/******************************************************************************
  * This function was copied from:
  * http://www.qtcentre.org/threads/36131-Attempting-to-use-Sqlite-backup-api-from-driver-handle-fails?p=207558#post207558
  * on November 10, 2011.  The function has been released to the Public Domain
  * by its deveveloper.
  *
*******************************************************************************/

#include "sqlite3_util.h"
#include <sqlite3.h>
#include <QVariant>
#include <QSqlDriver>
/*
** This function is used to load the contents of a database file on disk
** into the "main" database of open database connection pInMemory, or
** to save the current contents of the database opened by pInMemory into
** a database file on disk. pInMemory is probably an in-memory database,
** but this function will also work fine if it is not.
**
** Parameter zFilename points to a nul-terminated string containing the
** name of the database file on disk to load from or save to. If parameter
** isSave is non-zero, then the contents of the file zFilename are
** overwritten with the contents of the database opened by pInMemory. If
** parameter isSave is zero, then the contents of the database opened by
** pInMemory are replaced by data loaded from the file zFilename.
**
** If the operation is successful, SQLITE_OK is returned. Otherwise, if
** an error occurs, an SQLite error code is returned.
*/
bool sqlite3_util::sqliteDBMemFile( QSqlDatabase memdb, QString filename, bool save )
{
    bool state = false;
    QVariant v = memdb.driver()->handle();
    if( v.isValid() && qstrcmp(v.typeName(),"sqlite3*") == 0 )
    {
        // v.data() returns a pointer to the handle
        sqlite3 * handle = *static_cast<sqlite3 **>(v.data());
        if( handle != 0 ) // check that it is not NULL
        {
            sqlite3 * pInMemory = handle;
            QByteArray array = filename.toLocal8Bit();
            const char * zFilename = array.data();
            int rc;                   /* Function return code */
            sqlite3 *pFile;           /* Database connection opened on zFilename */
            sqlite3_backup *pBackup;  /* Backup object used to copy data */
            sqlite3 *pTo;             /* Database to copy to (pFile or pInMemory) */
            sqlite3 *pFrom;           /* Database to copy from (pFile or pInMemory) */

            /* Open the database file identified by zFilename. Exit early if this fails
            ** for any reason. */
            rc = sqlite3_open( zFilename, &pFile );
            if( rc==SQLITE_OK ){

              /* If this is a 'load' operation (isSave==0), then data is copied
              ** from the database file just opened to database pInMemory.
              ** Otherwise, if this is a 'save' operation (isSave==1), then data
              ** is copied from pInMemory to pFile.  Set the variables pFrom and
              ** pTo accordingly. */
              pFrom = ( save ? pInMemory : pFile);
              pTo   = ( save ? pFile     : pInMemory);

              /* Set up the backup procedure to copy from the "main" database of
              ** connection pFile to the main database of connection pInMemory.
              ** If something goes wrong, pBackup will be set to NULL and an error
              ** code and  message left in connection pTo.
              **
              ** If the backup object is successfully created, call backup_step()
              ** to copy data from pFile to pInMemory. Then call backup_finish()
              ** to release resources associated with the pBackup object.  If an
              ** error occurred, then  an error code and message will be left in
              ** connection pTo. If no error occurred, then the error code belonging
              ** to pTo is set to SQLITE_OK.
              */
              pBackup = sqlite3_backup_init(pTo, "main", pFrom, "main");
              if( pBackup ){
                (void)sqlite3_backup_step(pBackup, -1);
                (void)sqlite3_backup_finish(pBackup);
              }
              rc = sqlite3_errcode(pTo);
            }

            /* Close the database connection opened on database file zFilename
            ** and return the result of this function. */
            (void)sqlite3_close(pFile);

            if( rc == SQLITE_OK ) state = true;
        }
    }
    return state;
}