/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
**]  All rights reserved.
*
* vi:ts=4 sw=4 tw=75
*
* Distributable under the terms and conditions of the 2-clause BSD license;
* see the file COPYING for a complete text of the license.
*
**************************************************************************/

/**
 * \file Thread.hh
 * Light C++ wrapper around the SDL threads API.
 */

#ifndef _MOOF_THREAD_HH_
#define _MOOF_THREAD_HH_

#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <SDL/SDL.h>

#include <Moof/Math.hh>


namespace Mf {


/**
 * Represents a thread which may be running.  You cannot instantiate a
 * thread object directly; new threads are created by detaching functions
 * using the detach() method.  Once a thread is detached, it will continue
 * running until the function returns.  You don't need to keep the thread
 * object you want to wait() or kill() the thread later.
 */
class Thread
{
public:

	typedef boost::function<int(void)> Function;


	/**
	 * Construct an invalid thread object which has no association with any
	 * real thread.
	 */
	Thread() :
		mThread(0) {}

	/**
	 * Execute a function in a new thread.
	 * \param function The function to execute.
	 * \return The new thread, or an invalid thread if an error occurred.
	 */
	static Thread detach(const Function& function)
	{
		Function* fcopy = new Function(function);
		SDL_Thread* thread = SDL_CreateThread(&Thread::run, (void*)fcopy);
		if (thread == 0) delete fcopy;
		return Thread(thread);
	}


	/**
	 * Wait for the thread to terminate, getting its return value.  The
	 * thread will be invalidated.
	 * \return The integer value returned by the detached function.
	 */
	int wait()
	{
		int i;
		SDL_WaitThread(mThread, &i);
		mThread = 0;
		return i;
	}

	/**
	 * Forcefully kill the thread without giving it a chance to clean up
	 * after itself.  The thread will be invalidated.  Don't use this.
	 */
	void kill()
	{
		SDL_KillThread(mThread);
		mThread = 0;
	}

	/**
	 * Get whether or not the thread object is associated with a real
	 * thread.
	 * \return True if the thread is valid, false otherwise.
	 */
	bool isValid() const
	{
		return mThread != 0;
	}


	/**
	 * Get a unique identifier for this thread, if it is valid.
	 * \return The identifier.
	 */
	uint32_t identifier() const
	{
		return SDL_GetThreadID(mThread);
	}

	/**
	 * Get the unique identifier of the calling thread.
	 * \return The identifier.
	 */
	static uint32_t currentIdentifier()
	{
		return SDL_ThreadID();
	}


private:

	Thread(SDL_Thread* thread) :
		mThread(thread) {}

	static int run(void* arg)
	{
		int code = (*(Function*)arg)();
		delete (Function*)arg;
		return code;
	}


	SDL_Thread* mThread;
};


/**
 * An abstract class representing some task that is to be run
 * asynchronously.
 */
class AsyncTask
{
public:

	/**
	 * Deconstruct the task.
	 */
	virtual ~AsyncTask() {}

	/**
	 * Get whether or not the task is done.
	 * \return True if the task is done, false otherwise.
	 */
	virtual bool isDone() const = 0;

	/**
	 * Begin the task.
	 */
	virtual void run() = 0;

	/**
	 * Block the current thread until the task is finished.
	 * \return A value representing the state of the finished task.
	 */
	virtual int wait() = 0;
};

/**
 * An asynchronous task that is run to be executed in a separated thread.
 */
class ThreadedTask
{
public:

	/**
	 * Get the thread object the task is executing in.
	 * \return The thread.
	 */
	const Thread& thread() const { return mThread; }

	/**
	 * Block the current thread until the task thread is finished.
	 * \return The integer value returned by the task function.
	 */
	int wait()
	{
		return mThread.wait();
	}


protected:

	Thread mThread;
};


/**
 * A mutex to protect sensitive sections of code from threads which might
 * otherwise cause unpredictable results.
 */
class Mutex
{
public:

	/**
	 * Construct a mutex.
	 */
    Mutex() :
		mMutex(SDL_CreateMutex()) {}

	/**
	 * Deconstruct a mutex.
	 */
    ~Mutex()
	{
		SDL_DestroyMutex(mMutex);
	}


	/**
	 * Block until the calling thread can secure exclusive access to the
	 * code protected by the mutex.
	 * \return True if the lock was acquired, false otherwise.
	 * \see Lock
	 */
    bool acquireLock()
	{
		return (SDL_LockMutex(mMutex) == 0);
	}

	/**
	 * Unlock the mutex.  Call this after the sensitive block of code to
	 * allow another thread to acquire the lock.
	 * \return True if the mutex was unlocked, false otherwise.
	 * \see Lock
	 */
    bool releaseLock()
	{
		return (SDL_UnlockMutex(mMutex) == 0);
	}


	/**
	 * As an alternative method for locking, objects of this class will
	 * automagically release the lock if it is still locked at
	 * deconstruction.  Therefore, it's generally safer to use this method
	 * since it makes it much more difficult to forget to unlock a mutex.
	 */
    class Lock
    {
    public:

		/**
		 * Construct a lock.
		 * \param mutex The mutex.
		 */
        explicit Lock(Mutex& mutex) :
			mMutex(mutex),
			mIsLocked(false) {}

		/**
		 * Deconstruct a lock.  The lock is automagically released if it is
		 * still locked.
		 */
        ~Lock()
		{
			if (mIsLocked) release();
		}


		/**
		 * Try to acquire a lock on the mutex.
		 * \return True if the mutex was locked, false otherwise.
		 */
        bool acquire()
		{
			return (mIsLocked = mMutex.acquireLock());
		}

		/**
		 * Release the lock.
		 * \return True if the mutex was unlocked, false otherwise.
		 */
        bool release()
		{
			bool result = mMutex.releaseLock();
			mIsLocked = false;
			return result;
		}


		/**
		 * Get whether or not the mutex is locked.
		 * \return True if the mutex is locked, false otherwise.
		 */
        bool isLocked() const
		{
			return mIsLocked;
		}


    protected:

        Mutex&	mMutex;
        bool	mIsLocked;

        friend class Condition;
    };

	/**
	 * This type of lock tries to acquire a lock on the mutex during
	 * construction and releases the lock on deconstruction.
	 */
    class ScopedLock : private Lock
    {
	public:

		/**
		 * Construct a lock.
		 * \param mutex The mutex.
		 */
		explicit ScopedLock(Mutex& mutex) :
			Lock(mutex)
		{
			acquire();
		}

		/**
		 * Get whether or not the mutex is locked.
		 * \return True if the mutex is locked, false otherwise.
		 */
		bool isLocked() const
		{
			return Lock::isLocked();
		}
    };


private:

    SDL_mutex* mMutex;

    friend class Condition;
};


/**
 * A class representing a condition variable.
 */
class Condition
{
public:

	/**
	 * Construct a condition.
	 */
    Condition()
	{
		mCondition = SDL_CreateCond();
	}

	/**
	 * Deconstruct a condition.
	 */
    ~Condition()
	{
		SDL_DestroyCond(mCondition);
	}


	/**
	 * Unlock the mutex and wait for another thread to notify the thread,
	 * at which point the mutex will be re-locked and the method will
	 * return.
	 * \param mutex The mutex.
	 * \return True if the thread was notified, false otherwise.
	 */
	bool wait(Mutex& mutex)
	{
        return (SDL_CondWait(mCondition, mutex.mMutex) == 0);
	}

	/**
	 * Unlock the mutex associated with a lock and wait for another thread
	 * to notify the thread, at which point the lock will be re-locked and
	 * the method will return.
	 * \param lock The lock.
	 * \return True if the thread was notified, false otherwise.
	 */
    bool wait(Mutex::Lock& lock)
	{
        return (SDL_CondWait(mCondition, lock.mMutex.mMutex) == 0);
    }

	/**
	 * Unlock the mutex and wait for another thread to notify the thread,
	 * at which point the mutex will be re-locked and the method will
	 * return.  If the thread was not notified before a certain number of
	 * seconds, the method will return anyway.
	 * \param mutex The mutex.
	 * \param timeout Number of seconds to wait.
	 * \return True if the thread was notified, false otherwise.
	 */
    bool wait(Mutex& mutex, Scalar timeout)
	{
		Uint32 ms = timeout * SCALAR(1000.0);
        return (SDL_CondWaitTimeout(mCondition, mutex.mMutex, ms) == 0);
	}

	/**
	 * Unlock the mutex associated with a lock and wait for another thread
	 * to notify the thread, at which point the lock will be re-locked and
	 * the method will return.  If the thread was not notified before a
	 * certain number of seconds, the method will return anyway.
	 * \param lock The lock.
	 * \param timeout Number of seconds to wait.
	 * \return True if the thread was notified, false otherwise.
	 */
    bool wait(Mutex::Lock& lock, Scalar timeout)
	{
		Uint32 ms = timeout * SCALAR(1000.0);
        return (SDL_CondWaitTimeout(mCondition,
									lock.mMutex.mMutex, ms) == 0);
	}


	/**
	 * Notify one other thread that is waiting on the condition.
	 * \return True on success, false otherwise.
	 */
    bool notify()
	{
		return (SDL_CondSignal(mCondition) == 0);
	}

	/**
	 * Notify all other threads that are waiting on the condition.
	 * \return True on success, false otherwise.
	 */
    bool notifyAll()
	{
		return (SDL_CondBroadcast(mCondition) == 0);
	}


private:

    SDL_cond* mCondition;
};


/**
 * A semaphore class.
 */
class Semaphore
{
public:

	/**
	 * Construct a semaphore.
	 * \param value The initial value of the semaphore.
	 */
    explicit Semaphore(uint32_t value)
	{
		mSemaphore = SDL_CreateSemaphore(value);
	}

	/**
	 * Deconstruct a semaphore.
	 */
    ~Semaphore()
	{
		SDL_DestroySemaphore(mSemaphore);
	}


	/**
	 * Block until the calling thread can secure exclusive access to the
	 * code protected by the semaphore.
	 * \return True if the lock was acquired, false otherwise.
	 * \see Lock
	 */
    bool acquireLock()
	{
		return (SDL_SemWait(mSemaphore) == 0);
	}

	/**
	 * Block until the calling thread can secure exclusive access to the
	 * code protected by the semaphore, or until the timeout expires.
	 * \param timeout Number of seconds to try.
	 * \return True if the lock was acquired, false otherwise.
	 */
	bool acquireLock(Scalar timeout)
	{
		Uint32 ms = timeout * SCALAR(1000.0);
		return (SDL_SemWaitTimeout(mSemaphore, ms) == 0);
	}

	/**
	 * Unlock the semaphore.  Call this after the sensitive block of code
	 * to allow another thread to acquire the lock.
	 * \return True if the semaphore was unlocked, false otherwise.
	 * \see Lock
	 */
    bool releaseLock()
	{
		return (SDL_SemPost(mSemaphore) == 0);
	}

	/**
	 * Try to lock the semaphore, but don't block if the lock is not
	 * immediately available.
	 * \return True if the semaphore was locked, false otherwise.
	 */
    bool tryLock()
	{
		return (SDL_SemTryWait(mSemaphore) == 0);
	}

	/**
	 * As an alternative method for locking, objects of this class will
	 * automagically release the lock if it is still locked at
	 * deconstruction.  Therefore, it's generally safer to use this method
	 * since it makes it much more difficult to forget to unlock a
	 * semaphore.
	 */
    class Lock
    {
    public:

		/**
		 * Construct a lock.
		 * \param semaphore The semaphore.
		 */
        explicit Lock(Semaphore& semaphore) :
			mSemaphore(semaphore),
			mIsLocked(false) {}

		/**
		 * Deconstruct a lock.  The lock is automagically released if it is
		 * still locked.
		 */
        ~Lock()
		{
			if (mIsLocked) release();
		}
        

		/**
		 * Try to acquire a lock on the semaphore.
		 * \return True if the semaphore was locked, false otherwise.
		 */
        bool acquire()
		{
			return (mIsLocked = mSemaphore.acquireLock());
		}

		/**
		 * Release the lock.
		 * \return True if the semaphore was unlocked, false otherwise.
		 */
        bool release()
		{
			bool result = mSemaphore.releaseLock();
			mIsLocked = false;
			return result;
		}

		/**
		 * Get whether or not the semaphore is locked.
		 * \return True if the semaphore is locked, false otherwise.
		 */
        bool isLocked() const
		{
			return mIsLocked;
		}
        

    protected:

        Semaphore&	mSemaphore;
        bool		mIsLocked;
    };
    
	/**
	 * This type of lock tries to acquire a lock on the semaphore during
	 * construction and releases the lock on deconstruction.
	 */
    class ScopedLock : private Lock
    {
    public:

		/**
		 * Construct a lock.
		 * \param semaphore The semaphore.
		 */
        explicit ScopedLock(Semaphore& semaphore) :
			Lock(semaphore)
		{
			acquire();
		}

		/**
		 * Get whether or not the semaphore is locked.
		 * \return True if the semaphore is locked, false otherwise.
		 */
		bool isLocked() const
		{
			return Lock::isLocked();
		}
    };


private:

    SDL_sem* mSemaphore;
};


} // namespace Mf

#endif // _MOOF_THREAD_HH_