// Based on RSDN RusCurrency class
using System;
using System.Collections.Generic;
using System.Text;

namespace FastReport.Functions
{
    internal abstract class NumToWordsBase
    {
        #region Private Methods
        private string Str(decimal value, WordInfo senior, WordInfo junior)
        {
            bool minus = false;
            if (value < 0)
            {
                value = -value;
                minus = true;
            }

            long n = (long)value;
            int remainder = (int)((value - n + 0.005m) * 100);
            if (remainder >= 100)
            {
                n++;
                remainder = 0;
            }

            StringBuilder r = new StringBuilder();

            Str(n, senior, r);

            if (minus)
                r.Insert(0, GetMinus() + " ");

            if (junior != null)
            {
                r.Append(GetDecimalSeparator() + remainder.ToString("00 "));
                r.Append(Case(remainder, junior));
            }

            r[0] = char.ToUpper(r[0]);
            return r.ToString();
        }
        #endregion

        #region Protected Methods
        protected abstract string GetFixedWords(bool male, long value);
        protected abstract string GetTen(bool male, long value);
        protected abstract string GetHund(bool male, long value);
        protected abstract WordInfo GetThousands();
        protected abstract WordInfo GetMillions();
        protected abstract WordInfo GetMilliards();
        protected abstract WordInfo GetTrillions();
        protected abstract CurrencyInfo GetCurrency(string currencyName);
        protected abstract string GetZero();
        protected abstract string GetMinus();

        protected virtual void Str(long value, WordInfo senior, StringBuilder result)
        {
            if (value == 0)
                result.Append(GetZero() + " " + senior.many + " ");
            else
            {
                if (value % 1000 != 0)
                    result.Append(Str1000(value, senior, 1));
                else
                    result.Append(" " + senior.many + " ");

                value /= 1000;
                result.Insert(0, Str1000(value, GetThousands(), 2));

                value /= 1000;
                result.Insert(0, Str1000(value, GetMillions(), 3));

                value /= 1000;
                result.Insert(0, Str1000(value, GetMilliards(), 4));

                value /= 1000;
                result.Insert(0, Str1000(value, GetTrillions(), 5));
                result.Replace("  ", " ");
            }
        }

        protected virtual string Str1000(long value, WordInfo info, int counter)
        {
            long val = value % 1000;
            if (val == 0)
                return "";

            StringBuilder r = new StringBuilder();
            // add hundred
            string hund = GetHund(info.male, val);
            if (hund != "")
                r.Append(hund);

            // decide whether to use the 100-10 separator or not
            string sep100_10 = Get100_10Separator();
            if (value < 1000 && hund == "")
                sep100_10 = "";

            val = val % 100;
            if (val < GetFixedWordsCount())
            {
                // val is less than fixed words count (usually 20), get fixed words
                string frac20 = GetFixedWords(info.male, val);
                if (frac20 != "")
                    r.Append(sep100_10 + frac20);
            }
            else
            {
                // val is greater than fixed words count (usually 20), get tens separately
                string ten = GetTen(info.male, val / 10);
                string frac10 = GetFixedWords(info.male, val % 10);

                // decide whether to use 10-1 separator or not
                if (ten != "" && frac10 != "")
                    r.Append(sep100_10 + ten + Get10_1Separator() + frac10);
                else if (ten != "")
                    r.Append(sep100_10 + ten);
                else if (frac10 != "")
                    r.Append(sep100_10 + frac10);
            }

            // add currency/group word
            r.Append(" ");
            r.Append(Case(value, info));

            // make the result starting with letter and ending with space
            if (r.Length != 0)
                r.Append(" ");
            return r.ToString().TrimStart(' ');
        }

        protected virtual int GetFixedWordsCount()
        {
            return 20;
        }

        protected virtual string GetDecimalSeparator()
        {
            return "";
        }

        protected virtual string Get10_1Separator()
        {
            return " ";
        }

        protected virtual string Get100_10Separator()
        {
            return " ";
        }

        protected virtual string Case(long value, WordInfo info)
        {
            if (value % 100 == 1)
                return info.one;
            return info.many;
        }
        #endregion

        #region Public Methods
        public string ConvertCurrency(decimal value, string currencyName)
        {
            try
            {
                CurrencyInfo currency = GetCurrency(currencyName);
                return Str(value, currency.senior, currency.junior);
            }
            catch (KeyNotFoundException e)
            {
                throw new Exception($"Currency \"{currencyName}\" is not defined in the \"{GetType().Name}\" converter.");
            }
            catch (NotImplementedException e)
            {
                throw new Exception("Method " + e.TargetSite.ToString() + " wasn't implemented");
            }
            catch (Exception e)
            {
                throw new Exception("There is an exception - " + e.ToString());
            }
        }

        public string ConvertNumber(decimal value, bool male, string one, string two, string many)
        {
            return Str(value, new WordInfo(male, one, two, many), null);
        }

        public string ConvertNumber(decimal value, bool male,
          string seniorOne, string seniorTwo, string seniorMany,
          string juniorOne, string juniorTwo, string juniorMany)
        {
            return Str(value,
              new WordInfo(male, seniorOne, seniorTwo, seniorMany),
              new WordInfo(male, juniorOne, juniorTwo, juniorMany));
        }
        #endregion
    }

    internal class WordInfo
    {
        public bool male;
        public string one;
        public string two;
        public string many;

        public WordInfo(bool male, string one, string two, string many)
        {
            this.male = male;
            this.one = one;
            this.two = two;
            this.many = many;
        }

        public WordInfo(string one, string many)
          : this(true, one, many, many)
        {
        }

        public WordInfo(string all)
          : this(true, all, all, all)
        {
        }
    }

    internal class CurrencyInfo
    {
        public WordInfo senior;
        public WordInfo junior;

        public CurrencyInfo(WordInfo senior, WordInfo junior)
        {
            this.senior = senior;
            this.junior = junior;
        }
    }
}