/**

 * Relational pipes

 * Copyright © 2018 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, either version 3 of the License, or

 * (at your option) any later version.

 *

 * 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 <iostream>

#include <sstream>

#include <string>

#include <vector>

#include <codecvt>

#include <locale>

#include "RelpipeXMLWriterException.h"

using namespace std;

namespace relpipe {

namespace xmlwriter {

/**

 * A simple library for writing XML streams.

 * 

 * Does:

 *  - convert wstring values to UTF-8

 *  - escape values of text nodes and attributes

 *  - indent elements

 *  - preserve whitespace of text nodes

 *  - in comments: replace - with –

 * Does not:

 *  - understand XML namespaces:

 *     - handles xmlns:x="y" as ordinary attributes

 *     - thus can not check whether elements/attributes belong to an declared namespace

 *     - thus can generate invalid XML – namespaces and their prefixes must be checked on the caller side

 */

class XMLWriter {

private:

	const char* INDENT = "\t";

	ostream& output;

	wstring_convert<codecvt_utf8<wchar_t>> convertor; // XML output will be always in UTF-8

	vector<wstring> treePosition;

	bool lastWasTextNode = false;

	const string escapeXmlText(const wstring& value) {

		// TODO: really bad performance → rewrite

		// 72 % of whole relpipe-out-xml according to valgrind/callgrind

		// Moved here from XmlHandler.h (relpipe-out-xml).

		std::wstringstream result;

		for (auto & ch : value) {

			switch (ch) {

				case L'&': result << L"&amp;";

					break;

				case L'<': result << L"&lt;";

					break;

				case L'>': result << L"&gt;";

					break;

				case L'\'': result << L"&apos;"; // TODO: escape ' and " only in attributes

					break;

				case L'"': result << L"&quot;"; // TODO: escape ' and " only in attributes

					break;

				default: result << ch;

			}

		}

		return convertor.to_bytes(result.str());

	}

	const string escapeXmlAttribute(const wstring& value) {

		// TODO: escaping of ' is not necessary.

		return escapeXmlText(value);

	}

	const string escapeComment(const wstring& value) {

		// TODO: really bad performance → rewrite

		// 72 % of whole relpipe-out-xml according to valgrind/callgrind

		std::wstringstream result;

		for (auto & ch : value) {

			switch (ch) {

				case L'-': result << L"–";

					break;

				default: result << ch;

			}

		}

		return convertor.to_bytes(result.str());

	}

	void checkName(const wstring& name) {

		// FIXME: throw exception on invalid names

	}

	void writeAttributes(const vector<wstring>& attributes) {

		if (attributes.size() % 2) throw RelpipeXMLWriterException(L"attributes vector must contain name/value pairs (even number of elements)");

		for (int i = 0; i < attributes.size(); i = i + 2) {

			wstring name = attributes[i];

			wstring value = attributes[i + 1];

			checkName(name);

			output << " " << convertor.to_bytes(name) << "=\"" << escapeXmlAttribute(value) << "\"";

		}

	}

	void writeIndentation(bool resetState = true) {

		if (lastWasTextNode) {

			if (resetState) lastWasTextNode = false;

		} else {

			output << endl;

			for (int i = 0; i < treePosition.size(); i++) {

				output << INDENT;

			}

		}

	}

public:

	XMLWriter(std::ostream& output) : output(output) {

		output << "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";

	}

	virtual ~XMLWriter() {

		output << endl;

		output.flush();

	}

	void writeStartElement(const wstring& name, const vector<wstring>& attributes = {}) {

		checkName(name);

		writeIndentation();

		treePosition.push_back(name);

		output << "<" << convertor.to_bytes(name);

		writeAttributes(attributes);

		output << ">";

	}

	void writeEndElement() {

		if (treePosition.empty()) throw RelpipeXMLWriterException(L"unable to close element – all elements are already closed");

		wstring name = treePosition.back();

		treePosition.pop_back();

		writeIndentation();

		output << "</" << convertor.to_bytes(name) << ">";

	}

	void writeEmptyElement(const wstring& name, const vector<wstring>& attributes = {}) {

		checkName(name);

		writeIndentation();

		output << "<" << convertor.to_bytes(name);

		writeAttributes(attributes);

		output << "/>";

	}

	void writeTextElement(const wstring& name, const vector<wstring>& attributes, const wstring& text) {

		writeStartElement(name, attributes);

		writeCharacters(text);

		writeEndElement();

	}

	void writeCharacters(const wstring& text) {

		output << escapeXmlText(text);

		lastWasTextNode = true;

	}

	void writeComment(const wstring& text, bool addSpaces = true) {

		writeIndentation(false);

		output << (addSpaces ? "<!-- " : "<!--");

		output << escapeComment(text);

		output << (addSpaces ? " -->" : "-->");

	}

};

}

}