/*
 * Copyright 2002-2014 the original author or authors.
 *
 * 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
 *
 *      https://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 org.springframework.util;

import java.io.Serializable;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Simple customizable helper class for creating new {@link Thread} instances.
 * Provides various bean properties: thread name prefix, thread priority, etc.
 *
 * <p>Serves as base class for thread factories such as
 * {@link org.springframework.scheduling.concurrent.CustomizableThreadFactory}.
 *
 * @author Juergen Hoeller
 * @since 2.0.3
 * @see org.springframework.scheduling.concurrent.CustomizableThreadFactory
 */
@SuppressWarnings("serial")
public class CustomizableThreadCreator implements Serializable {

        private String threadNamePrefix;

        private int threadPriority = Thread.NORM_PRIORITY;

        private boolean daemon = false;

        private ThreadGroup threadGroup;

        private final AtomicInteger threadCount = new AtomicInteger(0);


        /**
         * Create a new CustomizableThreadCreator with default thread name prefix.
         */
        public CustomizableThreadCreator() {
                this.threadNamePrefix = getDefaultThreadNamePrefix();
        }

        /**
         * Create a new CustomizableThreadCreator with the given thread name prefix.
         * @param threadNamePrefix the prefix to use for the names of newly created threads
         */
        public CustomizableThreadCreator(String threadNamePrefix) {
                this.threadNamePrefix = (threadNamePrefix != null ? threadNamePrefix : getDefaultThreadNamePrefix());
        }


        /**
         * Specify the prefix to use for the names of newly created threads.
         * Default is "SimpleAsyncTaskExecutor-".
         */
        public void setThreadNamePrefix(String threadNamePrefix) {
                this.threadNamePrefix = (threadNamePrefix != null ? threadNamePrefix : getDefaultThreadNamePrefix());
        }

        /**
         * Return the thread name prefix to use for the names of newly
         * created threads.
         */
        public String getThreadNamePrefix() {
                return this.threadNamePrefix;
        }

        /**
         * Set the priority of the threads that this factory creates.
         * Default is 5.
         * @see java.lang.Thread#NORM_PRIORITY
         */
        public void setThreadPriority(int threadPriority) {
                this.threadPriority = threadPriority;
        }

        /**
         * Return the priority of the threads that this factory creates.
         */
        public int getThreadPriority() {
                return this.threadPriority;
        }

        /**
         * Set whether this factory is supposed to create daemon threads,
         * just executing as long as the application itself is running.
         * <p>Default is "false": Concrete factories usually support explicit cancelling.
         * Hence, if the application shuts down, Runnables will by default finish their
         * execution.
         * <p>Specify "true" for eager shutdown of threads which still actively execute
         * a {@link Runnable} at the time that the application itself shuts down.
         * @see java.lang.Thread#setDaemon
         */
        public void setDaemon(boolean daemon) {
                this.daemon = daemon;
        }

        /**
         * Return whether this factory should create daemon threads.
         */
        public boolean isDaemon() {
                return this.daemon;
        }

        /**
         * Specify the name of the thread group that threads should be created in.
         * @see #setThreadGroup
         */
        public void setThreadGroupName(String name) {
                this.threadGroup = new ThreadGroup(name);
        }

        /**
         * Specify the thread group that threads should be created in.
         * @see #setThreadGroupName
         */
        public void setThreadGroup(ThreadGroup threadGroup) {
                this.threadGroup = threadGroup;
        }

        /**
         * Return the thread group that threads should be created in
         * (or {@code null} for the default group).
         */
        public ThreadGroup getThreadGroup() {
                return this.threadGroup;
        }


        /**
         * Template method for the creation of a new {@link Thread}.
         * <p>The default implementation creates a new Thread for the given
         * {@link Runnable}, applying an appropriate thread name.
         * @param runnable the Runnable to execute
         * @see #nextThreadName()
         */
        public Thread createThread(Runnable runnable) {
                Thread thread = new Thread(getThreadGroup(), runnable, nextThreadName());
                thread.setPriority(getThreadPriority());
                thread.setDaemon(isDaemon());
                return thread;
        }

        /**
         * Return the thread name to use for a newly created {@link Thread}.
         * <p>The default implementation returns the specified thread name prefix
         * with an increasing thread count appended: e.g. "SimpleAsyncTaskExecutor-0".
         * @see #getThreadNamePrefix()
         */
        protected String nextThreadName() {
                return getThreadNamePrefix() + this.threadCount.incrementAndGet();
        }

        /**
         * Build the default thread name prefix for this factory.
         * @return the default thread name prefix (never {@code null})
         */
        protected String getDefaultThreadNamePrefix() {
                return ClassUtils.getShortName(getClass()) + "-";
        }

}