package com.fr.third.googlecode.javaewah32;

import static com.fr.third.googlecode.javaewah.EWAHCompressedBitmap.wordinbits;

import com.fr.third.googlecode.javaewah.IntIterator;

/*
 * Copyright 2009-2013, Daniel Lemire, Cliff Moon, David McIntosh, Robert Becho, Google Inc., Veronika Zenz and Owen Kaser
 * Licensed under the Apache License, Version 2.0.
 */
/**
 * Implementation of an IntIterator over an IteratingRLW.
 * 
 *
 */
public class IntIteratorOverIteratingRLW32 implements IntIterator {
        IteratingRLW32 parent;
        private int position;
        private int runningLength;
        private int word;
        private int wordPosition;
        private int wordLength;
        private int literalPosition;
        private boolean hasnext;

        /**
         * @param p iterator we wish to iterate over
         */
        public IntIteratorOverIteratingRLW32(final IteratingRLW32 p) {
                this.parent = p;
                this.position = 0;
                setupForCurrentRunningLengthWord();
                this.hasnext = moveToNext(); 
        }

        /**
         * @return whether we could find another set bit; don't move if there is an unprocessed value
         */
        private final boolean moveToNext() {
            while (!runningHasNext() && !literalHasNext()) {
                if (this.parent.next())
                    setupForCurrentRunningLengthWord();
                else return false;
            }
            return true;
        }

        @Override
        public boolean hasNext() {
                return this.hasnext;
        }

        @Override
        public final int next() {
                final int answer;
                if (runningHasNext()) {
                        answer = this.position++;
                } else {
                        final int bit = Long.numberOfTrailingZeros(this.word);
                        this.word ^= (1l << bit);
                        answer = this.literalPosition + bit;
                }
                this.hasnext = this.moveToNext();
                return answer;
        }

        private final void setupForCurrentRunningLengthWord() {
                this.runningLength = wordinbits * this.parent.getRunningLength()
                                + this.position;

                if (!this.parent.getRunningBit()) {
                        this.position = this.runningLength;
                }
                this.wordPosition = 0;  
                this.wordLength = this.parent.getNumberOfLiteralWords();
        }

        private final boolean runningHasNext() {
                return this.position < this.runningLength;
        }

        private final boolean literalHasNext() {
                while (this.word == 0 && this.wordPosition < this.wordLength) {
                        this.word = this.parent.getLiteralWordAt(this.wordPosition++);
                        this.literalPosition = this.position;
                        this.position += wordinbits;
                }
                return this.word != 0;
        }
}