/**
 * @file Common/inifile_p.h
 * @brief Internal implementation of the class for reading and writing parameter values in INI files.
 * @author Enar Vaikene
 *
 * Copyright (c) 2011-2019 Enar Vaikene
 *
 * This file is part of the eVaf C++ cross-platform application development framework.
 *
 * This file can be used under the terms of the GNU General Public License
 * version 3.0 as published by the Free Software Foundation and appearing in
 * the file LICENSE included in the packaging of this file. Please review the
 * the following information to ensure the GNU General Public License version
 * 3.0 requirements will be met: http://www.gnu.org/copyleft/gpl.html.
 *
 * Alternatively, this file may be used in accordance with the Commercial License
 * Agreement provided with the Software.
 */

#ifndef __COMMON_INIFILE_P_H
#define   __COMMON_INIFILE_P_H

#include <QSharedData>
#include <QExplicitlySharedDataPointer>
#include <QHash>
#include <QString>
#include <QVariant>
#include <QDateTime>
#include <QFile>


namespace eVaf {
namespace Common {
namespace Internal {

/**
 * INI file value in the internal cache
 */
class IniFileValue : public QSharedData
{
public:

    IniFileValue(qint64 pos)
        : QSharedData()
        , filePos(pos)
        , thisOsOnly(false)
    {}

    /**
     * File position
     *
     * Offset of the parameter in the INI file. By seeking the file to this offset value,
     * the next character read or written will be the beginning of the key name.
     */
    qint64 filePos;

    /**
     * Key name of the parameter
     */
    QByteArray name;

    /**
     * Value from the INI file
     */
    QByteArray paramValue;

    /**
     * Value converted to the final type (defaults to QVariant::Invalid
     */
    QVariant value;

    /**
     * Flag indicating that this value is valid on this OS only
     */
    bool thisOsOnly;
};

/**
 * INI file section in the internal cache
 */
class IniFileSection : public QSharedData
{
public:

    IniFileSection(qint64 pos)
        : QSharedData()
        , filePos(pos)
    {}

    /**
     * File position
     *
     * Offset of the section in the INI file. By seeking the file to this offset value,
     * the next character read or written will be the first character of the section.
     */
    qint64 filePos;

    /**
     * Name of the section
     */
    QByteArray name;

    /**
     * List of all the known parameter values in this section
     *
     * The key to the hash table is the name of the key for the parameters value.
     */
    QHash<QByteArray, QExplicitlySharedDataPointer<IniFileValue> > values;

};

/**
 * Internal implementation of the IniFile class.
 */
class IniFileImpl
{
public:

    IniFileImpl(QString const & fileName, QIODevice::OpenMode mode);

    ~IniFileImpl();

    QVariant getValue(QByteArray const & paramName, QVariant const & defaultValue);

    bool setValue(QByteArray const & paramName, QVariant const & value);

    inline bool isValid() const { return mValid; }

    inline QString const & fileName() const { return mFileName; }

    inline QString const & errorString() const { return mErrorString; }


private: // Members

    /// Flag indicating that the INI file object is valid and can be used to access the INI file
    bool mValid;

    /// Name of the INI file
    QString mFileName;

    /// INI file opening mode
    QIODevice::OpenMode mMode;

    /// Last human-readable error message if an operation with the INI file failed
    QString mErrorString;

    /**
     * Internal cache of sections and parameter values.
     *
     * The key to the hash table is the name of the section.
     */
    QHash<QByteArray, QExplicitlySharedDataPointer<IniFileSection> > mCache;

    /// When was the INI file modified.
    QDateTime mLastModified;


private: /// Methods

    /**
     * Updates items in the internal cache after changes to the INI file
     * @param pos File offset from where the cache should be updated
     * @param diff Difference between old and new file offsets
     *
     * When a parameter value is modified or a new value inserted, the length of the INI file changes.
     * Sections and parameters that come after the modified parameter value are shifted and their file
     * positions changed. This method updates items in the internal cache after changes to the INI file.
     */
    void updateCache(qint64 pos, qint64 diff);

    /**
     * Looks for a section in the INI file
     * @param file The file object
     * @param sectionName Name of the section
     * @return The section object or an invalid object if not found
     *
     * This method reads the INI file and looks for the section with the given name. If found, returns the section
     * object and seeks the file to the first character after the section name.
     *
     * If the section is not found, returns an invalid section object and seeks the file to the end of the file.
     *
     * The file object is expected to be opened if the mValid flag is true. If the mValid flag is false, looks
     * only in the cache.
     */
    QExplicitlySharedDataPointer<IniFileSection> getSection(QFile & file, QByteArray const & sectionName);

    /**
     * Looks for a parameter in the INI file
     * @param file The file object
     * @param section The section object
     * @param paramName Name of the parameter
     * @return The value object or an invalid object if not found
     *
     * This method reads the INI file and looks for the parameter with the given name. If found, returns the value
     * object and seeks the file to the beginning of the line containing the parameter.
     *
     * If not found, returns an invalid value object and seeks the file to the end of the section.
     *
     * The file object is expected to be opened if the mValid flag is true. If the mValid flag is false, looks
     * only in the cache.
     */
    QExplicitlySharedDataPointer<IniFileValue> getParameter(QFile & file, IniFileSection & section, QByteArray const & paramName);

};


} // namespace eVaf::Common::Internal
} // namespace eVaf::Common
} // namespace eVaf

#endif // inifile_p.h