>
     *    <ul>
     *      <li> The docName is not on the posting list, add the docName
     *           to the posting list.
     *      <li> The docName is already on the posting list, update the 
     *           term frequency.
     *    </ul>
     *
     * <p>Precondition: The term is on the term list, thus a valid "termIndex"
     *                  has been found.</p>
     * <p>Postcondition: The term and document information updated 
     *                   accordingly.</p>
     *
     * @param termIndex The index in the term array list
     * @param docName   The name of the document
     */
    public void updateTerm(int termIndex, String docName) {

	int index = this.getDocIndex(termIndex, docName);
	if (index == -1) { // the doc node is not on the posting list
	    PostingNode pNode = new PostingNode(docName, 1);
	    this.termList.get(termIndex).postList.add(pNode);
	    this.termList.get(termIndex).incDocFreq();
	} else {  // the doc node exists, update frequency
	    this.termList.get(termIndex).postList.get(index).incTF();
	}
    }

    /**
     * <p>Find the index of the document named 'dName' on the posting list.</p>
     *
     * <p>Precondition: the document name is given as 'dName'</p>
     * <p>Postcondition: the index of the doucment is given. If not found, a 
     *                   -1 is returned.</p>
     *
     * @param termIndex The index of the term on the term list.
     * @param dName The name of the doucment
     * @return The index of the document, if found; -1 if not found.
     */
    public int getDocIndex(int termIndex, String dName) {

	for (int i = 0; 
	     i < this.termList.get(termIndex).postList.size(); 
	     i ++) {
	    PostingNode pNode = this.termList.get(termIndex).postList.get(i);
	    if (dName.compareToIgnoreCase(pNode.getDocName()) == 0)
		return i;  // found
	}

	return -1;  // not found
    }

    /**
     * <p>Find the index of the term in the term list. Returns -1
     * if the term has not been in the list yet.</p>
     *
     * @param term The term to be searched
     * @return The location of the term in the term list, -1 if not existing.
     */
    public int getTermIndex(String term) {

	for (int i = 0; i < this.termList.size(); i ++) {
	    String head = this.termList.get(i).term;
	    if (term.compareToIgnoreCase(head) == 0)
		return i;  // found
	}

	return -1;  // not found
    }

    /**
     * <P>Print the entire term list, along with each postig list.</p>
     */
    public String toString() {

	String retString = "";
	// for each term
	for (int t = 0; t < this.termList.size(); t ++) {
	    PostingHeader ph = this.termList.get(t);
	    retString += "Term : " + ph.term + "\n";
	    retString += "   Doc Frequency : " + ph.docFrequency + "\n";
	    retString += "   Doc List : ";
	    ArrayList<PostingNode> pl = ph.postList;
	    // for each node on the posting list of the term
	    for (int d = 0; d < pl.size(); d ++) {
		retString += " | " + pl.get(d).docName + ", " +
		    pl.get(d).tf + " | ";
	    }
	    retString += "\n";
	}

	return retString;
    }

    public static void main(String args[]) {

	// some simple test cases
	PostingList plist = new PostingList();

	plist.addTerm("hello", "d1.txt");
	plist.addTerm("world", "d2.txt");
	plist.addTerm("how", "d1.txt");
	plist.addTerm("are", "d1.txt");
	plist.addTerm("you", "d2.txt");

	int i = plist.getTermIndex("hello");
	if (i != -1) {
	    System.out.println("found 'hello' at " + i + " updating ...");
	    plist.updateTerm(i, "d1.txt");
	    plist.updateTerm(i, "d2.txt");
	    plist.updateTerm(i, "d3.txt");
	}

	i = plist.getTermIndex("you");
	if (i != -1) {
	    System.out.println("found 'you' at " + i + " updating ...");
	    plist.updateTerm(i, "d2.txt");
	    plist.updateTerm(i, "d2.txt");
	    plist.updateTerm(i, "d2.txt");
	    plist.updateTerm(i, "d1.txt");
	    plist.updateTerm(i, "d4.txt");
	    plist.updateTerm(i, "d5.txt");
	}

	System.out.println(plist);
    }
}