/**
 * @file Common/ienv.h
 * @brief Environment interface
 * @author Enar Vaikene
 *
 * Copyright (c) 2011 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_IENV_H
#define __COMMON_IENV_H

#include "libcommon.h"

#include <QObject>
#include <QString>

namespace eVaf {
namespace Common {

/**
 * Environment interface for eVaf applications
 * @code#include <Common/iEnv>@endcode
 *
 * The iEnv interface provides information about the environment where the application is running.
 * Functions in this interface return names of directories where different resources are located.
 * Modules should always use the iEnv interface for directory names and locations.
 *
 * Directory names returned by functions in this interface are UNIX path names and they are quaranteed
 * to end with the '/' character.
 *
 * All the directories have reasonable default values, that should work in most of the cases. For example,
 * the binary directory is set to the same directory where the application's main executable is located.
 * The root directory is the parent of the binary directory etc.
 *
 * Default values can be overwritten with environment variables and command line arguments. If both are used,
 * then command line arguments have higher priorities.
 */
class COMMON_EXPORT iEnv : public QObject
{
    Q_OBJECT

public:

    /// Interface constructor
    iEnv() : QObject() {}

    /// Empty virtual destructor
    virtual ~iEnv() {}

    /**
     * Returns the iEnv interface instance
     * @return The iEnv interface
     *
     * This function returns the global iEnv interface instance. As all the eVaf modules and applications
     * are expected to be linked against the common library, then this is the preferred method of obtaining
     * the iEnv interface. The other method is by using the iRegistry interface.
     */
    static iEnv * instance();

    /**
     * Returns the name of the eVaf root directory
     *
     * The root directory is the base directory where the eVaf application is installed. The default root
     * directory is the parent of the binary directory.
     *
     * Write access to the root directory is not required to run the application.
     *
     * This directory can be changed with the EVAF_ROOT_DIR environment variable or with the -root[dir]=&lt;directory&gt;
     * command line argument.
     */
    virtual QString const rootDir() const = 0;

    /**
     * Returns the name of the eVaf data directory.
     *
     * The data root directory is the base directory for all the directories that require write access.
     *
     * The default data directory on Windows is \%APPDATA\%/\%EVAF_APP_NAME\%. The default data directory
     * on Linux is ${HOME}/.${EVAF_APP_NAME}.
     *
     * This directory can be changed with the EVAF_DATA_ROOT_DIR environment variable or with the
     * -dataroot[dir]=&lt;directory&gt; command line argument.
     */
    virtual QString const dataRootDir() const = 0;

    /**
     * Returns the name of the binary files directory.
     *
     * The binary directory is the directory where all the application's binary files (main executable and
     * modules) are located. The default binary directory is where the main executable is located.
     *
     * NB! Changing the application's root directory does not change the location of the binary directory.
     */
    virtual QString const binDir() const = 0;

    /**
     * Returns the configuration files directory.
     *
     * This is the directory where all the application's configuration files are located. The default
     * configuration files directory is 'etc' in the data root directory.
     *
     * This directory can be changed with the EVAF_ETC_DIR environment variable or with the -etc[dir]=&lt;directory&gt;
     * command line argument.
     */
    virtual QString const etcDir() const = 0;

    /**
     * Returns the log files directory.
     *
     * This is the directory where the application outputs all the log files. The default log files
     * directory is 'log' in the data root directory.
     *
     * This directory can be changed with the EVAF_LOG_DIR environment variable or with the
     * -log[dir]=&lt;directory&gt; command line argument.
     */
    virtual QString const logDir() const = 0;

    /**
     * Returns the documentation directory.
     *
     * This is the directory where all the documentation and help files are located. The default
     * documentation directory is 'doc' in the root directory.
     *
     * This directory can be changed with the EVAF_DOC_DIR environment variable or with the
     * -doc[dir]=&lt;directory&gt; command line argument.
     */
    virtual QString const docDir() const = 0;

    /**
     * Returns the Qt plugins directory.
     *
     * The Qt plugins directory is where additional Qt plugins are located. These Qt plugins
     * are loaded manually by the application and specified in the application's XML file.
     *
     * Changing this directory does not affect the way how Qt itself loads its plugins.
     *
     * This directory can be changed with the EVAF_QT_PLUGINS_DIR environment variable or with the
     * -qtplugins[dir]=&lt;directory&gt; command line argument.
     */
    virtual QString const qtPluginsDir() const = 0;

};

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

#endif