using System;
using System.Collections;
using System.Collections.Generic;

    public static class SimpleMathParser
    {
        static List<String> OperationOrder = new List<string>();
        static Dictionary<string, double> Parameters { get; set; }

        static SimpleMathParser()
        {
            Parameters = new Dictionary<string, double>();
            Parameters.Add("Pi", Math.PI);
            Parameters.Add("E", Math.E);
            OperationOrder.AddRange(new string[] { "%", "^", "/", "*", "-", "+" });
        }

        public static string Calculate(string Formula)
        {
            try
            {
                string[] arr = Formula.Split("/+-*()".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
                foreach (KeyValuePair<string, double> de in Parameters)
                {
                    foreach (string s in arr)
                        if (s != de.Key && s.EndsWith(de.Key))
                            Formula = Formula.Replace(s, (Convert.ToDouble(s.Replace(de.Key, "")) * de.Value).ToString());
                    Formula = Formula.Replace(de.Key, de.Value.ToString());
                }
                while (Formula.LastIndexOf("(") > -1)
                {
                    int lastOpenPhrantesisIndex = Formula.LastIndexOf("("),
                    firstClosePhrantesisIndexAfterLastOpened = Formula.IndexOf(")", lastOpenPhrantesisIndex);

                    double result = ProcessOperation(Formula.Substring(lastOpenPhrantesisIndex + 1, firstClosePhrantesisIndexAfterLastOpened - lastOpenPhrantesisIndex - 1));

                    bool AppendAsterix = false;

                    if (lastOpenPhrantesisIndex > 0)
                        if (Formula.Substring(lastOpenPhrantesisIndex - 1, 1) != "(" && !OperationOrder.Contains(Formula.Substring(lastOpenPhrantesisIndex - 1, 1)))
                            AppendAsterix = true;

                    Formula = Formula.Substring(0, lastOpenPhrantesisIndex) +
                        (AppendAsterix ? "*" : "") +
                        result.ToString() +
                        Formula.Substring(firstClosePhrantesisIndexAfterLastOpened + 1);
                }
                return ProcessOperation(Formula).ToString();
            }
            catch { return Formula; }
        }

        static double ProcessOperation(string operation)
        {
            var arr = new ArrayList(); string s = "";

            for (int i = 0; i < operation.Length; i++)
            {
                string currentCharacter = operation.Substring(i, 1);

                if (OperationOrder.IndexOf(currentCharacter) > -1)
                {
                    if (s != "") arr.Add(s);
                    arr.Add(currentCharacter); s = "";
                }
                else s += currentCharacter;
            }

            arr.Add(s); s = "";

            foreach (string op in OperationOrder)
            {
                while (arr.IndexOf(op) > -1)
                {
                    int operatorIndex = arr.IndexOf(op);
                    double digitBeforeOperator = Convert.ToDouble(arr[operatorIndex - 1]);
                    double digitAfterOperator = 0;

                    if (arr[operatorIndex + 1].ToString() == "-")
                    {
                        arr.RemoveAt(operatorIndex + 1);
                        digitAfterOperator = Convert.ToDouble(arr[operatorIndex + 1]) * -1;
                    }
                    else digitAfterOperator = Convert.ToDouble(arr[operatorIndex + 1]);

                    arr[operatorIndex] = CalculateByOperator(digitBeforeOperator, digitAfterOperator, op);
                    arr.RemoveAt(operatorIndex - 1);
                    arr.RemoveAt(operatorIndex);
                }
            }
            return Convert.ToDouble(arr[0]);
        }

        static double CalculateByOperator(double a, double b, string Operator)
        {
            if (Operator == "^") return Math.Pow(a, b);
            else if (Operator == "%") return a % b;
            else if (Operator == "/") return a / b;
            else if (Operator == "*") return a * b;
            else if (Operator == "-") return a - b;
            else if (Operator == "+") return a + b;
            else return Double.NaN;
        }
    }