// Standard C++
#include <array>
#include <memory>
#include <span>
#include <sstream>

// Project
#include "xml.hpp"

// Expat XML Parser
#include "expat.h"

using namespace std;

void
XML::parse(istream& ins)
{
	unique_ptr<XML_ParserStruct, decltype(&::XML_ParserFree)> parser(::XML_ParserCreate(nullptr), ::XML_ParserFree);

	if ( !parser ) {
		throw bad_alloc();
	}

	// setup expat
	::XML_SetUserData(parser.get(), this);
	::XML_SetElementHandler(parser.get(), tag_start, tag_end);
	::XML_SetCdataSectionHandler(parser.get(), cdata_start, cdata_end);
	::XML_SetCharacterDataHandler(parser.get(), data);

	constexpr auto buffer_size = 2048;

	array<char, buffer_size> buffer{};

	for ( bool done = false; !done; ) {
		ins.read(buffer.data(), buffer_size);
		done = ins.gcount() < buffer_size;

		if ( ::XML_Parse(parser.get(), buffer.data(), static_cast<int>(ins.gcount()), static_cast<int>(done)) != XML_STATUS_OK ) {
			stringstream msg;

			msg << ::XML_ErrorString(XML_GetErrorCode(parser.get()));
			msg << " in line " << ::XML_GetCurrentLineNumber(parser.get());

			throw runtime_error(msg.str());
		}
	}
}

void
XML::tag_start(void* self, const char* name, const char** attr)
{
	vector<tuple<string_view, string_view>> attr_temp;

	for ( auto i = 0; attr[i] != nullptr; i += 2 ) {
		attr_temp.emplace_back(attr[i], attr[i + 1]);
	}

	static_cast<XML*>(self)->handle_start(name, attr_temp);
}

void
XML::tag_end(void* self, const char* name)
{
	static_cast<XML*>(self)->handle_end(name);
}

void
XML::cdata_start(void* self)
{
	static_cast<XML*>(self)->handle_cdata_start();
}

void
XML::cdata_end(void* self)
{
	static_cast<XML*>(self)->handle_cdata_end();
}

void
XML::data(void* self, const char* dat, int len)
{
	static_cast<XML*>(self)->handle_character_data({ dat, static_cast<size_t>(len) });
}