//
// System.Security.SecurityElement.cs
//
// Authors:
//	Miguel de Icaza (miguel@ximian.com)
//	Lawrence Pit (loz@cable.a2000.nl)
//	Sebastien Pouliot  <sebastien@ximian.com>
//
// (C) Ximian, Inc. http://www.ximian.com
// Copyright (C) 2004-2005 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.Globalization;
using System.Collections;
using System.Runtime.InteropServices;
using System.Text;

using Mono.Xml;

namespace System.Security {

#if NET_2_0
	[ComVisible (true)]
#endif
	[Serializable]
	public sealed class SecurityElement 
	{
		internal class SecurityAttribute {
			
			private string _name;
			private string _value;

			public SecurityAttribute (string name, string value) 
			{
				if (!IsValidAttributeName (name))
					throw new ArgumentException (Locale.GetText ("Invalid XML attribute name") + ": " + name);

				if (!IsValidAttributeValue (value))
					throw new ArgumentException (Locale.GetText ("Invalid XML attribute value") + ": " + value);

				_name = name;
				_value = SecurityElement.Unescape (value);
			}

			public string Name {
				get { return _name; }
			}

			public string Value {
				get { return _value; }
			}
		}

		string text;
		string tag;
		ArrayList attributes;
		ArrayList children;
		
		// these values are determined by a simple test program against the MS.Net implementation:
		//	for (int i = 0; i < 256; i++) {
		//		if (!SecurityElement.IsValidTag ("" + ((char) i))) {
		//			System.Console.WriteLine ("TAG: " + i);
		//		}
		//	}		
		// note: this is actually an incorrect implementation of MS, as for example the &
		// character is not a valid character in tag names.
		private static readonly char [] invalid_tag_chars = new char [] { ' ', '<', '>' };
		private static readonly char [] invalid_text_chars = new char [] { '<', '>' };
		private static readonly char [] invalid_attr_name_chars = new char [] { ' ', '<', '>' };
		private static readonly char [] invalid_attr_value_chars = new char [] { '"', '<', '>' };
		private static readonly char [] invalid_chars = new char [] { '<', '>', '"', '\'', '&' };
		
		public SecurityElement (string tag) : this (tag, null)
		{
		}
		
		public SecurityElement (string tag, string text)
		{
			if (tag == null)
				throw new ArgumentNullException ("tag");
			if (!IsValidTag (tag))
				throw new ArgumentException (Locale.GetText ("Invalid XML string") + ": " + tag);
			this.tag = tag;

			Text = text;
		}

		// not a deep copy (childs are references)
		internal SecurityElement (SecurityElement se)
		{
			this.Tag = se.Tag;
			this.Text = se.Text;

			if (se.attributes != null) {
				foreach (SecurityAttribute sa in se.attributes) {
					this.AddAttribute (sa.Name, sa.Value);
				}
			}
			if (se.children != null) {
				foreach (SecurityElement child in se.children) {
					this.AddChild (child);
				}
			}
		}
		
		public Hashtable Attributes {
			get {
				if (attributes == null) 
					return null;
					
				Hashtable result = new Hashtable (attributes.Count);
				foreach (SecurityAttribute sa in attributes) {
					result.Add (sa.Name, sa.Value);
				}
				return result;
			}

			set {
				if (value == null || value.Count == 0) {
					attributes.Clear ();
					return;
				}
				
				if (attributes == null)
					attributes = new ArrayList ();
				else
					attributes.Clear ();
				IDictionaryEnumerator e = value.GetEnumerator ();
				while (e.MoveNext ()) {
					attributes.Add (new SecurityAttribute ((string) e.Key, (string) e.Value));
				}
			}
		}

		public ArrayList Children {
			get {
				return children;
			}

			set {
				if (value != null) {
					foreach (object o in value) {
						if (o == null)
							throw new ArgumentNullException ();
						// shouldn't we also throw an exception 
						// when o isn't an instance of SecurityElement?
					}
				}
				children = value;
			}
		}

		public string Tag {
			get {
				return tag;
			}
			set {
				if (value == null)
					throw new ArgumentNullException ("Tag");
				if (!IsValidTag (value))
					throw new ArgumentException (Locale.GetText ("Invalid XML string") + ": " + value);
				tag = value;
			}
		}

		public string Text {
			get {
				return text;
			}

			set {
				if (value != null) {
					if (!IsValidText (value))
						throw new ArgumentException (
							Locale.GetText ("Invalid XML string")
							+ ": " + value);
				}
				text = Unescape (value);
			}
		}

		public void AddAttribute (string name, string value)
		{
			if (name == null)
				throw new ArgumentNullException ("name");
			if (value == null)
				throw new ArgumentNullException ("value");
			if (GetAttribute (name) != null)
				throw new ArgumentException (Locale.GetText ("Duplicate attribute : " + name));

			if (attributes == null)
				attributes = new ArrayList ();
			attributes.Add (new SecurityAttribute (name, value));
		}

		public void AddChild (SecurityElement child)
		{
			if (child == null)
				throw new ArgumentNullException ("child");

			if (children == null)
				children = new ArrayList ();

			children.Add (child);
		}

		public string Attribute (string name)
		{
			if (name == null)
				throw new ArgumentNullException ("name");

			SecurityAttribute sa = GetAttribute (name);
			return ((sa == null) ? null : sa.Value);
		}

#if NET_2_0
		[ComVisible (false)]
		public SecurityElement Copy ()
		{
			return new SecurityElement (this);
		}
#endif

		public bool Equal (SecurityElement other)
		{
			if (other == null)
				return false;
				
			if (this == other)
				return true;

			if (this.text != other.text)
				return false;

			if (this.tag != other.tag)
				return false;

			if (this.attributes == null && other.attributes != null && other.attributes.Count != 0)
				return false;
				
			if (other.attributes == null && this.attributes != null && this.attributes.Count != 0)
				return false;

			if (this.attributes != null && other.attributes != null) {
				if (this.attributes.Count != other.attributes.Count) 
					return false;
				foreach (SecurityAttribute sa1 in attributes) {
					SecurityAttribute sa2 = other.GetAttribute (sa1.Name);
					if ((sa2 == null) || (sa1.Value != sa2.Value))
						return false;
				}
			}
			
			if (this.children == null && other.children != null && other.children.Count != 0)
				return false;
					
			if (other.children == null && this.children != null && this.children.Count != 0)
				return false;
				
			if (this.children != null && other.children != null) {
				if (this.children.Count != other.children.Count)
					return false;
				for (int i = 0; i < this.children.Count; i++) 
					if (!((SecurityElement) this.children [i]).Equal ((SecurityElement) other.children [i]))
						return false;
			}
			
			return true;
		}

		public static string Escape (string str)
		{
			StringBuilder sb;

			if (str == null)
				return null;

			if (str.IndexOfAny (invalid_chars) == -1)
				return str;

			sb = new StringBuilder ();
			int len = str.Length;
			
			for (int i = 0; i < len; i++) {
				char c = str [i];

				switch (c) {
				case '<':  sb.Append ("&lt;"); break;
				case '>':  sb.Append ("&gt;"); break;
				case '"':  sb.Append ("&quot;"); break;
				case '\'': sb.Append ("&apos;"); break;
				case '&':  sb.Append ("&amp;"); break;
				default:   sb.Append (c); break;
				}
			}

			return sb.ToString ();
		}

		private static string Unescape (string str)
		{
			StringBuilder sb;

			if (str == null)
				return null;

			sb = new StringBuilder (str);
			sb.Replace ("&lt;", "<");
			sb.Replace ("&gt;", ">");
			sb.Replace ("&amp;", "&");
			sb.Replace ("&quot;", "\"");
			sb.Replace ("&apos;", "'");
			return sb.ToString ();
		}

#if NET_2_0
		public
#else
		internal
#endif
		static SecurityElement FromString (string xml)
		{
			if (xml == null)
				throw new ArgumentNullException ("xml");
			if (xml.Length == 0)
				throw new XmlSyntaxException (Locale.GetText ("Empty string."));

			try {
				SecurityParser sp = new SecurityParser ();
				sp.LoadXml (xml);
				return sp.ToXml ();
			} catch (Exception e) {
				string msg = Locale.GetText ("Invalid XML.");
				throw new XmlSyntaxException (msg, e);
			}
		}

		public static bool IsValidAttributeName (string name)
		{
			return name != null && name.IndexOfAny (invalid_attr_name_chars) == -1;
		}

		public static bool IsValidAttributeValue (string value)
		{
			return value != null && value.IndexOfAny (invalid_attr_value_chars) == -1;
		}

		public static bool IsValidTag (string value)
		{
			return value != null && value.IndexOfAny (invalid_tag_chars) == -1;
		}

		public static bool IsValidText (string value)
		{
			return value != null && value.IndexOfAny (invalid_text_chars) == -1;
		}

		public SecurityElement SearchForChildByTag (string tag) 
		{
			if (tag == null)
				throw new ArgumentNullException ("tag");
				
			if (this.children == null)
				return null;
				
			for (int i = 0; i < children.Count; i++) {
				SecurityElement elem = (SecurityElement) children [i];
				if (elem.tag == tag)
					return elem;
			}
			return null;
		}

		public string SearchForTextOfTag (string tag) 
		{
			if (tag == null)
				throw new ArgumentNullException ("tag");
				
			if (this.tag == tag)
				return this.text;
				
			if (this.children == null)
				return null;
			
			for (int i = 0; i < children.Count; i++) {
				string result = ((SecurityElement) children [i]).SearchForTextOfTag (tag);
				if (result != null) 
					return result;
			}

			return null;
		}
		
		public override string ToString ()
		{
			StringBuilder s = new StringBuilder ();
			ToXml (ref s, 0);
			return s.ToString ();
		}
		
		private void ToXml (ref StringBuilder s, int level)
		{
#if ! NET_2_0
			s.Append (' ', level * 3);
#endif
			s.Append ("<");
			s.Append (tag);
			
			if (attributes != null) {
#if NET_2_0
				s.Append (" ");
#endif
				for (int i=0; i < attributes.Count; i++) {
					SecurityAttribute sa = (SecurityAttribute) attributes [i];
#if ! NET_2_0
					s.Append (" ");
					// all other attributes must align with the first one
					if (i != 0)
						s.Append (' ', (level * 3) + tag.Length + 1);
#endif
					s.Append (sa.Name)
					 .Append ("=\"")
					 .Append (Escape (sa.Value))
					 .Append ("\"");
					if (i != attributes.Count - 1)
						s.Append (Environment.NewLine);
				}
			}
			
			if ((text == null || text == String.Empty) && 
			    (children == null || children.Count == 0))
				s.Append ("/>").Append (Environment.NewLine);
			else {
				s.Append (">").Append (Escape (text));
				if (children != null) {
					s.Append (Environment.NewLine);
					foreach (SecurityElement child in children) {
						child.ToXml (ref s, level + 1);
					}
#if ! NET_2_0
					s.Append (' ', level * 3);
#endif
				}
				s.Append ("</")
				 .Append (tag)
				 .Append (">")
				 .Append (Environment.NewLine);
			}
		}

		internal SecurityAttribute GetAttribute (string name) 
		{
			if (attributes != null) {
				foreach (SecurityAttribute sa in attributes) {
					if (sa.Name == name)
						return sa;
				}
			}
			return null;
		}
	}
}