/*
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.Collections.Generic;
using System.Globalization;
using System.Text;

namespace GreenshotPlugin.Core {
	/// <summary>
	/// This parses a JSON response, a modified version of the code found at:
	/// See: http://techblog.procurios.nl/k/n618/news/view/14605/14863/How-do-I-write-my-own-parser-for-JSON.html
	/// 
	/// This file is under the MIT License, which is GPL Compatible and according to: http://en.wikipedia.org/wiki/MIT_License
	/// can be used under the GPL "umbrella".
	/// 
	/// TODO: code should be replaced when upgrading to .NET 3.5 or higher!!
	/// </summary>
	public class JSONHelper {
		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 IDictionary<string, 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 IDictionary<string, object> JsonDecode(string json, ref bool success) {
			success = true;
			if (json != null) {
				char[] charArray = json.ToCharArray();
				int index = 0;
				IDictionary<string, object> value = ParseValue(charArray, ref index, ref success) as IDictionary<string, object>;
				return value;
			} else {
				return null;
			}
		}

		protected static IDictionary<string, object> ParseObject(char[] json, ref int index, ref bool success) {
			IDictionary<string, object> table = new Dictionary<string, object>();
			int token;

			// {
			NextToken(json, ref index);

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

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

					table.Add(name, value);
				}
			}

			return table;
		}

		protected static IList<object> ParseArray(char[] json, ref int index, ref bool success) {
			IList<object> array = new List<object>();

			// [
			NextToken(json, ref index);

			bool done = false;
			while (!done) {
				int token = LookAhead(json, index);
				if (token == TOKEN_NONE) {
					success = false;
					return null;
				} else if (token == TOKEN_COMMA) {
					NextToken(json, ref index);
				} else if (token == 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 TOKEN_STRING:
					return ParseString(json, ref index, ref success);
				case TOKEN_NUMBER:
					return ParseNumber(json, ref index, ref success);
				case TOKEN_CURLY_OPEN:
					return ParseObject(json, ref index, ref success);
				case TOKEN_SQUARED_OPEN:
					return ParseArray(json, ref index, ref success);
				case TOKEN_TRUE:
					NextToken(json, ref index);
					return true;
				case TOKEN_FALSE:
					NextToken(json, ref index);
					return false;
				case TOKEN_NULL:
					NextToken(json, ref index);
					return null;
				case 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 TOKEN_NONE;
			}

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

			return TOKEN_NONE;
		}
	}
}