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/***************************************************************************
 *
 * File:    SQLModule.h
 * Created: Sun Dec 12 1999
 * (C) 1999 by David M. <captjay@superlink.net>
 *
 ***************************************************************************/
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
#ifndef SQLMODULE_H
#define SQLMODULE_H

#include <qstring.h>
#include <mysql.h>
#include <qobject.h>
#include "CustomException.h"

/**
* @author David M.
* @short Transparent handling of SQL queries.
*
* the SQLModule class encapsulates access to a mySQL database.
* It provides methods to access, update, and delete data from
* the database.
*
*/
class SQLModule : public QObject {
public:
  SQLModule(); //default constructor
  ~SQLModule();

//Public Methods
  /**
  * Connect to a mySQL database with a given username and password.
  *
  * @param host The hostname of the machine running the database server.
  * @param dbaseName The name of the database to connect to.
  * @param userName the user name to use to establish connection.
  * @param password the password to use for the connection.
  *
  * @return true if the connection succeeded, false otherwise.
  */
  bool connectTo(QString host,QString dbaseName,QString userName,QString password);
  /*
  * Send a SELECT type query to the server. After the query, the module will
  * contain the retrieved data and have the first row active.
  * You can access each field with the [] operator, and advance in rows
  * with the @ref nextRow() method.
  *
  * PRECONDITIONS: The module must have an active connection to a server.
  *               (succesful call to connectTo())
  *
  * @param query A string containing the SQL statement to execute.
  *
  */
  void query(const char* query);
  /*
  * Send an update type query to the server. Use this method for SQL statements
  * that do not return rows (UPDATE, DELETE, INSERT, CREATE, DROP, etc)
  *
  * PRECONDITIONS: The module must have an active connection to a server.
  *               (succesful call to connectTo())
  *
  * @param query A string containing the SQL statement to execute.
  *
  */
  void update(const char* query);

  /**
  * Fetch the next row of the result set, if there is one. This function can only
  * be used after a SELECT query that returned a non-empty result set.
  *
  * PRECONDITIONS: mode() == ModeQuery
  *
  * @return true if a new row was fetched, false otherwise.
  *
  * Here is an example of a typical multiple-row query.
  * <pre>
  * sqlmod.query("SELECT * from emp where salary > 500");
  * for (; !sqlmod.atEnd(); sqlmod.nextRow())
  *   cout << sqlmod[0] << " " << sqlmod[1] << endl;
  * </pre>
  */
  bool nextRow();

  /**
  * Determine what mode the module is in currently.
  *
  * @return Either of ModeUndefied, ModeQuery or ModeUpdate.
  */
  int mode() const;

  /**
  * Determine if the result set is at end position.
  *
  * PRECONDITIONS: mode() == ModeQuery
  *
  * @return true if there are no more rows in the result set, false otherwise.
  */
  bool atEnd() const;

  /**
  * Determine if the query returned an empty result set.
  *
  * PRECONDITIONS: mode() == ModeQuery
  *
  * @return true if the result set is empty, false otherwise.
  */
  bool isEmpty() const;

  /**
  * Get the number of rows that were returned by the query.
  *
  * PRECONDITIONS: mode() == ModeQuery
  *
  * @return The number of rows returned by the SELECT query.
  */
  int rowCount() const;

  /**
  * Get the number of fields (columns) in the result set.
  *
  * PRECONDITIONS: mode() == ModeQuery
  *
  * @return The number of fields in the result set.
  */
  int fieldCount() const;

  /**
  * Get the error message recieved from the server in case
  * of an SQL error.
  *
  * @return A string containing the error message.
  */
  QString error() const;

  /**
  * Get a specific field of the result set, by number.
  *
  * PRECONDITIONS: mode() == ModeQuery ; index < fieldCount()
  *
  * @return A string containing the value of the field.
  *         a NULL field generates an empty string.
  */
  QString fields(int index) const;

//Public Operators

  /**
  * Get a specific field of the result set, by number. Same as @ref fields().
  *
  * PRECONDITIONS: mode() == ModeQuery ; index < fieldCount()
  *
  * @return A string containing the value of the field.
  *         a NULL field generates an empty string.
  */
  QString operator[](int index);

  /**
  * Move to the next row in the result set. Same as @ref nextRow().
  *
  * PRECONDITIONS: mode() == ModeQuery
  *
  * @return true if the module could move to the next row, or
  *              false if it is at the end of the set.
  */
  bool operator++();
  bool operator++(int);

//Public Constants
  static const int ModeUndefined = 0;
  static const int ModeQuery = 1;
  static const int ModeUpdate = 2;

protected:
//Protected Fields
  MYSQL* _mysql; //main MySQL handle
  MYSQL_RES* _res; //result set for a SELECT query
  MYSQL_ROW _row;  //Holds the rows fetched by a SELECT query
  QString _error; //Error message
  int _rowCount; //Number of rows matched
  int _rowsFetched; //Number of rows currently fetched
  int _numFields; //Number of fields in one row
  int _mode; //Current control's mode

};

/**
* @short Exception for SQL errors.
* This class is used to represent errors related to SQL query handling.
*/
class ESQLError : public CustomException {
Q_OBJECT
public:
  ESQLError(QString message);
};

#endif