mirage/src/widget/layout/stack.h

#pragma once
#include "widget.h"
#include "render_command.h"
#include "dynamic_list.h"
#include "culling_config.h"
#include "event_target.h"
#include "modifiers/modifiers.h"

#include <tuple>
#include <vector>
#include <optional>

namespace mirage {
	// ============================================================================
	// 辅助函数：统一的属性提取
	// ============================================================================

	namespace stack_detail {
		/// @brief 从子控件中提取 stretch 信息
		template <typename Child>
		std::optional<float> extract_stretch_factor(const Child& child) {
			// 新系统：检测 stretch_modifier
			if constexpr (modifier::is_stretch_modifier<Child>) {
				return modifier::get_flex_factor(child);
			}
			return std::nullopt;
		}

		/// @brief 判断子控件是否应该 stretch
		template <typename Child>
		bool should_stretch(const Child& child) {
			// 新系统：检测 stretch_modifier
			if constexpr (modifier::is_stretch_modifier<Child>) {
				return true;
			}
			// 旧系统
			return extract_stretch_factor(child).has_value();
		}

		/// @brief 获取 stretch 的 flex 因子
		template <typename Child>
		float get_flex_factor(const Child& child) {
			// 新系统：检测 stretch_modifier
			if constexpr (modifier::is_stretch_modifier<Child>) {
				return modifier::get_flex_factor(child);
			}
			// 旧系统
			if (auto factor = extract_stretch_factor(child)) {
				return *factor;
			}
			return 0.0f;
		}

		/// @brief 检测是否为布局修饰器
		template <typename Child>
		constexpr bool is_layout_modifier() {
			return modifier::is_layout_modifier<Child>;
		}
	}

	// ============================================================================
	// v_stack 实现
	// ============================================================================

	template <widget... children>
	class v_stack : public event_target, public z_order_mixin<v_stack<children...>> {
	public:
		constexpr explicit v_stack(children&&... in_children) : children_(std::forward<children>(in_children)...) {
		}

		auto measure(const vec2f_t& available_size) const -> vec2f_t {
			float max_width    = 0.0f;
			float total_height = 0.0f;

			std::apply([&](const auto&... child) {
				(process_child_measure(child, available_size, max_width, total_height), ...);
			}, children_);

			return vec2f_t{max_width, total_height};
		}

		void arrange(const layout_state& state) {
			// 保存布局状态用于事件处理
			m_layout_state = state;

			// 第一遍：计算固定尺寸和stretch总权重
			float fixed_height = 0.0f;
			float total_flex   = 0.0f;

			std::apply([&](const auto&... child) {
				(calculate_flex_info(child, state.size(), fixed_height, total_flex), ...);
			}, children_);

			// 计算可用于stretch的剩余空间
			const float available_stretch_height = std::max(0.0f, state.size().y() - fixed_height);

			// 第二遍：实际布局
			float current_y = 0.0f;

			std::apply([&](auto&... child) {
				(process_child_arrange_with_stretch(child, state, current_y, available_stretch_height, total_flex), ...
				);
			}, children_);
		}

		void build_render_commands(render_command_builder& builder) const {
			// 应用 z_order 到构建器
			this->apply_z_order_to_builder(builder);

			std::apply([&builder](const auto&... child) {
				(child.build_render_commands(builder), ...);
			}, children_);
		}

		void build_render_commands(render_command_builder& builder, const culling_context& context) const {
			// 应用 z_order 到构建器
			this->apply_z_order_to_builder(builder);

			std::apply([&builder, &context](const auto&... child) {
				(invoke_build_render_commands(child, builder, context), ...);
			}, children_);
		}

		const auto& get_children() const { return children_; }

		// event_target 接口实现
		bool contains_point(double global_x, double global_y) const override {
			return m_layout_state.
					contains_global_point(vec2f_t(static_cast<float>(global_x), static_cast<float>(global_y)));
		}

		std::pair<double, double> global_to_local(double global_x, double global_y) const override {
			auto local = m_layout_state.to_local(vec2f_t(static_cast<float>(global_x), static_cast<float>(global_y)));
			return {local.x(), local.y()};
		}

		std::vector<event_target*> get_event_children() const override {
			std::vector<event_target*> event_children;

			std::apply([&]<typename... T>(T&... child) {
				(
					[&]() {
						using ChildType = std::remove_cvref_t<T>;

						// 情况 1: dynamic_list
						if constexpr (std::is_same_v<ChildType, dynamic_list>) {
							event_children.push_back(const_cast<dynamic_list*>(&child));
						}
						// 情况 2: 布局修饰器 - 穿透获取内部事件目标
						else if constexpr (modifier::is_layout_modifier<ChildType>) {
							if (auto* target = modifier::get_inner_event_target(const_cast<ChildType&>(child))) {
								event_children.push_back(target);
							}
						}
						// 情况 3: 继承自 event_target 的普通 widget
						else if constexpr (std::is_base_of_v<event_target, ChildType>) {
							event_children.push_back(const_cast<ChildType*>(&child));
						}
					}()
				  , ...);
			}, children_);

			return event_children;
		}

	private:
		/// @brief 计算flex布局信息（第一遍）
		template <typename Child>
		void calculate_flex_info(const Child& child, const vec2f_t& available_size,
		                         float&       fixed_height, float&  total_flex) const {
			if constexpr (std::is_same_v<std::decay_t<Child>, dynamic_list>) {
				// dynamic_list 的子组件都按固定尺寸处理
				for (const auto& sub_child : child.get_children()) {
					const auto child_size = sub_child.measure(available_size);
					fixed_height += child_size.y();
				}
			}
			else if constexpr (modifier::is_stretch_modifier<Child>) {
				// 新系统：stretch_modifier
				total_flex += modifier::get_flex_factor(child);
			}
			else if constexpr (modifier::is_layout_modifier<Child>) {
				// 其他布局修饰器（padding, align）：按固定尺寸处理
				const auto child_size = child.measure(available_size);
				fixed_height += child_size.y();
			}
			else {
				// 直接处理普通 widget（总是固定尺寸）
				const auto child_size = child.measure(available_size);
				fixed_height += child_size.y();
			}
		}

		// 辅助函数：处理单个子组件的测量
		template <typename Child>
		void process_child_measure(const Child& child, const vec2f_t& available_size,
		                           float&       max_width, float&     total_height) const {
			if constexpr (std::is_same_v<std::decay_t<Child>, dynamic_list>) {
				// 展开 dynamic_list 的子组件
				for (const auto& sub_child : child.get_children()) {
					const auto child_size = sub_child.measure(available_size);
					max_width             = std::max(max_width, child_size.x());
					total_height += child_size.y();
				}
			}
			else if constexpr (modifier::is_stretch_modifier<Child>) {
				// stretch 子组件在 measure 时不贡献高度
				// 但仍需测量宽度
				const auto child_size = child.measure(available_size);
				max_width             = std::max(max_width, child_size.x());
			}
			else {
				// 直接处理普通 widget 或其他修饰器
				const auto child_size = child.measure(available_size);
				max_width             = std::max(max_width, child_size.x());
				total_height += child_size.y();
			}
		}

		// 辅助函数：处理单个子组件的布局（支持stretch）
		template <typename Child>
		void process_child_arrange_with_stretch(Child& child, const layout_state&      state, float& current_y,
		                                        float  available_stretch_height, float total_flex) const {
			if constexpr (std::is_same_v<std::decay_t<Child>, dynamic_list>) {
				// 展开 dynamic_list 的子组件
				for (auto& sub_child : child.get_children()) {
					const auto child_size  = sub_child.measure(state.size());
					const auto child_state = state.derive_child(vec2f_t{0.0f, current_y}, child_size);
					sub_child.arrange(child_state);
					current_y += child_size.y();
				}
			}
			else if constexpr (modifier::is_stretch_modifier<Child>) {
				// 新系统：stretch_modifier
				vec2f_t child_size;
				if (total_flex > 0.0f) {
					const float flex_factor    = modifier::get_flex_factor(child);
					const float stretch_height = (flex_factor / total_flex) * available_stretch_height;
					const auto  measured_size  = child.measure(state.size());
					child_size                 = vec2f_t{measured_size.x(), stretch_height};
				}
				else {
					child_size = child.measure(state.size());
				}
				const auto child_state = state.derive_child(vec2f_t{0.0f, current_y}, child_size);
				child.arrange(child_state);
				current_y += child_size.y();
			}
			else {
				// 直接处理普通 widget 或其他修饰器
				const auto child_size  = child.measure(state.size());
				const auto child_state = state.derive_child(vec2f_t{0.0f, current_y}, child_size);
				child.arrange(child_state);
				current_y += child_size.y();
			}
		}

		std::tuple<children...> children_;
		layout_state            m_layout_state;
	};

	// ============================================================================
	// h_stack 实现
	// ============================================================================

	template <widget... children>
	class h_stack : public event_target, public z_order_mixin<h_stack<children...>> {
	public:
		explicit constexpr h_stack(children&&... in_children) : children_(std::forward<children>(in_children)...) {
		}

		[[nodiscard]] auto measure(const vec2f_t& available_size) const -> vec2f_t {
			float total_width = 0.0f;
			float max_height  = 0.0f;

			std::apply([&](const auto&... child) {
				(process_child_measure(child, available_size, total_width, max_height), ...);
			}, children_);

			return vec2f_t{total_width, max_height};
		}

		void arrange(const layout_state& state) {
			m_layout_state = state;

			// 第一遍：计算固定尺寸和stretch总权重
			float fixed_width = 0.0f;
			float total_flex  = 0.0f;

			std::apply([&](const auto&... child) {
				(calculate_flex_info(child, state.size(), fixed_width, total_flex), ...);
			}, children_);

			// 计算可用于stretch的剩余空间
			const float available_stretch_width = std::max(0.0f, state.size().x() - fixed_width);

			// 第二遍：实际布局
			float current_x = 0.0f;

			std::apply([&](auto&... child) {
				(process_child_arrange_with_stretch(child, state, current_x, available_stretch_width, total_flex), ...);
			}, children_);
		}

		void build_render_commands(render_command_builder& builder) const {
			// 应用 z_order 到构建器
			this->apply_z_order_to_builder(builder);

			std::apply([&builder](const auto&... child) {
				(child.build_render_commands(builder), ...);
			}, children_);
		}

		void build_render_commands(render_command_builder& builder, const culling_context& context) const {
			// 应用 z_order 到构建器
			this->apply_z_order_to_builder(builder);

			std::apply([&builder, &context](const auto&... child) {
				(invoke_build_render_commands(child, builder, context), ...);
			}, children_);
		}

		[[nodiscard]] const auto& get_children() const {
			return children_;
		}

		// event_target 接口实现
		bool contains_point(double global_x, double global_y) const override {
			return m_layout_state.
					contains_global_point(vec2f_t(static_cast<float>(global_x), static_cast<float>(global_y)));
		}

		std::pair<double, double> global_to_local(double global_x, double global_y) const override {
			auto local = m_layout_state.to_local(vec2f_t(static_cast<float>(global_x), static_cast<float>(global_y)));
			return {local.x(), local.y()};
		}

		std::vector<event_target*> get_event_children() const override {
			std::vector<event_target*> event_children;

			auto func = [&](auto&... child) {
				(
					[&]() {
						using ChildType = std::remove_cvref_t<decltype(child)>;
						// 情况 1: dynamic_list
						if constexpr (std::is_same_v<ChildType, dynamic_list>) {
							event_children.push_back(const_cast<dynamic_list*>(&child));
						}
						// 情况 2: 布局修饰器 - 穿透获取内部事件目标
						else if constexpr (modifier::is_layout_modifier<ChildType>) {
							if (auto* target = modifier::get_inner_event_target(const_cast<ChildType&>(child))) {
								event_children.push_back(target);
							}
						}
						// 情况 3: 继承自 event_target 的普通 widget
						else if constexpr (std::is_base_of_v<event_target, ChildType>) {
							event_children.push_back(const_cast<ChildType*>(&child));
						}
					}()
				  , ...);
			};
			std::apply(func, children_);

			return event_children;
		}

	private:
		/// @brief 计算flex布局信息（第一遍）
		template <typename Child>
		void calculate_flex_info(const Child& child, const vec2f_t& available_size,
		                         float&       fixed_width, float&   total_flex) const {
			if constexpr (std::is_same_v<std::decay_t<Child>, dynamic_list>) {
				// dynamic_list 的子组件都按固定尺寸处理
				for (const auto& sub_child : child.get_children()) {
					const auto child_size = sub_child.measure(available_size);
					fixed_width += child_size.x();
				}
			}
			else if constexpr (modifier::is_stretch_modifier<Child>) {
				// 新系统：stretch_modifier
				total_flex += modifier::get_flex_factor(child);
			}
			else if constexpr (modifier::is_layout_modifier<Child>) {
				// 其他布局修饰器（padding, align）：按固定尺寸处理
				const auto child_size = child.measure(available_size);
				fixed_width += child_size.x();
			}
			else {
				// 直接处理普通 widget（总是固定尺寸）
				const auto child_size = child.measure(available_size);
				fixed_width += child_size.x();
			}
		}

		// 辅助函数：处理单个子组件的测量
		template <typename Child>
		void process_child_measure(const Child& child, const vec2f_t& available_size,
		                           float&       total_width, float&   max_height) const {
			if constexpr (std::is_same_v<std::decay_t<Child>, dynamic_list>) {
				// 展开 dynamic_list 的子组件
				for (const auto& sub_child : child.get_children()) {
					const auto child_size = sub_child.measure(available_size);
					total_width += child_size.x();
					max_height = std::max(max_height, child_size.y());
				}
			}
			else if constexpr (modifier::is_stretch_modifier<Child>) {
				// stretch 子组件在 measure 时不贡献宽度
				// 但仍需测量高度
				const auto child_size = child.measure(available_size);
				max_height            = std::max(max_height, child_size.y());
			}
			else {
				// 直接处理普通 widget 或其他修饰器
				const auto child_size = child.measure(available_size);
				total_width += child_size.x();
				max_height = std::max(max_height, child_size.y());
			}
		}

		// 辅助函数：处理单个子组件的布局（支持stretch）
		template <typename Child>
		void process_child_arrange_with_stretch(Child& child, const layout_state&     state, float& current_x,
		                                        float  available_stretch_width, float total_flex) const {
			if constexpr (std::is_same_v<std::decay_t<Child>, dynamic_list>) {
				// 展开 dynamic_list 的子组件
				for (auto& sub_child : child.get_children()) {
					const auto child_size  = sub_child.measure(state.size());
					const auto child_state = state.derive_child(vec2f_t{current_x, 0.0f}, child_size);
					sub_child.arrange(child_state);
					current_x += child_size.x();
				}
			}
			else if constexpr (modifier::is_stretch_modifier<Child>) {
				// 新系统：stretch_modifier
				vec2f_t child_size;
				if (total_flex > 0.0f) {
					const float flex_factor   = modifier::get_flex_factor(child);
					const float stretch_width = (flex_factor / total_flex) * available_stretch_width;
					const auto  measured_size = child.measure(state.size());
					child_size                = vec2f_t{stretch_width, measured_size.y()};
				}
				else {
					child_size = child.measure(state.size());
				}
				const auto child_state = state.derive_child(vec2f_t{current_x, 0.0f}, child_size);
				child.arrange(child_state);
				current_x += child_size.x();
			}
			else {
				// 直接处理普通 widget 或其他修饰器
				const auto child_size  = child.measure(state.size());
				const auto child_state = state.derive_child(vec2f_t{current_x, 0.0f}, child_size);
				child.arrange(child_state);
				current_x += child_size.x();
			}
		}

		std::tuple<children...> children_;
		layout_state            m_layout_state;
	};
}