// Calculator Bot
// Acts like a simple calculator. Advanced bot for students that are done with the tutorial

using System;
namespace ChatBot 
{
	class CalculatorBot : BasicBot 
	{
		string number1;  //Global strings
		string operand;
		public override string HandleMessage(string message, string user) 
		{
			if (state == "1") 
			{
				if (User.RegexMatch("[0-9]+", message)) 
				{ 
					number1 = message;  //Saves the number
					state = "2";
                    			return "Please enter an operand (+, -, /, *): ";
				}
				else 
					return "Please type a number.";
			}
			else if (state == "2") 
			{
				if (User.RegexMatch("[/+-/*//]", message)) 
				{
					operand = message;  //Saves the operator
					state = "3";
                    			return "Please enter the second integer: ";
				}
				else 
					return "Please type an operator.";
			}
			else if (state == "3") 
			{
				if (User.RegexMatch("[0-9]+", message)) 
				{
					state = "0";  //Resets the state
					int num1 = Convert.ToInt32(number1);  //Convert the string into an int
					int num2 = Convert.ToInt32(message);  //Convert the string into and int
					double answer;
					if (operand.CompareTo("+") == 0)
						answer = num1 + num2;
					else if (operand.CompareTo("*") == 0)
						answer = num1 * num2;
					else if (operand.CompareTo("/") == 0)
						answer = (double)num1 / num2;  //Type cast into a double
					else if (operand.CompareTo("-") == 0)
						answer = num1 - num2;
					else
						answer = 0;
					return num1 + " " + operand + " " + num2 + " = " + answer;
				}
				else
					return "Please type a number.";
			}
			else 
			{
				state = "1";
                		return "Please enter the first integer: ";
			}
		}
	}
}