using System;
using System.IO;

namespace NTERA.EmuEra.Game.EraEmu.Sub
{
	/// <summary>
	/// 文字列を1文字ずつ評価するためのクラス
	/// </summary>
	internal sealed class StringStream
	{
		public StringStream(string s)
		{
			source = s ?? "";
		    CurrentPosition = 0;
		}

		string source;
		public const char EndOfString = '\0';
	    public string RowString => source;

	    public int CurrentPosition { get; set; }

	    public char Current
		{
			get
			{
				if (CurrentPosition >= source.Length)
					return EndOfString;
				return source[CurrentPosition];
			}
		}
		
		public void AppendString(string str)
		{
			if (CurrentPosition > source.Length)
				CurrentPosition = source.Length;
			source += " " + str;
		}
		
		/// <summary>
		/// 文字列終端に達した
		/// </summary>
		public bool EOS => CurrentPosition >= source.Length;

		///変数の区切りである"[["と"]]"の先読みなどに使用
		public char Next
		{
			get
			{
				if (CurrentPosition + 1 >= source.Length)
					return EndOfString;
				return source[CurrentPosition + 1];
			}
		}

		public string Substring()
		{
			if (CurrentPosition >= source.Length)
				return "";
			if (CurrentPosition == 0)
				return source;
			return source.Substring(CurrentPosition);
		}

		public string Substring(int start, int length)
		{
			if (start >= source.Length || length == 0)
				return "";
			if (start + length > source.Length)
				length = source.Length - start;
			return source.Substring(start, length);
		}

		internal void Replace(int start, int count, string src)
		{
			//引数に正しい数字が送られてくること前提
			source = (source.Remove(start, count)).Insert(start, src);
			CurrentPosition = start;
		}

		public void ShiftNext()
		{
			CurrentPosition++;
		}

        public void Jump(int skip)
        {
            CurrentPosition += skip;
        }

		/// <summary>
		/// 検索文字列の相対位置を返す。見つからない場合、負の値。
		/// </summary>
		/// <param name="str"></param>
		public int Find(string str)
		{
			return source.IndexOf(str, CurrentPosition) - CurrentPosition;
		}

		/// <summary>
		/// 検索文字列の相対位置を返す。見つからない場合、負の値。
		/// </summary>
		public int Find(char c)
		{
			return source.IndexOf(c, CurrentPosition) - CurrentPosition;
		}

		public override string ToString()
		{
			if (source == null)
				return "";
			return source;
		}

		public bool CurrentEqualTo(string rother)
		{
			if (CurrentPosition + rother.Length > source.Length)
				return false;

			for (int i = 0;  i < rother.Length;i++)
			{
				if (source[CurrentPosition + i] != rother[i])
					return false;
			}
			return true;
		}

		public bool TripleSymbol()
		{
			if (CurrentPosition + 3 > source.Length)
				return false;
			return (source[CurrentPosition] == source[CurrentPosition + 1]) && (source[CurrentPosition] == source[CurrentPosition + 2]);
		}


		public bool CurrentEqualTo(string rother, StringComparison comp)
		{
			if (CurrentPosition + rother.Length > source.Length)
				return false;
			string sub = source.Substring(CurrentPosition, rother.Length);
			return sub.Equals(rother, comp);
		}

		public void Seek(int offset, SeekOrigin origin)
		{
			if (origin == SeekOrigin.Begin)
				CurrentPosition = offset;
			else if (origin == SeekOrigin.Current)
				CurrentPosition = CurrentPosition + offset;
			else if (origin == SeekOrigin.End)
				CurrentPosition = source.Length + offset;
			if (CurrentPosition < 0)
				CurrentPosition = 0;
		}
	}
}