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

namespace ConverterDictionaryComposition
{
    /// <summary>
    /// Converts a real number to string.
    /// </summary>
    public class Converter
    {
        private readonly CharsDictionary dictionary;

        /// <summary>
        /// Initializes a new instance of the <see cref="Converter"/> class.
        /// </summary>
        /// <param name="dictionaryFactory">Factory of the dictionary with rules of converting.</param>
        /// <exception cref="System.ArgumentNullException">Thrown when dictionary factory is null.</exception>
        public Converter(ICharsDictionaryFactory? dictionaryFactory)
        {
            if (dictionaryFactory == null)
            {
                throw new ArgumentNullException(nameof(dictionaryFactory));
            }

            this.dictionary = dictionaryFactory.CreateDictionary();
        }

        /// <summary>
        /// Converts double number into string.
        /// </summary>
        /// <param name="number">Double number to convert.</param>
        /// <returns>A number string representation.</returns>
        public string Convert(double number)
        {
            switch (number)
            {
                case double.NaN:
                    return this.dictionary.Dictionary[Сharacter.NaN];
                case double.Epsilon:
                    return this.dictionary.Dictionary[Сharacter.Epsilon];
                case double.NegativeInfinity:
                    return this.dictionary.Dictionary[Сharacter.NegativeInfinity];
                case double.PositiveInfinity:
                    return this.dictionary.Dictionary[Сharacter.PositiveInfinity];
            }

            string stringNumber = number.ToString(new CultureInfo(this.dictionary.CultureName));
            StringBuilder result = new StringBuilder();

            for (int i = 0; i < stringNumber.Length; i++)
            {
                result.Append(' ').Append(this.dictionary.Dictionary[CharToWord(stringNumber[i])]);
            }

            return result.ToString()[1..];
        }

        private static Сharacter CharToWord(char digit) =>
            digit switch
            {
                '-' => Сharacter.Minus,
                '+' => Сharacter.Plus,
                '.' => Сharacter.Point,
                ',' => Сharacter.Comma,
                'E' => Сharacter.Exponent,
                '0' => Сharacter.Zero,
                '1' => Сharacter.One,
                '2' => Сharacter.Two,
                '3' => Сharacter.Three,
                '4' => Сharacter.Four,
                '5' => Сharacter.Five,
                '6' => Сharacter.Six,
                '7' => Сharacter.Seven,
                '8' => Сharacter.Eight,
                '9' => Сharacter.Nine
            };
    }
}