roleditemsmodel.h

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/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/
 
#pragma once
 
#include "flatitemsmodeltypedbase.h"
 
namespace LC::Util
{
    template<size_t N>
    struct Literal
    {
        char Chars_ [N];
 
        constexpr Literal (const char (&s) [N])
        {
            std::copy_n (s, N, Chars_);
        }
    };
 
    template<Literal RoleArg, auto GetterArg>
    struct RoledMemberField
    {
        static constexpr auto Getter = GetterArg;
        static constexpr auto Role = RoleArg;
    };
 
    template<Literal RoleArg, auto GetterArg>
    RoledMemberField<RoleArg, GetterArg> RoledMemberField_v;
 
    template<typename T>
    class RoledItemsModel : public FlatItemsModelTypedBase<T>
    {
    public:
        using FieldGetter_t = QVariant (*) (const T&);
        using FieldsList_t = QVector<QPair<QByteArray, FieldGetter_t>>;
    private:
        const QVector<FieldGetter_t> Fields_;
        const QHash<int, QByteArray> Roles_;
    public:
        template<typename... Fields>
        RoledItemsModel (QObject *parent, Fields...) noexcept
        : FlatItemsModelTypedBase<T> { QStringList { {} }, parent }
        , Fields_ { +[] (const T& t) -> QVariant { return t.*(Fields::Getter); }... }
        , Roles_ { MakeRoles ({ QByteArray { Fields::Role.Chars_ }... }) }
        {
        }
 
        QHash<int, QByteArray> roleNames () const override
        {
            return Roles_;
        }
    protected:
        QVariant GetData (int row, int, int role) const override
        {
            if (const auto getter = Fields_.value (role - this->DataRole - 1))
                return getter (this->Items_.at (row));
            return {};
        }
    private:
        QHash<int, QByteArray> MakeRoles (QVector<QByteArray> fields) const
        {
            auto result = FlatItemsModelTypedBase<T>::roleNames ();
            result.reserve (result.size () + fields.size ());
            for (int i = 0; i < fields.size (); ++i)
                result [this->DataRole + i + 1] = std::move (fields [i]);
            return result;
        }
    };
}