// Glaze Library
// For the license information refer to glaze.hpp

#pragma once

#include <concepts>
#include <cstdint>
#include <ranges>
#include <utility>
#include <vector>
#include <version>

// Over time we want most concepts to use the nomenclature:
// is_
// has_
// _like
// Avoid the use of _t as that makes it seem like a type and not a concept

namespace glz
{
   template <class T, class... U>
   concept is_any_of = (std::same_as<T, U> || ...);

   template <class T>
   concept has_value_type = requires { typename T::value_type; };

   template <class T>
   concept has_element_type = requires { typename T::element_type; };

   template <class T>
   concept has_first_type = requires { typename T::first_type; };

   template <class T>
   concept has_second_type = requires { typename T::second_type; };

   template <class T>
   concept resizable = requires(T v) { v.resize(0); };

   template <class T>
   concept erasable = requires(T v) { v.erase(v.cbegin(), v.cend()); };

   template <class T>
   concept has_size = requires(T v) { v.size(); };

   template <class T>
   concept has_empty = requires(T v) {
      { v.empty() } -> std::convertible_to<bool>;
   };

   template <class T>
   concept has_data = requires(T v) { v.data(); };

   template <class T>
   concept has_reserve = requires(T t) { t.reserve(size_t(1)); };

   template <class T>
   concept has_capacity = requires(T t) {
      { t.capacity() } -> std::integral;
   };

   template <class T>
   concept contiguous = has_size<T> && has_data<T>;

   template <class Buffer>
   concept non_const_buffer = !std::is_const_v<Buffer>;

   template <class T>
   concept byte_like =
      std::same_as<std::remove_cvref_t<T>, std::byte> || std::same_as<std::remove_cvref_t<T>, unsigned char> ||
      std::same_as<std::remove_cvref_t<T>, std::uint8_t>;
}

namespace glz
{
   template <class T>
   concept char_t = std::same_as<std::remove_cvref_t<T>, char>;

   template <class T>
   concept wide_char_t =
      std::same_as<std::remove_cvref_t<T>, char16_t> || std::same_as<std::remove_cvref_t<T>, char32_t> ||
      std::same_as<std::remove_cvref_t<T>, wchar_t>;

   template <class T>
   concept bool_t = std::same_as<std::remove_cvref_t<T>, bool> ||
                    std::same_as<std::remove_cvref_t<T>, std::vector<bool>::reference> ||
                    std::same_as<std::remove_cvref_t<T>, std::vector<bool>::const_reference>;

   template <class T>
   concept int_t = std::integral<std::remove_cvref_t<T>> && !char_t<T> && !wide_char_t<T> && !bool_t<T>;

   template <class T>
   concept num_t = std::floating_point<std::remove_cvref_t<T>> || int_t<T>;

   template <class T>
   concept is_float128 = requires(T x) {
      requires sizeof(x) == 16;
      requires std::floating_point<T>;
   };

   template <typename T>
   concept complex_t = requires(T a, T b) {
      { a.real() } -> std::convertible_to<typename T::value_type>;
      { a.imag() } -> std::convertible_to<typename T::value_type>;
      { T(a.real(), a.imag()) } -> std::same_as<T>;
      { a + b } -> std::same_as<T>;
      { a - b } -> std::same_as<T>;
      { a * b } -> std::same_as<T>;
      { a / b } -> std::same_as<T>;
   };

   template <class T>
   concept optional_like = requires(T t, typename T::value_type v) {
      { T() } -> std::same_as<T>;
      { T(v) } -> std::same_as<T>;
      { t.has_value() } -> std::convertible_to<bool>;
      { t.value() };
      { t = v };
      { t.reset() };
      { t.emplace() };
   };

   template <class T>
   concept pair_t = requires(T pair) {
      typename std::decay_t<T>::first_type;
      typename std::decay_t<T>::second_type;
      { pair.first };
      { pair.second };
   };

   // glz::pair - a simple pair type for use in glaze
   template <class T1, class T2>
   struct pair
   {
      using first_type = T1;
      using second_type = T2;
      T1 first{};
      T2 second{};
   };

   template <class T1, class T2>
   pair(T1, T2) -> pair<T1, T2>;

   template <size_t I, pair_t T>
   constexpr decltype(auto) get(T&& p) noexcept
   {
      if constexpr (I == 0) {
         return p.first;
      }
      else if constexpr (I == 1) {
         return p.second;
      }
      else {
         static_assert(I < 2, "Invalid index for pair::get");
      }
   }

   template <class T>
   concept emplaceable = requires(T container) {
      { container.emplace(std::declval<typename T::value_type>()) };
   };

   template <class T>
   concept push_backable = requires(T container) {
      { container.push_back(std::declval<typename T::value_type>()) };
   };

   template <class T>
   concept emplace_backable = requires(T container) {
      { container.emplace_back() } -> std::same_as<typename T::reference>;
   };

   // Accepts both the C++23 return type (T*) and the C++26 P3981 return type
   // (std::optional<T&>); both are contextually convertible to bool.
   template <class T>
   concept has_try_emplace_back = requires(T container) {
      { static_cast<bool>(container.try_emplace_back()) };
   };

   template <class T>
   concept has_append = requires(T t, typename T::const_iterator it) { t.append(it, it); };

   template <class T>
   concept has_assign = requires(T t, const typename T::value_type* v, typename T::size_type sz) { t.assign(v, sz); };

   template <class T>
   concept accessible = requires(T container) {
      { container[size_t{}] } -> std::same_as<typename T::reference>;
   };

   template <class T>
   concept vector_like =
      resizable<std::remove_cvref_t<T>> && accessible<std::remove_cvref_t<T>> && has_data<std::remove_cvref_t<T>>;

   template <class T>
   concept is_inplace_vector =
      has_try_emplace_back<T> && accessible<std::remove_cvref_t<T>> && has_data<std::remove_cvref_t<T>>;

   template <class T>
   concept map_subscriptable = requires(T container) {
      { container[std::declval<typename T::key_type>()] };
   };

   template <typename T>
   concept string_like = requires(T s) {
      { s.size() } -> std::integral;
      { s.data() };
      { s.empty() } -> std::convertible_to<bool>;
      { s.substr(0, 1) };
   };

   template <typename T>
   concept is_bitset = requires(T bitset) {
      bitset.flip();
      bitset.set(0);
      requires string_like<decltype(bitset.to_string())>;
      { bitset.count() } -> std::same_as<size_t>;
   };

   template <class T>
   concept is_span = requires(T t) {
      T::extent;
      typename T::element_type;
   };

   template <class T>
   concept is_dynamic_span = T::extent == static_cast<size_t>(-1);

   template <class Map, class Key>
   concept findable = requires(Map& map, const Key& key) { map.find(key); };

   template <class T>
   concept filesystem_path = requires(T path) {
      path.native();
      requires string_like<decltype(path.string())>;
      path.filename();
      path.extension();
      path.parent_path();
      { path.has_filename() } -> std::convertible_to<bool>;
      { path.has_extension() } -> std::convertible_to<bool>;
   };
}

namespace glz
{
   template <class T>
   concept range = requires(T& t) {
      requires !std::same_as<void, decltype(t.begin())>;
      requires !std::same_as<void, decltype(t.end())>;
      requires std::input_iterator<decltype(t.begin())>;
   };

   // Concept for a matrix type (not a vector, which is a range)
   template <class T>
   concept matrix_t = requires(T matrix) {
      matrix.resize(2, 4);
      matrix.data();
      { matrix.rows() } -> std::convertible_to<int>;
      { matrix.cols() } -> std::convertible_to<int>;
      { matrix.size() } -> std::convertible_to<int>;
   } && !range<T>;

   // concept for the Eigen library: matrices and vectors
   template <class T>
   concept eigen_t = requires(T matrix) {
      matrix.data();
      { matrix.rows() } -> std::convertible_to<int>;
      { matrix.cols() } -> std::convertible_to<int>;
      { matrix.size() } -> std::convertible_to<int>;
   };

   // range like
   template <class T>
   using iterator_t = decltype(std::begin(std::declval<T&>()));

   template <range R>
   using range_value_t = std::iter_value_t<iterator_t<R>>;

   template <range R>
   [[nodiscard]] constexpr bool empty_range(R&& rng)
   {
#ifdef __cpp_lib_ranges
      return std::ranges::empty(rng);
#else
      // in lieu of std::ranges::empty
      if constexpr (requires() {
                       { rng.empty() } -> std::convertible_to<bool>;
                    }) {
         return rng.empty();
      }
      else if constexpr (requires() {
                            { rng.size() } -> std::same_as<std::size_t>;
                         }) {
         return rng.size() == std::size_t{0};
      }
      else {
         return std::cbegin(rng) == std::cend(rng);
      }
#endif
   }
}

namespace glz
{
   template <class Buffer>
   concept raw_buffer = std::same_as<std::decay_t<Buffer>, char*> && non_const_buffer<Buffer>;

   // A resizable buffer MUST be vector_like to safely support resize and memcpy operations
   // vector_like requires: resize(), operator[], data() (for contiguous storage), and reference typedef
   // This prevents heap corruption from buffers that lack data() (like std::deque) or are missing reference typedef
   template <class Buffer>
   concept safe_resizable_buffer = !resizable<Buffer> || vector_like<Buffer>;

   template <class Buffer>
   concept output_buffer = range<Buffer> && (sizeof(range_value_t<Buffer>) == sizeof(char)) &&
                           non_const_buffer<Buffer> && safe_resizable_buffer<Buffer>;

   template <class Range>
   concept contiguous_byte_range = contiguous<Range> && byte_like<range_value_t<Range>>;

   template <class T>
   constexpr bool const_value_v = std::is_const_v<std::remove_pointer_t<std::remove_reference_t<T>>>;
}

namespace glz::detail
{
   template <class Container>
   using iterator_pair_type =
      typename std::iterator_traits<decltype(std::begin(std::declval<Container&>()))>::value_type;

   template <class Container, typename Iterator = iterator_pair_type<Container>>
   struct iterator_second_impl;

   template <class Container, typename Iterator>
      requires has_value_type<Iterator>
   struct iterator_second_impl<Container, Iterator>
   {
      using type = typename Iterator::value_type;
   };

   template <class Container, typename Iterator>
      requires(!has_value_type<Iterator> && has_second_type<Iterator>)
   struct iterator_second_impl<Container, Iterator>
   {
      using type = typename Iterator::second_type;
   };

   template <class Container>
   using iterator_second_type = typename iterator_second_impl<Container>::type;

   template <class Container, typename Iterator = iterator_pair_type<Container>>
   struct iterator_first_impl;

   template <class Container, typename Iterator>
      requires has_value_type<Iterator>
   struct iterator_first_impl<Container, Iterator>
   {
      using type = typename Iterator::value_type;
   };

   template <class Container, typename Iterator>
      requires(!has_value_type<Iterator> && has_first_type<Iterator>)
   struct iterator_first_impl<Container, Iterator>
   {
      using type = typename Iterator::first_type;
   };

   template <class Container>
   using iterator_first_type = typename iterator_first_impl<Container>::type;
}
