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

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

            foreach (var sentence  in sentences)
            {
                if(sentence.Length != 0)
                {
                    listOfWords = MakingSomeWords(sentence);
                    if (listOfWords.Count != 0)
                        listOfSentences.Add(listOfWords);
                }
            }
            return listOfSentences;
        }

        public static List<string> MakingSomeWords(string sentence)
        {
            List<string> words = new List<string>();
            var word = new StringBuilder();
            foreach (var letter in sentence)
            {
                if (char.IsLetter(letter) || letter == '\'')
                    word.Append(letter);
                else
                {
                    if (word.Length != 0)
                        words.Add(word.ToString());
                    word.Clear();
                }
            }
            if (word.Length != 0)
                words.Add(word.ToString());
            return words;
        }
    }
}