/*]  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 moof {


/**
 * 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() :
		thread_(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)
	{
		thread::function* fcopy = new thread::function(function);
		SDL_Thread* thread = SDL_CreateThread(&thread::run, (void*)fcopy);
		if (thread == 0) delete fcopy;
		return moof::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(thread_, &i);
		thread_ = 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(thread_);
		thread_ = 0;
	}

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


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

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


private:

	thread(SDL_Thread* thread) :
		thread_(thread) {}

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


	SDL_Thread* thread_;
};


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

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

	/**
	 * Get whether or not the task is done.
	 * \return True if the task is done, false otherwise.
	 */
	virtual bool is_done() 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 threaded_task
{
public:

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

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


protected:

	class thread thread_;
};


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

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

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


	/**
	 * 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 acquire_lock()
	{
		return (SDL_LockMutex(mutex_) == 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 release_lock()
	{
		return (SDL_UnlockMutex(mutex_) == 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) :
			mutex_(mutex),
			is_locked_(false) {}

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


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

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


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


    protected:

        mutex&	mutex_;
        bool	is_locked_;

        friend class condition;
    };

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

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

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


private:

    SDL_mutex* mutex_;

    friend class condition;
};


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

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

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


	/**
	 * 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(condition_, mutex.mutex_) == 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(condition_, lock.mutex_.mutex_) == 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(condition_, mutex.mutex_, 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(condition_,
									lock.mutex_.mutex_, ms) == 0);
	}


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

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


private:

    SDL_cond* condition_;
};


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

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

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


	/**
	 * 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 acquire_lock()
	{
		return (SDL_SemWait(semaphore_) == 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 acquire_lock(scalar timeout)
	{
		Uint32 ms = timeout * SCALAR(1000.0);
		return (SDL_SemWaitTimeout(semaphore_, 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 release_lock()
	{
		return (SDL_SemPost(semaphore_) == 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 try_lock()
	{
		return (SDL_SemTryWait(semaphore_) == 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) :
			semaphore_(semaphore),
			is_locked_(false) {}

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

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

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

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

    protected:

        semaphore&	semaphore_;
        bool		is_locked_;
    };
    
	/**
	 * This type of lock tries to acquire a lock on the semaphore during
	 * construction and releases the lock on deconstruction.
	 */
    class scoped_lock : private lock
    {
    public:

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

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


private:

    SDL_sem* semaphore_;
};


} // namespace moof

#endif // _MOOF_THREAD_HH_