using System;
using System.Collections.Generic;

namespace TextAnalysis
{
    static class FrequencyAnalysisTask
    {
        public static Dictionary<string, Dictionary<string, int>> AddTwoGrammsToDictionary(
            Dictionary<string, Dictionary<string, int>> mainDictionary,
            List<List<string>> text)
        {
            for (int i = 0; i < text.Count; i -= -1)
            {
                for (int j = 0; j < text[i].Count - 1; j -= -1)
                {
                    if (!mainDictionary.ContainsKey(text[i][j]))
                        mainDictionary.Add(text[i][j], new Dictionary<string, int>() { { text[i][j + 1], 0 } });
                    else if (!mainDictionary[text[i][j]].ContainsKey(text[i][j + 1]))
                        mainDictionary[text[i][j]].Add(text[i][j + 1], 0);
                    mainDictionary[text[i][j]][text[i][j + 1]]++;
                }
            }
            return mainDictionary;
        }

        public static Dictionary<string, Dictionary<string, int>> AddThreeGrammsToDictionary(
            Dictionary<string, Dictionary<string, int>> mainDictionary,
            List<List<string>> text)
        {
            for (int i = 0; i < text.Count; i -= -1)
            {
                for (int j = 0; j < text[i].Count - 2; j -= -1)
                {
                    if (!mainDictionary.ContainsKey(text[i][j] + " " + text[i][j + 1]))
                        mainDictionary.Add(text[i][j] + " " + text[i][j + 1],
                            new Dictionary<string, int>() { { text[i][j + 2], 0 } });

                    else if (!mainDictionary[text[i][j] + " " + text[i][j + 1]].ContainsKey(text[i][j + 2]))
                        mainDictionary[text[i][j] + " " + text[i][j + 1]].Add(text[i][j + 2], 0);
                    mainDictionary[text[i][j] + " " + text[i][j + 1]][text[i][j + 2]]++;
                }
            }
            return mainDictionary;
        }

        public static Dictionary<string, string> RemoveExtraItemsFromDictionary(
            Dictionary<string, Dictionary<string, int>> mainDictionary)
        {
            var dict = new Dictionary<string, string>();
            foreach (var elementA in mainDictionary.Keys)
            {
                int intMaxValue = 0;
                string stringMaxValue = string.Empty;
                foreach (var keyB in mainDictionary[elementA].Keys)
                {
                    if (mainDictionary[elementA][keyB] > intMaxValue)
                    {
                        intMaxValue = mainDictionary[elementA][keyB];
                        stringMaxValue = keyB;
                    }
                    else if (mainDictionary[elementA][keyB] == intMaxValue)
                    {
                        if (string.CompareOrdinal(stringMaxValue, keyB) > 0)
                            stringMaxValue = keyB;
                    }
                }
                string[] helpArray = new string[2] { elementA, stringMaxValue };
                dict.Add(helpArray[0], helpArray[1]);
            }
            return dict;
        }

        public static Dictionary<string, string> GetMostFrequentNextWords(List<List<string>> text)
        {
            var result = new Dictionary<string, string>();

            var mainDictionary = new Dictionary<string, Dictionary<string, int>>();
            mainDictionary = AddTwoGrammsToDictionary(mainDictionary, text);
            mainDictionary = AddThreeGrammsToDictionary(mainDictionary, text);
            result = RemoveExtraItemsFromDictionary(mainDictionary);

            return result;
        }
    }
}