/**

 * 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/>.

 */

#include "streamlet-common.h"

#include <unistd.h>

#include <regex>

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

/**

 * This streamlet provides values from XML files.

 * It uses the XPath language to define, what portion of XML should be returned.

 * 

 * With no options it does not provide any attributes.

 * 

 * XPath expressions are passed as 'attribute' options.

 * e.g. --option 'attribute' 'name()' will return single attribute with the name of the root node.

 * 

 * Attributes can be renamed using aliases: --option 'attribute' 'name()' --as 'name'. Otherwise the full XPath expression is used as a name.

 * Number of aliases should match the number of attributes (otherwise only first attributes are renamed, because aliases are global, not relative to the --option).

 * 

 * Like relpipe-in-xmltable, this streamlet supports several modes:

 *  - string

 *  - boolean

 *  - raw-xml

 *  - line-number

 *  - xpath

 * 

 * TODO: more OOP, move to separate repository, proper CMake project, clean-up, stabilize API

 */

class XPathStreamlet : public Streamlet {

private:

	xmlpp::Node::PrefixNsMap ns;

	void findXmlnsInEnvironment() {

		std::regex xmlnsEnvPattern("xmlns_(.*)=(.*)");

		std::cmatch match;

		for (char **env = environ; *env; env++) if (std::regex_match(*env, match, xmlnsEnvPattern)) ns[std::string(match[1])] = match[2];

	}

	void findXmlnsInOptions() {

		for (Option o : getOptions(std::wregex(L"xmlns[:_](.*)"))) ns[toBytes(o.nameMatch[1])] = toBytes(o.value);

		for (Option o : getOptions(std::wregex(L"xmlns"), std::wregex(L"([^:]+):(.*)"))) ns[toBytes(o.valueMatch[1])] = toBytes(o.valueMatch[2]);

	}

	// Modes should share the logic of relpipe-in-xmltable

	enum class Mode {

		STRING,

		BOOLEAN,

		// TODO: support also XML number, when we have a rational or decimal numbers in Relational pipes

		RAW_XML,

		LINE_NUMBER,

		XPATH

	};

	Mode toMode(std::wstring modeName) {

		if (modeName == L"string") return Mode::STRING;

		else if (modeName == L"boolean") return Mode::BOOLEAN;

		else if (modeName == L"raw-xml") return Mode::RAW_XML;

		else if (modeName == L"line-number") return Mode::LINE_NUMBER;

		else if (modeName == L"xpath") return Mode::XPATH;

		else throw std::invalid_argument("Unsupported mode: " + toBytes(modeName));

	}

	std::wstring toType(Mode mode) {

		if (mode == Mode::BOOLEAN) return BOOLEAN;

		else if (mode == Mode::LINE_NUMBER) return INTEGER;

		else return STRING;

	}

	class XPathAttribute {

	public:

		std::wstring name;

		std::wstring xpath;

		Mode mode = Mode::STRING;

	};

	std::vector<XPathAttribute> xpathAttributes;

protected:

	std::vector<AttributeMetadata> getOutputAttributesMetadata() override {

		findXmlnsInEnvironment();

		findXmlnsInOptions();

		std::vector<AttributeMetadata> oam;

		std::vector<Option> modeOptions = getOptions(L"mode");

		std::vector<Option> attributeOptions = getOptions(L"attribute");

		for (int i = 0, limit = attributeOptions.size(); i < limit; i++) {

			Mode mode = i < modeOptions.size() ? toMode(modeOptions[i].value) : Mode::STRING;

			std::wstring alias = getAlias(i, attributeOptions[i].value);

			xpathAttributes.push_back({alias, attributeOptions[i].value, mode});

			oam.push_back({alias, toType(mode)});

		}

		return oam;

	}

	std::vector<OutputAttribute> getOutputAttributes() override {

		std::vector<OutputAttribute> oa;

		try {

			xmlpp::DomParser parser;

			parser.parse_file(toBytes(getCurrentFile()));

			xmlpp::Element* root = parser.get_document()->get_root_node();

			for (XPathAttribute xpathAttribute : xpathAttributes) {

				std::string xpath = toBytes(xpathAttribute.xpath);

				std::wstring result;

				bool isNull = false;

				if (xpathAttribute.mode == Mode::STRING) {

					result = fromBytes(root->eval_to_string(xpath, ns));

				} else if (xpathAttribute.mode == Mode::BOOLEAN) {

					result = root->eval_to_boolean(xpath, ns) ? L"true" : L"false";

				} else if (xpathAttribute.mode == Mode::LINE_NUMBER) {

					xmlpp::NodeSet attributeNodes = root->find(xpath, ns);

					if (attributeNodes.size()) result = std::to_wstring(attributeNodes[0]->get_line());

					else isNull = true;

				} else if (xpathAttribute.mode == Mode::XPATH) {

					xmlpp::NodeSet attributeNodes = root->find(xpath, ns);

					if (attributeNodes.size()) result = fromBytes(attributeNodes[0]->get_path());

					else isNull = true;

				} else if (xpathAttribute.mode == Mode::RAW_XML) {

				} else {

					throw std::logic_error("Unsupported mode."); // should never happer

				}

				oa.push_back({result, isNull});

			}

		} catch (xmlpp::parse_error& e) {

			for (XPathAttribute xpathAttribute : xpathAttributes) oa.push_back({L"", true});

			// invalid XML → xmlpp::parse_error → just skip this file

			// invalid XPath → xmlpp::exception → failure

		}

		return oa;

	}

};

STREAMLET_RUN(XPathStreamlet)