/** 
 * @file llthread.h
 * @brief Base classes for thread, mutex and condition handling.
 *
 * $LicenseInfo:firstyear=2004&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010-2013, Linden Research, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * 
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_LLTHREAD_H
#define LL_LLTHREAD_H

#include "llapp.h"
#include "llapr.h"
#include "llrefcount.h"
#include <thread>

namespace LLTrace
{
    class ThreadRecorder;
}

class LL_COMMON_API LLThread
{
private:
    friend class LLMutex;

public:
    typedef enum e_thread_status
    {
        STOPPED = 0,    // The thread is not running.  Not started, or has exited its run function
        RUNNING = 1,    // The thread is currently running
        QUITTING= 2,    // Someone wants this thread to quit
        CRASHED = -1    // An uncaught exception was thrown by the thread
    } EThreadStatus;
    typedef std::thread::id id_t;

    LLThread(const std::string& name, apr_pool_t *poolp = NULL);
    virtual ~LLThread(); // Warning!  You almost NEVER want to destroy a thread unless it's in the STOPPED state.
    virtual void shutdown(); // stops the thread
    
    bool isQuitting() const { return (QUITTING == mStatus); }
    bool isStopped() const { return (STOPPED == mStatus) || (CRASHED == mStatus); }
    bool isCrashed() const { return (CRASHED == mStatus); } 
    
    static id_t currentID(); // Return ID of current thread
    static void yield(); // Static because it can be called by the main thread, which doesn't have an LLThread data structure.
    
public:
    // PAUSE / RESUME functionality. See source code for important usage notes.
    // Called from MAIN THREAD.
    void pause();
    void unpause();
    bool isPaused() { return isStopped() || mPaused == TRUE; }
    
    // Cause the thread to wake up and check its condition
    void wake();

    // Same as above, but to be used when the condition is already locked.
    void wakeLocked();

    // Called from run() (CHILD THREAD). Pause the thread if requested until unpaused.
    void checkPause();

    // this kicks off the apr thread
    void start(void);

    LLVolatileAPRPool* getLocalAPRFilePool() { return mLocalAPRFilePoolp ; }

    id_t getID() const { return mID; }

    // Called by threads *not* created via LLThread to register some
    // internal state used by LLMutex.  You must call this once early
    // in the running thread to prevent collisions with the main thread.
    static void registerThreadID();
    
private:
    bool                mPaused;
    std::thread::native_handle_type mNativeHandle; // for termination in case of issues
    
    // static function passed to APR thread creation routine
    void threadRun();

protected:
    std::string         mName;
    class LLCondition*  mRunCondition;
    LLMutex*            mDataLock;

    std::thread        *mThreadp;
    EThreadStatus       mStatus;
    id_t                mID;
    LLTrace::ThreadRecorder* mRecorder;

    //a local apr_pool for APRFile operations in this thread. If it exists, LLAPRFile::sAPRFilePoolp should not be used.
    //Note: this pool is used by APRFile ONLY, do NOT use it for any other purposes.
    //      otherwise it will cause severe memory leaking!!! --bao
    LLVolatileAPRPool  *mLocalAPRFilePoolp ; 

    void setQuitting();
    
    // virtual function overridden by subclass -- this will be called when the thread runs
    virtual void run(void) = 0; 
    
    // virtual predicate function -- returns true if the thread should wake up, false if it should sleep.
    virtual bool runCondition(void);

    // Lock/Unlock Run Condition -- use around modification of any variable used in runCondition()
    void lockData();
    void unlockData();
    
    // This is the predicate that decides whether the thread should sleep.  
    // It should only be called with mDataLock locked, since the virtual runCondition() function may need to access
    // data structures that are thread-unsafe.
    bool shouldSleep(void) { return (mStatus == RUNNING) && (isPaused() || (!runCondition())); }

    // To avoid spurious signals (and the associated context switches) when the condition may or may not have changed, you can do the following:
    // mDataLock->lock();
    // if(!shouldSleep())
    //     mRunCondition->signal();
    // mDataLock->unlock();
};


//============================================================================

// Simple responder for self destructing callbacks
// Pure virtual class
class LL_COMMON_API LLResponder : public LLThreadSafeRefCount
{
protected:
    virtual ~LLResponder() = default;
public:
    virtual void completed(bool success) = 0;
};

//============================================================================

extern LL_COMMON_API void assert_main_thread();
extern LL_COMMON_API bool on_main_thread();

#endif // LL_LLTHREAD_H
