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package org.jruby.ext.thread;

import java.util.concurrent.locks.ReentrantLock;
import org.jruby.Ruby;
import org.jruby.RubyBoolean;
import org.jruby.RubyClass;
import org.jruby.RubyObject;
import org.jruby.RubyThread;
import org.jruby.RubyTime;
import org.jruby.anno.JRubyClass;
import org.jruby.anno.JRubyMethod;
import org.jruby.runtime.Block;
import org.jruby.runtime.ObjectAllocator;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;

/**
 * The "Mutex" class from the 'thread' library.
 */
@JRubyClass(name = "Mutex")
public class Mutex extends RubyObject {
    ReentrantLock lock = new ReentrantLock();

    @JRubyMethod(name = "new", rest = true, meta = true)
    public static Mutex newInstance(ThreadContext context, IRubyObject recv, IRubyObject[] args, Block block) {
        Mutex result = new Mutex(context.runtime, (RubyClass) recv);
        result.callInit(context, args, block);
        return result;
    }

    public Mutex(Ruby runtime, RubyClass type) {
        super(runtime, type);
    }

    public static void setup(Ruby runtime) {
        RubyClass cMutex = runtime.getThread().defineClassUnder("Mutex", runtime.getObject(), new ObjectAllocator() {

            public IRubyObject allocate(Ruby runtime, RubyClass klass) {
                return new Mutex(runtime, klass);
            }
        });
        cMutex.setReifiedClass(Mutex.class);
        cMutex.defineAnnotatedMethods(Mutex.class);
        runtime.getObject().setConstant("Mutex", cMutex);
    }

    @JRubyMethod(name = "locked?")
    public synchronized RubyBoolean locked_p(ThreadContext context) {
        return context.runtime.newBoolean(lock.isLocked());
    }

    @JRubyMethod
    public RubyBoolean try_lock(ThreadContext context) {
        if (lock.isHeldByCurrentThread()) {
            return context.fals;
        }
        return context.runtime.newBoolean(context.getThread().tryLock(lock));
    }

    @JRubyMethod
    public IRubyObject lock(ThreadContext context) {
        RubyThread thread = context.getThread();
        try {
            thread.enterSleep();
            checkRelocking(context);
            thread.lock(lock);
        } finally {
            thread.exitSleep();
        }
        return this;
    }

    @JRubyMethod
    public synchronized IRubyObject unlock(ThreadContext context) {
        Ruby runtime = context.runtime;
        if (!lock.isLocked()) {
            throw runtime.newThreadError("Mutex is not locked");
        }
        if (!lock.isHeldByCurrentThread()) {
            throw runtime.newThreadError("Mutex is not owned by calling thread");
        }

        boolean hasQueued = lock.hasQueuedThreads();
        context.getThread().unlock(lock);
        return hasQueued ? context.nil : this;
    }

    @JRubyMethod
    public IRubyObject sleep(ThreadContext context) {
        long beg = System.currentTimeMillis();
        try {
            unlock(context);
            context.getThread().sleep(0);
        } catch (InterruptedException ex) {
            // ignore interrupted
        } finally {
            lock(context);
        }
        return context.runtime.newFixnum((System.currentTimeMillis() - beg) / 1000);
    }

    @JRubyMethod
    public IRubyObject sleep(ThreadContext context, IRubyObject timeout) {
        final long beg = System.currentTimeMillis();
        double t = RubyTime.convertTimeInterval(context, timeout);

        unlock(context);

        try {
            long millis = (long) (t * 1000);

            if (Double.compare(t, 0.0d) == 0 || millis == 0) {
                // wait time is zero or smaller than 1ms, so we just proceed
            } else {
                context.getThread().sleep(millis);
            }
        } catch (InterruptedException ex) {
            // ignore interrupted
        } finally {
            lock(context);
        }

        return context.runtime.newFixnum((System.currentTimeMillis() - beg) / 1000);
    }

    @JRubyMethod
    public IRubyObject synchronize(ThreadContext context, Block block) {
        lock(context);
        try {
            return block.yieldSpecific(context);
        } finally {
            unlock(context);
        }
    }

    @JRubyMethod(name = "owned?")
    public IRubyObject owned_p(ThreadContext context) {
        return context.runtime.newBoolean(lock.isHeldByCurrentThread());
    }

    private void checkRelocking(ThreadContext context) {
        if (lock.isHeldByCurrentThread()) {
            throw context.runtime.newThreadError("Mutex relocking by same thread");
        }
    }

}