//Zamiana liczby na slowa z polska gramatyka
//Lesław Pawlaczyk
//www.algorytm.org

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

namespace LanguageModelFilter
{
    public class NumbersToText
    {
        # region Constant Arrays

        protected static string[] SINGLES = { "", "jeden", "dwa", "trzy", "cztery", "pięć", "sześć", "siedem", "osiem", "dziewięć" };
        protected static string[] TEENS = { "", "jedenaście", "dwanaście", "trzynaście", "czternaście", "piętnaście", "szesnaście", "siedemnaście", "osiemnaście", "dziewiętnaście" };
        protected static string[] TENS = { "", "dziesięć", "dwadzieścia", "trzydzieści", "czterdzieści", "pięćdziesiąt", "sześćdziesiąt", "siedemdziesiąt", "osiemdziesiąt", "dziewięćdziesiąt" };
        protected static string[] HUNDREDS = { "", "sto", "dwieście", "trzysta", "czterysta", "pięćset", "sześćset", "siedemset", "osiemset", "dziewięćset" };
        protected static string[,] CONJUGATIONS = new string[,]
			{
				{ "", "", ""                           },
				{ "tysiąc", "tysiące", "tysięcy"       },
				{ "milion" , "miliony" , "milionów"    },
				{ "miliard", "miliardy", "miliardów"   },
				{ "bilion" , "biliony" , "bilionow"    },	
				{ "biliard", "biliardy", "biliardow"   },
				{ "trylion" , "tryliony", "trylionow" }
			};

        # endregion // Constant Arrays

        # region Implementation

        public static String DigitsStringToSpokenString(string input)
        {
            StringBuilder builder = new StringBuilder();

            Int64 number = 0;
            if (!Int64.TryParse(input, out number))
            {
                return input;
            }

            if (number < 0)
            {
                builder.Append("minus ");
                number = -number;
            }

            Int64 sHundreds = 0;
            Int64 dTens = 0;
            Int64 jSingles = 0;
            Int64 nTeens = 0;
            Int64 gMagnitude = 0;
            Int64 kConjugation = 0;

            List<string> groups = new List<string>();

            while (number != 0)
            {
                //get hundreds, tens and singles from a number to process
                sHundreds = (number % 1000) / 100;
                dTens = (number % 100) / 10;
                jSingles = number % 10;

                //check if teens form should be used
                if (dTens == 1 && jSingles > 0)
                {
                    nTeens = jSingles;
                    dTens = 0;
                    jSingles = 0;
                }
                else
                {
                    nTeens = 0;
                }

                //choose conjugation form
                if (jSingles == 1 && sHundreds + dTens + nTeens == 0)
                {
                    kConjugation = 0;
                }
                else if (jSingles >= 2 && jSingles <= 4)
                {
                    kConjugation = 1;
                }
                else
                {
                    kConjugation = 2;
                }

                //add text if there is any houndred, ten, teen or single
                if (sHundreds + dTens + nTeens + jSingles > 0)
                {
                    if (sHundreds + dTens + nTeens == 0 && jSingles == 1 && !String.IsNullOrWhiteSpace(CONJUGATIONS[gMagnitude, kConjugation]))
                    {
                        // we do not say 'jeden tysiąc' but 'tysiąc'
                        jSingles = 0;
                    }
                    groups.Add(string.Format(" {0} {1} {2} {3} {4}", HUNDREDS[sHundreds], TENS[dTens], TEENS[nTeens], SINGLES[jSingles], CONJUGATIONS[gMagnitude, kConjugation]));
                }

                //process next three digits
                gMagnitude++;
                number = number / 1000;
            }

            groups.Reverse();
            groups.ForEach(x => builder.Append(x));

            string result = builder.ToString();
            result = Regex.Replace(result, @"\s+", " ").Trim();

            return result;
        }

        # endregion // Implementation

        # region Example

        static void Main(string[] args)
        {
            Console.WriteLine("-1000 => " + DigitsStringToSpokenString("-1000"));
            Console.WriteLine("1000 => " + DigitsStringToSpokenString("1000"));
            Console.WriteLine("-1 => " + DigitsStringToSpokenString("-1"));
            Console.WriteLine("1 => " + DigitsStringToSpokenString("1"));
            Console.WriteLine("123456789 => " + DigitsStringToSpokenString("123456789"));
            Console.WriteLine("71351 => " + DigitsStringToSpokenString("71351"));
        }

        # endregion // Example
    }
}