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package org.javimmutable.collections.iterators;

import javax.annotation.Nonnull;
import java.util.Iterator;

public class IteratorHelper
{
    public static boolean iteratorEquals(@Nonnull Iterator a,
                                         @Nonnull Iterator b)
    {
        while (a.hasNext() && b.hasNext()) {
            final Object av = a.next();
            final Object bv = b.next();
            if ((av != bv) && (av == null || !av.equals(bv))) {
                return false;
            }
        }
        return a.hasNext() == b.hasNext();
    }

    public static int iteratorHashCode(@Nonnull Iterator a)
    {
        int hashCode = 0;
        while (a.hasNext()) {
            final Object value = a.next();
            final int valueHashCode = (value == null) ? 0 : value.hashCode();
            hashCode = 31 * hashCode + valueHashCode;
        }
        return hashCode;
    }

    public static String iteratorToString(Iterator iterator)
    {
        StringBuilder sb = new StringBuilder();
        sb.append("[");
        while (iterator.hasNext()) {
            if (sb.length() > 1) {
                sb.append(",");
            }
            Object value = iterator.next();
            if (value == null) {
                sb.append("null");
            } else {
                sb.append(value);
            }
        }
        sb.append("]");
        return sb.toString();
    }

    /**
     * Utility method, useful in unit tests, that essentially casts away actual type of an object
     * so that Iterable version of an overload is triggered instead of more specific class.
     */
    public static  Iterable plainIterable(Iterable values)
    {
        return () -> values.iterator();
    }
}