/******************************************************************************
 * Copyright (C) 2017 Kitsune Ral <kitsune-ral@users.sf.net>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
 */

#pragma once

#include "util.h"

#include <QtCore/QDate>
#include <QtCore/QJsonArray> // Includes <QtCore/QJsonValue>
#include <QtCore/QJsonDocument>
#include <QtCore/QJsonObject>
#include <QtCore/QSet>
#include <QtCore/QUrlQuery>
#include <QtCore/QVector>

#include <unordered_map>
#include <vector>
#if 0 // Waiting for C++17
#include <experimental/optional>

template <typename T>
using optional = std::experimental::optional<T>;
#endif

// Enable std::unordered_map<QString, T>
namespace std {
    template <> struct hash<QString> {
        size_t operator()(const QString& s) const Q_DECL_NOEXCEPT
        {
            return qHash(s
#if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
                         ,
                         uint(qGlobalQHashSeed())
#endif
            );
        }
    };
}

class QVariant;

namespace QMatrixClient {
    template <typename T> struct JsonObjectConverter {
        static void dumpTo(QJsonObject& jo, const T& pod) { jo = pod; }
        static void fillFrom(const QJsonObject& jo, T& pod) { pod = jo; }
    };

    template <typename T> struct JsonConverter {
        static QJsonObject dump(const T& pod)
        {
            QJsonObject jo;
            JsonObjectConverter<T>::dumpTo(jo, pod);
            return jo;
        }
        static T doLoad(const QJsonObject& jo)
        {
            T pod;
            JsonObjectConverter<T>::fillFrom(jo, pod);
            return pod;
        }
        static T load(const QJsonValue& jv) { return doLoad(jv.toObject()); }
        static T load(const QJsonDocument& jd) { return doLoad(jd.object()); }
    };

    template <typename T> inline auto toJson(const T& pod)
    {
        return JsonConverter<T>::dump(pod);
    }

    template <typename T> inline auto fillJson(QJsonObject& json, const T& data)
    {
        JsonObjectConverter<T>::dumpTo(json, data);
    }

    template <typename T> inline auto fromJson(const QJsonValue& jv)
    {
        return JsonConverter<T>::load(jv);
    }

    template <typename T> inline T fromJson(const QJsonDocument& jd)
    {
        return JsonConverter<T>::load(jd);
    }

    template <typename T> inline void fromJson(const QJsonValue& jv, T& pod)
    {
        if (!jv.isUndefined())
            pod = fromJson<T>(jv);
    }

    template <typename T> inline void fromJson(const QJsonDocument& jd, T& pod)
    {
        pod = fromJson<T>(jd);
    }

    // Unfolds Omittable<>
    template <typename T>
    inline void fromJson(const QJsonValue& jv, Omittable<T>& pod)
    {
        if (jv.isUndefined())
            pod = none;
        else
            pod = fromJson<T>(jv);
    }

    template <typename T> inline void fillFromJson(const QJsonValue& jv, T& pod)
    {
        if (jv.isObject())
            JsonObjectConverter<T>::fillFrom(jv.toObject(), pod);
    }

    // JsonConverter<> specialisations

    template <typename T> struct TrivialJsonDumper {
        // Works for: QJsonValue (and all things it can consume),
        // QJsonObject, QJsonArray
        static auto dump(const T& val) { return val; }
    };

    template <> struct JsonConverter<bool> : public TrivialJsonDumper<bool> {
        static auto load(const QJsonValue& jv) { return jv.toBool(); }
    };

    template <> struct JsonConverter<int> : public TrivialJsonDumper<int> {
        static auto load(const QJsonValue& jv) { return jv.toInt(); }
    };

    template <>
    struct JsonConverter<double> : public TrivialJsonDumper<double> {
        static auto load(const QJsonValue& jv) { return jv.toDouble(); }
    };

    template <> struct JsonConverter<float> : public TrivialJsonDumper<float> {
        static auto load(const QJsonValue& jv) { return float(jv.toDouble()); }
    };

    template <>
    struct JsonConverter<qint64> : public TrivialJsonDumper<qint64> {
        static auto load(const QJsonValue& jv) { return qint64(jv.toDouble()); }
    };

    template <>
    struct JsonConverter<QString> : public TrivialJsonDumper<QString> {
        static auto load(const QJsonValue& jv) { return jv.toString(); }
    };

    template <> struct JsonConverter<QDateTime> {
        static auto dump(const QDateTime& val) = delete; // not provided yet
        static auto load(const QJsonValue& jv)
        {
            return QDateTime::fromMSecsSinceEpoch(fromJson<qint64>(jv),
                                                  Qt::UTC);
        }
    };

    template <> struct JsonConverter<QDate> {
        static auto dump(const QDate& val) = delete; // not provided yet
        static auto load(const QJsonValue& jv)
        {
            return fromJson<QDateTime>(jv).date();
        }
    };

    template <>
    struct JsonConverter<QJsonArray> : public TrivialJsonDumper<QJsonArray> {
        static auto load(const QJsonValue& jv) { return jv.toArray(); }
    };

    template <> struct JsonConverter<QByteArray> {
        static QString dump(const QByteArray& ba) { return ba.constData(); }
        static auto load(const QJsonValue& jv)
        {
            return fromJson<QString>(jv).toLatin1();
        }
    };

    template <> struct JsonConverter<QVariant> {
        static QJsonValue dump(const QVariant& v);
        static QVariant load(const QJsonValue& jv);
    };

    template <typename VectorT, typename T = typename VectorT::value_type>
    struct JsonArrayConverter {
        static void dumpTo(QJsonArray& ar, const VectorT& vals)
        {
            for (const auto& v : vals)
                ar.push_back(toJson(v));
        }
        static auto dump(const VectorT& vals)
        {
            QJsonArray ja;
            dumpTo(ja, vals);
            return ja;
        }
        static auto load(const QJsonArray& ja)
        {
            VectorT vect;
            vect.reserve(typename VectorT::size_type(ja.size()));
            for (const auto& i : ja)
                vect.push_back(fromJson<T>(i));
            return vect;
        }
        static auto load(const QJsonValue& jv) { return load(jv.toArray()); }
        static auto load(const QJsonDocument& jd) { return load(jd.array()); }
    };

    template <typename T>
    struct JsonConverter<std::vector<T>>
        : public JsonArrayConverter<std::vector<T>> {
    };

    template <typename T>
    struct JsonConverter<QVector<T>> : public JsonArrayConverter<QVector<T>> {
    };

    template <typename T>
    struct JsonConverter<QList<T>> : public JsonArrayConverter<QList<T>> {
    };

    template <>
    struct JsonConverter<QStringList> : public JsonConverter<QList<QString>> {
        static auto dump(const QStringList& sl)
        {
            return QJsonArray::fromStringList(sl);
        }
    };

    template <> struct JsonObjectConverter<QSet<QString>> {
        static void dumpTo(QJsonObject& json, const QSet<QString>& s)
        {
            for (const auto& e : s)
                json.insert(toJson(e), QJsonObject {});
        }
        static auto fillFrom(const QJsonObject& json, QSet<QString>& s)
        {
            s.reserve(s.size() + json.size());
            for (auto it = json.begin(); it != json.end(); ++it)
                s.insert(it.key());
            return s;
        }
    };

    template <typename HashMapT> struct HashMapFromJson {
        static void dumpTo(QJsonObject& json, const HashMapT& hashMap)
        {
            for (auto it = hashMap.begin(); it != hashMap.end(); ++it)
                json.insert(it.key(), toJson(it.value()));
        }
        static void fillFrom(const QJsonObject& jo, HashMapT& h)
        {
            h.reserve(jo.size());
            for (auto it = jo.begin(); it != jo.end(); ++it)
                h[it.key()] =
                        fromJson<typename HashMapT::mapped_type>(it.value());
        }
    };

    template <typename T>
    struct JsonObjectConverter<std::unordered_map<QString, T>>
        : public HashMapFromJson<std::unordered_map<QString, T>> {
    };

    template <typename T>
    struct JsonObjectConverter<QHash<QString, T>>
        : public HashMapFromJson<QHash<QString, T>> {
    };

    // We could use std::conditional<> below but QT_VERSION* macros in C++ code
    // cause (kinda valid but useless and noisy) compiler warnings about
    // bitwise operations on signed integers; so use the preprocessor for now.
    using variant_map_t =
#if (QT_VERSION >= QT_VERSION_CHECK(5, 5, 0))
            QVariantHash;
#else
            QVariantMap;
#endif
    template <> struct JsonConverter<variant_map_t> {
        static QJsonObject dump(const variant_map_t& vh);
        static QVariantHash load(const QJsonValue& jv);
    };

    // Conditional insertion into a QJsonObject

    namespace _impl {
        template <typename ValT>
        inline void addTo(QJsonObject& o, const QString& k, ValT&& v)
        {
            o.insert(k, toJson(v));
        }

        template <typename ValT>
        inline void addTo(QUrlQuery& q, const QString& k, ValT&& v)
        {
            q.addQueryItem(k, QStringLiteral("%1").arg(v));
        }

        // OpenAPI is entirely JSON-based, which means representing bools as
        // textual true/false, rather than 1/0.
        inline void addTo(QUrlQuery& q, const QString& k, bool v)
        {
            q.addQueryItem(
                    k, v ? QStringLiteral("true") : QStringLiteral("false"));
        }

        inline void addTo(QUrlQuery& q, const QString& k,
                          const QStringList& vals)
        {
            for (const auto& v : vals)
                q.addQueryItem(k, v);
        }

        inline void addTo(QUrlQuery& q, const QString&, const QJsonObject& vals)
        {
            for (auto it = vals.begin(); it != vals.end(); ++it)
                q.addQueryItem(it.key(), it.value().toString());
        }

        // This one is for types that don't have isEmpty()
        template <typename ValT, bool Force = true, typename = bool>
        struct AddNode {
            template <typename ContT, typename ForwardedT>
            static void impl(ContT& container, const QString& key,
                             ForwardedT&& value)
            {
                addTo(container, key, std::forward<ForwardedT>(value));
            }
        };

        // This one is for types that have isEmpty()
        template <typename ValT>
        struct AddNode<ValT, false, decltype(std::declval<ValT>().isEmpty())> {
            template <typename ContT, typename ForwardedT>
            static void impl(ContT& container, const QString& key,
                             ForwardedT&& value)
            {
                if (!value.isEmpty())
                    AddNode<ValT>::impl(container, key,
                                        std::forward<ForwardedT>(value));
            }
        };

        // This is a special one that unfolds Omittable<>
        template <typename ValT, bool Force>
        struct AddNode<Omittable<ValT>, Force> {
            template <typename ContT, typename OmittableT>
            static void impl(ContT& container, const QString& key,
                             const OmittableT& value)
            {
                if (!value.omitted())
                    AddNode<ValT>::impl(container, key, value.value());
                else if (Force) // Edge case, no value but must put something
                    AddNode<ValT>::impl(container, key, QString {});
            }
        };

#if 0
        // This is a special one that unfolds optional<>
        template <typename ValT, bool Force>
        struct AddNode<optional<ValT>, Force>
        {
            template <typename ContT, typename OptionalT>
            static void impl(ContT& container,
                             const QString& key, const OptionalT& value)
            {
                if (value)
                    AddNode<ValT>::impl(container, key, value.value());
                else if (Force) // Edge case, no value but must put something
                    AddNode<ValT>::impl(container, key, QString{});
            }
        };
#endif

    } // namespace _impl

    static constexpr bool IfNotEmpty = false;

    template <bool Force = true, typename ContT, typename ValT>
    inline void addParam(ContT& container, const QString& key, ValT&& value)
    {
        _impl::AddNode<std::decay_t<ValT>, Force>::impl(
                container, key, std::forward<ValT>(value));
    }
} // namespace QMatrixClient