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package com.oracle.truffle.js.test.threading;

import static org.junit.Assert.assertTrue;

import java.util.Queue;
import java.util.concurrent.LinkedBlockingDeque;

import org.graalvm.polyglot.Context;
import org.graalvm.polyglot.HostAccess;
import org.graalvm.polyglot.Value;
import org.junit.Test;

public class JavaAsyncTaskScheduler {

    
Utility class simulating an asynchronous event from Java.
/**
     * Utility class simulating an asynchronous event from Java.
     */
    public static class Example {
        // a concurrent queue shared with Node
        private final Queue<Object> queue;

        public Example(Queue<Object> queue) {
            this.queue = queue;
        }

        public void doAsynchronousWork() {
            // simulate asynchronous events, e.g., an HTTP request, and notify back once received.
            Thread thread = new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        throw new AssertionError();
                    }
                    double data = Math.random() + 42;
                    // awake the Node.js worker, which is waiting on this queue
                    queue.offer(data);
                }
            });
            thread.start();
        }

        public static Object evalJsCode() {
            Context context = TestUtil.newContextBuilder().build();
            return context.eval("js", "42;");
        }
    }

    
Java synchronization (e.g., a blocking queue) can be used to "awake" JavaScript code.
/**
     * Java synchronization (e.g., a blocking queue) can be used to "awake" JavaScript code.
     */
    @Test
    public void testJavaWakeup() {
        Context cx = TestUtil.newContextBuilder().allowHostAccess(HostAccess.ALL).build();
        Queue<Object> sharedQueue = new LinkedBlockingDeque<>();
        Example async = new Example(sharedQueue);

        cx.getBindings("js").putMember("queue", sharedQueue);
        cx.getBindings("js").putMember("javaAsync", async);
        try {
            Value data = cx.eval("js", "javaAsync.doAsynchronousWork();" +
                            // Block until the queue has work to offer
                            "var data = queue.take();" +
                            "data;");
            assertTrue(data.fitsInDouble());
            assertTrue(data.asDouble() >= 42);
        } finally {
            cx.close();
        }
    }
}