//Because of https://www.reddit.com/r/programming/comments/4v6chu/why_json_doesnt_support_comments_douglas_crockford/d5w343r
using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;

namespace BetterConfig
{
    /// <summary>
    /// Provides loading and creation of human readable config files.
    /// </summary>
    public static class Config
    {
        /// <summary>
        /// Creates a configuration file
        /// </summary>
        /// <param name="Data">Binary data</param>
        /// <param name="Token0">First token</param>
        /// <param name="Token1">Second token</param>
        /// <returns>Configuration content</returns>
        public static string Save(byte[] Data, string Token0, string Token1)
        {
            StringBuilder OMG = new StringBuilder();
            BitArray BA = new BitArray(Data);

            if (!CheckTokens(Token0, Token1))
            {
                throw new ArgumentException("Tokens are ambiguous");
            }
            foreach (bool b in BA)
            {
                OMG.Append(b ? Token1 : Token0);
            }

            return OMG.ToString();
        }

        /// <summary>
        /// Loads a configuration file
        /// </summary>
        /// <param name="Data">Configuration data</param>
        /// <param name="Token0">First token</param>
        /// <param name="Token1">Second token</param>
        /// <returns>Binary Configuration</returns>
        public static byte[] Load(string Data, string Token0, string Token1)
        {
            return Load(Data, Token0, Token1, false);
        }

        /// <summary>
        /// Loads a configuration file
        /// </summary>
        /// <param name="Data">Configuration data</param>
        /// <param name="Token0">First token</param>
        /// <param name="Token1">Second token</param>
        /// <param name="FilterInvalid">Ignores invalid tokens in the file</param>
        /// <returns>Binary Configuration</returns>
        public static byte[] Load(string Data, string Token0, string Token1, bool FilterInvalid)
        {
            List<bool> ConfigValues = new List<bool>();
            bool[] Values = new bool[] { false, true };
            byte[] Result;
            int Pos = 0;
            if (!CheckTokens(Token0, Token1))
            {
                throw new ArgumentException("Tokens are ambiguous");
            }

            //swap tokens if needed so we always check for the longer token first.
            //Also swap values then
            if (Token1.Length > Token0.Length)
            {
                var temp = Token0;
                Token0 = Token1;
                Token1 = temp;
                Values[0] = true;
                Values[1] = false;
            }

            while (Pos < Data.Length)
            {
                if (Data.IndexOf(Token0, Pos) == Pos)
                {
                    ConfigValues.Add(Values[0]);
                    Pos += Token0.Length;
                }
                else if (Data.IndexOf(Token1, Pos) == Pos)
                {
                    ConfigValues.Add(Values[1]);
                    Pos += Token1.Length;
                }
                else if (FilterInvalid)
                {
                    ++Pos;
                }
                else
                {
                    throw new ArgumentException("Data is not a valid configuration");
                }
            }

            if (ConfigValues.Count % 8 != 0)
            {
                throw new ArgumentException("Data is not a valid configuration");
            }

            Result = new byte[ConfigValues.Count / 8];
            (new BitArray(ConfigValues.ToArray())).CopyTo(Result, 0);
            return Result;
        }

        /// <summary>
        /// Makes sure, tokens are unambiguous
        /// </summary>
        /// <param name="Token0">First token</param>
        /// <param name="Token1">Second token</param>
        /// <returns>true, if valid tokens</returns>
        public static bool CheckTokens(string Token0, string Token1)
        {
            //for tokens to be valid there are multiple conditions that all must be met:
            //- Neither token must be null or an empty string
            //- Tokens must not be identical
            //- A token must not be only made up of the other token multiple times
            if (string.IsNullOrEmpty(Token0) ||
                string.IsNullOrEmpty(Token1) ||
                Token0 == Token1 ||
                Token0.Replace(Token1,"").Length==0 ||
                Token1.Replace(Token0, "").Length == 0)
            {
                return false;
            }

            return true;
        }
    }
}