/**

 * OHP3D

 * Copyright © 2023 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 <string>

#include <cstring>

#include <stdexcept>

#include <vector>

#include <sys/xattr.h>

#include "XAttrs.h"

std::string xattrGet(

		const std::string fileName,

		const std::string name,

		bool* exists = nullptr) {

	std::string buffer;

	ssize_t size = getxattr(fileName.c_str(), name.c_str(), nullptr, 0);

	if (size > 0) {

		buffer.resize(size);

		getxattr(fileName.c_str(), name.c_str(), buffer.data(), buffer.size());

		if (exists) *exists = true;

		return buffer;

	} else if (size == 0) {

		if (exists) *exists = true;

		return "";

	} else if (errno == ENODATA) {

		if (exists) *exists = false;

		return "";

	} else if (errno == ERANGE) {

		// rare race condition - the value has changed between the two calls

		return xattrGet(fileName, name, exists);

	} else {

		throw std::logic_error(

				std::string("Unable to get extended attribute: ")

				+ strerror(errno));

	}

}

bool xattrSet(const std::string fileName,

		const std::string name,

		const std::string value,

		bool exists = true) {

	int result;

	if (exists) {

		result = setxattr(

				fileName.c_str(),

				name.c_str(),

				value.c_str(),

				value.size(),

				0);

	} else {

		result = removexattr(fileName.c_str(), name.c_str());

		if (result < 0 && errno == ENODATA) return false;

	}

	if (result < 0) throw std::logic_error(

			std::string("Unable to set extended attribute: ")

			+ strerror(errno));

	else return true;

}

std::vector<std::string> xattrList(const std::string fileName) {

	std::string buffer;

	ssize_t size = listxattr(fileName.c_str(), nullptr, 0);

	if (size >= 0) {

		buffer.resize(size);

		listxattr(fileName.c_str(), buffer.data(), buffer.size());

		std::vector<std::string> result;

		for (const char* k = buffer.c_str(); strlen(k); k += strlen(k) + 1) {

			result.push_back(k);

		}

		return result;

	} else if (errno == ERANGE) {

		// rare race condition - the list has changed between the two calls

		return xattrList(fileName);

	} else {

		throw std::logic_error(

				std::string("Unable to list extended attributes: ")

				+ strerror(errno));

	}

}

class XAttrs::Attribute::Impl {

public:

	Impl() {

	}

	virtual ~Impl() {

	}

	std::shared_ptr<XAttrs::Impl> xattrs;

	std::string name;

	std::string value;

	bool exists = true;

	bool loaded = false;

};

class XAttrs::Impl {

public:

	std::string nameSpace;

	std::string fileName;

	std::vector<Attribute> attributes;

	bool loaded = false;

	const XAttrs::Attribute& save(const XAttrs::Attribute& attribute);

	XAttrs::Attribute& load(XAttrs::Attribute& attribute);

};

XAttrs::XAttrs(const std::string& fileName, const std::string& nameSpace) :

impl(std::make_shared<Impl>()) {

	impl->nameSpace = nameSpace;

	impl->fileName = fileName;

}

XAttrs::~XAttrs() {

}

const std::string XAttrs::getFileName() const {

	return impl->fileName;

}

size_t XAttrs::size(bool reload) {

	if (reload || !impl->loaded) {

		impl->attributes.clear();

		std::vector<std::string> names = xattrList(impl->fileName);

		const std::string prefix = impl->nameSpace + ".";

		for (const std::string& name : names) {

			if (name.starts_with(prefix)) {

				Attribute a;

				a.impl->xattrs = impl;

				a.impl->name = name.substr(prefix.size());

				a.impl->value = xattrGet(impl->fileName, name, &a.impl->exists);

				impl->attributes.push_back(a);

			}

		}

		impl->loaded = true;

	}

	return impl->attributes.size();

}

XAttrs::Attribute* XAttrs::begin() {

	size();

	return &impl->attributes[0];

}

XAttrs::Attribute* XAttrs::end() {

	size();

	return &impl->attributes[impl->attributes.size()];

}

const XAttrs::Attribute&

XAttrs::Impl::save(const XAttrs::Attribute& attribute) {

	xattrSet(

			fileName,

			nameSpace + "." + attribute.impl->name,

			attribute.impl->value,

			attribute.impl->exists);

	loaded &= attribute.impl->exists;

	return attribute;

}

XAttrs::Attribute&

XAttrs::Impl::load(XAttrs::Attribute& attribute) {

	attribute.impl->value = xattrGet(fileName,

			nameSpace + "." + attribute.impl->name, &attribute.impl->exists);

	return attribute;

}

XAttrs::Attribute& XAttrs::operator[](std::string name) {

	for (XAttrs::Attribute& a : impl->attributes) {

		if (a.getName() == name) return a; // impl->load(a);

	}

	XAttrs::Attribute a;

	a.impl->xattrs = impl;

	a.impl->name = name;

	a.impl->exists = false;

	// impl->load(a);

	impl->attributes.push_back(a);

	return impl->attributes.back();

}

XAttrs::Attribute& XAttrs::operator[](std::size_t index) {

	if (impl->attributes.empty()) size();

	return impl->attributes[index];

}

XAttrs::Attribute::Attribute() : impl(std::make_shared<Impl>()) {

}

XAttrs::Attribute::~Attribute() {

}

const std::string XAttrs::Attribute::getName() {

	return impl->name;

}

const std::string XAttrs::Attribute::getValue(bool reload) {

	if (reload || !impl->loaded) impl->xattrs->load(*this);

	return impl->value;

}

bool XAttrs::Attribute::exists(bool reload) {

	if (reload || !impl->loaded) impl->xattrs->load(*this);

	return impl->exists;

}

bool XAttrs::Attribute::missing(bool reload) {

	return !exists(reload);

}

XAttrs::Attribute& XAttrs::Attribute::operator=(const std::string& value) {

	impl->value = value;

	impl->exists = true;

	impl->xattrs->save(*this);

	return *this;

}

XAttrs::Attribute& XAttrs::Attribute::

		operator=(const XAttrs::Attribute& value) {

	impl->value = value.impl->value;

	impl->exists = value.impl->exists;

	impl->xattrs->save(*this);

	return *this;

}

XAttrs::Attribute::operator std::string() {

	impl->xattrs->load(*this);

	return impl->value;

}

std::ostream& operator<<(std::ostream& s, XAttrs::Attribute& a) {

	s << a.getValue().c_str();

	return s;

}

std::ostream& operator>>(XAttrs::Attribute& a, std::ostream& s) {

	s << a.getValue().c_str();

	return s;

}

XAttrs::Null::Null() {

	impl->exists = false;

}