// <developer>niklas@protocol7.com</developer>
// <completed>80</completed>

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace SharpVectors.Dom.Css
{
	/// <summary>
	/// The CSSCharsetRule interface represents a @charset rule in a CSS style sheet. The value of the encoding attribute does not affect the encoding of text data in the DOM objects; this encoding is always UTF-16. After a stylesheet is loaded, the value of the encoding attribute is the value found in the @charset rule. If there was no @charset in the original document, then no CSSCharsetRule is created. The value of the encoding attribute may also be used as a hint for the encoding used on serialization of the style sheet.
	///	The value of the @charset rule (and therefore of the CSSCharsetRule) may not correspond to the encoding the document actually came in; character encoding information e.g. in an HTTP header, has priority (see CSS document representation) but this is not reflected in the CSSCharsetRule.
	/// </summary>
	public class CssCharsetRule : CssRule, ICssCharsetRule
	{
		#region Static members
		private static Regex regex = new Regex(@"^@charset\s""(?<charsetencoding>[^""]+)"";");

        internal static CssRule Parse(ref string css, object parent, bool readOnly, IList<string> replacedStrings, CssStyleSheetType origin)
		{
			Match match = regex.Match(css);
			if(match.Success)
			{
				CssCharsetRule rule = new CssCharsetRule(match, parent, readOnly, replacedStrings, origin);
				css = css.Substring(match.Length);
				return rule;
			}
			else
			{
				// didn't match => do nothing
				return null;
			}
		}
		#endregion

		#region Constructors

		/// <summary>
		/// The constructor for CssCharSetRule
		/// </summary>
		/// <param name="match">The Regex match that found the charset rule</param>
		/// <param name="parent">The parent rule or parent stylesheet</param>
		/// <param name="readOnly">True if this instance is readonly</param>
		/// <param name="replacedStrings">An array of strings that have been replaced in the string used for matching. These needs to be put back use the DereplaceStrings method</param>
		/// <param name="origin">The type of CssStyleSheet</param>
        internal CssCharsetRule(Match match, object parent, bool readOnly, 
            IList<string> replacedStrings, CssStyleSheetType origin)
            : base(parent, readOnly, replacedStrings, origin)
		{
			_Encoding = DeReplaceStrings(match.Groups["charsetencoding"].Value);
		}

		#endregion
		
		#region Implementation of ICssCharsetRule
		private string _Encoding;
		/// <summary>
		/// The encoding information used in this @charset rule
		/// </summary>
		public string Encoding
		{
			get
			{
				return _Encoding;
			}
			set
			{
				/*
				 * TODO: SYNTAX_ERR: Raised if the specified encoding value has a syntax error and is unparsable.
				 * */

				if (readOnly) 
                    throw new DomException(DomExceptionType.NoModificationAllowedErr);

				_Encoding = value;
			}
		}
		#endregion

		#region Implementation of ICssRule
		/// <summary>
		/// The type of the rule. The expectation is that binding-specific casting methods can be used to cast down from an instance of the CSSRule interface to the specific derived interface implied by the type.
		/// </summary>
		public override CssRuleType Type
		{
			get
			{
				return CssRuleType.CharsetRule;
			}
		}
		#endregion
	}
}