#pragma once

#include <atomic>
#include <concepts>

#include "mcc_concepts.h"
#include "mcc_error.h"
#include "mcc_traits.h"
#include "mcc_utils.h"

namespace mcc
{


struct mcc_serializer_interface_t {
    virtual ~mcc_serializer_interface_t() = default;

    template <std::derived_from<mcc_serializer_interface_t> SelfT,
              traits::mcc_output_char_range R,
              typename ValueT,
              typename FmtT>
        requires(std::same_as<std::format_string<ValueT>, FmtT> || std::same_as<std::string_view, FmtT>)
    mcc_error_c auto operator()(this SelfT&& self, R& output, ValueT const& value, FmtT fmt)
    {
        return std::forward<SelfT>(self).operator=(output, value, std::move(fmt));
    }
};

template <typename T>
concept mcc_serializer_c = std::derived_from<T, mcc_serializer_interface_t>;



/*  fallback template */
template <typename VT>
class MccSerializer : public mcc_serializer_interface_t
{
public:
    // default delimiter
    static constexpr std::string_view defaultDelimiter{","};

    typedef impl::MccError error_t;

    MccSerializer() = default;

    ~MccSerializer() = default;

    template <typename FmtT = std::nullptr_t>
    error_t operator()(traits::mcc_output_char_range auto& output, VT const& value, FmtT fmt = nullptr)
    {
        if constexpr (std::formattable<VT, char>) {
            if constexpr (std::is_null_pointer_v<FmtT>) {
                std::format_to(std::back_inserter(output), "{}", value);
            } else if constexpr (traits::mcc_input_char_range<FmtT>) {
                std::format_to(std::back_inserter(output), fmt, value);
            } else if constexpr (std::same_as<std::format_string<VT>, FmtT>) {
                std::string_view sfmt{fmt.begin(), fmt.end()};
                std::vformat_to(std::back_inserter(output), sfmt, std::make_format_args(value));
            } else {
                static_assert(false, "INVALID FORMAT STRING TYPE!!!");
            }
        } else if constexpr (std::convertible_to<VT, std::string>) {
            return MccSerializer<std::string>{}(output, static_cast<std::string>(value), std::move(fmt));
        } else if constexpr (std::ranges::range<VT>) {
            using value_t = std::remove_cv_t<std::ranges::range_value_t<VT>>;

            // special range (character sequence)
            if constexpr (std::same_as<value_t, char>) {
                std::string str;
                std::ranges::copy(value, std::back_inserter(str));

                return MccSerializer<std::string>{}(output, str, std::move(fmt));
            } else {
                MccSerializer<value_t> sr;

                size_t i = 0, N = std::ranges::size(value);
                for (auto const& el : value) {
                    error_t err = sr(output, el, std::move(fmt));
                    if (err) {
                        return err;
                    }
                    if (++i < N) {
                        std::format_to(std::back_inserter(output), "{}", _delimiter);
                    }
                }
            }
        }

        return {};
    }

protected:
    std::string _delimiter{defaultDelimiter};
};


/*                          SPECIALIZATION FOR THE SOME CONCEPTS                            */

template <typename VT>
    requires(mcc_angle_c<VT> ||
             (std::ranges::input_range<VT> && mcc_angle_c<std::remove_cv_t<std::ranges::range_value_t<VT>>>))
class MccSerializer<VT> : public mcc_serializer_interface_t
{
public:
    enum SerializedCoordFormat {
        CFMT_DEGREES,    // floating-point representation in degrees
        CFMT_SGM_HOURS,  // sexagesimal representation: HH:MM:SS.SSSSSS (hours:minutes:seconds)
        CFMT_SGM_DEGS    // sexagesimal representation: DD:MM:SS.SSSSS (degrees:arcmins::arcsecs)
    };

    struct SexagesimalCoordPrec {
        uint8_t hour_prec = 2;  // number of decimal places in hour seconds
        uint8_t deg_prec = 1;   // number of decimal places in arcseconds
    };

    typedef impl::MccError error_t;

    void setCoordFormat(SerializedCoordFormat format)
    {
        _coordFormat = format;
    }

    SerializedCoordFormat getCoordFormat() const
    {
        return _coordFormat;
    }


    void setCoordPrec(SexagesimalCoordPrec prec)
    {
        _coordPrec = std::move(prec);
    }

    SexagesimalCoordPrec getCoordPrec() const
    {
        return _coordPrec;
    }

    template <typename FmtT = std::nullptr_t>
    error_t operator()(traits::mcc_output_char_range auto& output, VT const& value, FmtT fmt = nullptr)
    {
        if constexpr (std::ranges::input_range<VT>) {
            MccSerializer<std::remove_cv_t<std::ranges::range_value_t<VT>>> sr;
            sr.setCoordFormat(_coordFormat);
            sr.setCoordPrec(_coordPrec);

            error_t err;
            size_t i = 0, N = std::ranges::size(value);
            for (auto const& el : value) {
                err = sr(output, el, std::move(fmt));
                if (err) {
                    return err;
                }

                if (++i < N) {
                    std::format_to(std::back_inserter(output), " ");
                }
            }

            return error_t{};
        } else {                       // scalar
            double v = (double)value;  // radians
            std::string sgm;

            switch (_coordFormat) {
                case MccSerializer::CFMT_DEGREES:
                    v *= 180.0 / std::numbers::pi;
                    return MccSerializer<double>{}(output, v, std::move(fmt));
                case MccSerializer::CFMT_SGM_HOURS:
                    sgm = utils::rad2sxg(value, true, _coordPrec.load().hour_prec);
                    break;
                case MccSerializer::CFMT_SGM_DEGS:
                    sgm = utils::rad2sxg(value, false, _coordPrec.load().deg_prec);
                    break;
                default:
                    break;
            }
            return MccSerializer<std::string>{}(output, sgm, std::move(fmt));
        }
    }

protected:
    std::atomic<SerializedCoordFormat> _coordFormat{MccSerializer::CFMT_DEGREES};
    std::atomic<SexagesimalCoordPrec> _coordPrec{SexagesimalCoordPrec{.hour_prec = 2, .deg_prec = 1}};
};


template <mcc_skypoint_c VT>
class MccSerializer<VT> : public mcc_serializer_interface_t
{
};



static_assert(mcc_serializer_c<MccSerializer<float>>, "!!!");

static_assert(mcc_serializer_c<MccSerializer<impl::MccAngle>>, "!!!");

static_assert(std::atomic<MccSerializer<impl::MccAngle>::SerializedCoordFormat>::is_always_lock_free, "!!!");
static_assert(std::atomic<MccSerializer<impl::MccAngle>::SexagesimalCoordPrec>::is_always_lock_free, "!!!");

static_assert(traits::mcc_formattable<impl::MccAngle>, "!!!");

void f()
{
    MccSerializer<impl::MccAngle> s;

    std::string str;
    s(str, impl::MccAngleALT{1.1});
}

}  // namespace mcc