/**
 * 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;
}