using System;
using System.Text;
using System.Collections.Generic;
using sharp.extensions;
using System.Globalization;

namespace sharp.json
{
	public class ByteParser
	{
		private static ASCIIEncoding encoding = new ASCIIEncoding();

		static System.Tuple<char,char>[] escapeCharacters = {
			System.Tuple.Create('\\','\\'),
			System.Tuple.Create('/','/'),
			System.Tuple.Create('"','"'),
			System.Tuple.Create('b','\b'),
			System.Tuple.Create('f','\f'),
			System.Tuple.Create('n','\n'),
			System.Tuple.Create('r','\r'),
			System.Tuple.Create('t','\t'),
		};

		static List<char> numberScan = new List<char>(new char[] { '-', '0', '1', '2', '3', '4', '5', '7', '8', '9', '.','E','e' });

		char[] buffer;
		int position;

		public ByteParser(string source)
		{
			this.buffer = source.ToCharArray();
			this.position = 0;
		}

		public char Peek(){
			//if (position >= buffer.Length){
			//	return 0;
			//}
			return buffer[position];
		}

		public string Peek(int len){
			return new String(buffer.Segment(position,len).Extend(len));
		}


		public char Read(){
			if (position < buffer.Length){
				return buffer[position++];
			}
			throw new Exception("End of buffer reached. No more characters available!");
		}
		public char[] Read(int len){
			if ((position) < buffer.Length){
				char[] r = buffer.Segment(position, len).Extend(len);
				position += r.Length;
				return r;
			}
			throw new Exception("End of buffer reached. No more characters available!");
		}

		private Int64 parseInt64(){
			Int64 t = 0;
			char ch = Read();
			bool neg = false;
			if (ch == '-'){
				neg = true;
				ch = Read();
			}

			if (!ch.isDigit()){
				throw new FormatException("JSON: Number format error");
			}

			while (true){
				t *= 10;
				t += (int)(ch - '0');
				if (!Peek().isDigit()){
					break;
				}
				ch = Read();
			}

			if (neg){
				t *= -1;
			}
			return t;
		}

		public JSON parseNumber(){
			List<char> digits = new List<char>();

			do
			{
				char n = (char)Peek();
				if (!numberScan.Contains(n)){
					break;
				}
				digits.Add(n);
				Read();
			} while (true);

			string sv = new String(digits.ToArray());

			if ((sv.IndexOf(".") > 0)||(sv.IndexOf("E") > 0)||(sv.IndexOf("e") > 0))
			{
				return new JSONNumber(double.Parse(sv,CultureInfo.InvariantCulture));
			} else {
				return new JSONNumber(Int64.Parse(sv));
			}

			//Int64 i64 = parseInt64();

			//if (Peek() == '.'){
			//	Read();
			//	Int64 dec = parseInt64();
			//	int lg10 = (int)Math.Log10(dec);
			//	i64 = i64 * lg10;
			//	if (i64 < 0){
			//		i64 -= dec;
			//	} else {
			//		i64 += dec;
			//	}
			//	return new JSONNumber(((double)i64) / (double)lg10 );
			//} else {
			//	return new JSONNumber(i64);
			//}
		}

		public JSON parseObject(){
			if (Read() != '{'){
				throw new FormatException("parser error: JSON Object should begin with '{'");
			}

			JSONObject o = new JSONObject();

			scanWhitespace();

			if (Peek() == '}'){
				return o;
			} else {
				while (true){
					string name = parseStringInternal();

					scanWhitespace();

					if (Read() != ':'){
						throw new FormatException(String.Format("parser error: expected ':' but got '{0}'",buffer[position-1]));
					}

					scanWhitespace();
					o[name] = parseValue();

					scanWhitespace();

					char n = Read();

					if (n == '}'){
						break;
					}
					if (n == ','){
						scanWhitespace();
						continue;
					}
					throw new FormatException("parser error: expected ',' or '}' but got '"+n+"'");
				}
			}
			return o;
		}

		public JSON parseArray(){
			if (Read() != '['){
				throw new FormatException("parser error: JSON array should begin with '['");
			}

			JSONArray o = new JSONArray();

			scanWhitespace();

			if (Peek() == ']'){
				return o;
			} else {
				while (true){
					o.Add(parseValue());

					scanWhitespace();

					char n = Read();

					if (n == ']'){
						break;
					}
					if (n == ','){
						scanWhitespace();
						continue;
					}
					throw new FormatException(String.Format("parser error: expected ',' or ']' but got '{0}'",n));
				}
			}
			return o;			
		}

		private string parseStringInternal(){
			StringBuilder sb = new StringBuilder();

			if (Read() != '"'){
				throw new FormatException(String.Format("JSON string must start with '\"' but got '{0}'",buffer[position-1]));
			}

			while (Peek() != '"'){
				char ch = Read();
				sb.Append(ch);
				if (ch == '\\')
				{
					ch = Read();
					sb.Append(ch);
				}
			}
			Read();

			return sb.ToString();
		}

		public JSON parseString(){
			return new JSONString(parseStringInternal());
		}

		public JSON parseValue(){
			scanWhitespace();
			char peek = Peek();

			switch (peek){
				case '{':
					return parseObject();
				case '[':
					return parseArray();
				case '"':
					return parseString();
			}

			if ((peek >= '0' && peek <= '9') || (peek == '-')){
				return parseNumber();
			}

			String p = Peek(4).ToLower();
			if (p.Equals("true")){
				position+=4;
				return JSONSpecial.True;
			}
			if (p.Equals("null")){
				position+=4;
				return JSONSpecial.Null;
			}
			p = Peek(5).ToLower();
			if (p.Equals("false")){
				position+=5;
				return JSONSpecial.False;
			}

			throw new FormatException(String.Format("Could not parse source at character '{0}' at position {1}",Peek(),position));
		}

		public JSON parse(){
			return parseValue();
		}

		private int findNext(char c){
			int p = position;
			while (p < buffer.Length){
				if (buffer[p] == c){
					return p - position;
				}
			}
			return -1;
		}

		private int scanWhitespace(){
			while (position < buffer.Length){
				if (buffer[position] > 0x20){
					return position;
				}
				position++;
			}
			return position;
		}

	}
}