using System;
using System.Diagnostics;
using System.Threading;
using DWORD = System.Int32;

namespace Community.CsharpSqlite
{
	public partial class Sqlite3
	{
		/*
		** 2007 August 14
		**
		** The author disclaims copyright to this source code.  In place of
		** a legal notice, here is a blessing:
		**
		**    May you do good and not evil.
		**    May you find forgiveness for yourself and forgive others.
		**    May you share freely, never taking more than you give.
		**
		*************************************************************************
		** This file contains the C functions that implement mutexes for win32
		*************************************************************************
		**  Included in SQLite3 port to C#-SQLite;  2008 Noah B Hart
		**  C#-SQLite is an independent reimplementation of the SQLite software library
		**
		**  SQLITE_SOURCE_ID: 2010-03-09 19:31:43 4ae453ea7be69018d8c16eb8dabe05617397dc4d
		**
		*************************************************************************
		*/
		//#include "sqliteInt.h"

		/*
		** The code in this file is only used if we are compiling multithreaded
		** on a win32 system.
		*/
#if SQLITE_MUTEX_W32

		/*
** Each recursive mutex is an instance of the following structure.
*/

		public partial class sqlite3_mutex
		{
			public Object mutex;    /* Mutex controlling the lock */
			public int id;         /* Mutex type */
			public int nRef;       /* Number of enterances */
			public DWORD owner;    /* Thread holding this mutex */
#if SQLITE_DEBUG
			public int trace;      /* True to trace changes */
#endif

			public sqlite3_mutex()
			{
				mutex = new Object();
			}

			public sqlite3_mutex(Mutex mutex, int id, int nRef, DWORD owner
#if SQLITE_DEBUG
, int trace
#endif
)
			{
				this.mutex = mutex;
				this.id = id;
				this.nRef = nRef;
				this.owner = owner;
#if SQLITE_DEBUG
				this.trace = 0;
#endif
			}
		};

		//#define SQLITE_W32_MUTEX_INITIALIZER { 0 }
		private static Mutex SQLITE_W32_MUTEX_INITIALIZER = null;

#if SQLITE_DEBUG
		//#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0, 0L, (DWORD)0, 0 }
#else
//#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0, 0L, (DWORD)0 }
#endif

		/*
** Return true (non-zero) if we are running under WinNT, Win2K, WinXP,
** or WinCE.  Return false (zero) for Win95, Win98, or WinME.
**
** Here is an interesting observation:  Win95, Win98, and WinME lack
** the LockFileEx() API.  But we can still statically link against that
** API as long as we don't call it win running Win95/98/ME.  A call to
** this routine is used to determine if the host is Win95/98/ME or
** WinNT/2K/XP so that we will know whether or not we can safely call
** the LockFileEx() API.
**
** mutexIsNT() is only used for the TryEnterCriticalSection() API call,
** which is only available if your application was compiled with
** _WIN32_WINNT defined to a value >= 0x0400.  Currently, the only
** call to TryEnterCriticalSection() is #ifdef'ed out, so #if
** this out as well.
*/
#if FALSE
#if SQLITE_OS_WINCE
//# define mutexIsNT()  (1)
#else
static int mutexIsNT(void){
static int osType = 0;
if( osType==0 ){
OSVERSIONINFO sInfo;
sInfo.dwOSVersionInfoSize = sizeof(sInfo);
GetVersionEx(&sInfo);
osType = sInfo.dwPlatformId==VER_PLATFORM_WIN32_NT ? 2 : 1;
}
return osType==2;
}
#endif //* SQLITE_OS_WINCE */
#endif

#if SQLITE_DEBUG
		/*
** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
** intended for use only inside Debug.Assert() statements.
*/

		private static bool winMutexHeld(sqlite3_mutex p)
		{
			return p.nRef != 0 && p.owner == GetCurrentThreadId();
		}

		private static bool winMutexNotheld2(sqlite3_mutex p, DWORD tid)
		{
			return p.nRef == 0 || p.owner != tid;
		}

		private static bool winMutexNotheld(sqlite3_mutex p)
		{
			DWORD tid = GetCurrentThreadId();
			return winMutexNotheld2(p, tid);
		}

#endif

		/*
** Initialize and deinitialize the mutex subsystem.
*/

		//No MACROS under C#; Cannot use SQLITE3_MUTEX_INITIALIZER,
		private static sqlite3_mutex[] winMutex_staticMutexes = new sqlite3_mutex[]{
new sqlite3_mutex( SQLITE_W32_MUTEX_INITIALIZER, 0, 0, (DWORD)0
#if SQLITE_DEBUG
  , 0
#endif
  ),//  SQLITE3_MUTEX_INITIALIZER,
new sqlite3_mutex( SQLITE_W32_MUTEX_INITIALIZER, 0, 0, (DWORD)0
#if SQLITE_DEBUG
  , 0
#endif
  ),//  SQLITE3_MUTEX_INITIALIZER,
new sqlite3_mutex( SQLITE_W32_MUTEX_INITIALIZER, 0, 0, (DWORD)0
#if SQLITE_DEBUG
  , 0
#endif
  ),//  SQLITE3_MUTEX_INITIALIZER,
new sqlite3_mutex( SQLITE_W32_MUTEX_INITIALIZER, 0, 0, (DWORD)0
#if SQLITE_DEBUG
  , 0
#endif
  ),//  SQLITE3_MUTEX_INITIALIZER,
new sqlite3_mutex( SQLITE_W32_MUTEX_INITIALIZER, 0, 0, (DWORD)0
#if SQLITE_DEBUG
  , 0
#endif
  ),//  SQLITE3_MUTEX_INITIALIZER,
new sqlite3_mutex( SQLITE_W32_MUTEX_INITIALIZER, 0, 0, (DWORD)0
#if SQLITE_DEBUG
  , 0
#endif
  ),//  SQLITE3_MUTEX_INITIALIZER,
};

		private static int winMutex_isInit = 0;
		/* As winMutexInit() and winMutexEnd() are called as part
		** of the sqlite3_initialize and sqlite3_shutdown()
		** processing, the "interlocked" magic is probably not
		** strictly necessary.
		*/
		private static long winMutex_lock = 0;

		private static System.Object lockThis = new System.Object();

		private static int winMutexInit()
		{
			/* The first to increment to 1 does actual initialization */

			lock (lockThis)
			//if ( Interlocked.CompareExchange(ref winMutex_lock, 1, 0 ) == 0 )
			{
				int i;
				for (i = 0; i < ArraySize(winMutex_staticMutexes); i++)
				{
					if (winMutex_staticMutexes[i].mutex == null) winMutex_staticMutexes[i].mutex = new Mutex();
					//InitializeCriticalSection( winMutex_staticMutexes[i].mutex );
				}
				winMutex_isInit = 1;
			}
			//else
			//{
			//  /* Someone else is in the process of initing the static mutexes */
			//  while ( 0 == winMutex_isInit )
			//  {
			//    Thread.Sleep( 1 );
			//  }
			//}
			return SQLITE_OK;
		}

		private static int winMutexEnd()
		{
			/* The first to decrement to 0 does actual shutdown
			** (which should be the last to shutdown.) */
			if (Interlocked.CompareExchange(ref winMutex_lock, 0, 1) == 1)
			{
				if (winMutex_isInit == 1)
				{
					int i;
					for (i = 0; i < ArraySize(winMutex_staticMutexes); i++)
					{
						DeleteCriticalSection(winMutex_staticMutexes[i].mutex);
					}
					winMutex_isInit = 0;
				}
			}
			return SQLITE_OK;
		}

		/*
		** The sqlite3_mutex_alloc() routine allocates a new
		** mutex and returns a pointer to it.  If it returns NULL
		** that means that a mutex could not be allocated.  SQLite
		** will unwind its stack and return an error.  The argument
		** to sqlite3_mutex_alloc() is one of these integer constants:
		**
		** <ul>
		** <li>  SQLITE_MUTEX_FAST
		** <li>  SQLITE_MUTEX_RECURSIVE
		** <li>  SQLITE_MUTEX_STATIC_MASTER
		** <li>  SQLITE_MUTEX_STATIC_MEM
		** <li>  SQLITE_MUTEX_STATIC_MEM2
		** <li>  SQLITE_MUTEX_STATIC_PRNG
		** <li>  SQLITE_MUTEX_STATIC_LRU
		** <li>  SQLITE_MUTEX_STATIC_LRU2
		** </ul>
		**
		** The first two constants cause sqlite3_mutex_alloc() to create
		** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
		** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
		** The mutex implementation does not need to make a distinction
		** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
		** not want to.  But SQLite will only request a recursive mutex in
		** cases where it really needs one.  If a faster non-recursive mutex
		** implementation is available on the host platform, the mutex subsystem
		** might return such a mutex in response to SQLITE_MUTEX_FAST.
		**
		** The other allowed parameters to sqlite3_mutex_alloc() each return
		** a pointer to a static preexisting mutex.  Six static mutexes are
		** used by the current version of SQLite.  Future versions of SQLite
		** may add additional static mutexes.  Static mutexes are for internal
		** use by SQLite only.  Applications that use SQLite mutexes should
		** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
		** SQLITE_MUTEX_RECURSIVE.
		**
		** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
		** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
		** returns a different mutex on every call.  But for the static
		** mutex types, the same mutex is returned on every call that has
		** the same type number.
		*/

		private static sqlite3_mutex winMutexAlloc(int iType)
		{
			sqlite3_mutex p;

			switch (iType)
			{
				case SQLITE_MUTEX_FAST:
				case SQLITE_MUTEX_RECURSIVE:
					{
						p = new sqlite3_mutex();//sqlite3MallocZero( sizeof(*p) );
						if (p != null)
						{
							p.id = iType;
							InitializeCriticalSection(p.mutex);
						}
						break;
					}
				default:
					{
						Debug.Assert(winMutex_isInit == 1);
						Debug.Assert(iType - 2 >= 0);
						Debug.Assert(iType - 2 < ArraySize(winMutex_staticMutexes));
						p = winMutex_staticMutexes[iType - 2];
						p.id = iType;
						break;
					}
			}
			return p;
		}

		/*
		** This routine deallocates a previously
		** allocated mutex.  SQLite is careful to deallocate every
		** mutex that it allocates.
		*/

		private static void winMutexFree(sqlite3_mutex p)
		{
			Debug.Assert(p != null);
			Debug.Assert(p.nRef == 0);
			Debug.Assert(p.id == SQLITE_MUTEX_FAST || p.id == SQLITE_MUTEX_RECURSIVE);
			DeleteCriticalSection(p.mutex);
			p.owner = 0;
			//sqlite3_free( p );
		}

		/*
		** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
		** to enter a mutex.  If another thread is already within the mutex,
		** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
		** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
		** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
		** be entered multiple times by the same thread.  In such cases the,
		** mutex must be exited an equal number of times before another thread
		** can enter.  If the same thread tries to enter any other kind of mutex
		** more than once, the behavior is undefined.
		*/

		private static void winMutexEnter(sqlite3_mutex p)
		{
			DWORD tid = GetCurrentThreadId();
			Debug.Assert(p.id == SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid));
			EnterCriticalSection(p.mutex);
			p.owner = tid;
			p.nRef++;
#if SQLITE_DEBUG
			if (p.trace != 0)
			{
				printf("enter mutex {0} ({1}) with nRef={2}\n", p.GetHashCode(), p.owner, p.nRef);
			}
#endif
		}

		private static int winMutexTry(sqlite3_mutex p)
		{
#if !NDEBUG
			DWORD tid = GetCurrentThreadId();
#endif
			int rc = SQLITE_BUSY;
			Debug.Assert(p.id == SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid));
			/*
			** The sqlite3_mutex_try() routine is very rarely used, and when it
			** is used it is merely an optimization.  So it is OK for it to always
			** fail.
			**
			** The TryEnterCriticalSection() interface is only available on WinNT.
			** And some windows compilers complain if you try to use it without
			** first doing some #defines that prevent SQLite from building on Win98.
			** For that reason, we will omit this optimization for now.  See
			** ticket #2685.
			*/
#if FALSE
if( mutexIsNT() && TryEnterCriticalSection(p.mutex) ){
p.owner = tid;
p.nRef++;
rc = SQLITE_OK;
}
#else
			UNUSED_PARAMETER(p);
#endif
#if SQLITE_DEBUG
			if (rc == SQLITE_OK && p.trace != 0)
			{
				printf("try mutex {0} ({1}) with nRef={2}\n", p.GetHashCode(), p.owner, p.nRef);
			}
#endif
			return rc;
		}

		/*
		** The sqlite3_mutex_leave() routine exits a mutex that was
		** previously entered by the same thread.  The behavior
		** is undefined if the mutex is not currently entered or
		** is not currently allocated.  SQLite will never do either.
		*/

		private static void winMutexLeave(sqlite3_mutex p)
		{
#if !NDEBUG
			DWORD tid = GetCurrentThreadId();
#endif
			Debug.Assert(p.nRef > 0);
			Debug.Assert(p.owner == tid);
			p.nRef--;
			Debug.Assert(p.nRef == 0 || p.id == SQLITE_MUTEX_RECURSIVE);
			if (p.nRef == 0) p.owner = 0;
			LeaveCriticalSection(p.mutex);
#if SQLITE_DEBUG
			if (p.trace != 0)
			{
				printf("leave mutex {0} ({1}) with nRef={2}\n", p.GetHashCode(), p.owner, p.nRef);
			}
#endif
		}

		private static sqlite3_mutex_methods sqlite3DefaultMutex()
		{
			sqlite3_mutex_methods sMutex = new sqlite3_mutex_methods(
	  (dxMutexInit)winMutexInit,
	  (dxMutexEnd)winMutexEnd,
	  (dxMutexAlloc)winMutexAlloc,
	  (dxMutexFree)winMutexFree,
	  (dxMutexEnter)winMutexEnter,
	  (dxMutexTry)winMutexTry,
	  (dxMutexLeave)winMutexLeave,
#if SQLITE_DEBUG
 (dxMutexHeld)winMutexHeld,
	  (dxMutexNotheld)winMutexNotheld
#else
null,
null
#endif
);

			return sMutex;
		}

#endif // * SQLITE_MUTEX_W32 */
	}
}