/*
 * Copyright 2019 Hippo Seven
 *
 * 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 com.hippo.util;

import androidx.annotation.NonNull;

import com.hippo.yorozuya.thread.PriorityThreadFactory;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class IoThreadPoolExecutor extends ThreadPoolExecutor {

    private final static ThreadPoolExecutor INSTANCE =
            IoThreadPoolExecutor.newInstance(3, 32, 1L, TimeUnit.SECONDS,
                    new PriorityThreadFactory("IO", android.os.Process.THREAD_PRIORITY_BACKGROUND));

    private IoThreadPoolExecutor(
            int corePoolSize,
            int maximumPoolSize,
            long keepAliveTime,
            TimeUnit unit,
            BlockingQueue<Runnable> workQueue,
            ThreadFactory threadFactory,
            RejectedExecutionHandler handler
    ) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
    }

    public static ThreadPoolExecutor getInstance() {
        return INSTANCE;
    }

    private static ThreadPoolExecutor newInstance(
            int corePoolSize,
            int maximumPoolSize,
            long keepAliveTime,
            TimeUnit unit,
            ThreadFactory threadFactory
    ) {
        ThreadQueue queue = new ThreadQueue();
        PutRunnableBackHandler handler = new PutRunnableBackHandler();
        IoThreadPoolExecutor executor = new IoThreadPoolExecutor(
                corePoolSize, maximumPoolSize, keepAliveTime, unit, queue, threadFactory, handler);
        queue.setThreadPoolExecutor(executor);
        return executor;
    }

    private static class ThreadQueue extends LinkedBlockingQueue<Runnable> {

        private ThreadPoolExecutor executor;

        void setThreadPoolExecutor(ThreadPoolExecutor executor) {
            this.executor = executor;
        }

        @Override
        public boolean offer(@NonNull Runnable o) {
            int allWorkingThreads = executor.getActiveCount() + super.size();
            return allWorkingThreads < executor.getPoolSize() && super.offer(o);
        }
    }

    public static class PutRunnableBackHandler implements RejectedExecutionHandler {
        public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
            try {
                executor.getQueue().put(r);
            } catch (InterruptedException e) {
                throw new RejectedExecutionException(e);
            }
        }
    }
}