[nostalgia/geo] Add iterators to Vec2

src/nostalgia/geo/vec.hpp

@@ -8,11 +8,123 @@
 #include <imgui.h>
 #endif
 
+#include <ox/std/bit.hpp>
+#include <ox/std/iterator.hpp>
+#include <ox/std/math.hpp>
 #include <ox/std/types.hpp>
 
 namespace nostalgia::geo {
 
 struct Vec2 {
+	using value_type = float;
+	using size_type = std::size_t;
+
+	template<typename RefType = value_type&, typename PtrType = value_type*, bool reverse = false>
+	struct iterator: public std::iterator<std::bidirectional_iterator_tag, value_type> {
+		private:
+			PtrType m_t = nullptr;
+			size_type m_offset = 0;
+			size_type m_max = 0;
+
+		public:
+			constexpr iterator() noexcept = default;
+
+			constexpr iterator(PtrType t, size_type offset, size_type max) noexcept {
+				m_t = t;
+				m_offset = offset;
+				m_max = max;
+			}
+
+			[[nodiscard]]
+			constexpr auto offset() const noexcept {
+				return m_offset;
+			}
+
+			constexpr iterator operator+(size_type s) const noexcept {
+				 if constexpr(reverse) {
+				 return iterator(m_t, ox::max<size_type>(m_offset - s, 0), m_max);
+				 } else {
+				 return iterator(m_t, ox::min<size_type>(m_offset + s, m_max), m_max);
+				 }
+			}
+
+			constexpr typename std::iterator<std::bidirectional_iterator_tag, value_type>::difference_type
+			operator-(const iterator &other) const noexcept {
+				if constexpr(reverse) {
+					return m_offset + other.m_offset;
+				} else {
+					return m_offset - other.m_offset;
+				}
+			}
+
+			constexpr iterator operator-(size_type s) const noexcept {
+				if constexpr(reverse) {
+					return iterator(m_t, ox::min<size_type>(m_offset + s, m_max), m_max);
+				} else {
+					return iterator(m_t, ox::max<size_type>(m_offset - s, 0), m_max);
+				}
+			}
+
+			constexpr iterator &operator+=(size_type s) noexcept {
+				if constexpr(reverse) {
+					m_offset = ox::max<size_type>(m_offset - s, 0);
+				} else {
+					m_offset = ox::min(m_offset + s, m_max);
+				}
+				return *this;
+			}
+
+			constexpr iterator &operator-=(size_type s) noexcept {
+				if constexpr(reverse) {
+					m_offset = ox::min(m_offset + s, m_max);
+				} else {
+					m_offset = ox::max<size_type>(m_offset - s, 0);
+				}
+				return *this;
+			}
+
+			constexpr iterator &operator++() noexcept {
+				return operator+=(1);
+			}
+
+			constexpr iterator &operator--() noexcept {
+				return operator-=(1);
+			}
+
+			constexpr RefType operator*() const noexcept {
+				return m_t[m_offset];
+			}
+
+			constexpr RefType operator[](size_type s) const noexcept {
+				return m_t[s];
+			}
+
+			constexpr bool operator<(const iterator &other) const noexcept {
+				return m_offset < other.m_offset;
+			}
+
+			constexpr bool operator>(const iterator &other) const noexcept {
+				return m_offset > other.m_offset;
+			}
+
+			constexpr bool operator<=(const iterator &other) const noexcept {
+				return m_offset <= other.m_offset;
+			}
+
+			constexpr bool operator>=(const iterator &other) const noexcept {
+				return m_offset >= other.m_offset;
+			}
+
+			constexpr bool operator==(const iterator &other) const noexcept {
+				return m_t == other.m_t && m_offset == other.m_offset && m_max == other.m_max;
+			}
+
+			constexpr bool operator!=(const iterator &other) const noexcept {
+				return m_t != other.m_t || m_offset != other.m_offset || m_max != other.m_max;
+			}
+
+	};
+
 	float x = 0;
 	float y = 0;
 
@@ -26,6 +138,46 @@ struct Vec2 {
 	}
 #endif
 
+	[[nodiscard]]
+	constexpr iterator<> begin() noexcept {
+		return {&x, 0, size()};
+	}
+
+	[[nodiscard]]
+	constexpr iterator<> end() noexcept {
+		return {&x, size(), size()};
+	}
+
+	[[nodiscard]]
+	constexpr iterator<const value_type&, const value_type*> begin() const noexcept {
+		return {&x, 0, size()};
+	}
+
+	[[nodiscard]]
+	constexpr iterator<const value_type&, const value_type*> end() const noexcept {
+		return {&x, size(), size()};
+	}
+
+	[[nodiscard]]
+	constexpr iterator<value_type&, value_type*, true> rbegin() noexcept {
+		return {&x, size() - 1, size()};
+	}
+
+	[[nodiscard]]
+	constexpr iterator<value_type&, value_type*, true> rend() noexcept {
+		return {&x, ox::MaxValue<size_type>, size()};
+	}
+
+	[[nodiscard]]
+	constexpr iterator<const value_type&, const value_type*, true> rbegin() const noexcept {
+		return {&x, size() - 1, size()};
+	}
+
+	[[nodiscard]]
+	constexpr iterator<const value_type&, const value_type*, true> rend() const noexcept {
+		return {&x, ox::MaxValue<size_type>, size()};
+	}
+
 	constexpr auto &operator[](std::size_t i) noexcept {
 		return (&x)[i];
 	}
@@ -34,6 +186,11 @@ struct Vec2 {
 		return (&x)[i];
 	}
 
+	[[nodiscard]]
+	constexpr std::size_t size() const noexcept {
+		return 2;
+	}
+
 #if __has_include(<imgui.h>)
 	explicit operator ImVec2() const noexcept {
 		return {x, y};