001/***************************************************
002 * Licensed under MIT No Attribution (SPDX: MIT-0) *
003 ***************************************************/
004
005package org.reactivestreams.tck.flow.support;
006
007import java.util.Collections;
008import java.util.Iterator;
009import java.util.concurrent.Executor;
010
011import org.reactivestreams.example.unicast.AsyncIterablePublisher;
012
013public class HelperPublisher<T> extends AsyncIterablePublisher<T> {
014  
015    public HelperPublisher(final int from, final int to, final Function<Integer, T> create, final Executor executor) {
016        super(new Iterable<T>() {
017          { if(from > to) throw new IllegalArgumentException("from must be equal or greater than to!"); }
018          @Override public Iterator<T> iterator() {
019            return new Iterator<T>() {
020              private int at = from;
021              @Override public boolean hasNext() { return at < to; }
022              @Override public T next() {
023                if (!hasNext()) return Collections.<T>emptyList().iterator().next();
024                else try {
025                  return create.apply(at++);
026                } catch (Throwable t) {
027                  throw new IllegalStateException(String.format("Failed to create element for id %d!", at - 1), t);
028                }
029              }
030              @Override public void remove() { throw new UnsupportedOperationException(); }
031            };
032          }
033        }, executor);
034    }
035}