path: root/src/openvic-simulation/types/Colour.hpp

#pragma once

#include <algorithm>
#include <array>
#include <cassert>
#include <climits>
#include <cstdint>
#include <limits>
#include <string>
#include <string_view>
#include <tuple>
#include <type_traits>
#include <utility>

#include "openvic-simulation/utility/Utility.hpp"

namespace OpenVic {
   template<typename ValueT, typename IntT>
   struct colour_traits {
      using value_type = ValueT;
      using integer_type = IntT;
      static_assert(sizeof(value_type) * 4 <= sizeof(integer_type), "value_type must be 4x smaller then colour_integer_type");

      /* When colour_t is used as an identifier, NULL_COLOUR is disallowed
       * and should be reserved as an error value.
       * When colour_t is used in a purely graphical context, NULL_COLOUR
       * should be allowed.
       */
      static constexpr integer_type null = 0;
      static constexpr integer_type component = std::numeric_limits<ValueT>::max();
      static constexpr integer_type component_bit_size = sizeof(ValueT) * CHAR_BIT;
      static constexpr integer_type blue_shift = 0;
      static constexpr integer_type green_shift = component_bit_size;
      static constexpr integer_type red_shift = component_bit_size * 2;
      static constexpr integer_type alpha_shift = component_bit_size * 3;
      static constexpr bool has_alpha = true;

      static constexpr integer_type make_rgb_integer(value_type red, value_type green, value_type blue) {
         return (red << red_shift) | (green << green_shift) | (blue << blue_shift);
      }
      static constexpr integer_type make_argb_integer(value_type red, value_type green, value_type blue, value_type alpha) {
         return make_rgb_integer(red, green, blue) | (alpha << alpha_shift);
      }

      static constexpr value_type red_from_integer(integer_type colour) {
         return (colour >> red_shift) & component;
      }
      static constexpr value_type blue_from_integer(integer_type colour) {
         return (colour >> blue_shift) & component;
      }
      static constexpr value_type green_from_integer(integer_type colour) {
         return (colour >> green_shift) & component;
      }
      static constexpr value_type alpha_from_integer(integer_type colour) {
         return (colour >> alpha_shift) & component;
      }

      static constexpr float component_to_float(value_type value) {
         return static_cast<float>(value) / static_cast<float>(component);
      }

      static constexpr value_type component_from_float(float f, float min = 0.0f, float max = 1.0f) {
         constexpr auto floor = [](float f) {
            const std::int64_t i = static_cast<std::int64_t>(f);
            return f < i ? i - 1 : i;
         };

         return floor(std::clamp(min + f * (max - min), min, max) * static_cast<float>(component));
      }

      static constexpr value_type component_from_fraction(int n, int d, float min = 0.0f, float max = 1.0f) {
         return component_from_float(static_cast<float>(n) / static_cast<float>(d), min, max);
      }

      static constexpr float red_to_float(value_type red) {
         return component_to_float(red);
      }
      static constexpr float green_to_float(value_type green) {
         return component_to_float(green);
      }
      static constexpr float blue_to_float(value_type blue) {
         return component_to_float(blue);
      }
      static constexpr float alpha_to_float(value_type alpha) {
         return component_to_float(alpha);
      }

      static constexpr value_type red_from_float(float red) {
         return component_from_float(red);
      }
      static constexpr value_type green_from_float(float green) {
         return component_from_float(green);
      }
      static constexpr value_type blue_from_float(float blue) {
         return component_from_float(blue);
      }
      static constexpr value_type alpha_from_float(float alpha) {
         return component_from_float(alpha);
      }

      static constexpr integer_type max_rgb = make_rgb_integer(component, component, component);
      static constexpr integer_type max_argb = make_argb_integer(component, component, component, component);
   };

   /* Colour represented by an unsigned integer, either 24-bit RGB or 32-bit ARGB. */
   template<typename ValueT, typename ColourIntT, typename ColourTraits = colour_traits<ValueT, ColourIntT>>
   struct basic_colour_t {
      /* PROPERTY generated getter functions will return colours by value, rather than const reference. */
      using ov_return_by_value = void;

      using colour_traits = ColourTraits;
      using value_type = typename colour_traits::value_type;
      using integer_type = typename colour_traits::integer_type;

      static_assert(std::same_as<ValueT, value_type> && std::same_as<ColourIntT, integer_type>);

      static constexpr auto max_value = colour_traits::component;

      struct empty_value {
         constexpr empty_value() {}
         constexpr empty_value(value_type) {}
         constexpr operator value_type() const {
            return max_value;
         }
      };

   private:
      using _alpha_t = std::conditional_t<colour_traits::has_alpha, value_type, empty_value>;

   public:
      value_type red;
      value_type green;
      value_type blue;
      [[no_unique_address]] _alpha_t alpha;

      static constexpr std::integral_constant<std::size_t, std::is_same_v<decltype(alpha), value_type> ? 4 : 3> size = {};

      static constexpr basic_colour_t fill_as(value_type value) {
         if constexpr (colour_traits::has_alpha) {
            return { value, value, value, value };
         } else {
            return { value, value, value };
         }
      }

      static constexpr basic_colour_t null() {
         return fill_as(colour_traits::null);
      }

      static constexpr basic_colour_t from_integer(integer_type integer) {
         if constexpr (colour_traits::has_alpha) {
            return {
               colour_traits::red_from_integer(integer), colour_traits::green_from_integer(integer),
               colour_traits::blue_from_integer(integer), colour_traits::alpha_from_integer(integer)
            };
         } else {
            assert(
               colour_traits::alpha_from_integer(integer) == colour_traits::null ||
               colour_traits::alpha_from_integer(integer) == max_value
            );
            return {
               colour_traits::red_from_integer(integer), colour_traits::green_from_integer(integer),
               colour_traits::blue_from_integer(integer)
            };
         }
      }

      static constexpr basic_colour_t
      from_floats(float r, float g, float b, float a = colour_traits::alpha_to_float(max_value))
      requires(colour_traits::has_alpha)
      {
         return {
            colour_traits::red_from_float(r), colour_traits::green_from_float(g), colour_traits::blue_from_float(b),
            colour_traits::alpha_from_float(a)
         };
      }

      static constexpr basic_colour_t from_floats(float r, float g, float b)
      requires(!colour_traits::has_alpha)
      {
         return { colour_traits::red_from_float(r), colour_traits::green_from_float(g), colour_traits::blue_from_float(b) };
      }

      constexpr integer_type as_rgb() const {
         return colour_traits::make_rgb_integer(red, green, blue);
      }

      constexpr integer_type as_argb() const {
         return colour_traits::make_argb_integer(red, green, blue, alpha);
      }

      constexpr basic_colour_t() : basic_colour_t { null() } {}

      constexpr basic_colour_t(value_type r, value_type g, value_type b, value_type a = max_value)
      requires(colour_traits::has_alpha)
         : red(r), green(g), blue(b), alpha(a) {}

      constexpr basic_colour_t(value_type r, value_type g, value_type b)
      requires(!colour_traits::has_alpha)
         : red(r), green(g), blue(b) {}

      template<typename _ColourTraits>
      requires(
         _ColourTraits::has_alpha && std::same_as<typename _ColourTraits::value_type, value_type> &&
         std::same_as<typename _ColourTraits::integer_type, integer_type>
      )
      explicit constexpr basic_colour_t(basic_colour_t<value_type, integer_type, _ColourTraits> const& colour)
      requires(colour_traits::has_alpha)
         : basic_colour_t { colour.red, colour.green, colour.blue, colour.alpha } {}

      template<typename _ColourTraits>
      requires(
         !_ColourTraits::has_alpha && std::same_as<typename _ColourTraits::value_type, value_type> &&
         std::same_as<typename _ColourTraits::integer_type, integer_type>
      )
      explicit constexpr basic_colour_t(
         basic_colour_t<value_type, integer_type, _ColourTraits> const& colour, value_type a = max_value
      )
      requires(colour_traits::has_alpha)
         : basic_colour_t { colour.red, colour.green, colour.blue, a } {}

      template<typename _ColourTraits>
      requires(
         std::same_as<typename _ColourTraits::value_type, value_type> &&
         std::same_as<typename _ColourTraits::integer_type, integer_type>
      )
      explicit constexpr basic_colour_t(basic_colour_t<value_type, integer_type, _ColourTraits> const& colour)
      requires(!colour_traits::has_alpha)
         : basic_colour_t { colour.red, colour.green, colour.blue } {}

      constexpr explicit operator integer_type() const {
         if constexpr (colour_traits::has_alpha) {
            return as_argb();
         } else {
            return as_rgb();
         }
      }

      constexpr basic_colour_t with_red(value_type r) const {
         if constexpr (colour_traits::has_alpha) {
            return { r, green, blue, alpha };
         } else {
            return { r, green, blue };
         }
      }

      constexpr basic_colour_t with_green(value_type g) const {
         if constexpr (colour_traits::has_alpha) {
            return { red, g, blue, alpha };
         } else {
            return { red, g, blue };
         }
      }

      constexpr basic_colour_t with_blue(value_type b) const {
         if constexpr (colour_traits::has_alpha) {
            return { red, green, b, alpha };
         } else {
            return { red, green, b };
         }
      }

      constexpr basic_colour_t with_alpha(value_type a) const
      requires(colour_traits::has_alpha)
      {
         return { red, green, blue, a };
      }

      constexpr float redf() const {
         return colour_traits::red_to_float(red);
      }

      constexpr float greenf() const {
         return colour_traits::green_to_float(green);
      }

      constexpr float bluef() const {
         return colour_traits::blue_to_float(blue);
      }

      constexpr float alphaf() const {
         return colour_traits::alpha_to_float(alpha);
      }

      inline std::string to_hex_string(bool alpha = false) const {
         using namespace std::string_view_literals;
         static constexpr std::string_view digits = "0123456789ABCDEF"sv;
         static constexpr std::size_t bits_per_digit = 4;
         static constexpr std::size_t digit_mask = (1 << bits_per_digit) - 1;
         static constexpr std::size_t argb_length = colour_traits::component_bit_size / bits_per_digit * 4;
         static constexpr std::size_t rgb_length = colour_traits::component_bit_size / bits_per_digit * 3;

         const std::size_t length = alpha ? argb_length : rgb_length;
         std::array<char, argb_length> address;
         const integer_type value = alpha ? as_argb() : as_rgb();

         for (std::size_t index = 0, j = (length - 1) * bits_per_digit; index < length; ++index, j -= bits_per_digit) {
            address[index] = digits[(value >> j) & digit_mask];
         }
         return { address.data(), length };
      }

      explicit operator std::string() const {
         return to_hex_string(colour_traits::has_alpha);
      }

      friend std::ostream& operator<<(std::ostream& stream, basic_colour_t const& colour) {
         return stream << colour.operator std::string();
      }

      constexpr bool is_null() const {
         return *this == null();
      }

      constexpr auto operator<=>(basic_colour_t const& rhs) const = default;
      constexpr auto operator<=>(integer_type rhs) const {
         return operator integer_type() <=> rhs;
      }

      constexpr value_type& operator[](std::size_t index) {
         return _array_access_helper<value_type>(*this, index);
      }

      constexpr const value_type& operator[](std::size_t index) const {
         return _array_access_helper<const value_type>(*this, index);
      }

   private:
      template<typename V, typename T>
      static constexpr V& _array_access_helper(T& t, std::size_t index) {
         switch (index) {
         case 0: return t.red;
         case 1: return t.green;
         case 2: return t.blue;
         }
         if constexpr (size() == 4) {
            if (index == 3) {
               return t.alpha;
            }
            assert(index < 4);
         } else {
            assert(index < 3);
         }
         /* Segfault if index is out of bounds and NDEBUG is defined! */
         OpenVic::utility::unreachable();
      }

   public:
      template<std::size_t Index>
      auto&& get() & {
         return get_helper<Index>(*this);
      }

      template<std::size_t Index>
      auto&& get() && {
         return get_helper<Index>(*this);
      }

      template<std::size_t Index>
      auto&& get() const& {
         return get_helper<Index>(*this);
      }

      template<std::size_t Index>
      auto&& get() const&& {
         return get_helper<Index>(*this);
      }

   private:
      template<std::size_t Index, typename T>
      static auto&& get_helper(T&& t) {
         static_assert(Index < size(), "Index out of bounds for OpenVic::basic_colour_t");
         if constexpr (Index == 0) {
            return std::forward<T>(t).red;
         }
         if constexpr (Index == 1) {
            return std::forward<T>(t).green;
         }
         if constexpr (Index == 2) {
            return std::forward<T>(t).blue;
         }
         if constexpr (Index == 3) {
            return std::forward<T>(t).alpha;
         }
      }
   };

   template<typename T>
   concept IsColour = OpenVic::utility::is_specialization_of_v<T, basic_colour_t>;

   template<typename ValueT, typename IntT>
   struct rgb_colour_traits : colour_traits<ValueT, IntT> {
      static constexpr bool has_alpha = false;
   };

   using colour_argb_t = basic_colour_t<std::uint8_t, std::uint32_t>;
   using colour_rgb_t = basic_colour_t<std::uint8_t, std::uint32_t, rgb_colour_traits<std::uint8_t, std::uint32_t>>;

   using colour_t = colour_rgb_t;

   namespace colour_literals {
      constexpr colour_t operator""_rgb(unsigned long long value) {
         return colour_t::from_integer(value);
      }

      constexpr colour_argb_t operator""_argb(unsigned long long value) {
         return colour_argb_t::from_integer(value);
      }
   }
}

namespace std {
   template<typename ValueT, typename ColourIntT, typename ColourTraits>
   struct tuple_size<::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>>
      : integral_constant<size_t, ::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>::size()> {};

   template<size_t Index, typename ValueT, typename ColourIntT, typename ColourTraits>
   struct tuple_element<Index, ::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>> {
      using type = decltype(::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>::red);
   };
   template<typename ValueT, typename ColourIntT, typename ColourTraits>
   struct tuple_element<1, ::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>> {
      using type = decltype(::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>::green);
   };
   template<typename ValueT, typename ColourIntT, typename ColourTraits>
   struct tuple_element<2, ::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>> {
      using type = decltype(::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>::blue);
   };
   template<typename ValueT, typename ColourIntT, typename ColourTraits>
   struct tuple_element<3, ::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>> {
      using type = decltype(::OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>::alpha);
   };

   template<typename ValueT, typename ColourIntT, typename ColourTraits>
   struct hash<OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits>> {
      size_t operator()(OpenVic::basic_colour_t<ValueT, ColourIntT, ColourTraits> const& s) const noexcept {
         return hash<decltype(s.as_argb())> {}(s.as_argb());
      }
   };
}