source/nl.nlsw.Identifiers.cs

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// __ _ ____ _ _ _ _ ____ ____ ____ ____ ____ ___ _ _ ____ ____ ____
// | \| |=== |/\| |___ | |--- |=== ==== [__] |--- | |/\| |--| |--< |===
//
/// @file nl.nlsw.Identifiers.cs
/// @copyright Ernst van der Pols, Licensed under the EUPL-1.2-or-later
 
 
using System;
using System.Collections;
using System.Collections.Specialized;
using System.Globalization;
using System.Text;
using System.Text.RegularExpressions;
 
///
/// Classes of Uniform Resource Identifiers.
///
/// @author Ernst van der Pols
/// @date 2021-06-01
/// @requires .NET Framework 4.5
///
namespace nl.nlsw.Identifiers {
 
    ///
    /// A Uniform Resource Identifier for Geographic Locations
    ///
    /// @see https://tools.ietf.org/html/rfc5870
    /// @see https://en.wikipedia.org/wiki/Geo_URI_scheme
    /// @see http://geouri.org/
    ///
    public class GeoUri : ParameterizedUri {
        public static readonly string UriSchemeGeo = "geo";
        /// Department of Defence World Geodetic System 1984
        public const string WGS84 = "wgs84";
        /// RFC5780 compliant reg-ex for a GeoUri
        /// @note You cannot capture the individual pname[=pvalue] pairs at once
        public static Regex GeoRegex = new Regex(@"^geo:(?<lat>[\-]?\d+(\.\d+)?),(?<lon>[\-]?\d+(\.\d+)?)(,(?<alt>[\-]?\d+(\.\d+)?))?(;crs=(?<crs>[A-Za-z0-9\-]+))?(;u=(?<unc>\d+(\.\d+)?))?(;(?<par>(?<pname>[A-Za-z0-9\-]+)(=(?<pvalue>([!\$&-+\-\.0-:A-Z\[\]_a-z~]|%[0-9A-F]{2})+))?))*",
            RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
        /// These parameters are specifically handled on compare
        public static readonly string[] ExcludeKnownParameters = { "crs","unc" };
 
        private string _CRS;
        private double? _Altitude;
        private double _Latitude;
        private double _Longitude;
        private double? _Uncertainty;
 
        /// The altitude in meter above/below sea level
        public double? Altitude {
            get { return _Altitude; }
        }
 
        /// The used coordinate reference system
        public string CoordinateReferenceSystem {
            get { return _CRS ?? WGS84; }
        }
 
        /// The latitude in decimal degrees
        public double Latitude {
            get { return _Latitude; }
        }
 
        /// The longitude in decimal degrees
        public double Longitude {
            get { return _Longitude; }
        }
     
        /// The Uncertainty in meter around the coordinate point in each dimension
        /// with which the location is known. Might by not specified or unknown (null).
        public double? Uncertainty {
            get { return _Uncertainty; }
        }
 
        /// Initializing constructor
        public GeoUri(double latitude, double longitude, double? altitude = null, double? uncertainty = null, string crs = WGS84)
            : base(String.Format("{0}:{1},{2}{3}{4}{5}",UriSchemeGeo,latitude,longitude,
                ((altitude != null) ? String.Format(",{0}",altitude) : null),
                ((!String.IsNullOrEmpty(crs) && crs != WGS84) ? String.Format(";crs={0}",crs.ToLower()) : null),
                ((uncertainty != null) ? String.Format(";u={0}",uncertainty) : null))
                )
        {
            ParseGeoScheme(OriginalString);
        }
         
        /// Conversion constructor from string
        public GeoUri(string uri) : base(uri) {
            ParseGeoScheme(OriginalString);
        }
 
        /// Conversion constructor from base
        /// @note The combining constructor can be used with an empty relative uri to get the result.
        public GeoUri(System.Uri uri) : base(uri,(string)null) {
            ParseGeoScheme(OriginalString);
        }
         
        public override int GetHashCode() {
            // a simpler solution than using the Uri implementation
            return StringComparer.InvariantCultureIgnoreCase.GetHashCode(OriginalString);
            // return base.GetHashCode();
        }
         
        ///
        /// Equals
        ///
        /// Overrides default function (in Uri class)
        ///
        /// @pre <comparand> is an object of class GeoUri, Uri, or String
        ///
        /// @return true if objects have the same value, else false
        /// @exception none
        ///
        public override bool Equals(object comparand) {
            if ((object)comparand == null) {
                return false;
            }
            if ((object)this == (object)comparand) {
                return true;
            }
 
            GeoUri other = comparand as GeoUri;
 
            //
            // we allow comparisons of Uri and String objects only. If a string
            // is passed, convert to GeoUri. This is inefficient, but allows us to
            // canonicalize the comparand, making comparison possible
            //
            if ((object)other == null) {
                Uri u = comparand as Uri;
                string s = ((object)u != null) ? u.ToString() : (comparand as string);
                if ((object)s == null) {
                    return false;
                }
                Match m = GeoRegex.Match(s);
                if (!m.Success) {
                    return false;
                }
                // the string or Uri -is- a geo uri: create one (but catch exceptions)
                try {
                    other = new GeoUri(s);
                }
                catch (Exception) {
                    return false;
                }
            }
            // apply the RFC5870 comparison rules
            if (String.Compare(CoordinateReferenceSystem,other.CoordinateReferenceSystem,StringComparison.OrdinalIgnoreCase) != 0) {
                return false;
            }
            if (Latitude != other.Latitude || Altitude != other.Altitude || Uncertainty != other.Uncertainty) {
                return false;
            }
            if (CoordinateReferenceSystem == WGS84) {
                double lat = Latitude;
                if (Latitude != 90.0 && Latitude != -90.0) {
                    if (Longitude != other.Longitude) {
                        // this should never happen, since we have normalized the Longitude on creation
                        if ((Math.Abs(Longitude) != 180.0) || (Math.Abs(other.Longitude) != 180.0)) {
                            return false;
                        }
                    }
                }
            }
            else if (Longitude != other.Longitude) {
                return false;
            }
            // match additional parameters (with "binary" value compare)
            if (!HasEqualParameters(other,ExcludeKnownParameters,StringComparison.Ordinal)) {
                return false;
            }
            return true;
        }
         
        /// Parse the string for decoding the GEO URI scheme.
        /// @exception UriFormatException in case the scheme and string format does not comply
        /// @exception ArgumentOutOfRangeException in case any of the geo-properties is out of range
        private void ParseGeoScheme(string uri) {
            Match m = GeoRegex.Match(uri);
            if (!m.Success || (Scheme != UriSchemeGeo)) {
                Exception e = new UriFormatException("not a 'geo:' URI");
                e.Data.Add("uri",uri);
                throw e;
            }
            if (m.Groups["crs"].Success) {
                _CRS = m.Groups["crs"].Value.ToLower();
            }
            _Latitude = Convert.ToDouble(m.Groups["lat"].Value, CultureInfo.InvariantCulture);
            _Longitude = Convert.ToDouble(m.Groups["lon"].Value, CultureInfo.InvariantCulture);
            if (m.Groups["alt"].Success) {
                _Altitude = Convert.ToDouble(m.Groups["alt"].Value, CultureInfo.InvariantCulture);
            }
            if (m.Groups["unc"].Success) {
                _Uncertainty = Convert.ToDouble(m.Groups["unc"].Value, CultureInfo.InvariantCulture);
                if (_Uncertainty < 0) {
                    throw new ArgumentOutOfRangeException("uncertainty", m.Groups["unc"].Value);
                }
            }
            if (m.Groups["par"].Success) {
                ParseParameterCaptures(m.Groups["par"].Captures);
            }
            if (CoordinateReferenceSystem == WGS84) {
                if ((_Latitude < -90.0) || (_Latitude > 90.0)) {
                    throw new ArgumentOutOfRangeException("latitude", m.Groups["lat"].Value);
                }
                // first test user input
                if ((_Longitude < -180.0) || (_Longitude > 180.0)) {
                    throw new ArgumentOutOfRangeException("longitude", m.Groups["lon"].Value);
                }
                // normalize longitude in case of Pole-location
                if (_Latitude == 90.0 || _Latitude == -90.0) {
                    _Longitude = 0.0;
                }
            }
        }
 
        ///
        /// Tries to convert the specified URI string to a GEO URI
        public static bool TryCreate(string uriString, out GeoUri uri) {
            try {
                uri = new GeoUri(uriString);
            }
            catch (Exception) {
                uri = null;
                return false;
            }
            return true;
        }
 
        public static bool TryCreate(out GeoUri uri, double latitude, double longitude, double? altitude = null, double? uncertainty = null, string crs = WGS84) {
            try {
                uri = new GeoUri(latitude,longitude,altitude,uncertainty,crs);
            }
            catch (Exception) {
                uri = null;
                return false;
            }
            return true;
        }
    }
 
    ///
    /// A Uniform Resource Identifier for addressing Internet mail resources.
    ///
    /// The 'mailto' URI scheme is used to identify resources that are reached using Internet mail, e.g. a mailbox.
    /// In its simplest form, a 'mailto' URI contains an Internet mail address. For interactions that require
    /// message headers or message bodies to be specified, the 'mailto' URI scheme also allows providing mail
    /// header fields and the message body.
    ///
    /// @note Althoug the mailto-URI has parameters in the form of header fields, the MailtoUri class is not
    /// a ParameterizedUri. The header fields are supported by the Query parameters of the URI Generic Syntax.
    ///
    /// @note The scope of MailtoUri currently is only the support of a single mail address.
    ///
    /// @see https://tools.ietf.org/html/rfc6068
    ///
    public class MailtoUri : Uri {
        // public static readonly string UriSchemeMailto = "mailto";
        /// match a single internet email address
        /// atext = [!#-'\*\+\-/-9=\?A-Z\^-~]
        /// qtext = printables-excl-'\' | obs-qtext (obs-qtext laten we weg)
        /// local = ([atext]+ (. [atext]+)*) | ("([!#-\[\]-~]|(\\[\x21-\x7E\t ]))*")
        public static readonly Regex EmailAddressRegex = new Regex(@"^(?<local>(?<atom>[!#-'\*\+\-/-9=\?A-Z\^-~]+(\.[!#-'\*\+\-/-9=\?A-Z\^-~]+)*)|(?<qs>\x22([!#-\[\]-~]|(\\[\x21-\x7E\t ]))*\x22))@(?<domain>(?<atom>[!#-'\*\+\-/-9=\?A-Z\^-~]+(\.[!#-'\*\+\-/-9=\?A-Z\^-~]+)*)|(\[[!-Z\^-~]*\]))",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
        /// RFC6068 compliant reg-ex for a MailtoUri (partly)
        public static readonly Regex MailtoRegex = new Regex(@"^mailto:(?<local>(?<latom>[!#-'\*\+\-/-9=\?A-Z\^-~]+(\.[!#-'\*\+\-/-9=\?A-Z\^-~]+)*)|(?<qs>\x22([!#-\[\]-~]|(\\[\x21-\x7E\t ]))*\x22))@(?<domain>(?<datom>[!#-'\*\+\-/-9=\?A-Z\^-~]+(\.[!#-'\*\+\-/-9=\?A-Z\^-~]+)*)|(\[[!-Z\^-~]*\]))",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
 
        /// The (unquoted) local part of the mail address
        private string _LocalPart;
        /// The domain of the mail address
        private string _Domain;
         
        /// The mail address
        public string Address {
            get {
                return String.Concat(LocalPart,"@",Authority);
            }
        }
 
        /// The (unquoted?) local part of the mail address
        public string LocalPart {
            get { return _LocalPart; }
        }
 
        /// The domain of the mail address
        public string Domain {
            // could use Authority
            get { return _Domain; }
        }
         
        /// Initializing constructor
        /// @todo enquoting of localPart
        /// @todo encoding of international domain names
        public MailtoUri(string localPart, string domain)
            : base(String.Format("{0}:{1}@{2}",UriSchemeMailto,System.Uri.EscapeDataString(localPart),domain))
        {
            ParseMailtoScheme(OriginalString);
        }
         
        /// Conversion constructor from string
        public MailtoUri(string uriString) : base(uriString) {
            ParseMailtoScheme(OriginalString);
        }
 
        /// Conversion constructor from base
        /// @note The combining constructor can be used with an empty relative uri to get the result.
        public MailtoUri(System.Uri uri) : base(uri,(string)null) {
            ParseMailtoScheme(OriginalString);
        }
         
        /// Parse the string for decoding the tel URI scheme.
        /// @exception UriFormatException in case the scheme and string format does not comply
        /// @exception ArgumentOutOfRangeException in case any of the tel-properties is out of range
        private void ParseMailtoScheme(string uriString) {
            Match m = MailtoRegex.Match(uriString);
            if (!m.Success || (Scheme != UriSchemeMailto)) {
                Exception e = new UriFormatException("not a 'mailto:' URI");
                e.Data.Add("uri",uriString);
                throw e;
            }
            if (m.Groups["latom"].Success) {
                _LocalPart = UnescapeDataString(m.Groups["latom"].Value);
            }
            else if (m.Groups["qs"].Success) {
                _LocalPart = UnescapeDataString(m.Groups["qs"].Value);
            }
            _Domain = m.Groups["domain"].Value;
        }
 
        ///
        /// Tries to convert the specified string to a mailto URI.
        /// First is tried to match a mailto-URI.
        /// Second is tried to match an Internet mail address.
        public static bool TryCreate(string value, out MailtoUri uri) {
            try {
                if (!String.IsNullOrEmpty(value)) {
                    if (value.StartsWith("mailto:")) {
                        uri = new MailtoUri(value);
                        return true;
                    }
                    else {
                        Match m = EmailAddressRegex.Match(value);
                        uri = new MailtoUri(m.Groups["local"].Value,m.Groups["domain"].Value);
                        return true;
                    }
                }
            }
            catch (Exception) {
            }
            uri = null;
            return false;
        }
 
        public static bool TryCreate(out MailtoUri uri, string localPart, string domain) {
            try {
                uri = new MailtoUri(localPart,domain);
            }
            catch (Exception) {
                uri = null;
                return false;
            }
            return true;
        }
    }
     
    ///
    /// An abstract base class of Uniform Resource Identifiers that may carry a single set of parameters.
    /// Examples of these are the TEL and GEO URIs.
    ///
    /// A parameter consists of semi-colon delimiter, a parameter name, optionally followed by an equal
    /// sign and a parameter value.
    ///
    /// @note GetHashCode() is overridden to implement a simpler algorithm than in the System.Uri class,
    /// usually sufficient for this class of URIs.
    ///
    /// @see https://tools.ietf.org/html/rfc3986 (URI Generic Syntax, only references parameter usage)
    ///
    public class ParameterizedUri : Uri {
 
        /// StringDictionary uses CaseInsensitive key compare
        private StringDictionary _Parameters;
 
        /// Any additional parameters present
        public bool HasParameters {
            get { return (_Parameters != null) && (_Parameters.Count > 0); }
        }
         
        /// Tests whether the other uri has exactly the same parameters.
        /// Parameter names are treated case-insensitive, but the values are compared case-sensitive,
        /// actually by ordinal.
        /// @param other the other URI
        /// @param exclude these parameters are compared separately.
        /// @param valueComparison the type of comparison of the values
        ///
        public bool HasEqualParameters(ParameterizedUri other,
                string[] exclude, StringComparison valueComparison = StringComparison.OrdinalIgnoreCase) {
            // match additional parameters
            if (HasParameters ^ other.HasParameters) {
                return false;
            }
            if (HasParameters) {
                // match each individual parameter (with "binary" value compare)
                foreach (DictionaryEntry entry in Parameters) {
                    if (!Array.Exists(exclude, s => s == (string)entry.Key)) {
                        if (String.Compare((string)entry.Value,other.Parameters[(string)entry.Key],valueComparison) != 0) {
                            return false;
                        }
                    }
                }
            }
            return true;
        }
 
        /// Additional parameters.
        public StringDictionary Parameters {
            get { return _Parameters; }
        }
         
        public ParameterizedUri(string uriString) : base(uriString) {
        }
 
        public ParameterizedUri(string uriString, UriKind uriKind) : base(uriString,uriKind) {
        }
 
        public ParameterizedUri(System.Uri baseUri, string relativeUri) : base(baseUri,relativeUri) {
        }
 
        public ParameterizedUri(System.Uri baseUri, System.Uri relativeUri) : base(baseUri,relativeUri) {
        }
 
        public override int GetHashCode() {
            // a simpler solution than using the Uri implementation
            return StringComparer.InvariantCultureIgnoreCase.GetHashCode(OriginalString);
            // return base.GetHashCode();
        }
 
        /// Get the value of the specified parameter.
        public string GetParameter(string name) {
            return _Parameters == null ? null : _Parameters[name];
        }
 
        /// Parse the regular expression-captured parameters from the URI to a dictionary of strings.
        /// The captures should not contain the semi-colon delimiter, only name and optionally equals sign and value.
        /// Parameter names SHOULD be lower case, so we lower them to be sure.
        /// @exception ArgumentException A parameter with the same key already exists.
        protected void ParseParameterCaptures(CaptureCollection captures) {
            if (captures != null && captures.Count > 0) {
                if (_Parameters == null) {
                    _Parameters = new StringDictionary();
                }
                foreach (Capture c in captures) {
                    // look for a value
                    int eq = c.Value.IndexOf('=');
                    if (eq < 0) {
                        _Parameters.Add(c.Value.ToLower(), null);
                    }
                    else {
                        _Parameters.Add(c.Value.Substring(0,eq).ToLower(), System.Uri.UnescapeDataString(c.Value.Substring(eq+1)));
                    }
                }
            }
        }
    }
 
    ///
    /// A Uniform Resource Identifier for Telephone Numbers.
    ///
    /// A telephone number is an identifier for a termination point in the telephone network.
    /// The "tel"-scheme URI is specified in RFC3966.
    ///
    /// ITU-T E.123 recommends the use of space characters as visual separators in printed telephone numbers,
    /// but a "tel" URI MUST NOT use spaces in visual separators to avoid excessive escaping. You can convert E.123 numbers
    /// with NormalizeNumber().
    ///
    /// @see https://tools.ietf.org/html/rfc3966
    ///
    public class TelUri : ParameterizedUri {
        public static readonly string UriSchemeTel = "tel";
        /// match global and local numbers and the optional parameters after the number
        /// @note You cannot capture the individual pname[=pvalue] pairs at once
        /// RFC3966 compliant reg-ex for a TelUri
        public static readonly Regex TelRegex = new Regex(@"^tel:((?<global>\+[0-9\-\.\(\)]*[0-9][0-9\-\.\(\)]*)|(?<local>[0-9A-F\*\#\-\.\(\)]*[0-9A-F\*\#][0-9A-F\*\#\-\.\(\)]*))(;(?<par>[^;]+))*",
            RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
        /// A regex for matching or replacing visual separators of a phone number.
        public static readonly Regex ReplaceVisualSeparatorsRegex = new Regex(@"[\-\.\(\)]",
            RegexOptions.Compiled|RegexOptions.CultureInvariant);
        public static readonly Regex GlobalNumberRegex = new Regex(@"^(?<global>\+[0-9\-\.\(\)]*[0-9][0-9\-\.\(\)]*)",
            RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
        /// These parameters are specifically handled on compare
        public static readonly string[] ExcludeKnownParameters = { "phone-context" };
             
        /// Globally unique numbers are identified by the leading "+" character.
        /// Global numbers MUST be composed with the country (CC) and national (NSN) numbers as
        /// specified in E.123 [E.123] and E.164 [E.164].
        /// Globally unique numbers are unambiguous everywhere in the world and SHOULD be used.
        private bool _IsGlobal;
        /// The global-number-digits or local-number-digits of the phone number, with the visual separators removed.
        /// Includes global number prefix (if any) and visual separators.
        private string _Number;
        /// The normalized phone context descriptor of a local number.
        private string _Context;
 
        /// The global-number-digits or local-number-digits of the phone number, with any visual separators removed.
        public string Number {
            get { return _Number; }
        }
 
        /// Get the phone extension number
        public string Extension {
            get { return GetParameter("ext"); }
        }
         
        /// Checks if the Local Number Phone Context is a domain name (return value true) or a global number (return value false).
        /// If the phone number IsGlobal, false is returned also.
        public bool HasDomainNameContext {
            get { return !IsGlobal && !GlobalNumberRegex.Match(PhoneContext).Success; }
        }
 
        /// Is the number a global telephone number?
        /// Globally unique numbers are identified by the leading "+" character.
        /// Global numbers MUST be composed with the country (CC) and national (NSN) numbers as specified in E.123 and E.164.
        /// Globally unique numbers are unambiguous everywhere in the world.
        public bool IsGlobal {
            get { return _IsGlobal; }
        }
 
        ///
        /// Get the normalized phone context of the local number. Use GetParameter("phone-context") to get
        /// the non-normalized phone context parameter.
        ///
        /// Local numbers MUST have a 'phone-context' parameter that identifies the scope of their validity.
        /// The parameter MUST be chosen to identify the local context within which the number is unique unambiguously.
        /// Thus, the combination of the descriptor in the 'phone-context' parameter and local number is again globally unique.
        /// The parameter value is defined by the assignee of the local number. It does NOT indicate a prefix that turns
        /// the local number into a global (E.164) number.
        ///
        public string PhoneContext {
            get {
                return _IsGlobal ? null : _Context;
            }
        }
         
        /// Get the ISDN aubaddress
        public string Subaddress {
            get { return GetParameter("isub"); }
        }
 
        /// Initializing constructor
        /// @note Local phone numbers need a PhoneContext descriptor.
        public TelUri(string number, string phoneContext = null)
            : base(String.Format("{0}:{1}{2}",UriSchemeTel,number,
                ((phoneContext == null) ? null : String.Format(";phone-context={0}",phoneContext))
                ))
        {
            ParseTelScheme(OriginalString);
        }
         
        /// Conversion constructor from string
        public TelUri(string uriString) : base(uriString) {
            ParseTelScheme(OriginalString);
        }
 
        /// Conversion constructor from base
        /// @note The combining constructor can be used with an empty relative uri to get the result.
        public TelUri(System.Uri uri) : base(uri,(string)null) {
            ParseTelScheme(OriginalString);
        }
         
        ///
        /// Equals
        ///
        /// Overrides default function (in Uri class)
        ///
        /// @pre <comparand> is an object of class GeoUri, Uri, or String
        ///
        /// @return true if objects have the same value, else false
        /// @exception none
        ///
        public override bool Equals(object comparand) {
            if ((object)comparand == null) {
                return false;
            }
            if ((object)this == (object)comparand) {
                return true;
            }
 
            TelUri other = comparand as TelUri;
 
            //
            // we allow comparisons of Uri and String objects only. If a string
            // is passed, convert to TelUri. This is inefficient, but allows us to
            // canonicalize the comparand, making comparison possible
            //
            if ((object)other == null) {
                Uri u = comparand as Uri;
                string s = ((object)u != null) ? u.ToString() : (comparand as string);
                if ((object)s == null) {
                    return false;
                }
                Match m = TelRegex.Match(s);
                if (!m.Success) {
                    return false;
                }
                // the string or Uri -is- a tel uri: create one (but catch exceptions)
                try {
                    other = new TelUri(s);
                }
                catch (Exception) {
                    return false;
                }
            }
            // apply the RFC3966 comparison rules
            if (IsGlobal ^ other.IsGlobal) {
                return false;
            }
            if (String.Compare(Number,other.Number,StringComparison.OrdinalIgnoreCase) != 0) {
                return false;
            }
            if (!IsGlobal) {
                // compare the PhoneContext
                if (PhoneContext != other.PhoneContext) {
                    return false;
                }
            }
            // match additional parameters
            if (!HasEqualParameters(other,ExcludeKnownParameters,StringComparison.OrdinalIgnoreCase)) {
                return false;
            }
            return true;
        }
 
        /// Override required because override of Equals
        public override int GetHashCode() {
            return base.GetHashCode();
        }
         
        ///
        /// Convert an ITU-T E.123 telephone number, using SPACE characters as visual separators,
        /// to a "tel" URI format number, using a HYPHEN-MINUS as visual separator.
        ///
        public static string NormalizeNumber(string number) {
            return number == null ? null : number.Replace(' ','-');
        }
 
        /// Parse the string for decoding the tel URI scheme.
        /// @exception UriFormatException in case the scheme and string format does not comply
        /// @exception ArgumentOutOfRangeException in case any of the tel-properties is out of range
        private void ParseTelScheme(string uriString) {
            Match m = TelRegex.Match(uriString);
            if (!m.Success || (Scheme != UriSchemeTel)) {
                Exception e = new UriFormatException("not a 'tel:' URI");
                e.Data.Add("uri",uriString);
                throw e;
            }
            if (m.Groups["global"].Success) {
                _IsGlobal = true;
                _Number = ReplaceVisualSeparatorsRegex.Replace(m.Groups["global"].Value,"");
            }
            else if (m.Groups["local"].Success) {
                _IsGlobal = false;
                _Number = ReplaceVisualSeparatorsRegex.Replace(m.Groups["local"].Value,"");
            }
            if (m.Groups["par"].Success) {
                ParseParameterCaptures(m.Groups["par"].Captures);
                // check that ext and isub do not appear both
                if (Extension != null && Subaddress != null) {
                    Exception e = new UriFormatException("a phone extension number and an ISDN subaddress are mutually exclusive");
                    e.Data.Add("uri",uriString);
                    throw e;
                }
            }
            if (!IsGlobal) {
                _Context = GetParameter("phone-context");
                if (String.IsNullOrEmpty(_Context)) {
                    Exception e = new UriFormatException("a local phone number requires a 'phone-context' parameter");
                    e.Data.Add("uri",uriString);
                    throw e;
                }
                if (GlobalNumberRegex.Match(_Context).Success) {
                    // remove the visual separators
                    _Context = ReplaceVisualSeparatorsRegex.Replace(_Context,"");
                }
                else {
                    // _Context should be a domain name, normalize it to lower case for comparison
                    _Context = _Context.ToLower();
                }
            }
        }
 
        ///
        /// Tries to convert the specified string to a tel URI.
        /// - try a "tel" URI string
        /// - try a global telephone number
        public static bool TryCreate(string value, out TelUri uri) {
            try {
                if (!String.IsNullOrEmpty(value)) {
                    if (value.StartsWith("tel:")) {
                        uri = new TelUri(value);
                        return true;
                    }
                    else {
                        // try to match a (global) telephone number that we can convert into a telephone URI.
                        // For local numbers, we need a phone-context to be specified; to complex for this code.
                        // space is not allowed in a URI, but regularly used as visual separator: replace with allowed visual separator '-'
                        string val = NormalizeNumber(value);
                        if (GlobalNumberRegex.Match(val).Success) {
                            uri = new TelUri(val,null);
                            return true;
                        }
                    }
                }
            }
            catch (Exception) {
            }
            uri = null;
            return false;
        }
 
        public static bool TryCreate(out TelUri uri, string number, string phoneContext = null) {
            try {
                uri = new TelUri(number,phoneContext);
            }
            catch (Exception) {
                uri = null;
                return false;
            }
            return true;
        }
    }
     
    ///
    /// A base class of Uniform Resource Identifiers that provides an object representation of a URI.
    ///
    /// The main reason for this override of System.Uri is the behaviour of System.Uri.ToString(),
    /// which returns not a URI, but a (partly) unescaped display string.
    ///
    /// @see https://tools.ietf.org/html/rfc3986 (URI Generic Syntax)
    ///
    public class Uri : System.Uri {
        /// Match any percent-encoding with one or two lower case hex-digits 'a'..'f'.
        public static readonly Regex PercentHexNormalizeRegex = new Regex(@"%([a-z][0-9A-Za-z]|[0-9A-Fa-z][a-z])",
            RegexOptions.Compiled | RegexOptions.CultureInvariant);
        /// A regex for matching or replacing series of one or more white space characters.
        public static readonly Regex WhiteSpacesRegex = new Regex(@"\s+",
            RegexOptions.Compiled | RegexOptions.CultureInvariant);
 
        ///
        /// Default constructor.
        /// An empty URI is only possible as relative URI.
        public Uri() : base(null,UriKind.Relative) {
        }
 
        public Uri(string uriString) : base(uriString) {
        }
 
        public Uri(string uriString, UriKind uriKind) : base(uriString,uriKind) {
        }
 
        public Uri(System.Uri baseUri, string relativeUri) : base(baseUri,relativeUri) {
        }
 
        public Uri(System.Uri baseUri, System.Uri relativeUri) : base(baseUri,relativeUri) {
        }
/*
        /// A static short-cut to Uri.Equals
        public static bool operator == (Uri uri1, Uri uri2) {
            if ((object)uri1 == (object)uri2) {
                return true;
            }
            if ((object)uri1 == null || (object)uri2 == null) {
                return false;
            }
            return uri2.Equals(uri1);
        }
 
        /// A static short-cut to !Uri.Equals
        public static bool operator != (Uri uri1, Uri uri2) {
            if ((object)uri1 == (object)uri2) {
                return false;
            }
            if ((object)uri1 == null || (object)uri2 == null) {
                return true;
            }
            return !uri2.Equals(uri1);
        }
*/
        ///
        /// Normalize a percent-encoded string: convert any lower-case
        /// hexadecimal digits 'a'..'f' to 'A'..'F'.
        ///
        /// @see https://tools.ietf.org/html/rfc3986#section-2.1
        ///
        public static string NormalizePercentEncoding(string encodedString) {
            if (!String.IsNullOrEmpty(encodedString)) {
                return PercentHexNormalizeRegex.Replace(encodedString,delegate(Match m){
                    string lower = m.ToString();
                    char[] upper = {
                        lower[0],
                        (char.IsLower(lower[1]) ? char.ToUpper(lower[1]) : lower[1]),
                        (char.IsLower(lower[2]) ? char.ToUpper(lower[2]) : lower[2])
                    };
                    return new string(upper);
                });
            }
            return encodedString;
        }
 
        public override string ToString() {
            // @todo OriginalString might be replaced with GetComponents() ?
            return IsAbsoluteUri ? AbsoluteUri : OriginalString;
        }
 
        ///
        /// Tries to convert the specified URI string to a URI
        public static bool TryCreate(string uriString, out Uri uri) {
            try {
                uri = new Uri(uriString);
            }
            catch (Exception) {
                uri = null;
                return false;
            }
            return true;
        }
 
        ///
        /// Tries to convert the specified URI string to a URI
        public static bool TryCreate(string uriString, UriKind uriKind, out Uri uri) {
            try {
                uri = new Uri(uriString,uriKind);
            }
            catch (Exception) {
                uri = null;
                return false;
            }
            return true;
        }
    }
 
    ///
    /// A Uniform Resource Identifier for Uniform Resource Names.
    ///
    /// A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI)
    /// that is assigned under the "urn" URI scheme and a particular URN
    /// namespace, with the intent that the URN will be a persistent,
    /// location-independent resource identifier.
    /// The "urn"-scheme URI is specified in RFC8141.
    ///
    /// @todo support r-, q-, and f-components
    ///
    /// @see https://tools.ietf.org/html/rfc8141 (Uniform Resource Names)
    /// @see https://tools.ietf.org/html/rfc2141 (URN Syntax, obsolete)
    /// @see https://tools.ietf.org/html/rfc3986 (URI Generic Syntax)
    /// @see https://tools.ietf.org/html/rfc4122 (UUID namespace registration)
    ///
    public class UrnUri : Uri {
        public static readonly string UriSchemeUrn = "urn";
        public static readonly string UuidNamespace = "uuid";
        public static readonly string PublicIdNamespace = "publicid";
 
        /// Match the URI components of a URN
        /// @see https://www.ietf.org/rfc/rfc2141.txt (obsolete)
        /// @see https://tools.ietf.org/html/rfc8141
        public static Regex UrnRegex = new Regex(@"^(?i:urn:)(?<nid>[A-Za-z0-9][A-Za-z0-9\-]{0,30}[A-Za-z0-9]):(?<nss>[^\?#]+)(?<rq>\?[^#]+)?(?<f>#.*)?",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
        /// Match the URI components of a UUID URN (@todo rqf)
        public static Regex UuidUrnRegex = new Regex(@"^(?i:urn:)(?i:uuid:)(?<uuid>.+)",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
        /// Match the UUID format conform RFC4122
        /// @note for further decomposition: determine the UUID Variant from the clock_seq_reserved field
        /// and for RFC4122 variant "1 0 x" determine Version from the time_high_version field
        public static Regex UuidRegex = new Regex(@"^(?<time_low>[0-9a-fA-F]{8})-(?<time_mid>[0-9a-fA-F]{4})-(?<time_high_version>[0-9a-fA-F]{4})-(?<clock_seq_reserved>[0-9a-fA-F]{4})-(?<node>[0-9a-fA-F]{12})$",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
        /// Match the URI components of a PublicIdentifier URN (@todo rqf)
        public static Regex PublicIdUrnRegex = new Regex(@"^(?i:urn:)(?i:publicid:)(?<publicid>.+)",
            RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture);
        /// XML PubidChar ::= #x20 | #xD | #xA | [a-zA-Z0-9] | [-'()+,./:=?;!*#@$_%]
        /// @note We included HT as valid PubidChar, since during normalization HT is converted to SP,
        /// just like CR and LF, so it is odd not to allow HT
        public static Regex PublicIdentifierRegex = new Regex(@"[\t\r\n\x20!#$%'-;=\?-Z_a-z]+",
            RegexOptions.Compiled | RegexOptions.CultureInvariant);
 
        /// The Namespace Identifier.
        private string _NID;
        /// The Namespace Specific String.
        private string _NSS;
 
        /// The normalized Namespace Identifier.
        public string NID {
            get { return _NID; }
        }
 
        /// The normalized Namespace Specific String.
        public string NSS {
            get { return _NSS; }
        }
 
        /// Initializing constructor
        /// @param nid the Namespace Identifier
        /// @param nss the Namespace Specific String
        public UrnUri(string nid, string nss)
            : base(String.Format("{0}:{1}:{2}",UriSchemeUrn,nid,nss))
        {
            ParseUrnScheme(OriginalString);
        }
         
        /// Conversion constructor from string
        public UrnUri(string uriString) : base(uriString) {
            ParseUrnScheme(OriginalString);
        }
 
        /// Conversion constructor from base
        /// @note The combining constructor can be used with an empty relative uri to get the result.
        public UrnUri(System.Uri uri) : base(uri,(string)null) {
            ParseUrnScheme(OriginalString);
        }
         
        ///
        /// Equals
        ///
        /// Overrides default function (in Uri class) to determine URN-equivalence
        /// according to RFC8141.
        ///
        /// @pre <comparand> is an object of class UrnUri, Uri, or String
        ///
        /// @return true if objects have the same value, else false
        /// @exception none
        ///
        public override bool Equals(object comparand) {
            if ((object)comparand == null) {
                return false;
            }
            if ((object)this == (object)comparand) {
                return true;
            }
 
            UrnUri other = comparand as UrnUri;
 
            //
            // we allow comparisons of Uri and String objects only. If a string
            // is passed, convert to UrnUri. This is inefficient, but allows us to
            // canonicalize the comparand, making comparison possible
            //
            if ((object)other == null) {
                Uri u = comparand as Uri;
                string s = ((object)u != null) ? u.ToString() : (comparand as string);
                if ((object)s == null) {
                    return false;
                }
                // try to create an UrnUri from the string or Uri (catch exceptions)
                try {
                    other = new UrnUri(s);
                }
                catch (Exception) {
                    return false;
                }
            }
            // apply the RFC8141 comparison rules
            if (String.Compare(NID,other.NID,StringComparison.Ordinal) != 0) {
                return false;
            }
            if (String.Compare(NSS,other.NSS,StringComparison.Ordinal) != 0) {
                return false;
            }
            return true;
        }
 
        /// Override required because override of Equals
        public override int GetHashCode() {
            return base.GetHashCode();
        }
 
        /// Get the universally unique identifier (UUID) as string from the specified URI.
        /// @param uri the URI to get the UUID of
        /// @returns null the UUID or null if the uri does not contain a UUID.
        public static string GetUUIDString(Uri uri) {
            UrnUri urn = uri as UrnUri;
            if (urn != null && urn.NID == UuidNamespace) {
                return urn.NSS;
            }
            return null;
        }
 
        /// Get the public identifier.
        /// @returns null if the Identifier is not a public identifier.
        public string PublicIdentifier {
            get {
                if (NID == PublicIdNamespace) {
                    return UntranscribePublicIdentifier(NSS);
                }
                return null;
            }
        }
 
        /// Get the universally unique identifier.
        /// @returns null if the Identifier is not a UUID.
        public Guid? UUID {
            get {
                if (NID == UuidNamespace) {
                    return new System.Guid(NSS);
                }
                return null;
            }
        }
 
        /// Normalize a public identifier as specified in RFC3151 (or as for xml:id):
        /// compress white space to a single space and trim leading and trailing white space.
        /// @see https://www.w3.org/TR/xml-id/#id-avn
        public static string NormalizePublicIdentifier(string value) {
            return WhiteSpacesRegex.Replace(value," ").Trim();
        }
 
        /// Transcribe a public identifier as specified in RFC3151:
        /// encode a public identifier for storage in a URI.
        /// @pre the identifier is normalized
        /// @see https://www.ietf.org/rfc/rfc3151.txt
        public static string TranscribePublicIdentifier(string value) {
            StringBuilder sb = new StringBuilder(value.Length);
            for (int i = 0; i < value.Length; i++) {
                switch (value[i]) {
                case ' ': sb.Append('+'); break;
                case '+': sb.Append("%2B"); break;
                case '/':
                    if (((i+1) < value.Length) && (value[i+1] == '/')) {
                        sb.Append(':');
                        i++;
                    }
                    else {
                        sb.Append("%2F");
                    }
                    break;
                case ':':
                    if (((i+1) < value.Length) && (value[i+1] == ':')) {
                        sb.Append(';');
                        i++;
                    }
                    else {
                        sb.Append("%3A");
                    }
                    break;
                case ';': sb.Append("%3B"); break;
                case '\x27': sb.Append("%27"); break;
                case '?': sb.Append("%3F"); break;
                case '#': sb.Append("%23"); break;
                case '%': sb.Append("%25"); break;
                default: sb.Append(value[i]); break;
                }
            }
            return sb.ToString();
        }
 
        /// Decode the URI-representation of a public identifier as
        /// specified in RFC3151 back into a public identifier.
        /// @see https://www.ietf.org/rfc/rfc3151.txt
        public static string UntranscribePublicIdentifier(string value) {
            StringBuilder sb = new StringBuilder(value);
            sb.Replace(":","//");
            sb.Replace(";","::");
            sb.Replace('+',' ');
            return System.Uri.UnescapeDataString(sb.ToString());
        }
         
        /// Create a new Universally Unique Identifier (UUID) URI for the specified uuid.
        /// If no uuid is specified, a new one in generated.
        public static UrnUri NewUuidUrnUri(System.Guid? uuid = null) {
            if (uuid == null) {
                uuid = System.Guid.NewGuid();
            }
            return new UrnUri(UuidNamespace,uuid.ToString());
        }
 
        /// Parse the string for decoding the urn URI scheme.
        /// @exception UriFormatException in case the scheme and string format does not comply
        /// @exception ArgumentOutOfRangeException in case any of the urn-properties is out of range
        private void ParseUrnScheme(string uriString) {
            Match m = UrnRegex.Match(uriString);
            if (!m.Success || (Scheme != UriSchemeUrn)) {
                Exception e = new UriFormatException("not a 'urn:' URI");
                e.Data.Add("uri",uriString);
                throw e;
            }
            if (m.Groups["nid"].Success) {
                // normalize to lower case for URN equivalence
                _NID = m.Groups["nid"].Value.ToLower();
            }
            if (m.Groups["nss"].Success) {
                // normalize any percent-encoded characters in the NSS (that is, all character
                // triplets that match the <pct-encoding> production found in
                // Section 2.1 of the base URI specification [RFC3986]), by
                // conversion to upper case for the digits A-F.
                _NSS = NormalizePercentEncoding(m.Groups["nss"].Value);
            }
            // @todo rq and f parsing
        }
 
        ///
        /// Tries to convert the specified string to a urn URI.
        /// - try a "urn" URI string
        /// - try a GUID string to create a "urn:uuid" URI
        /// - try a Public Identifier string to create a "urn:publicid" URI
        public static bool TryCreate(string value, out UrnUri uri) {
            try {
                if (!String.IsNullOrEmpty(value)) {
                    if (value.StartsWith("urn:")) {
                        uri = new UrnUri(value);
                        return true;
                    }
                    else {
                        // try to match a UUID
                        Guid uuid;
                        if (System.Guid.TryParse((string)value,out uuid)) {
                            uri = NewUuidUrnUri(uuid);
                            return true;
                        }
                        else {
                            // let us try matching a (Formal) Public Identifier
                            // @note most URIs like a data-URI also qualify as PublicIdentfier!
                            // if we don't want those encoded as UrnUri, we need to recognize a URI first!!
                            string id = NormalizePublicIdentifier((string)value);
                            if (PublicIdentifierRegex.Match(id).Success) {
                                id = TranscribePublicIdentifier(id);
                                uri = new UrnUri(PublicIdNamespace, id );
                                return true;
                            }
                        }
                    }
                }
            }
            catch (Exception) {
            }
            uri = null;
            return false;
        }
 
        public static bool TryCreate(out UrnUri uri, string nid, string nss) {
            try {
                uri = new UrnUri(nid,nss);
            }
            catch (Exception) {
                uri = null;
                return false;
            }
            return true;
        }
    }
}