/*
 * Copyright (c) 2012-2016 Daniele Bartolini and individual contributors.
 * License: https://github.com/taylor001/crown/blob/master/LICENSE
 */

/*
 * Public Domain Niklas Frykholm
 */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;

namespace Crown
{
	/// <summary>
	/// Provides functions for encoding and decoding files in the simplified JSON format.
	/// </summary>
	public class SJSON
	{
		/// <summary>
		///  Encodes the Hashtable t in the simplified JSON format. The Hashtable can
		///  contain, numbers, bools, strings, ArrayLists and Hashtables.
		/// </summary>
		public static string Encode(Hashtable t)
		{
			StringBuilder builder = new StringBuilder();
			WriteRootObject(t, builder);
			return builder.ToString();
		}

		/// <summary>
		/// Encodes the object o in the simplified JSON format (not as a root object).
		/// </summary>
		/// <returns></returns>
		public static string EncodeObject(object o)
		{
			StringBuilder builder = new StringBuilder();
			Write(o, builder, 0);
			return builder.ToString();
		}

		/// <summary>
		/// Decodes a SJSON bytestream into a Hashtable with numbers, bools, strings,
		/// ArrayLists and Hashtables.
		/// </summary>
		public static Hashtable Decode(byte[] sjson)
		{
			int index = 0;
			return ParseRootObject(sjson, ref index);
		}

		/// <summary>
		/// Convenience function for loading a file.
		/// </summary>
		public static Hashtable Load(string path)
		{
			System.IO.FileStream fs = System.IO.File.Open(path, System.IO.FileMode.Open, System.IO.FileAccess.Read);
			byte[] bytes = new byte[fs.Length];
			fs.Read(bytes, 0, bytes.Length);
			fs.Close();
			return Decode(bytes);
		}

		/// <summary>
		/// Convenience function for saving a file.
		/// </summary>
		public static void Save(Hashtable h, string path)
		{
			string s = Encode(h);
			System.IO.FileStream fs = System.IO.File.Open(path, System.IO.FileMode.Create);
			byte[] bytes = System.Text.Encoding.UTF8.GetBytes(s);
			fs.Write(bytes, 0, bytes.Count());
			fs.Close();
		}

		static void WriteRootObject(Hashtable t, StringBuilder builder)
		{
		   WriteObjectFields(t, builder, 0);
		}

		static void WriteObjectFields(Hashtable t, StringBuilder builder, int indentation)
		{
			List<string> keys = t.Keys.Cast<string>().ToList();
			keys.Sort();
			foreach (string key in keys) {
				WriteNewLine(builder, indentation);
				builder.Append(key);
				builder.Append(" = ");
				Write(t[key], builder, indentation);
			}
		}

		static void WriteNewLine(StringBuilder builder, int indentation)
		{
			builder.Append('\n');
			for (int i = 0; i < indentation; ++i)
				builder.Append('\t');
		}

		static void Write(object o, StringBuilder builder, int indentation)
		{
			if (o == null)
				builder.Append("null");
			else if (o is Boolean && (bool)o == false)
				builder.Append("false");
			else if (o is Boolean)
				builder.Append("true");
			else if (o is byte)
				builder.Append((byte)o);
			else if (o is int)
				builder.Append((int)o);
			else if (o is float)
				builder.Append((float)o);
			else if (o is double)
				builder.Append((double)o);
			else if (o is string)
				WriteString((String)o, builder);
			else if (o is ArrayList)
				WriteArray((ArrayList)o, builder, indentation);
			else if (o is Hashtable)
				WriteObject((Hashtable)o, builder, indentation);
			else
				throw new ArgumentException("Unknown object");
		}

		static void WriteString(String s, StringBuilder builder)
		{
			builder.Append('"');
			for (int i=0; i<s.Length; ++i) {
				Char c = s[i];
				if (c == '"' || c == '\\')
					builder.Append('\\');
				builder.Append(c);
			}
			builder.Append('"');
		}

		static void WriteArray(ArrayList a, StringBuilder builder, int indentation)
		{
			builder.Append('[');
			foreach (object item in a) {
				WriteNewLine(builder, indentation+1);
				Write(item, builder, indentation+1);
			}
			WriteNewLine(builder, indentation);
			builder.Append(']');
		}

		static void WriteObject(Hashtable t, StringBuilder builder, int indentation)
		{
			builder.Append('{');
			WriteObjectFields(t, builder, indentation+1);
			WriteNewLine(builder, indentation);
			builder.Append('}');
		}

		static Hashtable ParseRootObject(byte [] json, ref int index)
		{
			Hashtable ht = new Hashtable();
			while (!AtEnd(json, ref index)) {
				String key = ParseIdentifier(json, ref index);
				Consume(json, ref index, "=");
				object value = ParseValue(json, ref index);
				ht[key] = value;
			}
			return ht;
		}

		static bool AtEnd(byte [] json, ref int index)
		{
			SkipWhitespace(json, ref index);
			return (index >= json.Length);
		}

		static void SkipWhitespace(byte [] json, ref int index)
		{
			while (index < json.Length) {
				byte c = json[index];
				if (c == '/')
					SkipComment(json, ref index);
				else if (c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == ',')
					++index;
				else
					break;
			}
		}

		static void SkipComment(byte [] json, ref int index)
		{
			byte next = json[index + 1];
			if (next == '/')
			{
				while (index + 1 < json.Length && json[index] != '\n')
					++index;
				++index;
			}
			else if (next == '*')
			{
				while (index + 2 < json.Length && (json[index] != '*' || json[index + 1] != '/'))
					++index;
				index += 2;
			}
			else
				throw new FormatException();
		}

		static String ParseIdentifier(byte [] json, ref int index)
		{
			SkipWhitespace(json, ref index);

			if (json[index] == '"')
				return ParseString(json, ref index);

			List<byte> s = new List<byte>();
			while (true) {
				byte c = json[index];
				if (c == ' ' || c == '\t' || c == '\n' || c == '=')
					break;
				s.Add(c);
				++index;
			}
			return new UTF8Encoding().GetString(s.ToArray());
		}

		static void Consume(byte [] json, ref int index, String consume)
		{
			SkipWhitespace(json, ref index);
			for (int i=0; i<consume.Length; ++i) {
				if (json[index] != consume[i])
					throw new FormatException();
				++index;
			}
		}

		static object ParseValue(byte [] json, ref int index)
		{
			byte c = Next(json, ref index);

			if (c == '{')
				return ParseObject(json, ref index);
			else if (c == '[')
				return ParseArray(json, ref index);
			else if (c == '"')
				return ParseString(json, ref index);
			else if (c == '-' || c >= '0' && c <= '9')
				return ParseNumber(json, ref index);
			else if (c == 't')
			{
				Consume(json, ref index, "true");
				return true;
			}
			else if (c == 'f')
			{
				Consume(json, ref index, "false");
				return false;
			}
			else if (c == 'n')
			{
				Consume(json, ref index, "null");
				return null;
			}
			else
				throw new FormatException();
		}

		static byte Next(byte [] json, ref int index)
		{
			SkipWhitespace(json, ref index);
			return json[index];
		}

		static Hashtable ParseObject(byte [] json, ref int index)
		{
			Hashtable ht = new Hashtable();
			Consume(json, ref index, "{");
			SkipWhitespace(json, ref index);

			while (Next(json, ref index) != '}') {
				String key = ParseIdentifier(json, ref index);
				Consume(json, ref index, "=");
				object value = ParseValue(json, ref index);
				ht[key] = value;
			}
			Consume(json, ref index, "}");
			return ht;
		}

		static ArrayList ParseArray(byte [] json, ref int index)
		{
			ArrayList a = new ArrayList();
			Consume(json, ref index, "[");
			while (Next(json, ref index) != ']') {
				object value = ParseValue(json, ref index);
				a.Add(value);
			}
			Consume(json, ref index, "]");
			return a;
		}

		static String ParseString(byte[] json, ref int index)
		{
			List<byte> s = new List<byte>();

			Consume(json, ref index, "\"");
			while (true) {
				byte c = json[index];
				++index;
				if (c == '"')
					break;
				else if (c != '\\')
					s.Add(c);
				else {
					byte q = json[index];
					++index;
					if (q == '"' || q == '\\' || q == '/')
						s.Add(q);
					else if (q == 'b') s.Add((byte)'\b');
					else if (q == 'f') s.Add((byte)'\f');
					else if (q == 'n') s.Add((byte)'\n');
					else if (q == 'r') s.Add((byte)'\r');
					else if (q == 't') s.Add((byte)'\t');
					else if (q == 'u')  {
						throw new FormatException();
					} else {
						throw new FormatException();
					}
				}
			}
			return new UTF8Encoding().GetString(s.ToArray());
		}

		static Double ParseNumber(byte[] json, ref int index)
		{
			int end = index;
			while (end < json.Length && "0123456789+-.eE".IndexOf((char)json[end]) != -1)
				++end;
			byte[] num = new byte[end - index];
			Array.Copy(json, index, num, 0, num.Length);
			index = end;
			String numstr = new UTF8Encoding().GetString(num);
			return Double.Parse(numstr);
		}
	}
}