using System;

​

namespace PalindromeTest {

    /* -------

    * Table - store palindromes : Multi Dimensional Array 

    * =========

    * Checks for palindrom

    * -  Each letter will be a palindrom

    * -  -  Set this as "True" in our Table AND set the new longest palindrome

    * -  Letters that are the same and are right next to eachother " i & i + 1 "

    * -  -  Set this as "True" in our Table AND set the new longest palindrome

    * -  First and Last letter are the same AND Table[(i +1), (j -1)] is "True" in our table

    * -  -  Set this as "True" in our Table AND set the new longest palindrome

    * -------

    */

    public interface IStringUtilities {

        String GetSubstring(String s, int start, int end);  

    }

    public class Utilities : IStringUtilities {

        public String GetSubstring(String s, int start, int end){

            int length = (end - start) + 1;

            if(end >= s.Length){

                return s.Substring(start, (s.Length -1));

            } else {

                return s.Substring(start, length);

            }

        }

    }

    public abstract class StringExtensions : IStringUtilities {

        private readonly IStringUtilities _u;

        public StringExtensions(IStringUtilities u){

            _u = u; 

        }

        public String GetSubstring(String s, int start, int end){

            return _u.GetSubstring(s, start, end);

        }

    }

    public class Palindrome : StringExtensions {

        public String chars;

        public int length;

        public bool[,] table;

        public String longest_palindrome;

        public int palindrome_length;

        public Palindrome(String val) : base(new Utilities())

        {

            this.chars = val;

            this.length = val.Length;

            this.table = new bool[this.length, this.length];

            this.longest_palindrome = "";

            this.palindrome_length = this.longest_palindrome.Length;

        }

        public void CheckAndSetPalidromeLevel1(int i){

            table[i, i] = true;

            if( GetSubstring(chars, i, i).Length > palindrome_length ){

                longest_palindrome = GetSubstring(chars, i, i);

            }   

        }

        public void CheckAndSetPalindromeLevel2(int i){

            if(chars[i] == chars[i + 1]){

                table[i, (i+1)] = true;

                if(GetSubstring(chars, i, (i + 1)).Length > length ){

                    longest_palindrome = GetSubstring(chars, i, (i + 1));

                }

            }

        }

        public void CheckAndSetPalindromeGreaterThan2(int k, int i){

            //do not allow "j" to be larger than or equal to palindromString.Length

            int j = 0;

            if((i + k) < length){

                j = i + k;

            } else {

                j = length -1;

            }

            Console.WriteLine("----- test ----- \n [i, j]: [{0}, {1}], \n palindromString[i]: {2}, \n palindromString[j]: {3}, \n String : {4} \n Table : {5}", i, j, chars[i], chars[j], GetSubstring(chars, i, j), table[(i + 1),(j - 1)]);

            if(chars[i] == chars[j] && table[(i + 1),(j - 1)] == true){

                if(GetSubstring(chars, i, j).Length > palindrome_length){

                    //Set new palindrome

                    Console.WriteLine("---- NEW LONGER ----{0}", GetSubstring(chars, i, j));

                    longest_palindrome = GetSubstring(chars, i, j);

                }

                table[i, j] = true;

            }   

        }

    }

    public class Program

    {

        public static void Main()

        {

            Palindrome palindrome = new Palindrome("abaxabaxabb");

            //Set all cells to "false" inside our table to hold values

            for(int i = 0; i < palindrome.length; i++){

                for(int k = 0; k < palindrome.length; k++){

                    palindrome.table[i,k] = false;

                }

            }

            Console.WriteLine("----- 1");

            for(int i = 0; i < palindrome.length; i++)

            {

                Console.WriteLine("value: {0}, k: [{1}, {1}]", palindrome.table[i, i], i);

                palindrome.CheckAndSetPalidromeLevel1(i);

            }

            Console.WriteLine("----- 2");

            //check to see if two characters side by side are equal

            for(int i = 0; i < palindrome.length - 1; i++){

                Console.WriteLine("value: {0}, k: [{1}, {2}]", palindrome.table[i, (i + 1)], i, (i + 1));

                palindrome.CheckAndSetPalindromeLevel2(i);

            }

            Console.WriteLine("----- > 2");

            for(int k = 2; k < palindrome.length - 2; k++){

                 for(int i = 0; i < palindrome.length - 2; i++){

                    palindrome.CheckAndSetPalindromeGreaterThan2(k, i);

                }

            }

            // ---------- DONE --------- Write out results -----------

            Console.WriteLine("==================== \n ");

            Console.WriteLine("Longest Palindrome is : {0}", palindrome.longest_palindrome);

        }

    }

}