using System;
using System.Linq;
using System.IO;
using System.Text;
using System.Collections.Generic;

namespace AniNIX.Crypto {
    public class Caesarian : Cipher {

        public override String Description() { return "Caesarian ciphers shift letters by a numeric offset. Key format is thus a number."; }
        public override String Command() { return "caesar"; }
        public Caesarian(Workbench w) : base (w) {}

        /// <summary>
        /// Decode the user's input and relate to an existing function.
        /// </summary>
        /// <param name="workSpace">The working copy of the cipher</param>
        /// <param name="inputText">The original cipher</param>
        /// <param name="line">The user input</param>
        /// <returns>The modified workspace string</returns>
        public override String RunCommand(String workSpace,String inputText,String[] line) {
            if (workSpace == null || line == null || line.Length < 2) {
                Console.Error.WriteLine("Malformed request.");
                return workSpace;
            }
            switch (line[1]) {
                case "encrypt": 
                    return Encrypt(workSpace,inputText,line);
                case "decrypt":
                    return Decrypt(workSpace,inputText,line);
                case "brute":
                    BruteForce(workSpace);
                    return workSpace;
                default: 
                    GetHelp();
                    return workSpace;
            } 
        }

        /// <summary>
        /// Show this help text
        /// </summary>
        public override void GetHelp() {
            Console.WriteLine(String.Format("Help for the {0} cipher suite.\n{1}\n",Command(),Description()));
            Console.WriteLine("caesar encrypt key         -- encrypt with the key\ncaesar decrypt key         -- decrypt with the key\ncaesar brute               -- brute-force for keys\ncaesar help                -- show this helptext.");
        }


        /// <summary>
        /// Encrypt a string with the cipher
        /// </summary>
        /// <param name="workSpace">The working copy of the cipher</param>
        /// <param name="inputText">The original cipher</param>
        /// <param name="line">The user input</param>
        /// <returns>The encrypted string</returns>
        public override String Encrypt(String workSpace,String inputText,String[] line) {
            // Validate input
            if (line.Length != 3) {
                Console.Error.WriteLine("Bad formatting");
                return workSpace;
            }
            int rotation = 0;
            try { 
                rotation = Int32.Parse(line[2]);
            } catch (Exception e) {
                Console.Error.WriteLine("Error in parsing rotation value -- should be numeric.");
                Console.Error.WriteLine(e.Message);
                return workSpace;
            }
            char[] modified = workSpace.ToCharArray(); 

            //For each character in the workSpace, rotate it by the offset given.
            for (int i = 0; i < modified.Length; i++) { 
                if (Char.IsLetter(modified[i])) {
                    int baseC;
                    int modC;
                    // Have to account for case.
                    if (modified[i] < 'a') {
                        baseC = (int)'A';
                        modC = (int)modified[i] - (int)'A';
                    } else {
                        baseC = (int)'a';
                        modC = (int)modified[i] - (int)'a';
                    }
                    modC = (modC + rotation)%26;
                    modified[i] = (char)(baseC+modC);
                }
            }
            return new String(modified);
        }
        
        // This is a dummy override.
        public override String Decrypt(String workSpace,String inputText,String[] line) {
            return Encrypt(workSpace,inputText,line);
        }

        /// <summary>
        /// Try rotating through all 26 possible combinations.
        /// </summary>
        public  void BruteForce(String workSpace) {
            String[] line = new String[3];
            line[0] = "rot";
            line[1] = "encrypt";
            for (int i=0; i<26; i++) {
                line[2]=i.ToString();
                Console.Write(String.Format("{0,2}: {1}\n",i,Encrypt(workSpace,null,line)));
            }
        }
    }
}