calamares/src/libcalamares/utils/NamedSuffix.h

/* === This file is part of Calamares - <https://github.com/calamares> ===
 *
 *   Copyright 2019, Adriaan de Groot <groot@kde.org>
 *
 *   Calamares 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 3 of the License, or
 *   (at your option) any later version.
 *
 *   Calamares 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 Calamares. If not, see <http://www.gnu.org/licenses/>.
 */

/** @brief Support for unit-suffixed values.
 *
 * This combines a value with an (enum) unit indicating what kind
 * of value it is, e.g. 10 meters, or 64 pixels. Includes simple
 * parsing support for the values written as strings like <value><unit>,
 * e.g. "10m" or "64px".
 *
 * When a suffixed unit value needs validation, define an isValid()
 * method; similarly for simple construction from a string (with a fixed
 * table of suffixes). Typical use then looks like:
 *
 * class MyUnit : public NamedSuffix<MyUnitEnum, MyUnitEnum::None>
 * {
 * public:
 *      using NamedSuffix::NamedSuffix;  // Keep existing constructors
 *      MyUnit( const QString& s );
 *      bool isValid() const;
 * } ;
 */

#ifndef LIBCALAMARES_NAMEDSUFFIX_H
#define LIBCALAMARES_NAMEDSUFFIX_H

#include "NamedEnum.h"

/** @brief Template that takes the enum type to work with and a special none-enum. */
template<typename T, T _none>
class NamedSuffix
{
public:
    using unit_t = T;

    static constexpr unit_t none = _none;

    /** @brief Empty value. */
    NamedSuffix()
        : m_value(0)
        , m_unit( none )
    {
    }

    /** @brief Specific value and unit. */
    NamedSuffix( int value, unit_t unit )
        : m_value( value )
        , m_unit( unit )
    {
    }

    /** @brief Construct value and unit from string.
     *
     * This parses the given string @p s by comparing with the suffixes
     * in @p table and uses the first matching suffix as the unit.
     */
    NamedSuffix( const NamedEnumTable<T>& table, const QString& s )
        : NamedSuffix()
    {
        for( const auto suffix : table.table )
            if ( s.endsWith( suffix.first ) )
            {
                m_value = s.left( s.length() - suffix.first.length() ).toInt();
                m_unit = suffix.second;
                break;
            }
    }


    /** @brief Construct value from string.
     *
     * This is not defined in the template, because it should probably
     * delegate to the constructor above with a fixed table.
     */
    NamedSuffix( const QString& s );

    int value() const { return m_value; }
    unit_t unit() const { return m_unit; }

    /** @brief Check that a value-unit combination is valid.
     *
     * This is not defined in the template, because validity (e.g.
     * range of acceptable values) depends on the kind of unit.
     */
    bool isValid() const;

protected:
    int m_value;
    unit_t m_unit;
};


#endif