//********************************************
// AEM.cpp
// -------------------------------------------
// Implementation of the AEM (AE Monitor) tool.
//
// This tool issues commands of operations to
// AE by sending SIGUSER2 signal. The operation
// parameters are passed through shared memory.
// 
// Author: Leiwen Deng
// Date: 12/10/2005
//********************************************

#include "AEM.h"

int main( int argc, char * argv[] )
{
  if ( argc < 2 )
  {
    Die( "Usage: AEM <operation>\n" );
  }

  const char * AE_pid_file = AE_PID_FILE_NAME;
  FILE * fp;
  if( ( fp = fopen( AE_pid_file, "r" ) ) == NULL )
  {
    Die( "AE pid file does not exist\n" );
  }
  int AE_pid;
  if ( fscanf( fp, "%d", &AE_pid ) != 1 )
  {
    Die( "File \"%s\" is corrupt\n", AE_pid_file );
  }
  fclose( fp );

  int shmid;
  key_t key = SHM_AEM_KEY;
  if ( ( shmid = shmget( key, sizeof( SHM_AEM ), 0666) ) < 0 )
  {
    Die( "Error: fail to locate the shared memory for AEM handler\n" );
  }
  SHM_AEM * shm_aem;
  if ( ( shm_aem = (SHM_AEM *)shmat( shmid, NULL, 0) ) == (SHM_AEM *)-1 )
  {
    Die( "Error: fail to attach to the shared memory for AEM handler\n" );
  }

  if ( argv[1][0] == '1' )
    shm_aem->operation = AEM_SHOW_TABLE;
  else if ( argv[1][0] == '2' )
    shm_aem->operation = AEM_SHOW_TABLE_STRUCTURE;
  else
    shm_aem->operation = AEM_NO_OPERATION;

  if ( kill( AE_pid, SIGUSR2 ) != 0 )
  {
    const char * reason = "Unknown reason";
    switch ( errno )
    {
    case EPERM:
      reason = "Operation is not permitted";
      break;
    case ESRCH:
      reason = "AE process is not found";
      break;
    }
    fprintf( stderr, "AEM operation fails because: %s\n", reason );
  }
  else
  {
    const char * result = "No AEM operation is performed";
    switch ( shm_aem->operation )
    {
    case AEM_SHOW_TABLE:
      result = "Table is successfully dumped";
      break;
    case AEM_SHOW_TABLE_STRUCTURE:
      result = "Table structure is successfully dumped";
      break;
    }
    fprintf( stderr, "%s\n", result );
  }
  
  return 0;
}

void Die( const char * format, ... )
{
  va_list param_list;
  va_start( param_list, format );
  vfprintf( stderr, format, param_list );
  exit( 1 );
}