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package org.jruby.ext.fiber;

import org.jruby.Ruby;
import org.jruby.RubyThread;
import org.jruby.exceptions.RaiseException;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

/**
 * A RubyThread-aware BlockingQueue wrapper used by Fiber for transferring values.
 */
public class FiberQueue {
    protected BlockingQueue queue;
    protected final Ruby runtime;

    public FiberQueue(Ruby runtime) {
        this.runtime = runtime;
        this.queue = new ArrayBlockingQueue<>(1, false);
    }

    final RubyThread.Task takeTask = new RubyThread.Task() {
        @Override
        public IRubyObject run(ThreadContext context, FiberQueue queue) throws InterruptedException {
            return queue.getQueueSafe().take();
        }

        @Override
        public void wakeup(RubyThread thread, FiberQueue data) {
            thread.getNativeThread().interrupt();
        }
    };

    final RubyThread.Task putTask = new RubyThread.Task() {
        @Override
        public IRubyObject run(ThreadContext context, IRubyObject[] args) throws InterruptedException {
            final BlockingQueue queue = getQueueSafe();
            if(args.length == 2 && args[1].isTrue() && queue.remainingCapacity() == 0) {
                throw context.runtime.newThreadError("queue full");
            }
            queue.put(args[0]);
            return context.nil;
        }

        @Override
        public void wakeup(RubyThread thread, IRubyObject[] data) {
            thread.getNativeThread().interrupt();
        }
    };

    public IRubyObject shutdown(ThreadContext context) {
        queue = null;
        return context.nil;
    }
    
    public synchronized void shutdown() {
        queue = null;
    }

    public boolean isShutdown() {
        return queue == null;
    }

    public BlockingQueue getQueueSafe() {
        BlockingQueue queue = this.queue;
        checkShutdown();
        return queue;
    }

    public synchronized void checkShutdown() {
        if (queue == null) {
            throw RaiseException.from(runtime, runtime.getThreadError(), "queue shut down");
        }
    }

    public IRubyObject pop(ThreadContext context) {
        return pop(context, true);
    }

    public IRubyObject pop(ThreadContext context, IRubyObject arg0) {
        return pop(context, !arg0.isTrue());
    }

    public void push(ThreadContext context, final IRubyObject[] args) {
        checkShutdown();
        try {
            context.getThread().executeTask(context, args, putTask);
        } catch (InterruptedException ie) {
            throw context.runtime.newThreadError("interrupted in FiberQueue.push");
        }
    }

    private IRubyObject pop(ThreadContext context, boolean should_block) {
        final BlockingQueue queue = getQueueSafe();
        if (!should_block && queue.size() == 0) {
            throw RaiseException.from(context.runtime, context.runtime.getThreadError(), "queue empty");
        }
        try {
            return context.getThread().executeTask(context, this, takeTask);
        } catch (InterruptedException ie) {
            throw context.runtime.newThreadError("interrupted in FiberQueue.pop");
        }
    }
    
}