itemsmodel.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 <util/sll/ctstring.h>
#include <util/sll/typegetter.h>
#include "flatitemsmodeltypedbase.h"

namespace LC::Util
{
    template<typename T, int RoleV>
    struct RoleOf
    {
        constexpr static auto Role = RoleV;

        using Type = T;

        T Value_ {};

        RoleOf () = default;

        RoleOf (const RoleOf& other) = default;
        RoleOf (RoleOf&& other) = default;

        RoleOf& operator= (const RoleOf& other) = default;
        RoleOf& operator= (RoleOf&& other) = default;

        template<typename U = T>
        RoleOf (U&& value)
        : Value_ (std::forward<U> (value))
        {
        }

        template<typename U = T>
        RoleOf& operator= (U&& value)
        {
            Value_ = std::forward<U> (value);
            return *this;
        }

        template<typename U = T>
            requires requires (T t, U u) { t == u; }
        bool operator== (const U& value) const
        {
            return Value_ == value;
        }

        T& operator* ()
        {
            return Value_;
        }

        const T& operator* () const
        {
            return Value_;
        }

        T* operator-> ()
        {
            return &Value_;
        }

        const T* operator-> () const
        {
            return &Value_;
        }

        operator T () const
            requires (!std::is_same_v<T, QVariant>)
        {
            return Value_;
        }

        operator QVariant () const
        {
            return Value_;
        }
    };

    namespace detail
    {
        constexpr auto GetFieldsCount (auto&& val)
        {
            auto&& [...elems] = val;
            return std::integral_constant<size_t, sizeof... (elems)> {};
        }

        template<size_t I>
        constexpr auto GetFieldAt (auto&& val)
        {
            auto&& [...elems] = val;
            return elems... [I];
        }

        template<typename T, size_t I>
        using FieldType_t = decltype (GetFieldAt<I> (std::declval<T> ()));

        template<typename T>
        constexpr size_t FieldsCount_v = decltype (GetFieldsCount (std::declval<T> ()))::value;

        template<typename T>
        using FieldGetter_t = QVariant (*) (const T&);

        template<typename T, size_t Ix>
        std::pair<int, FieldGetter_t<T>> Role2GetterPair ()
        {
            if constexpr (requires { FieldType_t<T, Ix>::Role; })
                return
                {
                    FieldType_t<T, Ix>::Role,
                    +[] (const T& t) { return QVariant::fromValue (*GetFieldAt<Ix> (t)); }
                };
            else
                return { -1, nullptr };
        }

        template<typename T>
        QHash<int, FieldGetter_t<T>> MkGetters ()
        {
            return []<size_t... Ixs> (std::index_sequence<Ixs...>)
            {
                return QHash<int, FieldGetter_t<T>> { Role2GetterPair<T, Ixs> ()... };
            } (std::make_index_sequence<FieldsCount_v<T>> {});
        }
    }

    template<auto F>
    constexpr auto FromField = +[] (const ArgType_t<decltype (F), 0>& t) { return QVariant::fromValue (t.*F); };

    template<typename T>
    class RoledItemsModel : public FlatItemsModelTypedBase<T>
    {
    public:
        using FieldGetter_t = detail::FieldGetter_t<T>;
    private:
        const QHash<int, FieldGetter_t> Role2Getter_;
    public:
        explicit RoledItemsModel (QObject *parent = nullptr)
        : FlatItemsModelTypedBase<T> { QStringList { {} }, parent }
        , Role2Getter_ { detail::MkGetters<T> () }
        {
        }

        explicit RoledItemsModel (const QHash<int, FieldGetter_t>& getters, QObject *parent = nullptr)
        : FlatItemsModelTypedBase<T> { QStringList { {} }, parent }
        , Role2Getter_ { getters }
        {
        }

        template<auto F, typename V>
        void SetField (int idx, V&& value)
        {
            if (this->Items_ [idx].*F == value)
                return;

            this->Items_ [idx].*F = std::forward<V> (value);
            emit this->dataChanged (this->index (idx, 0), this->index (idx, 0),
                    { std::decay_t<decltype (T {}.*F)>::Role });
        }

        template<auto... Fs, typename... Vs>
        void SetFields (int idx, Vs&&... values)
        {
            QList<int> changedRoles;
            changedRoles.reserve (sizeof... (values));
            (([&, this]
            {
                if (this->Items_ [idx].*Fs != std::forward<Vs> (values))
                {
                    this->Items_ [idx].*Fs = std::forward<Vs> (values);
                    changedRoles << std::decay_t<decltype (T {}.*Fs)>::Role;
                }
            } ()), ...);

            if (!changedRoles.isEmpty ())
                emit this->dataChanged (this->index (idx, 0), this->index (idx, 0), changedRoles);
        }
    protected:
        QVariant GetData (int row, int, int role) const override
        {
            if (const auto getter = Role2Getter_.value (role))
                return getter (this->Items_.at (row));
            return {};
        }
    };


    template<CtString RoleArg, auto GetterArg>
    struct NamedMemberField
    {
        static constexpr auto Getter = GetterArg;
        static constexpr auto Role = RoleArg;
    };

    template<CtString RoleArg, auto GetterArg>
    NamedMemberField<RoleArg, GetterArg> NamedMemberField_v;

    template<typename T>
    class NamedItemsModel : public FlatItemsModelTypedBase<T>
    {
    public:
        using FieldGetter_t = detail::FieldGetter_t<T>;
        using FieldsList_t = QVector<QPair<QByteArray, FieldGetter_t>>;
    private:
        const QVector<FieldGetter_t> Fields_;
        const QHash<int, QByteArray> Roles_;
    public:
        template<typename... Fields>
        explicit NamedItemsModel (QObject *parent, Fields...) noexcept
        : FlatItemsModelTypedBase<T> { QStringList { {} }, parent }
        , Fields_ { +[] (const T& t) -> QVariant { return t.*Fields::Getter; }... }
        , Roles_ { MakeRoles ({ ToByteArray<Fields::Role> ()... }) }
        {
        }

        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;
        }
    };

    template<auto Getter>
    struct Field
    {
        QString Name_;
    };

    namespace detail
    {
        template<Qt::ItemDataRole Role>
        using RoleTag = std::integral_constant<Qt::ItemDataRole, Role>;

        struct Extension
        {
            explicit Extension (auto&&...) {}

            static Qt::ItemFlags GetFlags (auto&&...) { return {}; }
            static bool SetData (auto&&...) { return false; }
            static void GetDataForRole () {}
        };

        template<typename P>
        struct ParameterizedExtension : Extension
        {
            struct Param
            {
                P Param_;
            };

            P Param_;

            template<typename... Params>
                requires (std::is_same_v<Param, Params> || ...)
            explicit ParameterizedExtension (const std::tuple<Params...>& args)
            : Param_ { std::get<Param> (args).Param_ }
            {
            }
        };
    }

    template<auto IconField>
    struct ItemsDecorated : detail::Extension
    {
        using Extension::Extension;

        static QVariant GetDataForRole (detail::RoleTag<Qt::DecorationRole>, const auto& item, int column)
        {
            if (column)
                return {};
            return item.*IconField;
        }
    };

    struct ItemsEditable : detail::ParameterizedExtension<QList<int>>
    {
        using ParameterizedExtension::ParameterizedExtension;

        Qt::ItemFlags GetFlags (int column) const
        {
            return Param_.contains (column) ? Qt::ItemIsEditable : Qt::ItemFlags {};
        }
    };

    template<auto CheckField>
    struct ItemsCheckable : detail::Extension
    {
        using Extension::Extension;

        static Qt::ItemFlags GetFlags (int column)
        {
            return column ? Qt::ItemFlags {} : Qt::ItemIsUserCheckable;
        }

        static QVariant GetDataForRole (detail::RoleTag<Qt::CheckStateRole>, const auto& item, int, int column)
        {
            if (column)
                return QVariant {};

            if constexpr (std::is_same_v<std::decay_t<decltype (item.*CheckField)>, Qt::CheckState>)
                return item.*CheckField;
            else if constexpr (std::is_same_v<std::decay_t<decltype (item.*CheckField)>, bool>)
                return item.*CheckField ? Qt::Checked : Qt::Unchecked;
            else
                static_assert (false, "expected Qt::CheckState or bool field");
        }

        template<typename Item>
        static bool SetData (Item& item, int, int column, const QVariant& value, int role)
        {
            if (role != Qt::CheckStateRole || column)
                return false;

            const auto state = value.value<Qt::CheckState> ();
            if constexpr (std::is_same_v<std::decay_t<decltype (item.*CheckField)>, Qt::CheckState>)
                item.*CheckField = state;
            else if constexpr (std::is_same_v<std::decay_t<decltype (item.*CheckField)>, bool>)
                item.*CheckField = state == Qt::Checked;
            else
                static_assert (false, "expected Qt::CheckState or bool field");
            return true;
        }
    };

    struct NoField {};
    inline constexpr auto NoField_v = NoField {};

    template<>
    struct ItemsCheckable<NoField_v> : detail::ParameterizedExtension<Qt::CheckState>
    {
        QHash<int, Qt::CheckState> RowsStates_;

        using ParameterizedExtension::ParameterizedExtension;

        static Qt::ItemFlags GetFlags (int column)
        {
            return column ? Qt::ItemFlags {} : Qt::ItemIsUserCheckable;
        }

        bool IsChecked (int row) const
        {
            return RowsStates_.value (row, Param_) == Qt::Checked;
        }

        QVariant GetDataForRole (detail::RoleTag<Qt::CheckStateRole>, const auto&, int row, int column)
        {
            return column ? QVariant {} : RowsStates_.value (row, Param_);
        }

        template<typename Item>
        bool SetData (Item&, int row, int column, const QVariant& value, int role)
        {
            if (role != Qt::CheckStateRole || column)
                return false;

            RowsStates_ [row] = value.value<Qt::CheckState> ();
            return true;
        }
    };

    template<typename T, typename... Extensions>
    class ItemsModel : public FlatItemsModelTypedBase<T>
                     , public Extensions...
    {
        using FieldGetter_t = QVariant (*) (const T&);
        const QVector<FieldGetter_t> Fields_;

        using FieldSetter_t = void (*) (T&, const QVariant&);
        const QVector<FieldSetter_t> Setters_;
    public:
        template<auto... Getter>
        explicit ItemsModel (const Field<Getter>&... fields)
        : ItemsModel { std::tuple {}, fields... }
        {
        }

        template<auto... Member, typename... ExtParams>
        explicit ItemsModel (const std::tuple<ExtParams...>& extParams, const Field<Member>&... fields)
        : FlatItemsModelTypedBase<T> { { fields.Name_... } }
        , Extensions { extParams }...
        , Fields_ { +[] (const T& t) -> QVariant { return t.*Member; }... }
        , Setters_ { +[] (T& t, const QVariant& v) { t.*Member = v.value<std::decay_t<decltype (t.*Member)>> (); }... }
        {
        }

        Qt::ItemFlags flags (const QModelIndex& index) const override
        {
            auto flags = FlatItemsModelTypedBase<T>::flags (index);
            flags |= (Extensions::GetFlags (index.column ()) | ...);
            return flags;
        }

        bool setData (const QModelIndex& index, const QVariant& value, int role) override
        {
            auto& item = this->Items_ [index.row ()];
            if ((Extensions::SetData (item, index.row (), index.column (), value, role) ||...))
            {
                emit this->dataChanged (index, index);
                return true;
            }

            if (role != Qt::EditRole)
                return false;

            Setters_ [index.column ()] (item, value);
            emit this->dataChanged (index, index);
            return true;
        }
    protected:
        QVariant GetData (int row, int column, int role) const override
        {
            const auto& item = this->Items_ [row];

            switch (role)
            {
            case Qt::DisplayRole:
            case Qt::EditRole:
                if (const auto getter = Fields_.value (column))
                    return getter (item);
                return {};
            case Qt::CheckStateRole:
                return this->GetDataForRole (detail::RoleTag<Qt::CheckStateRole> {}, item, row, column);
            case Qt::DecorationRole:
                return this->GetDataForRole (detail::RoleTag<Qt::DecorationRole> {}, item, row, column);
            default:
                return {};
            }
        }

        using Extensions::GetDataForRole...;

        static QVariant GetDataForRole (auto&&...)
        {
            return {};
        }
    };
}