#ifndef INPUTXSLT_SRC_FUNCTION_BASE_H_
#define INPUTXSLT_SRC_FUNCTION_BASE_H_

#include <xalanc/XPath/XObjectFactory.hpp>
#include <xalanc/XPath/Function.hpp>
#include <xalanc/XPath/XObject.hpp>

#include <boost/optional.hpp>

#include <memory>
#include <tuple>

#include "common.h"
#include "support/xalan_string.h"
#include "support/filesystem_context.h"
#include "support/include_entity_resolver.h"
#include "support/dom/document_cache.h"
#include "support/type/sequence.h"
#include "support/type/filter.h"
#include "support/type/xobject_value.h"

namespace InputXSLT {

template <
	typename Implementation,
	typename... Types
>
class FunctionBase : public xalan::Function {
	static const std::size_t maximum_parameter_count = sizeof...(Types);
	static const std::size_t minimum_parameter_count = maximum_parameter_count
	                                                 - std::tuple_size<
		typename filter_derived<
			boost::optional_detail::optional_tag,
			Types...
		>::type
	>::value;

	public:
		FunctionBase(IncludeEntityResolver* resolver):
			include_resolver_(resolver),
			document_cache_(std::make_shared<DomDocumentCache>()) { }

		virtual xalan::XObjectPtr execute(
			xalan::XPathExecutionContext& executionContext,
			xalan::XalanNode*             context,
			const XObjectArgVectorType&   parameters,
			const xalan::Locator*         locator
		) const {
			this->validateParameters(
				parameters,
				executionContext,
				context,
				locator
			);

			xalan::XalanDocument* const domDocument(
				this->callConstructDocument(
					parameters,
					typename IndexSequence<maximum_parameter_count>::type()
				)
			);

			xalan::XPathExecutionContext::BorrowReturnMutableNodeRefList nodes(
				executionContext
			);

			nodes->addNodes(
				*domDocument->getDocumentElement()->getChildNodes()
			);

			return executionContext.getXObjectFactory().createNodeSet(nodes);
		}

		virtual FunctionBase* clone(
			xalan::MemoryManager& manager) const {
			return xalan::XalanCopyConstruct(
				manager,
				static_cast<const Implementation&>(*this)
			);
		}

		FunctionBase& operator=(const FunctionBase&) = delete;
		bool operator==(const FunctionBase&) const   = delete;

	protected:
		IncludeEntityResolver* const include_resolver_;

	private:
		std::shared_ptr<DomDocumentCache> document_cache_;

		const xalan::XalanDOMString& getError(
			xalan::XalanDOMString& result) const {
			const std::string startText("The function expects ");
			const std::string endText(" parameter(s)");

			if ( minimum_parameter_count == maximum_parameter_count ) {
				result.assign(std::string(
					startText
					+ std::to_string(minimum_parameter_count)
					+ endText
				).data());
			} else {
				result.assign(std::string(
					startText
					+ "between "
					+ std::to_string(minimum_parameter_count) 
					+ " and "
					+ std::to_string(maximum_parameter_count) 
					+ endText
				).data());
			}

			return result;
		}

		template <std::size_t... Index>
		xalan::XalanDocument* callConstructDocument(
			const XObjectArgVectorType& parameters,
			Sequence<Index...>
		) const {
			const FilesystemContext context;
			XObjectValue valueGetter(&context, this->include_resolver_);

			return this->document_cache_->create(
				static_cast<const Implementation*>(this)->constructDocument(
					context,
					valueGetter.get<typename std::tuple_element<
						Index,
						std::tuple<Types...>
					>::type>(
						Index < parameters.size()
						? parameters[Index]
						: xalan::XObjectPtr()
					)...
				)
			);
		}

		void validateParameters(
			const XObjectArgVectorType&   parameters,
			xalan::XPathExecutionContext& executionContext,
			xalan::XalanNode*             context,
			const xalan::Locator*         locator
		) const {
			const bool anyNull = std::any_of(
				parameters.begin(),
				parameters.end(),
				[](const xalan::XObjectPtr& ptr) -> bool {
					return ptr.null();
				}
			);

			if ( parameters.size() > maximum_parameter_count ||
			     parameters.size() < minimum_parameter_count ||
			     anyNull ) {
				xalan::XPathExecutionContext::GetAndReleaseCachedString guard(
					executionContext
				);

				this->generalError(executionContext, context, locator);
			}
		}

};

}

#endif  // INPUTXSLT_SRC_FUNCTION_BASE_H_