/*
 * Copyright (c) 1998, 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */


package com.sun.tools.example.debug.tty;

import com.sun.jdi.ThreadGroupReference;
import com.sun.jdi.ThreadReference;
import java.util.List;
import java.util.Iterator;
import java.util.NoSuchElementException;

class ThreadIterator implements Iterator<ThreadReference> {
    Iterator<ThreadReference> it = null;
    ThreadGroupIterator tgi;
    Iterator<ThreadInfo> vthreadIter;

    ThreadIterator(ThreadGroupReference tg) {
        tgi = new ThreadGroupIterator(tg);
        if (tg == Env.vm().topLevelThreadGroups().get(0)) {
            // This means all groups are included, so include vthreads.
            vthreadIter = ThreadInfo.vthreads().iterator();
        }
    }

    ThreadIterator() {
        tgi = new ThreadGroupIterator();
        vthreadIter = ThreadInfo.vthreads().iterator();
    }

    @Override
    public boolean hasNext() {
        while (it == null || !it.hasNext()) {
            if (!tgi.hasNext()) {
                return (vthreadIter == null ? false : vthreadIter.hasNext());
            } else {
                it = tgi.nextThreadGroup().threads().iterator();
            }
        }
        return true;
    }

    @Override
    public ThreadReference next() {
        if (it.hasNext()) {
            return it.next();
        } else {
            if (vthreadIter == null) {
                throw new NoSuchElementException();
            } else {
                return vthreadIter.next().getThread();
            }
        }
    }

    public ThreadReference nextThread() {
        return next();
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }
}