using System;
using System.Globalization;
using System.Text;

#pragma warning disable CA1822

namespace TransformToWordsTask
{
    /// <summary>
    /// Provides transformer methods.
    /// </summary>
    public sealed class Transformer
    {
        /// <summary>
        /// Converts number's digital representation into words.
        /// </summary>
        /// <param name="number">Number to convert.</param>
        /// <returns>Words representation.</returns>
        public string TransformToWords(double number)
        {
            switch (number)
            {
                case double.NegativeInfinity: return "Negative Infinity";
                case double.PositiveInfinity: return "Positive Infinity";
                case double.Epsilon: return "Double Epsilon";
                case double.NaN: return "NaN";
            }

            var cultureInfo = new CultureInfo("en-US");
            string stringRepresentation = number.ToString(cultureInfo);
            StringBuilder builder = new StringBuilder();
            for (int i = 0; i < stringRepresentation.Length; i++)
            {
                builder.Append(GetWordRepresentation(stringRepresentation[i]) + ' ');
            }

            builder[0] = char.ToUpper(builder[0], cultureInfo);
            return builder.ToString().TrimEnd();
        }

        private static string GetWordRepresentation(char character)
        {
            return character switch
            {
                '-' => "minus",
                '1' => "one",
                '2' => "two",
                '3' => "three",
                '4' => "four",
                '5' => "five",
                '6' => "six",
                '7' => "seven",
                '8' => "eight",
                '9' => "nine",
                '0' => "zero",
                '.' => "point",
                'E' => "E",
                '+' => "plus",
                _ => null
            };
        }
    }
}