#ifdef WIN32
#include <windows.h>
#endif

#if defined LINUX || defined ANDROID
#include <string.h>
// use ICU for conversion
#include <unicode/ustring.h>
#endif

#include "GLTB/exception.h"
#include "GLTB/stringconvert.h"

namespace gltb {
	wchar_t *utf8ToUtf16WChar(const char *input)
	{
#if defined WIN32
		int bufferSize=MultiByteToWideChar(CP_UTF8,0,input,-1,NULL,0);

		if(bufferSize==0 && strlen(input)!=0) {
			wchar_t *windowsMessage;
			DWORD lastError = GetLastError(); 

			FormatMessage(
				FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
				NULL,
				lastError,
				MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
				(LPTSTR) &windowsMessage,
				0, 
				NULL );

			/*
			 * Now this is some fine insanity here: having encountered a charset conversion that went wrong,
			 * we now have to rely on another one on a totally unknown string in order to get an error
			 * message onto the screen.
			 */
			char *utf8WindowsMessage=utf16ToUtf8Char(windowsMessage);

			throw Exception("UTF8 to UTF16 string conversion failed; Windows error message claims " + std::string(utf8WindowsMessage),"gltb::utf8ToUtf16WChar()");
		}

		wchar_t *result=new wchar_t[bufferSize];

		if(MultiByteToWideChar(CP_UTF8,0,input,-1,result,bufferSize)!=bufferSize) {
			throw Exception("UTF8 to UTF16 string conversion failed","gltb::utf8ToUtf16WChar()");
		}

		return result;
#elif defined LINUX || defined ANDROID
		int bufferSize=0;
		UErrorCode errorCode=U_ZERO_ERROR;
		int numSubs;
		
		u_strFromUTF8WithSub(NULL,0,&bufferSize,input,-1,L' ',&numSubs,&errorCode);
		if(errorCode==U_STRING_NOT_TERMINATED_WARNING) {
			/*
			 * This is an interesting wrinkle in the behaviour of ICU: the
			 * library happily generates unterminated strings and indicates
			 * that using the error code. So here we are, having fit the
			 * converted string into 0 bytes without terminator. In other
			 * words: the output is the empty string.
			 */
			wchar_t *result=new wchar_t[1];
			result[0]=0;
			return result;
		} else if(errorCode!=U_BUFFER_OVERFLOW_ERROR) {
			throw Exception("UTF8 to UTF16 string conversion failed while trying to get temporary buffer size, error: " + std::string(u_errorName(errorCode)),"gltb::utf8ToUtf16WChar()");
		}
		
		UChar *temp=new UChar[bufferSize+1];
		memset(temp,0,(bufferSize+1)*sizeof(UChar));
		
		errorCode=U_ZERO_ERROR;
		u_strFromUTF8WithSub(temp,bufferSize,&bufferSize,input,-1,L' ',&numSubs,&errorCode);
		if(errorCode>0) {
			throw Exception("UTF8 to UTF16 string conversion failed, error: " + std::string(u_errorName(errorCode)),"gltb::utf8ToUtf16WChar()");
		}
		
		bufferSize=0;
		errorCode=U_ZERO_ERROR;
		u_strToWCS(NULL,0,&bufferSize,temp,-1,&errorCode);
		if(errorCode!=U_BUFFER_OVERFLOW_ERROR) {
			throw Exception("UTF8 to UTF16 string conversion failed while trying to get output buffer size, error: " + std::string(u_errorName(errorCode)),"gltb::utf8ToUtf16WChar()");
		}

		wchar_t *result=new wchar_t[bufferSize+1];
		memset(result,0,(bufferSize+1)*sizeof(wchar_t));
		
		errorCode=U_ZERO_ERROR;
		u_strToWCS(result,bufferSize,&bufferSize,temp,-1,&errorCode);
		if(errorCode>0) {
			throw Exception("UTF8 to UTF16 string conversion failed, error: " + std::string(u_errorName(errorCode)),"gltb::utf8ToUtf16WChar()");
		}
		delete[] temp;
		
		return result;
#else
#error unimplemented function on this target platform
#endif
	}

	char *utf16ToUtf8Char(const wchar_t *input)
	{
#ifdef WIN32
		int bufferSize=WideCharToMultiByte(CP_UTF8,0,input,-1,NULL,0,NULL,NULL);

		if(bufferSize==0 && wcslen(input)!=0) {
			wchar_t *windowsMessage;
			DWORD lastError = GetLastError(); 

			FormatMessage(
				FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
				NULL,
				lastError,
				MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
				(LPTSTR) &windowsMessage,
				0, 
				NULL );

			/*
			 * Now this is some fine insanity here: having encountered a charset conversion that went wrong,
			 * we now have to rely on another one on a totally unknown string in order to get an error
			 * message onto the screen.
			 */
			char *utf8WindowsMessage=utf16ToUtf8Char(windowsMessage);

			throw Exception("UTF16 to UTF8 string conversion failed; Windows error message claims " + std::string(utf8WindowsMessage),"gltb::utf16ToUtf8Char()");
		}

		char *result=new char[bufferSize];

		if(WideCharToMultiByte(CP_UTF8,0,input,-1,result,bufferSize,NULL,NULL)!=bufferSize) {
			throw Exception("UTF16 to UTF8 string conversion failed","gltb::utf16ToUtf8Char()");
		}

		return result;
#elif defined LINUX || defined ANDROID
		int bufferSize=0;
		UErrorCode errorCode=U_ZERO_ERROR;
		
		u_strFromWCS(NULL,0,&bufferSize,input,-1,&errorCode);
		if(errorCode==U_STRING_NOT_TERMINATED_WARNING) {
			/*
			 * This is an interesting wrinkle in the behaviour of ICU: the
			 * library happily generates unterminated strings and indicates
			 * that using the error code. So here we are, having fit the
			 * converted string into 0 bytes without terminator. In other
			 * words: the output is the empty string.
			 */
			char *result=new char[1];
			result[0]=0;
			return result;
		} else if(errorCode!=U_BUFFER_OVERFLOW_ERROR) {
			throw Exception("UTF16 to UTF8 string conversion failed while trying to get temporary buffer size, error: " + std::string(u_errorName(errorCode)),"gltb::utf16ToUtf8Char()");
		}
		
		UChar *temp=new UChar[bufferSize+1];
		memset(temp,0,(bufferSize+1)*sizeof(UChar));
		
		errorCode=U_ZERO_ERROR;
		u_strFromWCS(temp,bufferSize,&bufferSize,input,-1,&errorCode);
		if(errorCode>0) {
			throw Exception("UTF16 to UTF8 string conversion failed, error: " + std::string(u_errorName(errorCode)),"gltb::utf16ToUtf8har()");
		}

		bufferSize=0;
		errorCode=U_ZERO_ERROR;
		u_strToUTF8(NULL,0,&bufferSize,temp,-1,&errorCode);
		if(errorCode!=U_BUFFER_OVERFLOW_ERROR) {
			throw Exception("UTF16 to UTF8 string conversion failed while trying to get output buffer size, error: " + std::string(u_errorName(errorCode)),"gltb::utf16ToUtf8Char()");
		}
		
		char *result=new char[bufferSize+1];
		memset(result,0,bufferSize+1);
		
		errorCode=U_ZERO_ERROR;
		u_strToUTF8(result,bufferSize,&bufferSize,temp,-1,&errorCode);
		if(errorCode>0) {
			throw Exception("UTF16 to UTF8 string conversion failed, error: " + std::string(u_errorName(errorCode)),"gltb::utf16ToUtf8har()");
		}
		delete[] temp;
		
		return result;
#else
#error unimplemented function on this target platform
#endif
	}

	std::wstring utf8ToUtf16WString(std::string input)
	{
		wchar_t *result=utf8ToUtf16WChar(input.c_str());
		std::wstring resultStr=result;
		delete[] result;
		return resultStr;
	}

	std::string utf16ToUtf8String(std::wstring input)
	{
		char *result=utf16ToUtf8Char(input.c_str());
		std::string resultStr=result;
		delete[] result;
		return resultStr;
	}
}