web-security/XSSAttachs/StyleSheetsParser/CssParser.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace StyleSheetsParser
{
    public partial class CssDocument
    {
        private class CssParser
        {
            char[] Source;//, startChars = new char[] {'@','#','.'};
            long position;
            bool over = false;
            string encoding;
            public CssParser(string source)
            {
                position = 0;
                if (source != null)
                {
                    string s = Regex.Replace(source, @"\/\*[\w\W]*?\*\/", "", RegexOptions.Multiline | RegexOptions.Compiled);
                    Source = s.ToCharArray();
                }
            }
            char Read(bool move = true)
            {
                if (position >= Source.Length)
                {
                    over = true;
                    return '\0';
                }
                return Source[move ? position++ : position];
            }
            void Next()
            {
                if (over) return;
                position++;
                if (position >= Source.Length)
                {
                    over = true;
                }

            }
            char GetRuleNameStartChar()
            {
                char ch = Read();
                if (over || ch == '@' || ch == '[' || ch == '*' || ch == '#' || ch == '.' || (ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z'))
                {
                    return ch;
                }
                return GetRuleNameStartChar();
            }
            char ReadMainStartChar(string ruleName)
            {
                if (over) return '\0';
                char ch = Read();
                if ("@charset".Equals(ruleName, StringComparison.CurrentCultureIgnoreCase))
                {
                    if (ch != '\'' && ch != '"') return ReadMainStartChar(ruleName);
                    else { return ch; }
                }
                else if ("@import".Equals(ruleName, StringComparison.CurrentCultureIgnoreCase))
                {
                    if (ch != ' ' && ch != '\'' && ch != '"') return ReadMainStartChar(ruleName);
                    else { return ch; }
                }
                if (ch != '{') return ReadMainStartChar(ruleName);
                else { return ch; }
            }
            char GetRuleMainEndChar(string ruleName, char start)
            {
                return "@charset".Equals(ruleName, StringComparison.CurrentCultureIgnoreCase) ? start :
                    "@import".Equals(ruleName, StringComparison.CurrentCultureIgnoreCase) ? (start == '\'' || start == '"' ? start : ';') : start == '{' ? '}' : '\0';
            }
            string NextRuleName()
            {
                if (over) return string.Empty;
                char start = GetRuleNameStartChar();
                if (over) return string.Empty;
                StringBuilder sb = new StringBuilder(start.ToString());
                char ch, end = ' '; char[] ends = start == '@' ? new char[] { ' ','\'','"', '\n', '\r', '\t', '{' } : new char[] { '{' };
                Action action = () =>
                {
                    while ((ch = Read(false)) != '\0' && !ends.Any(o => (end = o) == ch))
                    {
                        sb.Append(ch);
                        Next();
                    }
                };
                action();
                if (over) return string.Empty;
                string s = sb.ToString().Trim();
                if (start == '@' && end != '{' && !("@import".Equals(s, StringComparison.CurrentCultureIgnoreCase) || "@charset".Equals(s, StringComparison.CurrentCultureIgnoreCase)))
                {
                    sb.Clear();
                    sb.Append(s + end);
                    ends = new char[] { '{' };
                    ch = Read();
                    action();
                    return sb.ToString();
                }

                return s;


            }
            void RemoveSpace()
            {
                char ch = Read(false);
                while ((ch == '\n' || ch == '\r' || ch == '\t' || ch == ' ') && !over)
                {
                    Next();
                    ch = Read(false);
                }
            }
            CssRule NextRule(Func<string, IList<CssAttribute>, CssRule> fn = null)
            {
                CssRule rule;
                string name = NextRuleName();
                if (name == string.Empty) return null;
                char ch, start = ReadMainStartChar(name), end = GetRuleMainEndChar(name, start);
                if (name.StartsWith("@media", StringComparison.CurrentCultureIgnoreCase))
                {
                    List<CssRule> slrs = new List<CssRule>();
                    while (!over)
                    {
                        rule = NextRule();
                        if (rule != null)
                        { slrs.Add(rule); }
                        RemoveSpace();
                        if (Read(false) == end || over) { Next(); break; }

                    }
                    return new CssMedia(name, slrs);
                }
                if (name.StartsWith("@") && name.IndexOf("keyframes", StringComparison.CurrentCultureIgnoreCase) > 0)
                {
                    List<CssKeyframeSelector> kfslrs = new List<CssKeyframeSelector>();
                    while (!over)
                    {
                        rule = NextRule((n, attrs) => new CssKeyframeSelector(n, attrs));
                        if (rule != null && rule is CssKeyframeSelector)
                        { kfslrs.Add((CssKeyframeSelector)rule); }
                        RemoveSpace();
                        if (Read(false) == end || over) { Next(); break; }
                    }
                    return new CssKeyframes(name, kfslrs);

                }
                Action<StringBuilder, char, char> ReadIncluding = (sb, startLetter, endLetter) =>
                {
                    if (startLetter == endLetter)
                    {
                        do
                        {
                            sb.Append(startLetter);
                        } while (!over && (startLetter = Read()) != endLetter);
                    }
                };
                Func<string> ReadString = () =>
                {
                    StringBuilder sb = new StringBuilder(start.ToString());
                    ch = Read();
                    while (!over && ch != end)
                    {
                        sb.Append(ch);
                        ch = Read();
                        if (ch != end)
                        {
                            ReadIncluding(sb, ch, '"');
                            ReadIncluding(sb, ch, '\'');
                        }
                    }
                    if (ch == end) sb.Append(ch);
                    return sb.ToString();
                };
                Func<IList<CssAttribute>> ReadAttribults = () =>
                {
                    List<CssAttribute> list = new List<CssAttribute>();
                    StringBuilder sb = new StringBuilder();
                    string attrName = null, attrValue;
                    RemoveSpace();
                    ch = Read();
                    while (!over)
                    {
                        if (ch == ':')
                        {
                            if (sb.Length > 0)
                            {
                                attrName = sb.ToString();
                                sb.Clear();
                                RemoveSpace();
                            }
                        }
                        else if (ch == ';' || ch == '}')
                        {
                            if (attrName != null && attrName != "")
                            {
                                attrValue = sb.ToString();
                                list.Add(new CssAttribute(attrName, attrValue));
                            }
                            if (ch == '}') { break; }
                            attrValue = attrName = null;
                            sb.Clear();
                            RemoveSpace();
                        }
                        else
                        {
                            sb.Append(ch);
                        }
                        ch = Read();
                        ReadIncluding(sb, ch, '"');
                        ReadIncluding(sb, ch, '\'');
                        if (ch == '{')
                        {
                            do
                            {
                                sb.Append(ch);
                            } while ((ch = Read()) != '}');
                            sb.Append(ch);
                            ch = Read();
                        }
                    }
                    return list;
                };

                if (name.StartsWith("@charset", StringComparison.CurrentCultureIgnoreCase))
                {
                    encoding = ReadString().Trim(' ', start);
                    return null;
                }
                else if (name.StartsWith("@import", StringComparison.CurrentCultureIgnoreCase))
                {
                    return new CssImport(ReadString());
                }
                return fn == null ? new CssSelector(name, ReadAttribults()) : fn(name, ReadAttribults());



            }

            CssDocument doc;
            public CssDocument Parse()
            {
                if (doc != null) return doc;
                List<CssRule> list = new List<CssRule>();
                while (!over)
                {
                    var r = NextRule();
                    if (r != null)
                    {
                        list.Add(r);
                    }
                }
                doc = new CssDocument(list, encoding);
                return doc;
            }

        }

        public static CssDocument Load(string data)
        {
            CssParser parer = new CssParser(data);
            return parer.Parse();
        }
    }
}