Implement string entity description in ecs

libs/ecs/include/psemek/ecs/accessor.hpp

@@ -107,7 +107,7 @@ namespace psemek::ecs
 	{
 		if (auto ptr = get_if<Component>())
 			return *ptr;
-		throw component_not_found_exception(typeid(std::remove_const_t<Component>), table_->entity_handles()[row_]);
+		throw component_not_found_exception(typeid(std::remove_const_t<Component>), table_->entity_handles()[row_], table_->describe(row_));
 	}
 
 	template <typename Component>
@@ -115,7 +115,7 @@ namespace psemek::ecs
 	{
 		if (auto ptr = get_if<Component const>())
 			return *ptr;
-		throw component_not_found_exception(typeid(std::remove_const_t<Component>), table_->entity_handles()[row_]);
+		throw component_not_found_exception(typeid(std::remove_const_t<Component>), table_->entity_handles()[row_], table_->describe(row_));
 	}
 
 	template <typename Component>

libs/ecs/include/psemek/ecs/container.hpp

@@ -93,6 +93,15 @@ namespace psemek::ecs
 		 */
 		accessor get(handle entity);
 
+		/** Compute a string representation of an entity, based on the contained components.
+		 *  A component has to implement a to_string() method in order to provide extra info.
+		 *
+		 *  @param entity A handle to the entity to describe
+		 *  @return A string representation of an entity
+		 *  @pre The entity was previously obtained by a `create()` call and is `alive()`
+		 */
+		std::string describe(handle entity) const;
+
 		/** Check if the entity can be cloned.
 		 *
 		 *  An entity can be cloned if all of its components are copy-constructible.

libs/ecs/include/psemek/ecs/detail/column.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <psemek/ecs/detail/stride.hpp>
+#include <psemek/ecs/detail/describe.hpp>
 #include <psemek/util/uuid.hpp>
 #include <psemek/util/assert.hpp>
 
@@ -53,6 +54,8 @@ namespace psemek::ecs::detail
 
 		virtual std::size_t memory_usage() const = 0;
 
+		virtual std::string describe(std::uint32_t row) const = 0;
+
 		virtual ~column() = default;
 
 	protected:
@@ -87,6 +90,8 @@ namespace psemek::ecs::detail
 
 		std::size_t memory_usage() const override;
 
+		std::string describe(std::uint32_t row) const override;
+
 		~column_impl() override;
 
 	private:
@@ -113,6 +118,8 @@ namespace psemek::ecs::detail
 
 		std::size_t memory_usage() const override;
 
+		std::string describe(std::uint32_t row) const override;
+
 		~column_impl() override;
 	};
 
@@ -208,6 +215,12 @@ namespace psemek::ecs::detail
 		return sizeof(Component) * row_count_;
 	}
 
+	template <typename Component, bool Empty>
+	std::string column_impl<Component, Empty>::describe(std::uint32_t row) const
+	{
+		return detail::describe(reinterpret_cast<Component const *>(data_)[row]);
+	}
+
 	template <typename Component, bool Empty>
 	column_impl<Component, Empty>::~column_impl()
 	{
@@ -286,6 +299,12 @@ namespace psemek::ecs::detail
 		return sizeof(Component);
 	}
 
+	template <typename Component>
+	std::string column_impl<Component, true>::describe(std::uint32_t) const
+	{
+		return detail::describe(*reinterpret_cast<Component const *>(data_));
+	}
+
 	template <typename Component>
 	column_impl<Component, true>::~column_impl()
 	{

libs/ecs/include/psemek/ecs/detail/describe.hpp

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <psemek/util/type_name.hpp>
+
+#include <string>
+
+namespace psemek::ecs::detail
+{
+
+	template <typename Component>
+	std::string describe(Component const & component)
+	{
+		if constexpr (requires {component.to_string();})
+		{
+			return component.to_string();
+		}
+		else
+		{
+			auto name = util::type_name<Component>();
+			if (auto pos = name.find_last_of(':'); pos != std::string::npos)
+				name = name.substr(pos + 1);
+			return name;
+		}
+	}
+
+}

libs/ecs/include/psemek/ecs/detail/table.hpp

@@ -12,6 +12,7 @@
 #include <memory>
 #include <vector>
 #include <optional>
+#include <string>
 
 namespace psemek::ecs::detail
 {
@@ -81,6 +82,8 @@ namespace psemek::ecs::detail
 
 		std::size_t memory_usage() const;
 
+		std::string describe(std::uint32_t row) const;
+
 	protected:
 		std::size_t hash_;
 		std::vector<std::unique_ptr<detail::column>> columns_;

libs/ecs/include/psemek/ecs/exceptions.hpp

@@ -13,8 +13,8 @@ namespace psemek::ecs
 	struct component_not_found_exception
 		: util::exception
 	{
-		component_not_found_exception(std::type_info const & type, handle const & handle, boost::stacktrace::stacktrace stacktrace = {})
+		component_not_found_exception(std::type_info const & type, handle const & handle, std::string const & description, boost::stacktrace::stacktrace stacktrace = {})
-			: util::exception(util::to_string("Component ", util::type_name(type), " not found for entity ", handle), std::move(stacktrace))
+			: util::exception(util::to_string("Component ", util::type_name(type), " not found for entity ", handle, " <", description, ">"), std::move(stacktrace))
 			, type_(type)
 			, handle_(handle)
 		{}

libs/ecs/source/container.cpp

@@ -27,6 +27,13 @@ namespace psemek::ecs
 		return {data.table, data.row};
 	}
 
+	std::string container::describe(handle entity) const
+	{
+		assert(alive(entity));
+		auto const data = entity_list_.get_entities()[entity.id];
+		return data.table->describe(data.row);
+	}
+
 	bool container::can_clone(handle entity) const
 	{
 		return entity_list_.get_entities()[entity.id].table->non_copyable_components().empty();

libs/ecs/source/detail/table.cpp

@@ -186,4 +186,16 @@ namespace psemek::ecs::detail
 		return result;
 	}
 
+	std::string table::describe(std::uint32_t row) const
+	{
+		std::string result;
+		for (std::size_t i = 0; i < columns_.size(); ++i)
+		{
+			if (i > 0)
+				result += ";";
+			result += columns_[i]->describe(row);
+		}
+		return result;
+	}
+
 }