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ixjava developed by David Karnok
There is a newer version: 1.0.0
/*
 * Copyright 2011-2016 David Karnok
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package ix;

import java.util.Iterator;
import java.util.concurrent.Callable;

final class IxFlattenIterable extends IxSource {

    final IxFunction> mapper;

    IxFlattenIterable(Iterable source, IxFunction> mapper) {
        super(source);
        this.mapper = mapper;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Iterator iterator() {
        if (source instanceof Callable) {
            return (Iterator)(mapper.apply(checkedCall((Callable)source)).iterator());
        }
        return new FlattenIterator(source.iterator(), mapper);
    }

    static final class FlattenIterator extends IxSourceIterator {

        final IxFunction> mapper;

        Iterator current;

        FlattenIterator(Iterator it, IxFunction> mapper) {
            super(it);
            this.mapper = mapper;
        }

        @SuppressWarnings("unchecked")
        @Override
        protected boolean moveNext() {
            Iterator c = current;

            while (c == null) {
                if (it.hasNext()) {
                    Iterable inner = mapper.apply(it.next());
                    if (inner instanceof Callable) {
                        value = checkedCall((Callable)inner);
                        hasValue = true;
                        return true;
                    }

                    c = inner.iterator();

                    if (c.hasNext()) {
                        current = c;
                        break;
                    } else {
                        c = null;
                    }
                } else {
                    done = true;
                    return false;
                }
            }

            value = c.next();
            hasValue = true;

            if (!c.hasNext()) {
                current = null;
            }
            return true;
        }

    }

}