#pragma once
#include "compat/integer-types.hpp"
#include <concepts>
#include <compare>
#include <type_traits>
#include <utility>
#include <tuple>
#include <typeinfo>
#include <compat/function2.hpp>
#include <Corrade/Containers/StringView.h>

namespace floormat {}

namespace floormat::entities {

template<typename T, typename = void> struct pass_by_value : std::bool_constant<std::is_fundamental_v<T>> {};
template<> struct pass_by_value<StringView> : std::true_type {};
template<typename T> struct pass_by_value<T, std::enable_if_t<std::is_trivially_copy_constructible_v<T> && sizeof(T) <= sizeof(void*)>> : std::true_type {};
template<typename T> constexpr inline bool pass_by_value_v = pass_by_value<T>::value;

template<typename T> using const_qualified = std::conditional_t<pass_by_value_v<T>, T, const T&>;
template<typename T> using ref_qualified = std::conditional_t<pass_by_value_v<T>, T, T&>;
template<typename T> using move_qualified = std::conditional_t<pass_by_value_v<T>, T, T&&>;

template<typename F, typename T, typename FieldType>
concept FieldReader_memfn = requires(const T x, F f) {
    { (x.*f)() } -> std::convertible_to<FieldType>;
};

template<typename F, typename T, typename FieldType>
concept FieldReader_ptr = requires(const T x, F f) {
    { x.*f } -> std::convertible_to<FieldType>;
};

template<typename F, typename T, typename FieldType>
concept FieldReader_function = requires(const T x, F f) {
    { f(x) } -> std::convertible_to<FieldType>;
};

template<typename F, typename T, typename FieldType>
concept FieldReader = requires {
    requires FieldReader_memfn<F, T, FieldType> ||
             FieldReader_ptr<F, T, FieldType> ||
             FieldReader_function<F, T, FieldType>;
};

template<typename F, typename T, typename FieldType>
concept FieldWriter_memfn = requires(T x, move_qualified<FieldType> value, F f) {
    { (x.*f)(value) } -> std::same_as<void>;
};

template<typename F, typename T, typename FieldType>
concept FieldWriter_ptr = requires(T x, move_qualified<FieldType> value, F f) {
    { x.*f = value };
};

template<typename F, typename T, typename FieldType>
concept FieldWriter_function = requires(T x, move_qualified<FieldType> value, F f) {
    { f(x, value) } -> std::same_as<void>;
};

template<typename F, typename T, typename FieldType>
concept FieldWriter = requires {
    requires FieldWriter_memfn<F, T, FieldType> ||
             FieldWriter_ptr<F, T, FieldType> ||
             FieldWriter_function<F, T, FieldType>;
};

namespace detail {

template<typename Obj, typename Type, FieldReader<Obj, Type> R>
struct read_field {
    static constexpr Type read(const Obj& x, R r) { return r(x); }
};

template<typename Obj, typename Type>
struct read_field<Obj, Type, Type (Obj::*)() const> {
    static constexpr Type read(const Obj& x, Type (Obj::*r)() const) { return (x.*r)(); }
};

template<typename Obj, typename Type>
struct read_field<Obj, Type, Type Obj::*> {
    static constexpr Type read(const Obj& x, Type Obj::*r) { return x.*r; }
};

template<typename Obj, typename Type, bool IsOwning, bool IsCopyable, typename Capacity, bool IsThrowing, bool HasStrongExceptionGuarantee>
struct read_field<Obj, Type, fu2::function_base<IsOwning, IsCopyable, Capacity, IsThrowing, HasStrongExceptionGuarantee, void(const Obj&, move_qualified<Type>) const>> {
    template<typename F> static constexpr Type read(const Obj& x, F&& fun) {
        return fun(x);
    }
};

template<typename Obj, typename FieldType, FieldWriter<Obj, FieldType> W> struct write_field {
    static constexpr void write(Obj& x, W w, move_qualified<FieldType> value) { w(x, value); }
};

template<typename Obj, typename FieldType>
struct write_field<Obj, FieldType, void(Obj::*)(move_qualified<FieldType>)> {
    static constexpr void write(Obj& x, void(Obj::*w)(move_qualified<FieldType>), move_qualified<FieldType> value) { (x.*w)(value); }
};

template<typename Obj, typename FieldType>
struct write_field<Obj, FieldType, FieldType Obj::*> {
    static constexpr void write(Obj& x, FieldType Obj::* w, move_qualified<FieldType> value) { x.*w = value; }
};

template<typename Obj, typename Type, bool IsOwning, bool IsCopyable, typename Capacity, bool IsThrowing, bool HasStrongExceptionGuarantee>
struct write_field<Obj, Type, fu2::function_base<IsOwning, IsCopyable, Capacity, IsThrowing, HasStrongExceptionGuarantee, void(Obj&, move_qualified<Type>) const>> {
    template<typename F> static constexpr void write(Obj& x, F&& fun, move_qualified<Type> value) {
        fun(x, value);
    }
};

template<typename F, typename Tuple, std::size_t N>
requires std::invocable<F, decltype(std::get<N>(std::declval<Tuple>()))>
constexpr CORRADE_ALWAYS_INLINE void visit_tuple(F&& fun, Tuple&& tuple)
{
    using Size = std::tuple_size<std::remove_cvref_t<Tuple>>;
    static_assert(N < Size());

    fun(std::get<N>(tuple));
    if constexpr(N+1 < Size())
        visit_tuple<F, Tuple, N+1>(std::forward<F>(fun), std::forward<Tuple>(tuple));
}

template<typename F, typename Tuple, std::size_t N>
requires std::is_invocable_r_v<bool, F, decltype(std::get<N>(std::declval<Tuple>()))>
constexpr CORRADE_ALWAYS_INLINE bool find_in_tuple(F&& fun, Tuple&& tuple)
{
    using Size = std::tuple_size<std::remove_cvref_t<Tuple>>;
    static_assert(N < Size());

    if (fun(std::get<N>(tuple)))
        return true;
    if constexpr(N+1 < Size())
        return find_in_tuple<F, Tuple, N+1>(std::forward<F>(fun), std::forward<Tuple>(tuple));
    return false;
}

} // namespace detail

struct erased_accessors final {
    struct erased_reader_t;
    struct erased_writer_t;
    const erased_reader_t* reader;
    const erased_writer_t* writer;
    const char *object_type, *field_type;
    void(*read_fun)(const void*, const erased_reader_t*, void*);
    void(*write_fun)(void*, const erased_writer_t*, void*);
};

struct EntityBase {};

template<typename Obj>
struct Entity final : EntityBase {
    static_assert(std::is_same_v<Obj, std::decay_t<Obj>>);

    struct type_base {};

    template<typename Type>
    struct type final : type_base
    {
        static_assert(std::is_same_v<Type, std::decay_t<Type>>);
        struct field_base {};

        template<FieldReader<Obj, Type> R, FieldWriter<Obj, Type> W>
        struct field final : field_base
        {
            using ObjectType = Obj;
            using FieldType = Type;
            using Reader = R;
            using Writer = W;

            StringView name;
            [[no_unique_address]] R reader;
            [[no_unique_address]] W writer;

            constexpr field(const field&) = default;
            constexpr field& operator=(const field&) = default;
            static constexpr decltype(auto) read(const R& reader, const Obj& x) { return detail::read_field<Obj, Type, R>::read(x, reader); }
            static constexpr void write(const W& writer, Obj& x, move_qualified<Type> v) { detail::write_field<Obj, Type, W>::write(x, writer, v); }
            constexpr decltype(auto) read(const Obj& x) const { return read(reader, x); }
            constexpr void write(Obj& x, move_qualified<Type> value) const { write(writer, x, value); }
            consteval field(StringView name, R r, W w) noexcept : name{name}, reader{r}, writer{w} {}

            erased_accessors accessors() const {
                using reader_t = typename erased_accessors::erased_reader_t;
                using writer_t = typename erased_accessors::erased_writer_t;
                return erased_accessors {
                    reinterpret_cast<const reader_t*>(&reader), reinterpret_cast<const writer_t*>(&writer),
                    typeid(Obj).name(), typeid(Type).name(),
                    [](const void* obj, const reader_t* reader, void* value) {
                        const auto& obj_ = *reinterpret_cast<const Obj*>(obj);
                        const auto& reader_ = *reinterpret_cast<const R*>(reader);
                        auto& value_ = *reinterpret_cast<Type*>(value);
                        value_ = read(reader_, obj_);
                    },
                    [](void* obj, const writer_t* writer, void* value) {
                        auto& obj_ = *reinterpret_cast<Obj*>(obj);
                        const auto& writer_ = *reinterpret_cast<const W*>(writer);
                        auto&& value_ = std::move(*reinterpret_cast<Type*>(value));
                        write(writer_, obj_, value_);
                    },
                };
            }
        };

        template<FieldReader<Obj, Type> R, FieldWriter<Obj, Type> W>
        field(StringView name, R r, W w) -> field<R, W>;
    };
};

template<typename F, typename Tuple>
constexpr void visit_tuple(F&& fun, Tuple&& tuple)
{
    using Size = std::tuple_size<std::decay_t<Tuple>>;
    if constexpr(Size() > 0)
        detail::visit_tuple<F, Tuple, 0>(std::forward<F>(fun), std::forward<Tuple>(tuple));
}

template<typename F, typename Tuple>
constexpr bool find_in_tuple(F&& fun, Tuple&& tuple)
{
    using Size = std::tuple_size<std::decay_t<Tuple>>;
    if constexpr(Size() > 0)
        return detail::find_in_tuple<F, Tuple, 0>(std::forward<F>(fun), std::forward<Tuple>(tuple));
    else
        return false;
}

enum class erased_field_type : std::uint32_t {
    none,
    string,
    u8, u16, u32, u64, s8, s16, s32, s64,
    user_type_start,
    MAX = (1u << 31) - 1u,
    DYNAMIC = (std::uint32_t)-1,
};

template<erased_field_type> struct type_of_erased_field;
template<typename T> struct erased_field_type_v_ : std::integral_constant<erased_field_type, erased_field_type::DYNAMIC> {};

#define FM_ERASED_FIELD_TYPE(TYPE, ENUM)                                                                                    \
    template<> struct erased_field_type_v_<TYPE> : std::integral_constant<erased_field_type, erased_field_type::ENUM> {};   \
    template<> struct type_of_erased_field<erased_field_type::ENUM> { using type = TYPE; }
FM_ERASED_FIELD_TYPE(std::uint8_t, u8);
FM_ERASED_FIELD_TYPE(std::uint16_t, u16);
FM_ERASED_FIELD_TYPE(std::uint32_t, u32);
FM_ERASED_FIELD_TYPE(std::uint64_t, u64);
FM_ERASED_FIELD_TYPE(std::int8_t, s8);
FM_ERASED_FIELD_TYPE(std::int16_t, s16);
FM_ERASED_FIELD_TYPE(std::int32_t, s32);
FM_ERASED_FIELD_TYPE(std::int64_t, s64);
FM_ERASED_FIELD_TYPE(StringView, string);
#undef FM_ERASED_FIELD_TYPE

} // namespace floormat::entities