main.cpp

import std;
using namespace std;

void error(string s)
{
	throw runtime_error{s};
}

void error(string s1, string s2)
{
	throw runtime_error{ s1 + s2 };
}

void edit_time(string& s)
{

	int T = 0;
	T = static_cast<int>(s.find('T'));
	string hour = s.substr(T + 1, 2);
	stringstream hourss{ hour };
	int int_hour = 0;
	hourss >> int_hour;
	if (!hourss)
		cerr << "error!" << '\n';
	int_hour += 8;
	string new_hour = to_string(int_hour);
	if (int_hour < 10)
		new_hour.insert(0, "0");
	s.replace(T + 1, 2, new_hour);


	const int Z = static_cast<int>(s.find('Z'));
	if (Z == string::npos)
		error("the file has been converted.");
	s.erase(Z, 1);

	//cout << s << '\n';
}

int main()
{
	try 
	{
		cout << "Please enter the name of file which you want to convert: " << "\n";
		string filename;
		cin >> filename;
		ifstream ifs{ filename };

		vector<string> readings;
		if (!ifs)
			error("can't open file: ", filename);
		string format;
		getline(ifs, format);

		for (string x; getline(ifs, x); )
		{
			edit_time(x);
			readings.push_back(x);
		}
		
		//if (!ifs)
		//	error("ifs is fail");

		ofstream ofs{ filename };
		for (const string& x : readings)
			ofs << x << '\n';

		if (!ofs)
			error("ofs is fail");

		cout << "The UTC in the file has been converted to UTC+8." << '\n';
		system("pause");
		return 0;
	}
	catch (exception& e)
	{
		cerr << "error: " << e.what() << '\n';
		system("pause");
		return 1;
	}
	catch (...)
	{
		cerr << "Oops: unknown exception!" << '\n';
		system("pause");
		return 2;
	}

}