#include "RPN.hpp"

int add(int first, int second) { return first + second; }
int subst(int first, int second) { return first - second; }
int mult(int first, int second) { return first * second; }
int div(int first, int second) {
	if (second == 0)
		throw std::invalid_argument("division by 0 is not possible");
	return first / second;
}


typedef int (*OperatorFunctions)(int, int);

void rpn(char *av)
{
	OperatorFunctions calc[128] = { NULL };
	calc[(int) '+'] = &add;
	calc[(int) '-'] = &subst;
	calc[(int) '*'] = &mult;
	calc[(int) '/'] = ÷

	std::istringstream	ss_input((std::string(av)));
	std::stack<int>		stack;

	std::string value;

	while (ss_input >> value)
	{
		if (value.size() != 1)
			throw std::invalid_argument("invalid value");

		if (isdigit(value[0]))
		{
			stack.push(value[0] - '0');
			continue ;
		}

		if (!calc[(int) value[0]])
			throw std::invalid_argument("invalid character");

		if (stack.size() < 2)
			throw std::range_error("not enough operands");

		int a = stack.top(); stack.pop();
		int b = stack.top(); stack.pop();
		stack.push(calc[(int) value[0]](b, a));
	}

	if (stack.size() != 1)
		throw std::range_error("there are too many operands");

	std::cout << stack.top() << std::endl;
}