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AngleSharp

, 3 Jul 2013 BSD
Bringing the DOM to C# with a HTML5/CSS3 parser written in C#.
Demo.zip
AngleSharp
Css
Tokens
DOM
Collections
Css
Properties
Rules
Selector
Values
Enums
Exception
Html
Basic
Formatting
Forms
Frames
Head
Lists
Media
Objects
Semantic
Tables
Interfaces
Mathml
Objects
Svg
Various
Xml
Foundation
Attributes
Helpers
Mutations
Html
Tokens
Properties
Stream
Xml
Tokens
packages
ModernUI.WPF.1.0.4
lib
net40
FirstFloor.ModernUI.dll
Microsoft.Windows.Shell.dll
net45
FirstFloor.ModernUI.dll
ModernUI.WPF.1.0.4.nupkg
ModernUI.WPF.1.0.4.nuspec
OxyPlot.Core.2013.1.49.1
lib
portable-net4+sl4+wp71+win8
OxyPlot.dll
OxyPlot.Core.2013.1.49.1.nupkg
OxyPlot.Core.2013.1.49.1.nuspec
OxyPlot.Wpf.2013.1.49.1
lib
NET40
OxyPlot.Wpf.dll
OxyPlot.Xps.dll
NET45
OxyPlot.Wpf.dll
OxyPlot.Xps.dll
OxyPlot.Wpf.2013.1.49.1.nupkg
OxyPlot.Wpf.2013.1.49.1.nuspec
Samples
Logo.ico
Pages
Properties
Settings.settings
ViewModels
Source.zip
Documents
using System;
using AngleSharp.DOM;
using AngleSharp.DOM.Css;
using AngleSharp.DOM.Collections;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Threading.Tasks;

namespace AngleSharp.Css
{
    /// <summary>
    /// The CSS parser.
    /// See http://dev.w3.org/csswg/css-syntax/#parsing for more details.
    /// </summary>
    public class CssParser : IParser
    {
        #region Members

        Boolean started;
        Boolean quirksFlag;
        CssTokenizer tokenizer;
        CSSStyleSheet sheet;
        TaskCompletionSource<Boolean> tcs;
        StringBuilder buffer;
        Stack<CSSRule> open;
        Boolean ignore;

        #endregion

        #region Events

        /// <summary>
        /// The event will be fired once an error has been detected.
        /// </summary>
        public event EventHandler<ParseErrorEventArgs> ErrorOccurred;

        #endregion

        #region ctor

        /// <summary>
        /// Creates a new CSS parser instance with a new stylesheet
        /// based on the given source.
        /// </summary>
        /// <param name="source">The source code as a string.</param>
        public CssParser(String source)
            : this(new CSSStyleSheet(), new SourceManager(source))
        {
        }

        /// <summary>
        /// Creates a new CSS parser instance with an new stylesheet
        /// based on the given stream.
        /// </summary>
        /// <param name="stream">The stream to use as source.</param>
        public CssParser(Stream stream)
            : this(new CSSStyleSheet(), new SourceManager(stream))
        {
        }

        /// <summary>
        /// Creates a new CSS parser instance with the specified stylesheet
        /// based on the given source.
        /// </summary>
        /// <param name="stylesheet">The stylesheet to be constructed.</param>
        /// <param name="source">The source code as a string.</param>
        public CssParser(CSSStyleSheet stylesheet, String source)
            : this(stylesheet, new SourceManager(source))
        {
        }

        /// <summary>
        /// Creates a new CSS parser instance with the specified stylesheet
        /// based on the given stream.
        /// </summary>
        /// <param name="stylesheet">The stylesheet to be constructed.</param>
        /// <param name="stream">The stream to use as source.</param>
        public CssParser(CSSStyleSheet stylesheet, Stream stream)
            : this(stylesheet, new SourceManager(stream))
        {
        }

        /// <summary>
        /// Creates a new CSS parser instance parser with the specified stylesheet
        /// based on the given source manager.
        /// </summary>
        /// <param name="stylesheet">The stylesheet to be constructed.</param>
        /// <param name="source">The source to use.</param>
        internal CssParser(CSSStyleSheet stylesheet, SourceManager source)
        {
            ignore = true;
            buffer = new StringBuilder();
            tokenizer = new CssTokenizer(source);

            tokenizer.ErrorOccurred += (s, ev) =>
            {
                if (ErrorOccurred != null)
                    ErrorOccurred(this, ev);
            };

            started = false;
            sheet = stylesheet;
            open = new Stack<CSSRule>();
        }

        #endregion

        #region Properties

        /// <summary>
        /// Gets if the parser has been started asynchronously.
        /// </summary>
        public Boolean IsAsync
        {
            get { return tcs != null; }
        }

        /// <summary>
        /// Gets the resulting stylesheet of the parsing.
        /// </summary>
        public CSSStyleSheet Result
        {
            get 
            {
                Parse();
                return sheet; 
            }
        }

        /// <summary>
        /// Gets or sets if the quirks-mode is activated.
        /// </summary>
        public Boolean IsQuirksMode
        {
            get { return quirksFlag; }
            set { quirksFlag = value; }
        }

        /// <summary>
        /// Gets the current rule if any.
        /// </summary>
        internal CSSRule CurrentRule
        {
            get { return open.Count > 0 ? open.Peek() : null; }
        }

        #endregion

        #region Methods

        /// <summary>
        /// Parses the given source asynchronously and creates the stylesheet.
        /// WARNING: This method is not yet implemented.
        /// </summary>
        /// <returns>The task which could be awaited or continued differently.</returns>
        public Task ParseAsync()
        {
            if (!started)
            {
                started = true;
                tcs = new TaskCompletionSource<bool>();
                //TODO
                return tcs.Task;
            }
            else if (tcs == null)
            {
                var temp = new TaskCompletionSource<bool>();
                temp.SetResult(true);
                return temp.Task;
            }

            return tcs.Task;
        }

        /// <summary>
        /// Parses the given source code.
        /// </summary>
        public void Parse()
        {
            if (!started)
            {
                started = true;
                AppendRules(tokenizer.Iterator, sheet.CssRules.List);
            }
        }

        #endregion

        #region Stylesheet construction

        /// <summary>
        /// Appends rules from the given source to the list of rules.
        /// </summary>
        /// <param name="source">The token iterator (source).</param>
        /// <param name="rules">The list of rules to append to.</param>
        void AppendRules(IEnumerator<CssToken> source, List<CSSRule> rules)
        {
            while (source.MoveNext())
            {
                switch (source.Current.Type)
                {
                    case CssTokenType.Cdc:
                    case CssTokenType.Cdo:
                    case CssTokenType.Whitespace:
                        break;

                    case CssTokenType.AtKeyword:
                        rules.Add(CreateAtRule(source));
                        break;

                    default:
                        rules.Add(CreateStyleRule(source));
                        break;
                }
            }
        }

        /// <summary>
        /// Appends declarations from the given source to the list of declarations.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <param name="declarations">The list of declarations to append to.</param>
        void AppendDeclarations(IEnumerator<CssToken> source, List<CSSProperty> declarations)
        {
            while (source.MoveNext())
            {
                switch (source.Current.Type)
                {
                    case CssTokenType.Whitespace:
                    case CssTokenType.Semicolon:
                        break;

                    case CssTokenType.Ident:
                        var tokens = LimitToSemicolon(source);
                        var it = tokens.GetEnumerator();
                        it.MoveNext();
                        var decl = CreateDeclaration(it);

                        if (decl != null)
                            declarations.Add(decl);

                        break;

                    default:
                        RaiseErrorOccurred(ErrorCode.InvalidCharacter);
                        SkipToNextSemicolon(source);
                        break;
                }
            }
        }

        /// <summary>
        /// Appends media labels from the given source to the medialist.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <param name="media">The medialist to append to.</param>
        /// <param name="endToken">The optional token type to finish appending to the list.</param>
        void AppendMediaList(IEnumerator<CssToken> source, MediaList media, CssTokenType endToken = CssTokenType.Semicolon)
        {
            do
            {
                if (source.Current.Type == CssTokenType.Whitespace)
                    continue;
                else if (source.Current.Type == endToken)
                    break;

                do
                {
                    if (source.Current.Type == CssTokenType.Comma || source.Current.Type == endToken)
                        break;
                    else if (source.Current.Type == CssTokenType.Whitespace)
                        buffer.Append(' ');
                    else
                        buffer.Append(source.Current.ToValue());
                }
                while (source.MoveNext());

                media.AppendMedium(buffer.ToString());
                buffer.Clear();

                if (source.Current.Type == endToken)
                    break;
            }
            while (source.MoveNext());
        }

        /// <summary>
        /// Creates a list of CSSValueList values from the given source.
        /// </summary>
        /// <param name="source">The token source.</param>
        /// <returns>The list of CSSValueList instances.</returns>
        List<CSSValueList> CreateMultipleValues(IEnumerator<CssToken> source)
        {
            var values = new List<CSSValueList>();

            do
            {
                var list = CreateValueList(source);

                if (list.Length > 0)
                    values.Add(list);
            }
            while (source.Current != null && source.Current.Type == CssTokenType.Comma);

            return values;
        }

        /// <summary>
        /// Creates a CSSValueList from the given source.
        /// </summary>
        /// <param name="source">The token source.</param>
        /// <returns>The CSSValueList instance.</returns>
        CSSValueList CreateValueList(IEnumerator<CssToken> source)
        {
            var list = new List<CSSValue>();

            while (SkipToNextNonWhitespace(source))
            {
                if (source.Current.Type == CssTokenType.Semicolon)
                    break;
                else if (source.Current.Type == CssTokenType.Comma)
                    break;

                var value = CreateValue(source);

                if (value == null)
                {
                    SkipToNextSemicolon(source);
                    break;
                }

                list.Add(value);
            }

            return new CSSValueList(list);
        }

        /// <summary>
        /// Creates a single value from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The value or NULL.</returns>
        CSSValue CreateValue(IEnumerator<CssToken> source)
        {
            CSSValue value = null;

            switch (source.Current.Type)
            {
                case CssTokenType.String:// 'i am a string'
                    value = new CSSPrimitiveValue(UnitType.String, ((CssStringToken)source.Current).Data);
                    break;

                case CssTokenType.Url:// url('this is a valid URL')
                    value = new CSSPrimitiveValue(UnitType.Uri, ((CssStringToken)source.Current).Data);
                    break;

                case CssTokenType.Ident: // ident
                    value = new CSSPrimitiveValue(UnitType.Ident, ((CssKeywordToken)source.Current).Data);
                    break;

                case CssTokenType.Percentage: // 5%
                    value = new CSSPrimitiveValue(UnitType.Percentage, ((CssUnitToken)source.Current).Data);
                    break;

                case CssTokenType.Dimension: // 3px
                    value = new CSSPrimitiveValue(((CssUnitToken)source.Current).Unit, ((CssUnitToken)source.Current).Data);
                    break;

                case CssTokenType.Number: // 173
                    value = new CSSPrimitiveValue(UnitType.Number, ((CssNumberToken)source.Current).Data);
                    break;

                case CssTokenType.Hash: // #string
                    HtmlColor color;

                    if(HtmlColor.TryFromHex(((CssKeywordToken)source.Current).Data, out color))
                        value = new CSSPrimitiveValue(color);

                    break;

                case CssTokenType.Delim: // e.g. #0F3, #012345, ...
                    if (((CssDelimToken)source.Current).Data == '#')
                    {
                        String hash = String.Empty;

                        while (source.MoveNext())
                        {
                            var stop = false;

                            switch (source.Current.Type)
                            {
                                case CssTokenType.Number:
                                case CssTokenType.Dimension:
                                case CssTokenType.Ident:
                                    var rest = source.Current.ToValue();

                                    if (hash.Length + rest.Length <= 6)
                                        hash += rest;
                                    else
                                        stop = true;

                                    break;

                                default:
                                    stop = true;
                                    break;
                            }

                            if (stop || hash.Length == 6)
                                break;
                        }

                        if (HtmlColor.TryFromHex(hash, out color))
                            value = new CSSPrimitiveValue(color);
                    }
                    break;

                case CssTokenType.Function: // rgba(255, 255, 20, 0.5)
                    value = CreateFunction(source);
                    break;
            }

            return value;
        }

        /// <summary>
        /// Creates a function from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The created function.</returns>
        CSSFunction CreateFunction(IEnumerator<CssToken> source)
        {
            var name = ((CssKeywordToken)source.Current).Data;
            var args = new CSSValueList();

            //TODO

            while (source.MoveNext())
            {
                if (source.Current.Type == CssTokenType.RoundBracketClose)
                    break;
            }

            return CSSFunction.Create(name, args);
        }

        /// <summary>
        /// Creates a new style rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The style rule.</returns>
        CSSStyleRule CreateStyleRule(IEnumerator<CssToken> source)
        {
            var style = new CSSStyleRule();
            var ctor = new CssSelectorConstructor();
            ctor.IgnoreErrors = ignore;
            style.ParentStyleSheet = sheet;
            style.ParentRule = CurrentRule;
            open.Push(style);

            do
            {
                if (source.Current.Type == CssTokenType.CurlyBracketOpen)
                {
                    if (SkipToNextNonWhitespace(source))
                    {
                        var tokens = LimitToCurrentBlock(source);
                        AppendDeclarations(tokens.GetEnumerator(), style.Style.List);
                    }

                    break;
                }

                ctor.PickSelector(source);
            }
            while (source.MoveNext());

            style.Selector = ctor.Result;
            open.Pop();
            return style;
        }

        /// <summary>
        /// Creates a @-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @-rule.</returns>
        CSSRule CreateAtRule(IEnumerator<CssToken> source)
        {
            var name = ((CssKeywordToken)source.Current).Data;
            SkipToNextNonWhitespace(source);

            switch (name)
            {
                case CSSMediaRule.RuleName: return CreateMediaRule(source);
                case CSSPageRule.RuleName: return CreatePageRule(source);
                case CSSImportRule.RuleName: return CreateImportRule(source);
                case CSSFontFaceRule.RuleName: return CreateFontFaceRule(source);
                case CSSCharsetRule.RuleName: return CreateCharsetRule(source);
                case CSSNamespaceRule.RuleName: return CreateNamespaceRule(source);
                case CSSSupportsRule.RuleName: return CreateSupportsRule(source);
                case CSSKeyframesRule.RuleName: return CreateKeyframesRule(source);
                default: return CreateUnknownRule(name, source);
            }
        }

        /// <summary>
        /// Creates a new property from the given source.
        /// </summary>
        /// <param name="source">The token iterator starting at the name of the property.</param>
        /// <returns>The new property.</returns>
        CSSProperty CreateDeclaration(IEnumerator<CssToken> source)
        {
            String name = ((CssKeywordToken)source.Current).Data;
            CSSProperty property = null;
            CSSValue value = CSSValue.Inherit;
            Boolean hasValue = SkipToNextNonWhitespace(source) && source.Current.Type == CssTokenType.Colon;

            if (hasValue)
                value = CreateValueList(source);

            //TODO
            switch (name)
            {
                case "azimuth":
                case "animation":
                case "animation-delay":
                case "animation-direction":
                case "animation-duration":
                case "animation-fill-mode":
                case "animation-iteration-count":
                case "animation-name":
                case "animation-play-state":
                case "animation-timing-function":
                case "background-attachment":
                case "background-color":
                case "background-clip":
                case "background-origin":
                case "background-size":
                case "background-image":
                case "background-position":
                case "background-repeat":
                case "background":
                case "border-color":
                case "border-spacing":
                case "border-collapse":
                case "border-style":
                case "border-radius":
                case "box-shadow":
                case "box-decoration-break":
                case "break-after":
                case "break-before":
                case "break-inside":
                case "backface-visibility":
                case "border-top-left-radius":
                case "border-top-right-radius":
                case "border-bottom-left-radius":
                case "border-bottom-right-radius":
                case "border-image":
                case "border-image-outset":
                case "border-image-repeat":
                case "border-image-source":
                case "border-image-slice":
                case "border-image-width":
                case "border-top":
	            case "border-right":
                case "border-bottom":
                case "border-left":
                case "border-top-color":
                case "border-left-color":
                case "border-right-color":
                case "border-bottom-color":
                case "border-top-style":
                case "border-left-style":
                case "border-right-style":
                case "border-bottom-style":
                case "border-top-width":
                case "border-left-width":
                case "border-right-width":
                case "border-bottom-width":
                case "border-width":
                case "border":
                case "bottom":
                case "columns":
                case "column-count":
                case "column-fill":
                case "column-gap":
                case "column-rule-color":
                case "column-rule-style":
                case "column-rule-width":
                case "column-span":
                case "column-width":	
                case "caption-side":
                case "clear":
                case "clip":
                case "color":
                case "content":
                case "counter-increment":
                case "counter-reset":
                case "cue-after":
                case "cue-before":
                case "cue":
                case "cursor":
                case "direction":
                case "display":
                case "elevation":
                case "empty-cells":
                case "float":
                case "font-family":
                case "font-size":
                case "font-style":
                case "font-variant":
                case "font-weight":
                case "font":
                case "height":
                case "left":
                case "letter-spacing":
                case "line-height":
                case "list-style-image":
                case "list-style-position":
                case "list-style-type":
                case "list-style":
                case "marquee-direction":
                case "marquee-play-count":
                case "marquee-speed":
                case "marquee-style":
                case "margin-right":
                case "margin-left":
                case "margin-top":
		        case "margin-bottom":
                case "margin":
                case "max-height":
                case "max-width":
                case "min-height":
                case "min-width":
                case "opacity":
                case "orphans":
                case "outline-color":
                case "outline-style":
                case "outline-width":
                case "outline":
                case "overflow":
                case "padding-top":
                case "padding-right":
                case "padding-left":
                case "padding-bottom":
                case "padding":
                case "page-break-after":
                case "page-break-before":
                case "page-break-inside":
                case "pause-after":
                case "pause-before":
                case "pause":
                case "perspective":
                case "perspective-origin":
                case "pitch-range":
                case "pitch":
                case "play-during":
                case "position":
                case "quotes":
                case "richness":
                case "right":
                case "speak-header":
                case "speak-numeral":
                case "speak-punctuation":
                case "speak":
                case "speech-rate":
                case "stress":
                case "table-layout":
                case "text-align":
                case "text-decoration":
                case "text-indent":
                case "text-transform":
                case "transform":
                case "transform-origin":
                case "transform-style":
                case "transition":
                case "transition-delay":
                case "transition-duration":
                case "transition-timing-function":
                case "transition-property":
                case "top":
                case "unicode-bidi":
                case "vertical-align":
                case "visibility":
                case "voice-family":
                case "volume":
                case "white-space":
                case "widows":
                case "width":
                case "word-spacing":
                case "z-index":
                default:
                    property = new CSSProperty(name);
                    property.Value = value;
                    break;
            }

            if (hasValue && source.Current.Type == CssTokenType.Delim && ((CssDelimToken)source.Current).Data == Specification.EM && SkipToNextNonWhitespace(source))
                property.Important = source.Current.Type == CssTokenType.Ident && ((CssKeywordToken)source.Current).Data.Equals("important", StringComparison.OrdinalIgnoreCase);

            SkipBehindNextSemicolon(source);
            return property;
        }

        #endregion

        #region Rule creation

        /// <summary>
        /// Creates a new unknown @-rule from the given source.
        /// </summary>
        /// <param name="name">The name of the @-rule.</param>
        /// <param name="source">The token iterator.</param>
        /// <returns>The unknown @-rule.</returns>
        CSSUnknownRule CreateUnknownRule(String name, IEnumerator<CssToken> source)
        {
            var rule = new CSSUnknownRule();
            var endCurly = 0;
            rule.ParentStyleSheet = sheet;
            rule.ParentRule = CurrentRule;
            open.Push(rule);
            buffer.Append(name).Append(" ");

            do
            {
                if (source.Current.Type == CssTokenType.Semicolon && endCurly == 0)
                {
                    source.MoveNext();
                    break;
                }

                buffer.Append(source.Current.ToString());

                if (source.Current.Type == CssTokenType.CurlyBracketOpen)
                    endCurly++;
                else if (source.Current.Type == CssTokenType.CurlyBracketClose && --endCurly == 0)
                    break;
            }
            while (source.MoveNext());

            rule.SetText(buffer.ToString());
            buffer.Clear();
            open.Pop();
            return rule;
        }

        /// <summary>
        /// Creates a new @keyframes-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @keyframes-rule.</returns>
        CSSKeyframesRule CreateKeyframesRule(IEnumerator<CssToken> source)
        {
            var keyframes = new CSSKeyframesRule();
            keyframes.ParentStyleSheet = sheet;
            keyframes.ParentRule = CurrentRule;
            open.Push(keyframes);

            if (source.Current.Type == CssTokenType.Ident)
            {
                keyframes.Name = ((CssKeywordToken)source.Current).Data;
                SkipToNextNonWhitespace(source);

                if (source.Current.Type == CssTokenType.CurlyBracketOpen)
                {
                    SkipToNextNonWhitespace(source);
                    var tokens = LimitToCurrentBlock(source).GetEnumerator();

                    while (SkipToNextNonWhitespace(tokens))
                        keyframes.CssRules.List.Add(CreateKeyframeRule(tokens));
                }
            }

            open.Pop();
            return keyframes;
        }

        /// <summary>
        /// Creates a new keyframe-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The keyframe-rule.</returns>
        CSSKeyframeRule CreateKeyframeRule(IEnumerator<CssToken> source)
        {
            var keyframe = new CSSKeyframeRule();
            keyframe.ParentStyleSheet = sheet;
            keyframe.ParentRule = CurrentRule;
            open.Push(keyframe);

            do
            {
                if (source.Current.Type == CssTokenType.CurlyBracketOpen)
                {
                    if (SkipToNextNonWhitespace(source))
                    {
                        var tokens = LimitToCurrentBlock(source);
                        AppendDeclarations(tokens.GetEnumerator(), keyframe.Style.List);
                    }

                    break;
                }

                buffer.Append(source.Current.ToString());
            }
            while (source.MoveNext());

            keyframe.KeyText = buffer.ToString();
            buffer.Clear();
            open.Pop();
            return keyframe;
        }

        /// <summary>
        /// Creates a new @supports-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @supports-rule.</returns>
        CSSSupportsRule CreateSupportsRule(IEnumerator<CssToken> source)
        {
            var supports = new CSSSupportsRule();
            supports.ParentStyleSheet = sheet;
            supports.ParentRule = CurrentRule;
            open.Push(supports);

            do
            {
                if (source.Current.Type == CssTokenType.CurlyBracketOpen)
                {
                    if (SkipToNextNonWhitespace(source))
                    {
                        var tokens = LimitToCurrentBlock(source);
                        AppendRules(tokens.GetEnumerator(), supports.CssRules.List);
                    }

                    break;
                }

                buffer.Append(source.Current.ToString());
            }
            while (source.MoveNext());

            supports.ConditionText = buffer.ToString();
            buffer.Clear();
            open.Pop();
            return supports;
        }

        /// <summary>
        /// Creates a new @namespace-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @namespace-rule.</returns>
        CSSNamespaceRule CreateNamespaceRule(IEnumerator<CssToken> source)
        {
            var ns = new CSSNamespaceRule();
            ns.ParentStyleSheet = sheet;

            if (source.Current.Type == CssTokenType.Ident)
            {
                ns.Prefix = source.Current.ToValue();
                SkipToNextNonWhitespace(source);
                
                if (source.Current.Type == CssTokenType.String)
                    ns.NamespaceURI = source.Current.ToValue();
            }

            SkipToNextSemicolon(source);
            return ns;
        }

        /// <summary>
        /// Creates a new @charset-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @charset-rule.</returns>
        CSSCharsetRule CreateCharsetRule(IEnumerator<CssToken> source)
        {
            var charset = new CSSCharsetRule();
            charset.ParentStyleSheet = sheet;

            if (source.Current.Type == CssTokenType.String)
                charset.Encoding = ((CssStringToken)source.Current).Data;

            SkipToNextSemicolon(source);
            return charset;
        }

        /// <summary>
        /// Creates a new @font-face-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @font-face-rule.</returns>
        CSSFontFaceRule CreateFontFaceRule(IEnumerator<CssToken> source)
        {
            var fontface = new CSSFontFaceRule();
            fontface.ParentStyleSheet = sheet;
            fontface.ParentRule = CurrentRule;
            open.Push(fontface);

            if(source.Current.Type == CssTokenType.CurlyBracketOpen)
            {
                if (SkipToNextNonWhitespace(source))
                {
                    var tokens = LimitToCurrentBlock(source);
                    AppendDeclarations(tokens.GetEnumerator(), fontface.CssRules.List);
                }
            }

            open.Pop();
            return fontface;
        }

        /// <summary>
        /// Creates a new @import-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @import-rule.</returns>
        CSSImportRule CreateImportRule(IEnumerator<CssToken> source)
        {
            var import = new CSSImportRule();
            import.ParentStyleSheet = sheet;
            import.ParentRule = CurrentRule;
            open.Push(import);

            switch (source.Current.Type)
            {
                case CssTokenType.Semicolon:
                    source.MoveNext();
                    break;

                case CssTokenType.String:
                case CssTokenType.Url:
                    import.Href = ((CssStringToken)source.Current).Data;
                    AppendMediaList(source, import.Media, CssTokenType.Semicolon);
                    //TODO
                    //import.StyleSheet = DocumentBuilder.Css(new Uri(import.Href));
                    break;

                default:
                    SkipToNextSemicolon(source);
                    break;
            }

            open.Pop();
            return import;
        }

        /// <summary>
        /// Creates a new @page-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @page-rule.</returns>
        CSSPageRule CreatePageRule(IEnumerator<CssToken> source)
        {
            var page = new CSSPageRule();
            page.ParentStyleSheet = sheet;
            page.ParentRule = CurrentRule;
            open.Push(page);
            var ctor = new CssSelectorConstructor();
            ctor.IgnoreErrors = ignore;

            do
            {
                if (source.Current.Type == CssTokenType.CurlyBracketOpen)
                {
                    if (SkipToNextNonWhitespace(source))
                    {
                        var tokens = LimitToCurrentBlock(source);
                        AppendDeclarations(tokens.GetEnumerator(), page.Style.List);
                        break;
                    }
                }

                ctor.PickSelector(source);
            }
            while (source.MoveNext());

            page.Selector = ctor.Result;
            open.Pop();
            return page;
        }

        /// <summary>
        /// Creates a new @media-rule from the given source.
        /// </summary>
        /// <param name="source">The token iterator.</param>
        /// <returns>The @media-rule.</returns>
        CSSMediaRule CreateMediaRule(IEnumerator<CssToken> source)
        {
            var media = new CSSMediaRule();
            media.ParentStyleSheet = sheet;
            media.ParentRule = CurrentRule;
            open.Push(media);
            AppendMediaList(source, media.Media, CssTokenType.CurlyBracketOpen);

            if (source.Current.Type == CssTokenType.CurlyBracketOpen)
            {
                if (SkipToNextNonWhitespace(source))
                {
                    var tokens = LimitToCurrentBlock(source);
                    AppendRules(tokens.GetEnumerator(), media.CssRules.List);
                }
            }

            open.Pop();
            return media;
        }

        #endregion

        #region Value creation

        //TODO

        #endregion

        #region Helpers

        /// <summary>
        /// Moves from the current position to the next position that is not a whitespace
        /// token.
        /// </summary>
        /// <param name="source">The iterator to walk through.</param>
        /// <returns>True if a non-whitespace could be reached, otherwise false (EOF).</returns>
        static Boolean SkipToNextNonWhitespace(IEnumerator<CssToken> source)
        {
            while (source.MoveNext())
                if (source.Current.Type != CssTokenType.Whitespace)
                    return true;

            return false;
        }

        /// <summary>
        /// Moves from the current position to the next position that is a semicolon token.
        /// </summary>
        /// <param name="source">The iterator to walk through.</param>
        /// <returns>True if a semicolon could be reached, otherwise false (EOF).</returns>
        static Boolean SkipToNextSemicolon(IEnumerator<CssToken> source)
        {
            do
            {
                if (source.Current.Type == CssTokenType.Semicolon)
                    return true;
            }
            while (source.MoveNext());

            return false;
        }

        /// <summary>
        /// Moves from the current position to the next position that is following a
        /// semicolon token.
        /// </summary>
        /// <param name="source">The iterator to walk through.</param>
        /// <returns>True if a semicolon could be passed, otherwise false (EOF).</returns>
        static Boolean SkipBehindNextSemicolon(IEnumerator<CssToken> source)
        {
            do
            {
                if (source.Current.Type == CssTokenType.Semicolon)
                {
                    source.MoveNext();
                    return true;
                }
            }
            while (source.MoveNext());

            return false;
        }

        /// <summary>
        /// Limits the given iterator to the next semicolon.
        /// </summary>
        /// <param name="source">The iterator to consider.</param>
        /// <returns>An iterator within the specified tokens.</returns>
        static IEnumerable<CssToken> LimitToSemicolon(IEnumerator<CssToken> source)
        {
            do
            {
                if (source.Current.Type == CssTokenType.Semicolon)
                    yield break;

                yield return source.Current;
            }
            while (source.MoveNext());
        }

        /// <summary>
        /// Limits the given iterator to the current block (assuming a curly bracket is open).
        /// </summary>
        /// <param name="source">The iterator to consider.</param>
        /// <returns>An iterator within the specified tokens.</returns>
        static IEnumerable<CssToken> LimitToCurrentBlock(IEnumerator<CssToken> source)
        {
            int open = 1;

            do
            {
                if (source.Current.Type == CssTokenType.CurlyBracketOpen)
                    open++;
                else if (source.Current.Type == CssTokenType.CurlyBracketClose && --open == 0)
                    yield break;

                yield return source.Current;
            }
            while (source.MoveNext());
        }

        #endregion

        #region Static methods

        /// <summary>
        /// Takes a string and transforms it into a selector object.
        /// </summary>
        /// <param name="selector">The string to parse.</param>
        /// <param name="quirksMode">Optional: The status of the quirks mode flag (usually not set).</param>
        /// <returns>The Selector object.</returns>
        public static Selector ParseSelector(String selector, Boolean quirksMode = false)
        {
            var parser = new CssParser(selector);
            parser.IsQuirksMode = quirksMode;
            var tokens = parser.tokenizer.Iterator;
            var ctor = new CssSelectorConstructor();

            while (tokens.MoveNext())
                ctor.PickSelector(tokens);

            return ctor.Result;
        }

        /// <summary>
        /// Takes a string and transforms it into a CSS stylesheet.
        /// </summary>
        /// <param name="stylesheet">The string to parse.</param>
        /// <param name="quirksMode">Optional: The status of the quirks mode flag (usually not set).</param>
        /// <returns>The CSSStyleSheet object.</returns>
        public static CSSStyleSheet ParseStyleSheet(String stylesheet, Boolean quirksMode = false)
        {
            var parser = new CssParser(stylesheet);
            parser.IsQuirksMode = quirksMode;
            return parser.Result;
        }

        /// <summary>
        /// Takes a string and transforms it into a CSS rule.
        /// </summary>
        /// <param name="rule">The string to parse.</param>
        /// <param name="quirksMode">Optional: The status of the quirks mode flag (usually not set).</param>
        /// <returns>The CSSRule object.</returns>
        public static CSSRule ParseRule(String rule, Boolean quirksMode = false)
        {
            var parser = new CssParser(rule);
            parser.ignore = false;
            parser.IsQuirksMode = quirksMode;
            var it = parser.tokenizer.Iterator;

            if (SkipToNextNonWhitespace(it))
            {
                if (it.Current.Type == CssTokenType.Cdo || it.Current.Type == CssTokenType.Cdc)
                    throw new DOMException(ErrorCode.SyntaxError);

                return (it.Current.Type == CssTokenType.AtKeyword) ? parser.CreateAtRule(it) : parser.CreateStyleRule(it);
            }

            return new CSSUnknownRule();
        }

        /// <summary>
        /// Takes a string and transforms it into CSS declarations.
        /// </summary>
        /// <param name="declarations">The string to parse.</param>
        /// <param name="quirksMode">Optional: The status of the quirks mode flag (usually not set).</param>
        /// <returns>The CSSStyleDeclaration object.</returns>
        public static CSSStyleDeclaration ParseDeclarations(String declarations, Boolean quirksMode = false)
        {
            var parser = new CssParser(declarations);
            parser.IsQuirksMode = quirksMode;
            parser.ignore = false;
            var it = parser.tokenizer.Iterator;
            var decl = new CSSStyleDeclaration();
            parser.AppendDeclarations(it, decl.List);
            return decl;
        }

        /// <summary>
        /// Takes a string and transforms it into a CSS value.
        /// </summary>
        /// <param name="source">The string to parse.</param>
        /// <param name="quirksMode">Optional: The status of the quirks mode flag (usually not set).</param>
        /// <returns>The CSSValue object.</returns>
        public static CSSValue ParseValue(String source, Boolean quirksMode = false)
        {
            var parser = new CssParser(source);
            parser.IsQuirksMode = quirksMode;
            parser.ignore = false;
            var it = parser.tokenizer.Iterator;
            SkipToNextNonWhitespace(it);
            return parser.CreateValue(it);
        }

        /// <summary>
        /// Takes a string and transforms it into a list of CSS values.
        /// </summary>
        /// <param name="source">The string to parse.</param>
        /// <param name="quirksMode">Optional: The status of the quirks mode flag (usually not set).</param>
        /// <returns>The CSSValueList object.</returns>
        internal static CSSValueList ParseValueList(String source, Boolean quirksMode = false)
        {
            var parser = new CssParser(source);
            parser.IsQuirksMode = quirksMode;
            parser.ignore = false;
            var it = parser.tokenizer.Iterator;
            return parser.CreateValueList(it);
        }

        /// <summary>
        /// Takes a comma separated string and transforms it into a list of CSS values.
        /// </summary>
        /// <param name="source">The string to parse.</param>
        /// <param name="quirksMode">Optional: The status of the quirks mode flag (usually not set).</param>
        /// <returns>The CSSValueList object.</returns>
        internal static List<CSSValueList> ParseMultipleValues(String source, Boolean quirksMode = false)
        {
            var parser = new CssParser(source);
            parser.IsQuirksMode = quirksMode;
            parser.ignore = false;
            var it = parser.tokenizer.Iterator;
            return parser.CreateMultipleValues(it);
        }

        /// <summary>
        /// Takes a string and transforms it into a CSS keyframe rule.
        /// </summary>
        /// <param name="rule">The string to parse.</param>
        /// <param name="quirksMode">Optional: The status of the quirks mode flag (usually not set).</param>
        /// <returns>The CSSKeyframeRule object.</returns>
        internal static CSSKeyframeRule ParseKeyframeRule(String rule, Boolean quirksMode = false)
        {
            var parser = new CssParser(rule);
            parser.IsQuirksMode = quirksMode;
            parser.ignore = false;
            var it = parser.tokenizer.Iterator;

            if (SkipToNextNonWhitespace(it))
            {
                if (it.Current.Type == CssTokenType.Cdo || it.Current.Type == CssTokenType.Cdc)
                    throw new DOMException(ErrorCode.SyntaxError);

                return parser.CreateKeyframeRule(it);
            }

            return null;
        }

        #endregion

        #region Event-Helpers

        /// <summary>
        /// Fires an error occurred event.
        /// </summary>
        /// <param name="code">The associated error code.</param>
        void RaiseErrorOccurred(ErrorCode code)
        {
            if (ErrorOccurred != null)
            {
                var pck = new ParseErrorEventArgs((int)code, Errors.GetError(code));
                pck.Line = tokenizer.Stream.Line;
                pck.Column = tokenizer.Stream.Column;
                ErrorOccurred(this, pck);
            }
        }

        #endregion
    }
}

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About the Author

Florian Rappl
Chief Technology Officer
Germany Germany
Florian is from Regensburg, Germany. He started his programming career with Perl. After programming C/C++ for some years he discovered his favorite programming language C#. He did work at Siemens as a programmer until he decided to study Physics. During his studies he worked as an IT consultant for various companies.
 
Florian is also giving lectures in C#, HTML5 with CSS3 and JavaScript, and other topics. Having graduated from University with a Master's degree in theoretical physics he is currently busy doing his PhD in the field of High Performance Computing.
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