#include <sstream>

#include <locale>

/**

 * 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

 */

	const char* INDENT = "\t";

	ostream& output;

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

	vector<wstring> treePosition;

	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) << "\"";

		}

	}

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

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

		// FIXME: indentation

		checkName(name);

		treePosition.push_back(name);

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

		writeAttributes(attributes);

		output << ">";

		// FIXME: indentation

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

		output << "</" << convertor.to_bytes(treePosition.back()) << ">";

		treePosition.pop_back();

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

		// FIXME: indentation

		checkName(name);

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

		writeAttributes(attributes);

		output << "/>";

		writeStartElement(name, attributes);

		writeCharacters(text);

		writeEndElement();

		output << escapeXmlText(text);

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

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

		output << escapeComment(text);

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