package eu.siacs.conversations.crypto.sasl;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * A tokenizer for GS2 header strings
 */
public final class Tokenizer implements Iterator<String>, Iterable<String> {
	private final List<String> parts;
	private int index;

	public Tokenizer(final byte[] challenge) {
		final String challengeString = new String(challenge);
		parts = new ArrayList<>(Arrays.asList(challengeString.split(",")));
		// Trim parts.
		for (int i = 0; i < parts.size(); i++) {
			parts.set(i, parts.get(i).trim());
		}
		index = 0;
	}

	/**
	 * Returns true if there is at least one more element, false otherwise.
	 *
	 * @see #next
	 */
	@Override
	public boolean hasNext() {
		return parts.size() != index + 1;
	}

	/**
	 * Returns the next object and advances the iterator.
	 *
	 * @return the next object.
	 * @throws java.util.NoSuchElementException if there are no more elements.
	 * @see #hasNext
	 */
	@Override
	public String next() {
		if (hasNext()) {
			return parts.get(index++);
		} else {
			throw new NoSuchElementException("No such element. Size is: " + parts.size());
		}
	}

	/**
	 * Removes the last object returned by {@code next} from the collection.
	 * This method can only be called once between each call to {@code next}.
	 *
	 * @throws UnsupportedOperationException if removing is not supported by the collection being
	 *                                       iterated.
	 * @throws IllegalStateException         if {@code next} has not been called, or {@code remove} has
	 *                                       already been called after the last call to {@code next}.
	 */
	@Override
	public void remove() {
		if(index <= 0) {
			throw new IllegalStateException("You can't delete an element before first next() method call");
		}
		parts.remove(--index);
	}

	/**
	 * Returns an {@link java.util.Iterator} for the elements in this object.
	 *
	 * @return An {@code Iterator} instance.
	 */
	@Override
	public Iterator<String> iterator() {
		return parts.iterator();
	}
}
