using System.Collections.Generic;
using System.Linq;
using System;

namespace TextAnalysis
{
	static class SentencesParserTask
    {
		public static List<List<string>> ParseSentences(string text)
		{

            if (text == null) return null;
            text = text.ToLower();
			string[] sentences = text.Split('.', '!', '?', ';', ':', '(', ')');
			var listOfSentences = ParseToList(sentences);
			return listOfSentences;
		}
		public static List<List<string>> ParseToList(string[] sentences)
		{
			var listOfSentences = new List<List<string>>();
			foreach (var sentence in sentences)
			{
				var words = new List<string>();
				string temp = "";
				string tempSentence = sentence + " ";
				if (sentence.Length > 0)
				{

				for(int i = 0 ; i  < tempSentence.Length;i++)
				{
					if (char.IsLetter(tempSentence[i]) || tempSentence[i] == '\'' ) temp += tempSentence[i];
					else
					{
						if (temp.Length > 0)
						{words.Add(temp);
						temp = "";
						}
					}
								}
				listOfSentences.Add(words);
			}
			}
			return listOfSentences;

		}
	}
}