/**
 * Relational pipes
 * Copyright © 2020 František Kučera (Frantovo.cz, GlobalCode.info)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
#pragma once

#include <memory>
#include <string>
#include <vector>
#include <codecvt>
#include <regex>
#include <stdexcept>

#include <libxml++-2.6/libxml++/libxml++.h>

#include <relpipe/common/type/typedefs.h>
#include <relpipe/reader/TypeId.h>
#include <relpipe/reader/handlers/RelationalReaderStringHandler.h>
#include <relpipe/reader/handlers/AttributeMetadata.h>

#include <relpipe/writer/Factory.h>

#include <relpipe/cli/RelpipeCLIException.h>

#include "Configuration.h"
#include "XMLNameCodec.h"

namespace relpipe {
namespace tr {
namespace xpath {

class XPathHandler : public relpipe::reader::handlers::RelationalReaderStringHandler {
private:
	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // XML is in UTF-8
	shared_ptr<relpipe::writer::RelationalWriter> relationalWriter;
	Configuration configuration;
	RelationConfiguration* currentRelationConfiguration = nullptr;
	std::vector<relpipe::reader::handlers::AttributeMetadata> currentReaderMetadata;
	std::vector<relpipe::writer::AttributeMetadata> currentWriterMetadata;
	size_t currentAttributeIndex = 0;
	size_t currentRecordNumber = 1;


	xmlpp::Node::PrefixNsMap xmlns;
	xmlpp::Document dom;
	xmlpp::Element* recordElement = nullptr;
	relpipe::in::xmltable::XMLNameCodec xmlNameCodec; // TODO: move to a common library

	void copyInputAttributesToOutput() {
		for (auto rm : currentReaderMetadata) currentWriterMetadata.push_back({rm.getAttributeName(), relationalWriter->toTypeId(rm.getTypeName())});
	}

	bool isPrependingInputAttributes() {
		return currentRelationConfiguration->inputAttributePolicy == InputAttributePolicy::Prepend
				|| (currentRelationConfiguration->inputAttributePolicy == InputAttributePolicy::Auto && currentRelationConfiguration->outputAttributes.size() == 0);
	}

	bool isAppendingInputAttributes() {
		return currentRelationConfiguration->inputAttributePolicy == InputAttributePolicy::Append;
	}

	void resetRecordElement() {
		if (recordElement) dom.get_root_node()->remove_child(recordElement);
		recordElement = dom.get_root_node()->add_child("record");
	}

	const Glib::ustring s2x(relpipe::common::type::StringX value) {
		return Glib::ustring(convertor.to_bytes(value));
	}

	const relpipe::common::type::StringX x2s(const Glib::ustring& value) {
		return convertor.from_bytes(value);
	}

	bool isXmlAttribute(const relpipe::common::type::StringX& attributeName) {
		for (auto pattern : currentRelationConfiguration->xmlAttributes) if (std::regex_match(attributeName, std::wregex(pattern))) return true;
		return false;
	}

	const relpipe::common::type::StringX formatRawXML(const relpipe::common::type::StringX& rawXML) {
		// TODO: move to a common library (used also in relpipe-in-xmltable)
		std::wregex pattern(L"^<\\?xml version=\"1.0\" encoding=\"UTF-8\"\\?>\n|\n$");
		return std::regex_replace(rawXML, pattern, L"");
	}

	const relpipe::common::type::StringX serialize(xmlpp::Element* element, bool asXml) {
		if (element) {
			if (asXml) {
				xmlpp::Document d;
				d.create_root_node_by_import(element, true);
				return formatRawXML(x2s(d.write_to_string()));
			} else {
				return element->get_child_text() ? x2s(element->get_child_text()->get_content()) : L"";
			}
		} else {
			return L"";
		}
	}

	xmlpp::Element* findSingleElement(const xmlpp::NodeSet& nodeset) {
		if (nodeset.empty()) return nullptr;
		else if (nodeset.size() > 1) throw std::invalid_argument("XPath should find one or zero elements.");
		else if (xmlpp::Element * element = dynamic_cast<xmlpp::Element*> (nodeset[0])) return element;
		else if (nodeset[0]->get_path() == "/") return findSingleElement(nodeset[0]->find("*")); // support also "/" not only "/*" expressions (return root element in both cases)
		else throw std::invalid_argument("XPath should find an element, not other kinds of nodes.");
	}

	void writeInputAttributes() {
		for (xmlpp::Node* attributeNode : recordElement->get_children()) {
			if (xmlpp::Element * attributeElement = dynamic_cast<xmlpp::Element*> (attributeNode)) {
				bool asXml = isXmlAttribute(x2s(attributeElement->get_attribute("name")->get_value()));
				relationalWriter->writeAttribute(serialize(asXml ? dynamic_cast<xmlpp::Element*> (attributeElement->get_first_child()) : attributeElement, asXml));
			}
		}
	}

	void writeOutputAttributes() {
		for (auto oa : currentRelationConfiguration->outputAttributes) {
			relpipe::common::type::StringX value;
			if (isXmlAttribute(oa.name)) value = serialize(findSingleElement(recordElement->find(s2x(oa.xpath), xmlns)), true);
			else value = x2s(recordElement->eval_to_string(s2x(oa.xpath), xmlns));
			relationalWriter->writeAttribute(value);
		}
	}

public:

	XPathHandler(shared_ptr<relpipe::writer::RelationalWriter> relationalWriter, Configuration configuration) : relationalWriter(relationalWriter), configuration(configuration) {
		for (int i = 0; i < configuration.namespaceMappings.size(); i++) {
			std::string prefix = convertor.to_bytes(configuration.namespaceMappings[i]);
			std::string uri = convertor.to_bytes(configuration.namespaceMappings[++i]);
			xmlns[prefix] = uri;
		}
	}

	virtual ~XPathHandler() {
	}

	void startRelation(relpipe::common::type::StringX name, std::vector<relpipe::reader::handlers::AttributeMetadata> attributes) override {
		currentRelationConfiguration = nullptr;

		for (int i = 0; i < configuration.relationConfigurations.size(); i++) {
			if (std::regex_match(name, std::wregex(configuration.relationConfigurations[i].relation))) {
				currentRelationConfiguration = &configuration.relationConfigurations[i];
				break;
			}
		}

		currentReaderMetadata = attributes;
		currentWriterMetadata.clear();
		currentRecordNumber = 1;
		recordElement = nullptr;

		if (currentRelationConfiguration == nullptr) {
			copyInputAttributesToOutput();
		} else {
			if (isPrependingInputAttributes()) copyInputAttributesToOutput();
			for (auto oa : currentRelationConfiguration->outputAttributes) currentWriterMetadata.push_back({oa.name, oa.type});
			if (isAppendingInputAttributes()) copyInputAttributesToOutput();

			dom.create_root_node("relpipe-tr-xpath");
			dom.get_root_node()->add_child("relation-name")->add_child_text(s2x(name));
			resetRecordElement();
		}

		relationalWriter->startRelation(name, currentWriterMetadata, true);
	}

	void attribute(const relpipe::common::type::StringX& value) override {
		if (currentRelationConfiguration) {
			relpipe::reader::handlers::AttributeMetadata attributeMetadata = currentReaderMetadata[currentAttributeIndex];

			// TODO: Parallel processing of records like in relpipe-in-filesystem? Or share common code with the XPath streamlet? (streamlets are parallelized)

			xmlpp::Element* attributeElement = recordElement->add_child(xmlNameCodec.encode(s2x(attributeMetadata.getAttributeName())));
			attributeElement->set_attribute("name", s2x(attributeMetadata.getAttributeName()));
			attributeElement->set_attribute("type", s2x(attributeMetadata.getTypeName()));
			if (isXmlAttribute(attributeMetadata.getAttributeName())) {
				if (value.size()) {
					xmlpp::DomParser attributeParser;
					attributeParser.parse_memory(s2x(value));
					attributeElement->import_node(attributeParser.get_document()->get_root_node(), true);
				}
			} else {
				attributeElement->add_child_text(s2x(value));
			}

			if (currentAttributeIndex == 0) {
				recordElement->set_attribute("number", std::to_string(currentRecordNumber));
			}

			currentAttributeIndex++;

			if (currentAttributeIndex == currentReaderMetadata.size()) {
				if (currentRelationConfiguration->where.empty() || recordElement->eval_to_boolean(s2x(currentRelationConfiguration->where), xmlns)) {
					if (isPrependingInputAttributes()) writeInputAttributes();
					writeOutputAttributes();
					if (isAppendingInputAttributes()) writeInputAttributes();
				}

				resetRecordElement();
				currentAttributeIndex = 0;
				currentRecordNumber++;
			}
		} else {
			relationalWriter->writeAttribute(value);
		}
	}

	void endOfPipe() {

	}

};

}
}
}