static_assert( __cplusplus > 2020'99 );

#pragma once

#include <Alepha/Alepha.h>
#include <Alepha/UA_Key.h>

#include <map>
#include <string>
#include <any>
#include <iostream>
#include <vector>

/*!
 * @file
 * @todo consider dropping string arg versions in favor of just using UA_Key versions (after making conversion constructor not explicit)
 * @todo consider how operator >> and << should function.  JSON?  If so, using what?
 * @todo consider [] versions of at
 * @todo decide exceptions to throw (especially for not found)
 * @todo comment at()
 * @todo auto creating option for get (and for general use)
 * @todo need to constrain type stored in UniversalAggregate and coerce to those when possible
*/

namespace Alepha::Hydrogen  ::detail::  UniversalAggregate_m
{
	inline namespace exports
	{
		class UniversalAggregate;

		using MemberType= std::variant< UniversalAggregate, std::string, int, std::vector< UniversalAggregate > >;

		class UniversalAggregate
		{
			private:
				// The value could be a UA, a vector of UAs or anything else.
				using CoreMap= std::map< std::string, MemberType >;
				CoreMap data;

				UniversalAggregate &
				get( UA_Key key, bool create= false )
				{
					UniversalAggregate *ret= this;
					for( const auto &lv : key.levels )
					{
						if( std::holds_alternative< std::string >(lv) )
						{
							if( not ret->data.count( std::get< std::string >( lv ) ) )
							{
								if( not create ) // throw an error
								{
									throw std::runtime_error( "desired level not found: " + std::get< std::string >( lv ) );
								}
								else // create the missing level
								{
									ret->data[ std::get< std::string >( lv ) ]= UniversalAggregate{};
								}
							}
							ret= &(std::get<UniversalAggregate>(ret->data.at( std::get< std::string >( lv ) ) ) );
							continue;
						}
					}
					return *ret;
				}

				const UniversalAggregate &
				get( UA_Key key ) const
				{
					const UniversalAggregate *ret= this;
					for( const auto &lv : key.levels )
					{
						if( std::holds_alternative< std::string >(lv) )
						{
							if( not ret->data.count( std::get< std::string >( lv ) ) )
							{
								throw std::runtime_error( "desired level not found: " + std::get< std::string >( lv ) );
							}
							ret= &(std::get<UniversalAggregate>(ret->data.at( std::get< std::string >( lv ) ) ) );
							continue;
						}
					}
					return *ret;
				}

			public:
				UniversalAggregate()= default;

				/*! @brief
				 *  @note direct insert on a vector is not supported. Use at() to obtain a reference to the vector
				 */
				void
				insert( const UA_Key &key, const MemberType &value )
				{
					if( key.isVector() )
					{
						throw std::runtime_error( "Operation not supported on vector" );
					}
					auto& target= get( key.parent(), true );
					target.data[ std::get< std::string >( key.levels.back() ) ]= value;
				}

				/*! @brief
				 *
				 */
				void
				insert( const std::string &key, const MemberType &value )
				{
					insert( UA_Key( key ), value );
				}

				/*! @brief
				 *  @note direct erase on a vector is not supported. Use at() to obtain a reference to the vector
				 */
				void
				erase( const UA_Key &key )
				{
					if( key.isVector() )
					{
						throw std::runtime_error( "Operation not supported on vector" );
					}
					auto& target= get( key.parent() );
					target.data.erase( std::get< std::string >( key.levels.back() ) );
					return;
				}

				/*! @brief
				 *
				 */
				void
				erase( const std::string &key )
				{
					erase( UA_Key( key ) );
				}

				/*! @brief
				 *
				 */
				const MemberType &
				at( const std::string &key ) const
				{
					return at( UA_Key( key ) );
				}

				/*! @brief
				 *
				 */
				const MemberType &
				at( const UA_Key &key ) const
				{
					if( key.isVector() )
					{
						throw std::runtime_error( "Operation not supported on vector" );
					}
					auto& target= get( key.parent() );
					return target.data.at(  std::get< std::string >( key.levels.back() ) );
				}

				/*! @brief
				 *
				 */
				MemberType &
				at( const std::string &key )
				{
					return at( UA_Key( key ) );
				}

				/*! @brief
				 *
				 */
				MemberType &
				at( const UA_Key &key )
				{
					if( key.isVector() )
					{
						throw std::runtime_error( "Operation not supported on vector" );
					}
					auto& target= get( key.parent() );
					return target.data.at(  std::get< std::string >( key.levels.back() ) );
				}

				/*! @brief
				 *
				 */
				size_t
				count( const std::string &key )
				{
					return 0;
				}

				/*! @brief
				 *  @note direct count on a vector is not supported. Use at() to obtain a reference to the vector
				 */
				size_t
				count( const UA_Key &key )
				{
					return 0;
				}
		};
	}

}

namespace Alepha::Hydrogen::inline exports::inline UniversalAggregate_m
{
	using namespace detail::UniversalAggregate_m::exports;
}