using System;
using System.Numerics;
using System.Text.RegularExpressions;

namespace LinkedList
{
    static class EntryPoint
    {
        static readonly Regex ValidRegex = new Regex("^(0|-?[1-9][0-9]*|[A-Za-z][0-9A-Z_a-z]*)$", RegexOptions.Compiled);

        static bool IsValidString(string str) => ValidRegex.IsMatch(str);

        static bool InsertBefore(string val, Item<string> oth)
        {
            if (BigInteger.TryParse(val, out var x) && BigInteger.TryParse(oth.value, out var y))
            {
                return x <= y;
            }
            else
            {
                return val.CompareTo(oth.value) < 1;
            }
        }

        static bool ValueEquals(Item<string> item, string val) => item.value == val;

        static void Main()
        {
            Item<string> start = null;

            var begin = true;
            string input;

            while (true)
            {
                if (!begin)
                {
                    Console.WriteLine();
                }
                else
                {
                    begin = false;
                }

                Console.WriteLine("Awaiting input...");
                input = Console.ReadLine();

                if (input.Length == 0)
                {
                    Helpers.RemoveAll(ref start);
                    Console.WriteLine("\nProgram terminated!");
                    return;
                }
                else if (input.StartsWith('~'))
                {
                    if (input.Length == 1)
                    {
                        Console.WriteLine("\nDeleting list...");
                        Helpers.RemoveAll(ref start);
                    }
                    else
                    {
                        input = input.Substring(1);
                        if (IsValidString(input))
                        {
                            Console.WriteLine("\nRemoving item...");
                            Helpers.RemoveItem(ref start, input, ValueEquals);
                        }
                        else
                        {
                            Console.WriteLine("\nCould not parse input!");
                        }
                    }
                }
                else if (input.Equals("l"))
                {
                    Console.WriteLine("\nList print...");
                    Helpers.PrintList(start);
                }
                else if (input.Equals("i"))
                {
                    Console.WriteLine("\nIterator print...");
                    Helpers.PrintIterator(start);
                }
                else if (input.Equals("a"))
                {
                    Console.WriteLine("\nArray print...");
                    Helpers.PrintArray(start);
                }
                else if (input.Equals("r"))
                {
                    Console.WriteLine("\nRecursive print...");
                    Helpers.PrintRecursive(start);
                }
                else if (IsValidString(input))
                {
                    Console.WriteLine("\nInserting item...");
                    Helpers.InsertItem(ref start, input, InsertBefore);
                }
                else
                {
                    Console.WriteLine("\nCould not parse input!");
                }
            }
        }
    }
}