#include "config.h"
#include "backoffice.h"
#include <time.h>
#if defined(_WIN32)
# include <windows.h>
# include <stdio.h>
# include <process.h>
# define GETPID (int)GetCurrentProcessId
#else
# include <unistd.h>
# include <sys/types.h>
# include <signal.h>
# define GETPID getpid
#endif

/*
** The BKOFCE_LEASE_TIME is the amount of time for which a single backoffice
** processing run is valid.  Each backoffice run monopolizes the lease for
** at least this amount of time.  Hopefully all backoffice processing is
** finished much faster than this - usually in less than a second.  But

** never be a problem with waiting backoffice threads.  But in some cases
** a backoffice will delay a UI thread, so we don't want them to run for
** longer than needed.
*/
void backoffice_no_delay(void){
  backofficeNoDelay = 1;
}

/*
** Sleeps for the specified number of milliseconds -OR- until interrupted
** by another thread (if supported by the underlying platform).  Non-zero
** will be returned if the sleep was interrupted.
*/
static int backofficeSleep(int milliseconds){
#if defined(_WIN32)
  assert( milliseconds>=0 );
  if( SleepEx((DWORD)milliseconds, TRUE)==WAIT_IO_COMPLETION ){
    return 1;
  }
#else
  sqlite3_sleep(milliseconds);
#endif
  return 0;
}

/*
** Parse a unsigned 64-bit integer from a string.  Return a pointer
** to the character of z[] that occurs after the integer.
*/
static const char *backofficeParseInt(const char *z, sqlite3_uint64 *pVal){
  *pVal = 0;

  db_multi_exec(
    "REPLACE INTO repository.config(name,value,mtime)"
    " VALUES('backoffice','%lld %lld %lld %lld',now())",
    pLease->idCurrent, pLease->tmCurrent,
    pLease->idNext, pLease->tmNext);
}

/*
** Check to see if the specified Win32 process is still alive.  It
** should be noted that even if this function returns non-zero, the
** process may die before another operation on it can be completed.
*/
#if defined(_WIN32)
#ifndef PROCESS_QUERY_LIMITED_INFORMATION
#  define PROCESS_QUERY_LIMITED_INFORMATION  (0x1000)
#endif
static int backofficeWin32ProcessExists(DWORD dwProcessId){
  HANDLE hProcess;
  hProcess = OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION,FALSE,dwProcessId);
  if( hProcess==NULL ) return 0;
  CloseHandle(hProcess);
  return 1;
}
#endif

/*
** Check to see if the process identified by pid is alive.  If
** we cannot prove the the process is dead, return true.
*/
static int backofficeProcessExists(sqlite3_uint64 pid){
#if defined(_WIN32)
  return pid>0 && backofficeWin32ProcessExists((DWORD)pid)!=0;
#else
  return pid>0 && kill((pid_t)pid, 0)==0;
#endif 
}

/*
** Check to see if the process identified by pid has finished.  If
** we cannot prove the the process is still running, return true.
*/
static int backofficeProcessDone(sqlite3_uint64 pid){
#if defined(_WIN32)
  return pid<=0 || backofficeWin32ProcessExists((DWORD)pid)==0;
#else
  return pid<=0 || kill((pid_t)pid, 0)!=0;
#endif 
}

/*
** Return a process id number for the current process
*/
static sqlite3_uint64 backofficeProcessId(void){

  return (sqlite3_uint64)GETPID();



}

/*
** Set an alarm to cause the process to exit after "x" seconds.  This
** prevents any kind of bug from keeping a backoffice process running
** indefinitely.
*/

static void backofficeSigalrmHandler(int x){
  fossil_panic("backoffice timeout (%d seconds)", x);
}
#if defined(_WIN32)
static void *threadHandle = NULL;
static void __stdcall backofficeWin32NoopApcProc(ULONG_PTR pArg){} /* NO-OP */
static void backofficeWin32ThreadCleanup(){
  if( threadHandle!=NULL ){
    /* Queue no-op asynchronous procedure call to the sleeping
     * thread.  This will cause it to wake up with a non-zero
     * return value. */
    if( QueueUserAPC(backofficeWin32NoopApcProc, threadHandle, 0) ){
      /* Wait for the thread to wake up and then exit. */
      WaitForSingleObject(threadHandle, INFINITE);
    }
    CloseHandle(threadHandle);
    threadHandle = NULL;
  }
}
static unsigned __stdcall backofficeWin32SigalrmThreadProc(
  void *pArg /* IN: Pointer to integer number of whole seconds. */
){
  int seconds = FOSSIL_PTR_TO_INT(pArg);
  if( SleepEx((DWORD)seconds * 1000, TRUE)==0 ){
    backofficeSigalrmHandler(seconds);
  }
  _endthreadex(0);
  return 0; /* NOT REACHED */
}
#endif
static void backofficeTimeout(int x){
#if defined(_WIN32)
  backofficeWin32ThreadCleanup();
  threadHandle = (void*)_beginthreadex(
    0, 0, backofficeWin32SigalrmThreadProc, FOSSIL_INT_TO_PTR(x), 0, 0
  );
#else
  signal(SIGALRM, backofficeSigalrmHandler);
  alarm(x);
#endif
}


/*

      x.tmCurrent = tmNow + BKOFCE_LEASE_TIME;
      x.idNext = 0;
      x.tmNext = 0;
      backofficeWriteLease(&x);
      db_end_transaction(0);
      if( g.fAnyTrace ){
        fprintf(stderr, "/***** Begin Backoffice Processing %d *****/\n",
                        GETPID());
      }
      backoffice_work();
      break;
    }
    if( backofficeNoDelay || db_get_boolean("backoffice-nodelay",1) ){
      /* If the no-delay flag is set, exit immediately rather than queuing
      ** up.  Assume that some future request will come along and handle any
      ** necessary backoffice work. */
      db_end_transaction(0);
      break;
    }
    /* This process needs to queue up and wait for the current lease
    ** to expire before continuing. */
    x.idNext = idSelf;
    x.tmNext = (tmNow>x.tmCurrent ? tmNow : x.tmCurrent) + BKOFCE_LEASE_TIME;
    backofficeWriteLease(&x);
    db_end_transaction(0);
    if( g.fAnyTrace ){
      fprintf(stderr, "/***** Backoffice On-deck %d *****/\n",  GETPID());
    }
    if( x.tmCurrent >= tmNow ){
      if( backofficeSleep(1000*(x.tmCurrent - tmNow + 1)) ){
        /* The sleep was interrupted by a signal from another thread. */
        if( g.fAnyTrace ){
          fprintf(stderr, "/***** Backoffice Interrupt %d *****/\n", GETPID());
        }
        db_end_transaction(0);
        break;
      }
    }else{
      if( lastWarning+warningDelay < tmNow ){
        fossil_warning(
           "backoffice process %lld still running after %d seconds",
           x.idCurrent, (int)(BKOFCE_LEASE_TIME + tmNow - x.tmCurrent));
        lastWarning = tmNow;
        warningDelay *= 2;
      }
      if( backofficeSleep(1000) ){
        /* The sleep was interrupted by a signal from another thread. */
        if( g.fAnyTrace ){
          fprintf(stderr, "/***** Backoffice Interrupt %d *****/\n", GETPID());
        }
        db_end_transaction(0);
        break;
      }
    }
  }
#if defined(_WIN32)
  backofficeWin32ThreadCleanup();
#endif
  return;
}

/*
** This routine runs to do the backoffice processing.  When adding new
** backoffice processing tasks, add them here.
*/