using System;
using System.Diagnostics;
using System.Reflection.Metadata.Ecma335;
using System.Text;
using System.Xml;

namespace TransformerToWords
{
    /// <summary>
    /// Implements transformer class.
    /// </summary>
    public class Transformer
    {
        /// <summary>
        /// Transforms each element of source array into its 'word format'.
        /// </summary>
        /// <param name="source">Source array.</param>
        /// <returns>Array of 'word format' of elements of source array.</returns>
        /// <exception cref="ArgumentNullException">Thrown when array is null.</exception>
        /// <exception cref="ArgumentException">Thrown when array is empty.</exception>
        /// <example>
        /// new[] { 2.345, -0.0d, 0.0d, 0.1d } => { "Two point three four five", "Minus zero", "Zero", "Zero point one" }.
        /// </example>
        public string[] Transform(double[]? source)
        {
            string buffer = string.Empty;
            string[] result = new string[source.Length];

            for (int i = 0; i < source.Length; i++)
            {
                switch (source[i])
                {
                    case double.NaN:
                        result[i] = "Not a Number";
                        continue;
                    case double.NegativeInfinity:
                        result[i] = "Negative Infinity";
                        continue;
                    case double.PositiveInfinity:
                        result[i] = "Positive Infinity";
                        continue;
                }

                buffer = source[i].ToString();

                for (int j = 0; j < buffer.Length; j++)
                {
                    switch (buffer[i])
                    {
                        case '-':
                            result[i] += " minus";
                            break;
                        case '.':
                            result[i] += " point";
                            break;
                        case 'e':
                            result[i] += " E plus";
                            break;
                        case '0':
                            result[i] += " zero";
                            break;
                        case '1':
                            result[i] += " one";
                            break;
                        case '2':
                            result[i] += " two";
                            break;
                        case '3':
                            result[i] += " three";
                            break;
                        case '4':
                            result[i] += " four";
                            break;
                        case '5':
                            result[i] += " five";
                            break;
                        case '6':
                            result[i] += " six";
                            break;
                        case '7':
                            result[i] += " seven";
                            break;
                        case '8':
                            result[i] += " eight";
                            break;
                        case '9':
                            result[i] += " nine";
                            break;
                    }
                }

                result[i] = result[i].Remove(0, 1);
                result[i] = result[i].ToUpper() + result[i].Substring(1).ToLower();
            }

            return result;
        }
    }
}