using System;
using System.Text;
using System.Collections.Generic;

namespace TextAnalysis
{
    static class SentencesParserTask
    {
        public static List<List<string>> ParseSentences(string text)
        {
            var sentences = new List<List<string>>();
            var separators = new char[] { '.', '!', '?', ':', ';', '(', ')' };
            var arrayProcessedSentences = text.ToLower().Split(separators);

            foreach (var currentSentence in arrayProcessedSentences)
            {
                var listWords = ConvertSentencesToWords(currentSentence);
                if (listWords.Count > 0)
                    sentences.Add(listWords);
            }

            return sentences;
        }

        public static List<string> ConvertSentencesToWords(string currentString)
        {
            var builderString = new StringBuilder();
            var listWords = new List<string>();

            for (var j = 0; j < currentString.Length; j++)
            {
                var currentChar = currentString[j];
                if (char.IsLetter(currentChar) | currentChar == '\'')
                    builderString.Append(currentChar);
                if (!char.IsLetter(currentChar) && !(currentChar == '\'') || j == currentString.Length - 1)
                {
                    if (builderString.Length > 0)
                        listWords.Add(builderString.ToString());
                    builderString.Clear();
                }
            }

            return listWords;
        }
    }
}