//
// JsonWriter.cs
//
// Author:
//	Atsushi Enomoto  <atsushi@ximian.com>
//
// Copyright (C) 2007 Novell, Inc (http://www.novell.com)
//
// 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.Generic;
using System.Globalization;
using System.IO;
using System.Text;
using System.Xml;

namespace System.Runtime.Serialization.Json
{
	class PushbackReader : StreamReader
	{
		Stack<int> pushback;

		public PushbackReader (Stream stream, Encoding encoding) : base (stream, encoding)
		{
			pushback = new Stack<int>();
		}

		public PushbackReader (Stream stream) : base (stream, true)
		{
			pushback = new Stack<int>();
		}

		public override void Close ()
		{
			pushback.Clear ();
		}

		public override int Peek ()
		{
			if (pushback.Count > 0) {
				return pushback.Peek ();
			}
			else {
				return base.Peek ();
			}
		}

		public override int Read ()
		{
			if (pushback.Count > 0) {
				return pushback.Pop ();
			}
			else {
				return base.Read ();
			}
		}

		public void Pushback (int ch)
		{
			pushback.Push (ch);
		}
	}

	// FIXME: quotas check
	class JsonReader : XmlDictionaryReader, IXmlJsonReaderInitializer, IXmlLineInfo
	{
		class ElementInfo
		{
			public readonly string Name;
			public readonly string Type;
			public bool HasContent;

			public ElementInfo (string name, string type)
			{
				this.Name = name;
				this.Type = type;
			}
		}

		enum AttributeState
		{
			None,
			Type,
			TypeValue,
			RuntimeType,
			RuntimeTypeValue
		}

		PushbackReader reader;
		XmlDictionaryReaderQuotas quotas;
		OnXmlDictionaryReaderClose on_close;
		XmlNameTable name_table = new NameTable ();

		XmlNodeType current_node;
		AttributeState attr_state;
		string simple_value;
		string next_element;
		string current_runtime_type, next_object_content_name;
		ReadState read_state = ReadState.Initial;
		bool content_stored;
		bool finished;
		Stack<ElementInfo> elements = new Stack<ElementInfo> ();

		int line = 1, column = 0;

		// Constructors

		public JsonReader (byte [] buffer, int offset, int count, Encoding encoding, XmlDictionaryReaderQuotas quotas, OnXmlDictionaryReaderClose onClose)
		{
			SetInput (buffer, offset, count, encoding, quotas, onClose);
		}

		public JsonReader (Stream stream, Encoding encoding, XmlDictionaryReaderQuotas quotas, OnXmlDictionaryReaderClose onClose)
		{
			SetInput (stream, encoding, quotas, onClose);
		}

		internal bool LameSilverlightLiteralParser { get; set; }

		// IXmlLineInfo

		public bool HasLineInfo ()
		{
			return true;
		}

		public int LineNumber {
			get { return line; }
		}

		public int LinePosition {
			get { return column; }
		}

		// IXmlJsonReaderInitializer

		public void SetInput (byte [] buffer, int offset, int count, Encoding encoding, XmlDictionaryReaderQuotas quotas, OnXmlDictionaryReaderClose onClose)
		{
			SetInput (new MemoryStream (buffer, offset, count), encoding, quotas, onClose);
		}

		public void SetInput (Stream stream, Encoding encoding, XmlDictionaryReaderQuotas quotas, OnXmlDictionaryReaderClose onClose)
		{
			if (encoding != null)
				reader = new PushbackReader (stream, encoding);
			else
				reader = new PushbackReader (stream);
			if (quotas == null)
				throw new ArgumentNullException ("quotas");
			this.quotas = quotas;
			this.on_close = onClose;
		}

		// XmlDictionaryReader

		public override int AttributeCount {
			get { return current_node != XmlNodeType.Element ? 0 : current_runtime_type != null ? 2 : 1; }
		}

		public override string BaseURI {
			get { return String.Empty; }
		}

		public override int Depth {
			get {
				int mod = 0;
				switch (attr_state) {
				case AttributeState.Type:
				case AttributeState.RuntimeType:
					mod++;
					break;
				case AttributeState.TypeValue:
				case AttributeState.RuntimeTypeValue:
					mod += 2;
					break;
				case AttributeState.None:
					if (NodeType == XmlNodeType.Text)
						mod++;
					break;
				}
				return read_state != ReadState.Interactive ? 0 : elements.Count - 1 + mod;
			}
		}

		public override bool EOF {
			get {
				switch (read_state) {
				case ReadState.Closed:
				case ReadState.EndOfFile:
					return true;
				default:
					return false;
				}
			}
		}

		public override bool HasValue {
			get {
				switch (NodeType) {
				case XmlNodeType.Attribute:
				case XmlNodeType.Text:
					return true;
				default:
					return false;
				}
			}
		}

		public override bool IsEmptyElement {
			get { return false; }
		}

		public override string LocalName {
			get {
				switch (attr_state) {
				case AttributeState.Type:
					return "type";
				case AttributeState.RuntimeType:
					return "__type";
				}
				switch (NodeType) {
				case XmlNodeType.Element:
				case XmlNodeType.EndElement:
					return elements.Peek ().Name;
				default:
					return String.Empty;
				}
			}
		}

		public override string NamespaceURI {
			get { return String.Empty; }
		}

		public override XmlNameTable NameTable {
			get { return name_table; }
		}

		public override XmlNodeType NodeType {
			get {
				switch (attr_state) {
				case AttributeState.Type:
				case AttributeState.RuntimeType:
					return XmlNodeType.Attribute;
				case AttributeState.TypeValue:
				case AttributeState.RuntimeTypeValue:
					return XmlNodeType.Text;
				default:
					return current_node;
				}
			}
		}

		public override string Prefix {
			get { return String.Empty; }
		}

		public override ReadState ReadState {
			get { return read_state; }
		}

		public override string Value {
			get {
				switch (attr_state) {
				case AttributeState.Type:
				case AttributeState.TypeValue:
					return elements.Peek ().Type;
				case AttributeState.RuntimeType:
				case AttributeState.RuntimeTypeValue:
					return current_runtime_type;
				default:
					return current_node == XmlNodeType.Text ? simple_value : String.Empty;
				}
			}
		}

		public override void Close ()
		{
			if (on_close != null) {
				on_close (this);
				on_close = null;
			}
			read_state = ReadState.Closed;
		}

		public override string GetAttribute (int index)
		{
			if (index == 0 && current_node == XmlNodeType.Element)
				return elements.Peek ().Type;
			else if (index == 1 && current_runtime_type != null)
				return current_runtime_type;
			throw new ArgumentOutOfRangeException ("index", "Index is must be either 0 or 1 when there is an explicit __type in the object, and only valid on an element on this XmlDictionaryReader");
		}

		public override string GetAttribute (string name)
		{
			if (current_node != XmlNodeType.Element)
				return null;
			switch (name) {
			case "type":
				return elements.Peek ().Type;
			case "__type":
				return current_runtime_type;
			default:
				return null;
			}
		}

		public override string GetAttribute (string localName, string ns)
		{
			if (ns == String.Empty)
				return GetAttribute (localName);
			else
				return null;
		}

		public override string LookupNamespace (string prefix)
		{
			if (prefix == null)
				throw new ArgumentNullException ("prefix");
			else if (prefix.Length == 0)
				return String.Empty;
			return null;
		}

		public override bool MoveToAttribute (string name)
		{
			if (current_node != XmlNodeType.Element)
				return false;
			switch (name) {
			case "type":
				attr_state = AttributeState.Type;
				return true;
			case "__type":
				if (current_runtime_type == null)
					return false;
				attr_state = AttributeState.RuntimeType;
				return true;
			default:
				return false;
			}
		}

		public override bool MoveToAttribute (string localName, string ns)
		{
			if (ns != String.Empty)
				return false;
			return MoveToAttribute (localName);
		}

		public override bool MoveToElement ()
		{
			if (attr_state == AttributeState.None)
				return false;
			attr_state = AttributeState.None;
			return true;
		}

		public override bool MoveToFirstAttribute ()
		{
			if (current_node != XmlNodeType.Element)
				return false;
			attr_state = AttributeState.Type;
			return true;
		}

		public override bool MoveToNextAttribute ()
		{
			if (attr_state == AttributeState.None)
				return MoveToFirstAttribute ();
			else
				return MoveToAttribute ("__type");
		}

		public override bool ReadAttributeValue ()
		{
			switch (attr_state) {
			case AttributeState.Type:
				attr_state = AttributeState.TypeValue;
				return true;
			case AttributeState.RuntimeType:
				attr_state = AttributeState.RuntimeTypeValue;
				return true;
			}
			return false;
		}

		public override void ResolveEntity ()
		{
			throw new NotSupportedException ();
		}

		public override bool Read ()
		{
			switch (read_state) {
			case ReadState.EndOfFile:
			case ReadState.Closed:
			case ReadState.Error:
				return false;
			case ReadState.Initial:
				read_state = ReadState.Interactive;
				next_element = "root";
				current_node = XmlNodeType.Element;
				break;
			}

			MoveToElement ();

			if (content_stored) {
				if (current_node == XmlNodeType.Element) {
					if (elements.Peek ().Type == "null") {
						// since null is not consumed as text content, it skips Text state.
						current_node = XmlNodeType.EndElement;
						content_stored = false;
					}
					else
						current_node = XmlNodeType.Text;
					return true;
				} else if (current_node == XmlNodeType.Text) {
					current_node = XmlNodeType.EndElement;
					content_stored = false;
					return true;
				}
			}
			else if (current_node == XmlNodeType.EndElement) {
				// clear EndElement state
				elements.Pop ();
				if (elements.Count > 0)
					elements.Peek ().HasContent = true;
				else
					finished = true;
			}

			SkipWhitespaces ();

			attr_state = AttributeState.None;
			// Default. May be overriden only as EndElement or None.
			current_node = XmlNodeType.Element;

			if (!ReadContent (false))
				return false;
			if (finished)
				throw XmlError ("Multiple top-level content is not allowed");
			return true;
		}

		bool TryReadString (string str)
		{
			for (int i = 0; i < str.Length; i ++) {
				int ch = ReadChar ();
				if (ch != str[i]) {
					for (int j = i; j >= 0; j--)
						PushbackChar (j);
					return false;
				}
			}

			return true;
		}

		bool ReadContent (bool objectValue)
		{
			int ch = ReadChar ();
			if (ch < 0) {
				ReadEndOfStream ();
				return false;
			}

			bool itemMustFollow = false;

			if (!objectValue && elements.Count > 0 && elements.Peek ().HasContent) {
				if (ch == ',') {
					switch (elements.Peek ().Type) {
					case "object":
					case "array":
						SkipWhitespaces ();
						ch = ReadChar ();
						itemMustFollow = true;
						break;
					}
				}
				else if (ch != '}' && ch != ']')
					throw XmlError ("Comma is required unless an array or object is at the end");
			}

			if (elements.Count > 0 && elements.Peek ().Type == "array")
				next_element = "item";
			else if (next_object_content_name != null) {
				next_element = next_object_content_name;
				next_object_content_name = null;
				if (ch != ':')
					throw XmlError ("':' is expected after a name of an object content");
				SkipWhitespaces ();
				ReadContent (true);
				return true;
			}

			switch (ch) {
			case '{':
				ReadStartObject ();
				return true;
			case '[':
				ReadStartArray ();
				return true;
			case '}':
				if (itemMustFollow)
					throw XmlError ("Invalid comma before an end of object");
				if (objectValue)
					throw XmlError ("Invalid end of object as an object content");
				ReadEndObject ();
				return true;
			case ']':
				if (itemMustFollow)
					throw XmlError ("Invalid comma before an end of array");
				if (objectValue)
					throw XmlError ("Invalid end of array as an object content");
				ReadEndArray ();
				return true;
			case '"':
				bool lame = LameSilverlightLiteralParser && ch != '"';
				string s = ReadStringLiteral (lame);
				if (!objectValue && elements.Count > 0 && elements.Peek ().Type == "object") {
					next_element = s;
					SkipWhitespaces ();
					if (!lame)
						Expect (':');
					SkipWhitespaces ();
					ReadContent (true);
				}
				else
					ReadAsSimpleContent ("string", s);
				return true;
			case '-':
				ReadNumber (ch);
				return true;
			case 'n':
				if (TryReadString("ull")) {
					ReadAsSimpleContent ("null", "null");
					return true;
				}
				else {
					// the pushback for 'n' is taken care of by the
					// default case if we're in lame silverlight literal
					// mode
					goto default;
				}
			case 't':
				if (TryReadString ("rue")) {
					ReadAsSimpleContent ("boolean", "true");
					return true;
				}
				else {
					// the pushback for 't' is taken care of by the
					// default case if we're in lame silverlight literal
					// mode
					goto default;
				}
			case 'f':
				if (TryReadString ("alse")) {
					ReadAsSimpleContent ("boolean", "false");
					return true;
				}
				else {
					// the pushback for 'f' is taken care of by the
					// default case if we're in lame silverlight literal
					// mode
					goto default;
				}
			default:
				if ('0' <= ch && ch <= '9') {
					ReadNumber (ch);
					return true;
				}
				if (LameSilverlightLiteralParser) {
					PushbackChar (ch);
					goto case '"';
				}
				throw XmlError (String.Format ("Unexpected token: '{0}' ({1:X04})", (char) ch, (int) ch));
			}
		}

		void ReadStartObject ()
		{
			ElementInfo ei = new ElementInfo (next_element, "object");
			elements.Push (ei);

			SkipWhitespaces ();
			if (PeekChar () == '"') { // it isn't premise: the object might be empty
				ReadChar ();
				string s = ReadStringLiteral ();
				if (s == "__type") {
					SkipWhitespaces ();
					Expect (':');
					SkipWhitespaces ();
					Expect ('"');
					current_runtime_type = ReadStringLiteral ();
					SkipWhitespaces ();
					ei.HasContent = true;
				}
				else
					next_object_content_name = s;
			}
		}

		void ReadStartArray ()
		{
			elements.Push (new ElementInfo (next_element, "array"));
		}

		void ReadEndObject ()
		{
			if (elements.Count == 0 || elements.Peek ().Type != "object")
				throw XmlError ("Unexpected end of object");
			current_node = XmlNodeType.EndElement;
		}

		void ReadEndArray ()
		{
			if (elements.Count == 0 || elements.Peek ().Type != "array")
				throw XmlError ("Unexpected end of array");
			current_node = XmlNodeType.EndElement;
		}

		void ReadEndOfStream ()
		{
			if (elements.Count > 0)
				throw XmlError (String.Format ("{0} missing end of arrays or objects", elements.Count));
			read_state = ReadState.EndOfFile;
			current_node = XmlNodeType.None;
		}

		void ReadAsSimpleContent (string type, string value)
		{
			elements.Push (new ElementInfo (next_element, type));
			simple_value = value;
			content_stored = true;
		}

		void ReadNumber (int ch)
		{
			elements.Push (new ElementInfo (next_element, "number"));
			content_stored = true;

			int init = ch;
			int prev;
			bool floating = false, exp = false;

			StringBuilder sb = new StringBuilder ();
			bool cont = true;
			do {
				sb.Append ((char) ch);
				prev = ch;
				ch = ReadChar ();

				if (prev == '-' && !IsNumber (ch)) // neither '.', '-' or '+' nor anything else is valid
					throw XmlError ("Invalid JSON number");

				switch (ch) {
				case 'e':
				case 'E':
					if (exp)
						throw XmlError ("Invalid JSON number token. Either 'E' or 'e' must not occur more than once");
					if (!IsNumber (prev))
						throw XmlError ("Invalid JSON number token. only a number is valid before 'E' or 'e'");
					exp = true;
					break;
				case '.':
					if (floating)
						throw XmlError ("Invalid JSON number token. '.' must not occur twice");
					if (exp)
						throw XmlError ("Invalid JSON number token. '.' must not occur after 'E' or 'e'");
					floating = true;
					break;
				case '+':
				case '-':
					if (prev == 'E' || prev == 'e')
						break;
					goto default;
				default:
					if (!IsNumber (ch)) {
						PushbackChar (ch);
						cont = false;
					}
					break;
				}
			} while (cont);

			if (!IsNumber (prev)) // only number is valid at the end
				throw XmlError ("Invalid JSON number");

			simple_value = sb.ToString ();

			if (init == '0' && !floating && !exp && simple_value != "0")
				throw XmlError ("Invalid JSON number");
		}

		bool IsNumber (int c)
		{
			return '0' <= c && c <= '9';
		}

		StringBuilder vb = new StringBuilder ();

		string ReadStringLiteral ()
		{
			return ReadStringLiteral (false);
		}

		string ReadStringLiteral (bool endWithColon)
		{
			vb.Length = 0;
			while (true) {
				int c = ReadChar ();
				if (c < 0)
					throw XmlError ("JSON string is not closed");
				if (c == '"' && !endWithColon)
					return vb.ToString ();
				else if (c == ':' && endWithColon)
					return vb.ToString ();
				else if (c != '\\') {
					vb.Append ((char) c);
					continue;
				}

				// escaped expression
				c = ReadChar ();
				if (c < 0)
					throw XmlError ("Invalid JSON string literal; incomplete escape sequence");
				switch (c) {
				case '"':
				case '\\':
				case '/':
					vb.Append ((char) c);
					break;
				case 'b':
					vb.Append ('\x8');
					break;
				case 'f':
					vb.Append ('\f');
					break;
				case 'n':
					vb.Append ('\n');
					break;
				case 'r':
					vb.Append ('\r');
					break;
				case 't':
					vb.Append ('\t');
					break;
				case 'u':
					ushort cp = 0;
					for (int i = 0; i < 4; i++) {
						if ((c = ReadChar ()) < 0)
							throw XmlError ("Incomplete unicode character escape literal");
						cp *= 16;
						if ('0' <= c && c <= '9')
							cp += (ushort) (c - '0');
						if ('A' <= c && c <= 'F')
							cp += (ushort) (c - 'A' + 10);
						if ('a' <= c && c <= 'f')
							cp += (ushort) (c - 'a' + 10);
					}
					vb.Append ((char) cp);
					break;
				default:
					throw XmlError ("Invalid JSON string literal; unexpected escape character");
				}
			}
		}

		int PeekChar ()
		{
			return reader.Peek ();
		}

		int ReadChar ()
		{
			int v = reader.Read ();
			if (v == '\n') {
				line++;
				column = 0;
			}
			else
				column++;
			return v;
		}

		void PushbackChar (int ch)
		{
			// FIXME handle lines (and columns?  ugh, how?)
			reader.Pushback (ch);
		}

		void SkipWhitespaces ()
		{
			do {
				switch (PeekChar ()) {
				case ' ':
				case '\t':
				case '\r':
				case '\n':
					ReadChar ();
					continue;
				default:
					return;
				}
			} while (true);
		}

		void Expect (char c)
		{
			int v = ReadChar ();
			if (v < 0)
				throw XmlError (String.Format ("Expected '{0}' but got EOF", c));
			if (v != c)
				throw XmlError (String.Format ("Expected '{0}' but got '{1}'", c, (char) v));
		}

		Exception XmlError (string s)
		{
			return new XmlException (String.Format ("{0} ({1},{2})", s, line, column));
		}

		// This reads the current element and all its content as a string,
		// with no processing done except for advancing the reader.
		public override string ReadInnerXml ()
		{

			if (NodeType != XmlNodeType.Element)
				return base.ReadInnerXml ();

			StringBuilder sb = new StringBuilder ();
			bool isobject = elements.Peek ().Type == "object";
			char end = isobject ? '}' : ']';
			char start = isobject ? '{' : '[';
			int count = 1;

			sb.Append (start);

			// add the first child manually, it's already been read
			// but hasn't been processed yet
			if (isobject && !String.IsNullOrEmpty (next_object_content_name))
					sb.Append ("\"" + next_object_content_name + "\"");

			// keep reading until we hit the end marker, no processing is
			// done on anything
			do {
				char c = (char)ReadChar ();
				sb.Append (c);
				if (c == start)
					++count;
				else if (c == end)
					--count;
			} while (count > 0);

			// Replace the content we've read with an empty object so it gets
			// skipped on the following Read
			reader.Pushback (end);
			if (isobject) {
				reader.Pushback ('"');
				reader.Pushback ('"');
				reader.Pushback (':');
			}

			// Skip the element
			Read ();
			return sb.ToString ();
		}
	}
}