using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;

namespace Курсовая_Часть_5
{
    //exceptions about empty stack - user is dumbass can't use brackets properly

    public class Parser
    {
        public double parse(string input, double x1)
        {
            List<string> opz = OPZ(input, x1);
            double result = Calculate(opz);
            //Console.WriteLine("\nResult is {0}", result);
            return result;
        }
        private static bool IsOperation(char c)
        {
            if (c == '+' ||
                c == '-' ||
                c == '*' ||
                c == '/' ||
                c == '^')
                return true;
            else
                return false;
        }

        private static int GetOperationPriority(char c)
        {
            switch (c)
            {
                case '+': return 1;
                case '-': return 1;
                case '*': return 2;
                case '/': return 2;
                case '^': return 3;
                default: return 0;
            }
        }

        private static double ApplyOperation(string operation, double op1, double op2)
        {
            switch (operation)
            {
                case "+": return (op1 + op2);
                case "-": return (op1 - op2);
                case "*": return (op1 * op2);
                case "/": return (op1 / op2);
                case "^": return Math.Pow(op1, op2);
                default: return 0;
            }
        }
        private static List<string> OPZ(string input, double x1)
        {
            input = input.Replace("x", Convert.ToString(x1));
            /*if (input.Contains("--"))
            {
                input = input.Replace("--", "+");
            }*/
            Stack<char> operationsStack = new Stack<char>();
            char lastOperation;
            List<string> result = new List<string>();
            string temp;
            input = input.Replace(" ", "");
            int iterator = 0;
            for (int i = 0; i < input.Length; i++)
            {
                if (Char.IsDigit(input[i]) || Char.IsLetter(input[i]))
                {
                    temp = Convert.ToString(input[i]);
                    iterator = i+1;
                    while (iterator <input.Length && (Char.IsDigit(input[iterator]) || Char.IsLetter(input[iterator]) || input[iterator] == '.'))
                    {
                        temp += Convert.ToString(input[iterator]);
                        iterator++;
                    }
                    result.Add(temp);
                    i = iterator-1;
                }
                else if (IsOperation(input[i]))
                {
                    if (input[i].Equals('-'))
                    {
                        if (i == 0 || IsOperation(input[i - 1]) || input[i-1].Equals('('))
                            result.Add("0");
                    }
                    if (!(operationsStack.Count == 0))
                    {
                        lastOperation = operationsStack.Peek();
                        if (GetOperationPriority(lastOperation) < GetOperationPriority(input[i]))
                        {
                            operationsStack.Push(input[i]);
                        }
                        else
                        {
                            result.Add(Convert.ToString(operationsStack.Pop()));
                            operationsStack.Push(input[i]);
                        }
                    }
                    else
                    {
                        operationsStack.Push(input[i]);
                    }
                }
                else if (input[i].Equals('('))
                {
                    operationsStack.Push(input[i]);
                }
                else if (input[i].Equals(')'))
                {
                    while (operationsStack.Peek() != '(')
                    {
                        result.Add(Convert.ToString(operationsStack.Pop()));
                    }
                    operationsStack.Pop();
                }
            }
            while (!(operationsStack.Count == 0))
            {
                result.Add(Convert.ToString(operationsStack.Pop()));
            }
            /*foreach (String strings in result) {
                Console.Write(strings);
            }*/
            return result;
        }

        private static double Calculate(List<string> opzstring)
        {
            Stack<double> numbersStack = new Stack<double>();
            double op1, op2;
            /*for (int i = 0; i < opzstring.Count; i++)
            {
                if (Char.IsDigit(opzstring[i]))
                    numbersStack.Push(double.Parse(opzstring[i].ToString()));
                else
                {
                    op2 = numbersStack.Pop();
                    op1 = numbersStack.Pop();
                    numbersStack.Push(ApplyOperation(opzstring[i], op1, op2));
                }
            }*/
            foreach(String strings in opzstring)
            {
                if (!(IsOperation(Convert.ToChar(strings[0]))))
                    numbersStack.Push(double.Parse(strings));
                else
                {
                    op2 = numbersStack.Pop();
                    op1 = numbersStack.Pop();
                    numbersStack.Push(ApplyOperation(strings, op1, op2));
                }
            }
            return numbersStack.Pop();
        }
    }
    //в фибоначчи нужно вычислять значение функции в той или иной точке
    //парсер заключается в просто поиске необходимых выражений и перегрузке, а потом возвращении нужного
    class Fibonacci
    {
        public void MethodFibonacci()
        {
            //Parser parser = new Parser();
            Console.WriteLine("Enter left and right values of interval: ");
            double a = Convert.ToDouble(Console.ReadLine());
            double b = Convert.ToDouble(Console.ReadLine());
            double Ln = 0.00000001;
            List<int> fib = calculateNumbers(a, b, Ln);
            double xmin = methodFibonacci(a, b, Ln, fib);
            Console.WriteLine("xmin = {0}", xmin);
            Console.ReadKey();
        }
        private static List<int> calculateNumbers(double a, double b, double Ln)
        {
            List<int> listOfNumbers = new List<int>();
            listOfNumbers.Add(1);
            listOfNumbers.Add(1);
            while(listOfNumbers.ElementAt(listOfNumbers.Count()-1) < ((b - a) / Ln))
            {
                listOfNumbers.Add(listOfNumbers.ElementAt(listOfNumbers.Count()-1) + listOfNumbers.ElementAt(listOfNumbers.Count() - 2));
            }
            return listOfNumbers;
        }

        private static double methodFibonacci(double a, double b, double Ln, List<int> fib)
        {
            Parser parser = new Parser();

            double EPS = (b - a) / (fib.ElementAt(fib.Count()-1)+1);
            double L = Math.Abs(b - a);

            int n = fib.Count();
            int k = 1;
            double fibelem1 = fib.ElementAt(n - 3);
            double fibelem2 = fib.ElementAt(n - 2);
            double fibelem3 = fib.ElementAt(n - 1);
            double x1 = a + (fibelem1 / fibelem3 * (b - a));
            double x2 = a + (fibelem2 / fibelem3 * (b - a));
            double a1 = a;
            double b1 = b;
            double xmin;
            Console.WriteLine("Enter function: ");
            string function = Console.ReadLine();
            x1 = 2.5;
            double y1 = parser.parse(function, x1);
            double y2 = parser.parse(function, x2);
            while (k != n - 2)
            {
                if(parser.parse(function,x1) < parser.parse(function,x2))
                {
                    b1 = x2;
                    L = Math.Abs(b1 - a1);
                    x2 = x1;
                    //y2 = y1;
                    //if mistakes first check indexes cause there they are starts from 0 and in matlab they are starts from 1
                    fibelem1 = fib.ElementAt(n - k - 3);
                    fibelem2 = fib.ElementAt(n - k - 1);
                    x1 = a1 + L * fibelem1 / fibelem2;
                    //y1 = parser.parse(function, x1);
                }
                else
                {
                    a1 = x1;
                    L = Math.Abs(b1 - a1);
                    x1 = x2;
                    y1 = y2;
                    fibelem1 = fib.ElementAt(n - k - 2);
                    fibelem2 = fib.ElementAt(n - k - 1);
                    x2 = a1 + L * fibelem1 / fibelem2;
                    y2 = parser.parse(function, x2);
                }
                k++;
            }

            x2 = x1 + EPS;
            if (parser.parse(function, x1) > parser.parse(function, x2))
            {
                xmin = (x1 + b1) / 2;
            }
            else
                xmin = (a1 + x2) / x2;

            return xmin;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            //Parser pars = new Parser();
            Fibonacci fib = new Fibonacci();
            //string func = Console.ReadLine();
            //pars.parse(func);
            //Console.ReadKey();
            fib.MethodFibonacci();
            Console.ReadKey();
        }
    }
}