databaseConnector.h

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/******************************************************
 *  Presage, an extensible predictive text entry system
 *  ---------------------------------------------------
 *
 *  Copyright (C) 2008  Matteo Vescovi <matteo.vescovi@yahoo.co.uk>

    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.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
                                                                             *
                                                                **********(*)*/


#ifndef DATABASECONNECTOR_H
#define DATABASECONNECTOR_H

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "../../core/logger.h"

#include <map>
#include <vector>
#include <string>

typedef std::vector<std::string> Ngram;
typedef std::vector<Ngram> NgramTable;

class DatabaseConnector {
public:
    DatabaseConnector(const std::string database_name,
                      const size_t cardinality,
                      const bool read_write);
    DatabaseConnector(const std::string database_name,
                      const size_t cardinality,
                      const bool read_write,
                      const std::string& log_level);
    virtual ~DatabaseConnector();

    void createNgramTable(const size_t cardinality) const;
    void createUnigramTable() const { createNgramTable(1); }
    void createBigramTable()  const { createNgramTable(2); }
    void createTrigramTable() const { createNgramTable(3); }

    int getUnigramCountsSum() const;

    int getNgramCount(const Ngram ngram) const;

    NgramTable getNgramLikeTable(const Ngram ngram,
                                 const char** filter,
                                 const int count_threshold,
                                 int limit = -1) const;

    int incrementNgramCount(const Ngram ngram) const;

    void insertNgram(const Ngram ngram, const int count) const;

    void updateNgram(const Ngram ngram, const int count) const;

    void removeNgram(const Ngram ngram) const;

    virtual void beginTransaction() const;

    virtual void endTransaction() const;

    virtual void rollbackTransaction() const;

protected:
    // Following functions to be overridden by derived classes.
    virtual void openDatabase()                                  = 0;
    virtual void closeDatabase()                                 = 0;
    virtual NgramTable executeSql(const std::string query) const = 0;

    std::string get_database_filename () const;
    std::string set_database_filename (const std::string& filename);

    void   set_cardinality (const size_t cardinality);
    size_t get_cardinality () const;

    void set_read_write_mode (const bool read_write);
    bool get_read_write_mode () const;

    Logger<char> logger;

private:
    std::string buildSelectLikeClause(const int cardinality) const;

    std::string buildWhereClause(const Ngram ngram) const;

    std::string buildWhereLikeClause(const Ngram ngram,
                                     const char** filter,
                                     const int count_threshold) const;

    std::string buildValuesClause(const Ngram ngram, const int count) const;

    std::string sanitizeString(const std::string) const;

    int extractFirstInteger(const NgramTable&) const;


    std::string expand_variables (std::string filename) const;
    void substitute_variable_in_string (const std::string& variable_name, std::string& filepath) const;

    std::string database_filename;
    size_t cardinality;
    bool read_write_mode;

};

#endif // DATABASECONNECTOR_H