/**

 * Relational pipes

 * Copyright © 2019 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 <vector>

#include <filesystem>

#include <relpipe/writer/typedefs.h>

#include <relpipe/writer/AttributeMetadata.h>

#include <relpipe/writer/RelationalWriter.h>

#include "RequestedField.h"

namespace relpipe {

namespace in {

namespace filesystem {

namespace fs = std::filesystem;

using namespace relpipe::writer;

class XattrAttributeFinder : public AttributeFinder {

private:

	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings.

	string_t getXattr(const fs::path& file, const string_t& attributeName) {

		// TODO: review, test on multiple platforms

		// TODO: improve documentation in xattr.h in glibc

		// TODO: check XATTR_NAME_MAX in limits.h and if it is reasonably small on our system, allocate buffer for it instead of reading twice

		// TODO: avoid race condition (another process might change the attribute between reading its length and its value)

		ssize_t length = getxattr(file.c_str(), convertor.to_bytes(attributeName).c_str(), nullptr, 0);

		if (length > 0) {

			std::vector<char> buffer(length + 1);

			getxattr(file.c_str(), convertor.to_bytes(attributeName).c_str(), buffer.data(), buffer.size());

			return convertor.from_bytes(buffer.data());

		} else {

			return L"";

		}

	}

protected:

	virtual void writeFieldOfExistingFile(RelationalWriter* writer, const string_t& relationName, const RequestedField& field) override {

		for (string_t alias : field.getAliasesOrName()) {

			// TODO: support also other namespaces through CLI --option namespace someOtherNS

			string_t xattrName = L"user." + field.name;

			if (field.group == RequestedField::GROUP_XATTR) writer->writeAttribute(getXattr(currentFile, xattrName));

		}

	}

public:

	virtual vector<AttributeMetadata> toMetadata(RelationalWriter* writer, const string_t& relationName, const RequestedField& field) override {

		if (field.group == RequestedField::GROUP_XATTR) {

			vector<AttributeMetadata> metadata;

			for (string_t alias : field.getAliasesOrName()) metadata.push_back(AttributeMetadata{alias, TypeId::STRING});

			return metadata;

		} else {

			return {};

		}

	}

	virtual ~XattrAttributeFinder() override {

	}

};

}

}

}