// JSON parser, downloaded from http://techblog.procurios.nl/k/618/news/view/14605/14863/How-do-I-write-my-own-parser-for-JSON.html
// Copyright (c) 2008 Patrick van Bergen
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

using System;
using System.Collections;
using System.Globalization;
using System.Text;

namespace Procurios.Public
{
	/// <summary>
	/// This class encodes and decodes JSON strings.
	/// Spec. details, see http://www.json.org/
	///
	/// JSON uses Arrays and Objects. These correspond here to the datatypes ArrayList and Hashtable.
	/// All numbers are parsed to doubles.
	/// </summary>
	public class JSON
	{
		public const int TOKEN_NONE = 0;
		public const int TOKEN_CURLY_OPEN = 1;
		public const int TOKEN_CURLY_CLOSE = 2;
		public const int TOKEN_SQUARED_OPEN = 3;
		public const int TOKEN_SQUARED_CLOSE = 4;
		public const int TOKEN_COLON = 5;
		public const int TOKEN_COMMA = 6;
		public const int TOKEN_STRING = 7;
		public const int TOKEN_NUMBER = 8;
		public const int TOKEN_TRUE = 9;
		public const int TOKEN_FALSE = 10;
		public const int TOKEN_NULL = 11;

		private const int BUILDER_CAPACITY = 2000;

		/// <summary>
		/// Parses the string json into a value
		/// </summary>
		/// <param name="json">A JSON string.</param>
		/// <returns>An ArrayList, a Hashtable, a double, a string, null, true, or false</returns>
		public static object JsonDecode(string json)
		{
			bool success = true;

			return JsonDecode(json, ref success);
		}

		/// <summary>
		/// Parses the string json into a value; and fills 'success' with the successfullness of the parse.
		/// </summary>
		/// <param name="json">A JSON string.</param>
		/// <param name="success">Successful parse?</param>
		/// <returns>An ArrayList, a Hashtable, a double, a string, null, true, or false</returns>
		public static object JsonDecode(string json, ref bool success)
		{
			success = true;
			if (json != null) {
				char[] charArray = json.ToCharArray();
				int index = 0;
				object value = ParseValue(charArray, ref index, ref success);
				return value;
			} else {
				return null;
			}
		}

		/// <summary>
		/// Converts a Hashtable / ArrayList object into a JSON string
		/// </summary>
		/// <param name="json">A Hashtable / ArrayList</param>
		/// <returns>A JSON encoded string, or null if object 'json' is not serializable</returns>
		public static string JsonEncode(object json)
		{
			StringBuilder builder = new StringBuilder(BUILDER_CAPACITY);
			bool success = SerializeValue(json, builder);
			return (success ? builder.ToString() : null);
		}

		protected static Hashtable ParseObject(char[] json, ref int index, ref bool success)
		{
			Hashtable table = new Hashtable();
			int token;

			// {
			NextToken(json, ref index);

			bool done = false;
			while (!done) {
				token = LookAhead(json, index);
				if (token == JSON.TOKEN_NONE) {
					success = false;
					return null;
				} else if (token == JSON.TOKEN_COMMA) {
					NextToken(json, ref index);
				} else if (token == JSON.TOKEN_CURLY_CLOSE) {
					NextToken(json, ref index);
					return table;
				} else {

					// name
					string name = ParseString(json, ref index, ref success);
					if (!success) {
						success = false;
						return null;
					}

					// :
					token = NextToken(json, ref index);
					if (token != JSON.TOKEN_COLON) {
						success = false;
						return null;
					}

					// value
					object value = ParseValue(json, ref index, ref success);
					if (!success) {
						success = false;
						return null;
					}

					table[name] = value;
				}
			}

			return table;
		}

		protected static ArrayList ParseArray(char[] json, ref int index, ref bool success)
		{
			ArrayList array = new ArrayList();

			// [
			NextToken(json, ref index);

			bool done = false;
			while (!done) {
				int token = LookAhead(json, index);
				if (token == JSON.TOKEN_NONE) {
					success = false;
					return null;
				} else if (token == JSON.TOKEN_COMMA) {
					NextToken(json, ref index);
				} else if (token == JSON.TOKEN_SQUARED_CLOSE) {
					NextToken(json, ref index);
					break;
				} else {
					object value = ParseValue(json, ref index, ref success);
					if (!success) {
						return null;
					}

					array.Add(value);
				}
			}

			return array;
		}

		protected static object ParseValue(char[] json, ref int index, ref bool success)
		{
			switch (LookAhead(json, index)) {
				case JSON.TOKEN_STRING:
					return ParseString(json, ref index, ref success);
				case JSON.TOKEN_NUMBER:
					return ParseNumber(json, ref index, ref success);
				case JSON.TOKEN_CURLY_OPEN:
					return ParseObject(json, ref index, ref success);
				case JSON.TOKEN_SQUARED_OPEN:
					return ParseArray(json, ref index, ref success);
				case JSON.TOKEN_TRUE:
					NextToken(json, ref index);
					return true;
				case JSON.TOKEN_FALSE:
					NextToken(json, ref index);
					return false;
				case JSON.TOKEN_NULL:
					NextToken(json, ref index);
					return null;
				case JSON.TOKEN_NONE:
					break;
			}

			success = false;
			return null;
		}

		protected static string ParseString(char[] json, ref int index, ref bool success)
		{
			StringBuilder s = new StringBuilder(BUILDER_CAPACITY);
			char c;

			EatWhitespace(json, ref index);

			// "
			c = json[index++];

			bool complete = false;
			while (!complete) {

				if (index == json.Length) {
					break;
				}

				c = json[index++];
				if (c == '"') {
					complete = true;
					break;
				} else if (c == '\\') {

					if (index == json.Length) {
						break;
					}
					c = json[index++];
					if (c == '"') {
						s.Append('"');
					} else if (c == '\\') {
						s.Append('\\');
					} else if (c == '/') {
						s.Append('/');
					} else if (c == 'b') {
						s.Append('\b');
					} else if (c == 'f') {
						s.Append('\f');
					} else if (c == 'n') {
						s.Append('\n');
					} else if (c == 'r') {
						s.Append('\r');
					} else if (c == 't') {
						s.Append('\t');
					} else if (c == 'u') {
						int remainingLength = json.Length - index;
						if (remainingLength >= 4) {
							// parse the 32 bit hex into an integer codepoint
							uint codePoint;
							if (!(success = UInt32.TryParse(new string(json, index, 4), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out codePoint))) {
								return "";
							}
							// convert the integer codepoint to a unicode char and add to string
							s.Append(Char.ConvertFromUtf32((int)codePoint));
							// skip 4 chars
							index += 4;
						} else {
							break;
						}
					}

				} else {
					s.Append(c);
				}

			}

			if (!complete) {
				success = false;
				return null;
			}

			return s.ToString();
		}

		protected static double ParseNumber(char[] json, ref int index, ref bool success)
		{
			EatWhitespace(json, ref index);

			int lastIndex = GetLastIndexOfNumber(json, index);
			int charLength = (lastIndex - index) + 1;

			double number;
			success = Double.TryParse(new string(json, index, charLength), NumberStyles.Any, CultureInfo.InvariantCulture, out number);

			index = lastIndex + 1;
			return number;
		}

		protected static int GetLastIndexOfNumber(char[] json, int index)
		{
			int lastIndex;

			for (lastIndex = index; lastIndex < json.Length; lastIndex++) {
				if ("0123456789+-.eE".IndexOf(json[lastIndex]) == -1) {
					break;
				}
			}
			return lastIndex - 1;
		}

		protected static void EatWhitespace(char[] json, ref int index)
		{
			for (; index < json.Length; index++) {
				if (" \t\n\r".IndexOf(json[index]) == -1) {
					break;
				}
			}
		}

		protected static int LookAhead(char[] json, int index)
		{
			int saveIndex = index;
			return NextToken(json, ref saveIndex);
		}

		protected static int NextToken(char[] json, ref int index)
		{
			EatWhitespace(json, ref index);

			if (index == json.Length) {
				return JSON.TOKEN_NONE;
			}

			char c = json[index];
			index++;
			switch (c) {
				case '{':
					return JSON.TOKEN_CURLY_OPEN;
				case '}':
					return JSON.TOKEN_CURLY_CLOSE;
				case '[':
					return JSON.TOKEN_SQUARED_OPEN;
				case ']':
					return JSON.TOKEN_SQUARED_CLOSE;
				case ',':
					return JSON.TOKEN_COMMA;
				case '"':
					return JSON.TOKEN_STRING;
				case '0': case '1': case '2': case '3': case '4':
				case '5': case '6': case '7': case '8': case '9':
				case '-':
					return JSON.TOKEN_NUMBER;
				case ':':
					return JSON.TOKEN_COLON;
			}
			index--;

			int remainingLength = json.Length - index;

			// false
			if (remainingLength >= 5) {
				if (json[index] == 'f' &&
					json[index + 1] == 'a' &&
					json[index + 2] == 'l' &&
					json[index + 3] == 's' &&
					json[index + 4] == 'e') {
					index += 5;
					return JSON.TOKEN_FALSE;
				}
			}

			// true
			if (remainingLength >= 4) {
				if (json[index] == 't' &&
					json[index + 1] == 'r' &&
					json[index + 2] == 'u' &&
					json[index + 3] == 'e') {
					index += 4;
					return JSON.TOKEN_TRUE;
				}
			}

			// null
			if (remainingLength >= 4) {
				if (json[index] == 'n' &&
					json[index + 1] == 'u' &&
					json[index + 2] == 'l' &&
					json[index + 3] == 'l') {
					index += 4;
					return JSON.TOKEN_NULL;
				}
			}

			return JSON.TOKEN_NONE;
		}

		protected static bool SerializeValue(object value, StringBuilder builder)
		{
			bool success = true;

			if (value is string) {
				success = SerializeString((string)value, builder);
			} else if (value is Hashtable) {
				success = SerializeObject((Hashtable)value, builder);
			} else if (value is ArrayList) {
				success = SerializeArray((ArrayList)value, builder);
			} else if ((value is Boolean) && ((Boolean)value == true)) {
				builder.Append("true");
			} else if ((value is Boolean) && ((Boolean)value == false)) {
				builder.Append("false");
			} else if (value is ValueType) {
				// thanks to ritchie for pointing out ValueType to me
				success = SerializeNumber(Convert.ToDouble(value), builder);
			} else if (value == null) {
				builder.Append("null");
			} else {
				success = false;
			}
			return success;
		}

		protected static bool SerializeObject(Hashtable anObject, StringBuilder builder)
		{
			builder.Append("{");

			IDictionaryEnumerator e = anObject.GetEnumerator();
			bool first = true;
			while (e.MoveNext()) {
				string key = e.Key.ToString();
				object value = e.Value;

				if (!first) {
					builder.Append(", ");
				}

				SerializeString(key, builder);
				builder.Append(":");
				if (!SerializeValue(value, builder)) {
					return false;
				}

				first = false;
			}

			builder.Append("}");
			return true;
		}

		protected static bool SerializeArray(ArrayList anArray, StringBuilder builder)
		{
			builder.Append("[");

			bool first = true;
			for (int i = 0; i < anArray.Count; i++) {
				object value = anArray[i];

				if (!first) {
					builder.Append(", ");
				}

				if (!SerializeValue(value, builder)) {
					return false;
				}

				first = false;
			}

			builder.Append("]");
			return true;
		}

		protected static bool SerializeString(string aString, StringBuilder builder)
		{
			builder.Append("\"");

			char[] charArray = aString.ToCharArray();
			for (int i = 0; i < charArray.Length; i++) {
				char c = charArray[i];
				if (c == '"') {
					builder.Append("\\\"");
				} else if (c == '\\') {
					builder.Append("\\\\");
				} else if (c == '\b') {
					builder.Append("\\b");
				} else if (c == '\f') {
					builder.Append("\\f");
				} else if (c == '\n') {
					builder.Append("\\n");
				} else if (c == '\r') {
					builder.Append("\\r");
				} else if (c == '\t') {
					builder.Append("\\t");
				} else {
					int codepoint = Convert.ToInt32(c);
					if ((codepoint >= 32) && (codepoint <= 126)) {
						builder.Append(c);
					} else {
						builder.Append("\\u" + Convert.ToString(codepoint, 16).PadLeft(4, '0'));
					}
				}
			}

			builder.Append("\"");
			return true;
		}

		protected static bool SerializeNumber(double number, StringBuilder builder)
		{
			builder.Append(Convert.ToString(number, CultureInfo.InvariantCulture));
			return true;
		}
	}
}
