context: //
  // Options.cs
  //
  // Authors:
  //  Jonathan Pryor <jpryor@novell.com>
  //
  // Copyright (C) 2008 Novell (http://www.novell.com)
  //
  // Permission is hereby granted, free of charge, to any person obtaining
  // a copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to
  // permit persons to whom the Software is furnished to do so, subject to
  // the following conditions:
  // 
  // The above copyright notice and this permission notice shall be
  // included in all copies or substantial portions of the Software.
  // 
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  //
  
  // Compile With:
  //   gmcs -debug+ -r:System.Core Options.cs -o:NDesk.Options.dll
  //   gmcs -debug+ -d:LINQ -r:System.Core Options.cs -o:NDesk.Options.dll
  //
  // The LINQ version just changes the implementation of
  // OptionSet.Parse(IEnumerable<string>), and confers no semantic changes.
  
  //
  // A Getopt::Long-inspired option parsing library for C#.
  //
  // NDesk.Options.OptionSet is built upon a key/value table, where the
  // key is a option format string and the value is a delegate that is 
  // invoked when the format string is matched.
  //
  // Option format strings:
  //  Regex-like BNF Grammar: 
  //    name: .+
  //    type: [=:]
  //    sep: ( [^{}]+ | '{' .+ '}' )?
  //    aliases: ( name type sep ) ( '|' name type sep )*
  // 
  // Each '|'-delimited name is an alias for the associated action.  If the
  // format string ends in a '=', it has a required value.  If the format
  // string ends in a ':', it has an optional value.  If neither '=' or ':'
  // is present, no value is supported.  `=' or `:' need only be defined on one
  // alias, but if they are provided on more than one they must be consistent.
  //
  // Each alias portion may also end with a "key/value separator", which is used
  // to split option values if the option accepts > 1 value.  If not specified,
  // it defaults to '=' and ':'.  If specified, it can be any character except
  // '{' and '}' OR the *string* between '{' and '}'.  If no separator should be
  // used (i.e. the separate values should be distinct arguments), then "{}"
  // should be used as the separator.
  //
  // Options are extracted either from the current option by looking for
  // the option name followed by an '=' or ':', or is taken from the
  // following option IFF:
  //  - The current option does not contain a '=' or a ':'
  //  - The current option requires a value (i.e. not a Option type of ':')
  //
  // The `name' used in the option format string does NOT include any leading
  // option indicator, such as '-', '--', or '/'.  All three of these are
  // permitted/required on any named option.
  //
  // Option bundling is permitted so long as:
  //   - '-' is used to start the option group
  //   - all of the bundled options are a single character
  //   - at most one of the bundled options accepts a value, and the value
  //     provided starts from the next character to the end of the string.
  //
  // This allows specifying '-a -b -c' as '-abc', and specifying '-D name=value'
  // as '-Dname=value'.
  //
  // Option processing is disabled by specifying "--".  All options after "--"
  // are returned by OptionSet.Parse() unchanged and unprocessed.
  //
  // Unprocessed options are returned from OptionSet.Parse().
  //
  // Examples:
  //  int verbose = 0;
  //  OptionSet p = new OptionSet ()
  //    .Add ("v", v => ++verbose)
  //    .Add ("name=|value=", v => Console.WriteLine (v));
  //  p.Parse (new string[]{"-v", "--v", "/v", "-name=A", "/name", "B", "extra"});
  //
  // The above would parse the argument string array, and would invoke the
  // lambda expression three times, setting `verbose' to 3 when complete.  
  // It would also print out "A" and "B" to standard output.
  // The returned array would contain the string "extra".
  //
  // C# 3.0 collection initializers are supported and encouraged:
  //  var p = new OptionSet () {
  //    { "h|?|help", v => ShowHelp () },
  //  };
  //
  // System.ComponentModel.TypeConverter is also supported, allowing the use of
  // custom data types in the callback type; TypeConverter.ConvertFromString()
  // is used to convert the value option to an instance of the specified
  // type:
  //
  //  var p = new OptionSet () {
  //    { "foo=", (Foo f) => Console.WriteLine (f.ToString ()) },
  //  };
  //
  // Random other tidbits:
  //  - Boolean options (those w/o '=' or ':' in the option format string)
  //    are explicitly enabled if they are followed with '+', and explicitly
  //    disabled if they are followed with '-':
  //      string a = null;
  //      var p = new OptionSet () {
  //        { "a", s => a = s },
  //      };
  //      p.Parse (new string[]{"-a"});   // sets v != null
  //      p.Parse (new string[]{"-a+"});  // sets v != null
  //      p.Parse (new string[]{"-a-"});  // sets v == null
  //
  
  using System;
  using System.Collections;
  using System.Collections.Generic;
  using System.Collections.ObjectModel;
  using System.ComponentModel;
  using System.IO;
  using System.Linq;
  using System.Runtime.Serialization;
  using System.Security.Permissions;
  using System.Text;
  using System.Text.RegularExpressions;
  
  using NCrawler.HtmlProcessor.Properties;
  
  namespace NGet.Utils
  {
  	public class OptionValueCollection : IList, IList<string>
  	{
  		#region Readonly & Static Fields
  
  		private readonly OptionContext m_C;
  		private readonly List<string> m_Values = new List<string>();
  
  		#endregion
  
  		#region Constructors
  
  		internal OptionValueCollection(OptionContext c)
  		{
              this.m_C = c;
  		}
  
  		#endregion
  
  		#region Instance Methods
  
  		public override string ToString()
  		{
  			return string.Join(", ", this.m_Values.ToArray());
  		}
  
  		public string[] ToArray()
  		{
  			return this.m_Values.ToArray();
  		}
  
  		public List<string> ToList()
  		{
  			return new List<string>(this.m_Values);
  		}
  
  		/// <exception cref="InvalidOperationException">OptionContext.Option is null.</exception>
  		/// <exception cref="ArgumentOutOfRangeException"><c>index</c> is out of range.</exception>
  		/// <exception cref="OptionException"><c>OptionException</c>.</exception>
  		private void AssertValid(int index)
  		{
  			if (this.m_C.Option == null)
  			{
  				throw new InvalidOperationException("OptionContext.Option is null.");
  			}
  
  			if (index >= this.m_C.Option.MaxValueCount)
  			{
  				throw new ArgumentOutOfRangeException(nameof(index));
  			}
  
  			if (this.m_C.Option.OptionValueType == OptionValueType.Required && index >= this.m_Values.Count)
  			{
  				throw new OptionException(string.Format(
                      this.m_C.OptionSet.MessageLocalizer("Missing required value for option '{0}'."), this.m_C.OptionName),
                      this.m_C.OptionName);
  			}
  		}
  
  		#endregion
  
  		#region IList Members
  
  		void ICollection.CopyTo(Array array, int index)
  		{
  			(this.m_Values as ICollection).CopyTo(array, index);
  		}
  
  		bool ICollection.IsSynchronized
  		{
  			get { return (this.m_Values as ICollection).IsSynchronized; }
  		}
  
  		object ICollection.SyncRoot
  		{
  			get { return (this.m_Values as ICollection).SyncRoot; }
  		}
  
  		public void Clear()
  		{
              this.m_Values.Clear();
  		}
  
  		public int Count
  		{
  			get { return this.m_Values.Count; }
  		}
  
  		public bool IsReadOnly
  		{
  			get { return false; }
  		}
  
  		IEnumerator IEnumerable.GetEnumerator()
  		{
  			return this.m_Values.GetEnumerator();
  		}
  
  		int IList.Add(object value)
  		{
  			return (this.m_Values as IList).Add(value);
  		}
  
  		bool IList.Contains(object value)
  		{
  			return (this.m_Values as IList).Contains(value);
  		}
  
  		int IList.IndexOf(object value)
  		{
  			return (this.m_Values as IList).IndexOf(value);
  		}
  
  		void IList.Insert(int index, object value)
  		{
  			(this.m_Values as IList).Insert(index, value);
  		}
  
  		void IList.Remove(object value)
  		{
  			(this.m_Values as IList).Remove(value);
  		}
  
  		void IList.RemoveAt(int index)
  		{
  			(this.m_Values as IList).RemoveAt(index);
  		}
  
  		bool IList.IsFixedSize
  		{
  			get { return false; }
  		}
  
  		object IList.this[int index]
  		{
  			get { return this[index]; }
  			set { (this.m_Values as IList)[index] = value; }
  		}
  
  		#endregion
  
  		#region IList<string> Members
  
  		public void Add(string item)
  		{
              this.m_Values.Add(item);
  		}
  
  		public bool Contains(string item)
  		{
  			return this.m_Values.Contains(item);
  		}
  
  		public void CopyTo(string[] array, int arrayIndex)
  		{
              this.m_Values.CopyTo(array, arrayIndex);
  		}
  
  		public bool Remove(string item)
  		{
  			return this.m_Values.Remove(item);
  		}
  
  		public IEnumerator<string> GetEnumerator()
  		{
  			return this.m_Values.GetEnumerator();
  		}
  
  		public int IndexOf(string item)
  		{
  			return this.m_Values.IndexOf(item);
  		}
  
  		public void Insert(int index, string item)
  		{
              this.m_Values.Insert(index, item);
  		}
  
  		public void RemoveAt(int index)
  		{
              this.m_Values.RemoveAt(index);
  		}
  
  		public string this[int index]
  		{
  			get
  			{
                  this.AssertValid(index);
  				return index >= this.m_Values.Count ? null : this.m_Values[index];
  			}
  			set { this.m_Values[index] = value; }
  		}
  
  		#endregion
  	}
  
  	public class OptionContext
  	{
  		#region Readonly & Static Fields
  
  		#endregion
  
  		#region Constructors
  
  		public OptionContext(OptionSet set)
  		{
              this.OptionSet = set;
              this.OptionValues = new OptionValueCollection(this);
  		}
  
  		#endregion
  
  		#region Instance Properties
  
  		public Option Option { get; set; }
  		public int OptionIndex { get; set; }
  		public string OptionName { get; set; }
  		public OptionSet OptionSet { get; private set; }
  		public OptionValueCollection OptionValues { get; private set; }
  
  		#endregion
  	}
  
  	public enum OptionValueType
  	{
  		None,
  		Optional,
  		Required,
  	}
  
  	public abstract class Option
  	{
  		#region Readonly & Static Fields
  
  		private static readonly char[] s_nameTerminator = new[] {'=', ':'};
  
  		#endregion
  
  		#region Fields
  
  		#endregion
  
  		#region Constructors
  
  		protected Option(string prototype, string description)
  			: this(prototype, description, 1)
  		{
  		}
  
  		/// <exception cref="ArgumentNullException"><paramref name="prototype" /> is <c>null</c>.</exception>
  		/// <exception cref="ArgumentException">Cannot be the empty string.</exception>
  		/// <exception cref="ArgumentOutOfRangeException"><c>maxValueCount</c> is out of range.</exception>
  		protected Option(string prototype, string description, int maxValueCount)
  		{
  			if (prototype == null)
  			{
  				throw new ArgumentNullException(nameof(prototype));
  			}
  
  			if (prototype.Length == 0)
  			{
  				throw new ArgumentException(Resources.Option_Option_Cannot_be_the_empty_string_, nameof(prototype));
  			}
  
  			if (maxValueCount < 0)
  			{
  				throw new ArgumentOutOfRangeException(nameof(maxValueCount));
  			}
  
  			Prototype = prototype;
              this.Names = prototype.Split('|');
              this.Description = description;
              this.MaxValueCount = maxValueCount;
              this.OptionValueType = this.ParsePrototype();
  
  			if (this.MaxValueCount == 0 && this.OptionValueType != OptionValueType.None)
  			{
  				throw new ArgumentException(
  					Resources.Option_Option_Cannot_provide_maxValueCount_of_0_for_OptionValueType_Required_or_OptionValueType_Optional_,
  					nameof(maxValueCount));
  			}
  
  			if (this.OptionValueType == OptionValueType.None && maxValueCount > 1)
  			{
  				throw new ArgumentException(
  					string.Format("Cannot provide maxValueCount of {0} for OptionValueType.None.", maxValueCount),
  					nameof(maxValueCount));
  			}
  
  			if (Array.IndexOf(this.Names, "<>") >= 0 &&
  				((this.Names.Length == 1 && this.OptionValueType != OptionValueType.None) ||
  					(this.Names.Length > 1 && this.MaxValueCount > 1)))
  			{
  				throw new ArgumentException(
  					Resources.Option_Option_The_default_option_handler______cannot_require_values_,
  					nameof(prototype));
  			}
  		}
  
  		#endregion
  
  		#region Instance Properties
  
  		public string Description { get; private set; }
  		public int MaxValueCount { get; private set; }
  		public OptionValueType OptionValueType { get; private set; }
  		public static string Prototype { get; private set; }
  		internal string[] Names { get; private set; }
  		internal string[] ValueSeparators { get; private set; }
  
  		#endregion
  
  		#region Instance Methods
  
  		public override string ToString()
  		{
  			return Prototype;
  		}
  
  		public string[] GetNames()
  		{
  			return (string[])this.Names.Clone();
  		}
  
  		public string[] GetValueSeparators()
  		{
  			if (this.ValueSeparators == null)
  			{
  				return Array.Empty<string>();
  			}
  
  			return (string[])this.ValueSeparators.Clone();
  		}
  
  		public void Invoke(OptionContext c)
  		{
              this.OnParseComplete(c);
  			c.OptionName = null;
  			c.Option = null;
  			c.OptionValues.Clear();
  		}
  
  		protected abstract void OnParseComplete(OptionContext c);
  
  		/// <exception cref="ArgumentException">prototype</exception>
  		private OptionValueType ParsePrototype()
  		{
  			var type = '\0';
  			var seps = new List<string>();
  			for (var i = 0; i < this.Names.Length; ++i)
  			{
  				var name = this.Names[i];
  				if (name.Length == 0)
  				{
  					throw new ArgumentException(Resources.Option_ParsePrototype_Empty_option_names_are_not_supported_, Prototype);
  				}
  
  				var end = name.IndexOfAny(s_nameTerminator);
  				if (end == -1)
  				{
  					continue;
  				}
  
                  this.Names[i] = name.Substring(0, end);
  				if (type == '\0' || type == name[end])
  				{
  					type = name[end];
  				}
  				else
  				{
  					throw new ArgumentException(
  						string.Format("Conflicting option types: '{0}' vs. '{1}'.", type, name[end]), Prototype);
  				}
  
  				AddSeparators(name, end, seps);
  			}
  
  			if (type == '\0')
  			{
  				return OptionValueType.None;
  			}
  
  			if (this.MaxValueCount <= 1 && seps.Count != 0)
  			{
  				throw new ArgumentException(
  					string.Format("Cannot provide key/value separators for Options taking {0} value(s).", this.MaxValueCount), Prototype);
  			}
  
  			if (this.MaxValueCount > 1)
  			{
  				if (seps.Count == 0)
  				{
                      this.ValueSeparators = new[] {":", "="};
  				}
  				else if (seps.Count == 1 && seps[0].Length == 0)
  				{
                      this.ValueSeparators = null;
  				}
  				else
  				{
                      this.ValueSeparators = seps.ToArray();
  				}
  			}
  
  			return type == '=' ? OptionValueType.Required : OptionValueType.Optional;
  		}
  
  		#endregion
  
  		#region Class Methods
  
  		/// <exception cref="OptionException"><c>OptionException</c>.</exception>
  		protected static T Parse<T>(string value, OptionContext c)
  		{
  			var conv = TypeDescriptor.GetConverter(typeof (T));
  			var t = default (T);
  			try
  			{
  				if (value != null)
  				{
  					if (conv != null)
  					{
  						t = (T) conv.ConvertFromString(value);
  					}
  				}
  			}
  			catch (Exception e)
  			{
  				throw new OptionException(
  					string.Format(
  						c.OptionSet.MessageLocalizer("Could not convert string `{0}' to type {1} for option `{2}'."),
  						value, typeof (T).Name, c.OptionName),
  					c.OptionName, e);
  			}
  
  			return t;
  		}
  
  		/// <exception cref="ArgumentException">prototype</exception>
  		private static void AddSeparators(string name, int end, ICollection<string> seps)
  		{
  			var start = -1;
  			for (var i = end + 1; i < name.Length; ++i)
  			{
  				switch (name[i])
  				{
  					case '{':
  						if (start != -1)
  						{
  							throw new ArgumentException(
  								string.Format("Ill-formed name/value separator found in \"{0}\".", name), Prototype);
  						}
  
  						start = i + 1;
  						break;
  					case '}':
  						if (start == -1)
  						{
  							throw new ArgumentException(
  								string.Format("Ill-formed name/value separator found in \"{0}\".", name), Prototype);
  						}
  
  						seps.Add(name.Substring(start, i - start));
  						start = -1;
  						break;
  					default:
  						if (start == -1)
  						{
  							seps.Add(name[i].ToString());
  						}
  
  						break;
  				}
  			}
  			if (start != -1)
  			{
  				throw new ArgumentException(
  					string.Format("Ill-formed name/value separator found in \"{0}\".", name), Prototype);
  			}
  		}
  
  		#endregion
  	}
  
  	[Serializable]
  	public class OptionException : Exception
  	{
  		#region Constructors
  
  		public OptionException()
  		{
  		}
  
  		public OptionException(string message, string optionName)
  			: base(message)
  		{
              this.OptionName = optionName;
  		}
  
  		public OptionException(string message, string optionName, Exception innerException)
  			: base(message, innerException)
  		{
              this.OptionName = optionName;
  		}
  
  		protected OptionException(SerializationInfo info, StreamingContext context)
  			: base(info, context)
  		{
              this.OptionName = info.GetString("OptionName");
  		}
  
  		#endregion
  
  		#region Instance Properties
  
  		public string OptionName { get; private set; }
  
  		#endregion
  
  		#region Instance Methods
  
  		[SecurityPermission(SecurityAction.LinkDemand, SerializationFormatter = true)]
  		public override void GetObjectData(SerializationInfo info, StreamingContext context)
  		{
  			base.GetObjectData(info, context);
  			info.AddValue("OptionName", this.OptionName);
  		}
  
  		#endregion
  	}
  
  	public delegate void OptionAction<in TKey, in TValue>(TKey key, TValue value);
  
  	public class OptionSet : KeyedCollection<string, Option>
  	{
  		#region Constants
  
  		private const int OptionWidth = 29;
  
  		#endregion
  
  		#region Readonly & Static Fields
  
  		private readonly Regex m_ValueOption = new Regex(
  			@"^(?<flag>--|-|/)(?<name>[^:=]+)((?<sep>[:=])(?<value>.*))?$");
  
  		#endregion
  
  		#region Constructors
  
  		public OptionSet()
  			: this(f => f)
  		{
  		}
  
  		public OptionSet(Converter<string, string> localizer)
  		{
              this.MessageLocalizer = localizer;
  		}
  
  		#endregion
  
  		#region Instance Properties
  
  		public Converter<string, string> MessageLocalizer { get; private set; }
  
  		#endregion
  
  		#region Instance Methods
  
  		public new OptionSet Add(Option option)
  		{
  			base.Add(option);
  			return this;
  		}
  
  		public OptionSet Add(string prototype, Action<string> action)
  		{
  			return this.Add(prototype, null, action);
  		}
  
  		/// <exception cref="ArgumentNullException"><paramref name="action" /> is <c>null</c>.</exception>
  		public OptionSet Add(string prototype, string description, Action<string> action)
  		{
  			if (action == null)
  			{
  				throw new ArgumentNullException(nameof(action));
  			}
  
  			Option p = new ActionOption(prototype, description, 1, v => action(v[0]));
  			base.Add(p);
  			return this;
  		}
  
  		public OptionSet Add(string prototype, OptionAction<string, string> action)
  		{
  			return this.Add(prototype, null, action);
  		}
  
  		/// <exception cref="ArgumentNullException"><paramref name="action" /> is <c>null</c>.</exception>
  		public OptionSet Add(string prototype, string description, OptionAction<string, string> action)
  		{
  			if (action == null)
  			{
  				throw new ArgumentNullException(nameof(action));
  			}
  
  			Option p = new ActionOption(prototype, description, 2, v => action(v[0], v[1]));
  			base.Add(p);
  			return this;
  		}
  
  		public OptionSet Add<T>(string prototype, Action<T> action)
  		{
  			return this.Add(prototype, null, action);
  		}
  
  		public OptionSet Add<T>(string prototype, string description, Action<T> action)
  		{
  			return this.Add(new ActionOption<T>(prototype, description, action));
  		}
  
  		public OptionSet Add<TKey, TValue>(string prototype, OptionAction<TKey, TValue> action)
  		{
  			return this.Add(prototype, null, action);
  		}
  
  		public OptionSet Add<TKey, TValue>(string prototype, string description, OptionAction<TKey, TValue> action)
  		{
  			return this.Add(new ActionOption<TKey, TValue>(prototype, description, action));
  		}
  
  		public string[] Parse(IEnumerable<string> arguments)
  		{
  			var process = true;
  			var c = this.CreateOptionContext();
  			c.OptionIndex = -1;
  			var def = this["<>"];
  			var unprocessed =
  				from argument in arguments
  				where !(++c.OptionIndex >= 0 && (process || def != null)) || (process
  					? argument == "--"
  						? (process = false)
  						: !this.Parse(argument, c) && (def == null || Unprocessed(null, def, c, argument))
  					: def == null || Unprocessed(null, def, c, argument))
  				select argument;
  
  			if (c.Option != null)
  			{
  				c.Option.Invoke(c);
  			}
  
  			return unprocessed.ToArray();
  		}
  
  		public void WriteOptionDescriptions(TextWriter o)
  		{
  			foreach (var p in this)
  			{
  				var written = 0;
  				if (!this.WriteOptionPrototype(o, p, ref written))
  				{
  					continue;
  				}
  
  				if (written < OptionWidth)
  				{
  					o.Write(new string(' ', OptionWidth - written));
  				}
  				else
  				{
  					o.WriteLine();
  					o.Write(new string(' ', OptionWidth));
  				}
  
  				var lines = GetLines(this.MessageLocalizer(GetDescription(p.Description)));
  				o.WriteLine(lines[0]);
  				var prefix = new string(' ', OptionWidth + 2);
  				for (var i = 1; i < lines.Count; ++i)
  				{
  					o.Write(prefix);
  					o.WriteLine(lines[i]);
  				}
  			}
  		}
  
  		protected virtual OptionContext CreateOptionContext()
  		{
  			return new OptionContext(this);
  		}
  
  		protected virtual bool Parse(string argument, OptionContext c)
  		{
  			if (c.Option != null)
  			{
                  this.ParseValue(argument, c);
  				return true;
  			}
  
              if (!this.GetOptionParts(argument, out var f, out var n, out var s, out var v))
  			{
  				return false;
  			}
  
  			if (this.Contains(n))
  			{
  				var p = this[n];
  				c.OptionName = f + n;
  				c.Option = p;
  				switch (p.OptionValueType)
  				{
  					case OptionValueType.None:
  						c.OptionValues.Add(n);
  						c.Option.Invoke(c);
  						break;
  					case OptionValueType.Optional:
  					case OptionValueType.Required:
                          this.ParseValue(v, c);
  						break;
  				}
  				return true;
  			}
  			// no match; is it a bool option?
  			if (this.ParseBool(argument, n, c))
  			{
  				return true;
  			}
  
  			// is it a bundled option?
  			if (this.ParseBundledValue(f, string.Concat(n + s + v), c))
  			{
  				return true;
  			}
  
  			return false;
  		}
  
  		/// <exception cref="ArgumentNullException"><paramref name="item" /> is <c>null</c>.</exception>
  		/// <exception cref="InvalidOperationException">Option has no names!</exception>
  		protected override string GetKeyForItem(Option item)
  		{
  			if (item == null)
  			{
  				throw new ArgumentNullException(nameof(item));
  			}
  
  			if (item.Names != null && item.Names.Length > 0)
  			{
  				return item.Names[0];
  			}
  
  			// This should never happen, as it's invalid for Option to be
  			// constructed w/o any names.
  			throw new InvalidOperationException("Option has no names!");
  		}
  
  		protected override void InsertItem(int index, Option item)
  		{
  			base.InsertItem(index, item);
              this.AddImpl(item);
  		}
  
  		protected override void RemoveItem(int index)
  		{
  			base.RemoveItem(index);
  			var p = this.Items[index];
  			// KeyedCollection.RemoveItem() handles the 0th item
  			for (var i = 1; i < p.Names.Length; ++i)
  			{
                  this.Dictionary.Remove(p.Names[i]);
  			}
  		}
  
  		protected override void SetItem(int index, Option item)
  		{
  			base.SetItem(index, item);
              this.RemoveItem(index);
              this.AddImpl(item);
  		}
  
  		/// <exception cref="ArgumentNullException"><paramref name="option" /> is <c>null</c>.</exception>
  		[Obsolete("Use KeyedCollection.this[string]")]
  		protected Option GetOptionForName(string option)
  		{
  			if (option == null)
  			{
  				throw new ArgumentNullException(nameof(option));
  			}
  
  			try
  			{
  				return base[option];
  			}
  			catch (KeyNotFoundException)
  			{
  				return null;
  			}
  		}
  
  		/// <exception cref="ArgumentNullException"><paramref name="argument" /> is <c>null</c>.</exception>
  		protected bool GetOptionParts(string argument, out string flag, out string name, out string sep, out string value)
  		{
  			if (argument == null)
  			{
  				throw new ArgumentNullException(nameof(argument));
  			}
  
  			flag = name = sep = value = null;
  			var m = this.m_ValueOption.Match(argument);
  			if (!m.Success)
  			{
  				return false;
  			}
  
  			flag = m.Groups["flag"].Value;
  			name = m.Groups["name"].Value;
  			if (m.Groups["sep"].Success && m.Groups["value"].Success)
  			{
  				sep = m.Groups["sep"].Value;
  				value = m.Groups["value"].Value;
  			}
  
  			return true;
  		}
  
  		/// <exception cref="ArgumentNullException"><paramref name="option" /> is <c>null</c>.</exception>
  		private void AddImpl(Option option)
  		{
  			if (option == null)
  			{
  				throw new ArgumentNullException(nameof(option));
  			}
  
  			var added = new List<string>(option.Names.Length);
  			try
  			{
  				// KeyedCollection.InsertItem/SetItem handle the 0th name.
  				for (var i = 1; i < option.Names.Length; ++i)
  				{
                      this.Dictionary.Add(option.Names[i], option);
  					added.Add(option.Names[i]);
  				}
  			}
  			catch (Exception)
  			{
  				foreach (var name in added)
  				{
                      this.Dictionary.Remove(name);
  				}
  
  				throw;
  			}
  		}
  
  		private bool ParseBool(string option, string n, OptionContext c)
  		{
  			string rn;
  			if (n.Length >= 1 && (n[n.Length - 1] == '+' || n[n.Length - 1] == '-') &&
                  this.Contains((rn = n.Substring(0, n.Length - 1))))
  			{
  				var p = this[rn];
  				var v = n[n.Length - 1] == '+' ? option : null;
  				c.OptionName = option;
  				c.Option = p;
  				c.OptionValues.Add(v);
  				p.Invoke(c);
  				return true;
  			}
  			
  			return false;
  		}
  
  		/// <exception cref="OptionException"><c>OptionException</c>.</exception>
  		/// <exception cref="InvalidOperationException"><c>InvalidOperationException</c>.</exception>
  		private bool ParseBundledValue(string f, string n, OptionContext c)
  		{
  			if (f != "-")
  			{
  				return false;
  			}
  
  			for (var i = 0; i < n.Length; ++i)
  			{
  				var opt = f + n[i];
  				var rn = n[i].ToString();
  				if (!this.Contains(rn))
  				{
  					if (i == 0)
  					{
  						return false;
  					}
  					
  					throw new OptionException(string.Format(this.MessageLocalizer(
  						"Cannot bundle unregistered option '{0}'."), opt), opt);
  				}
  				var p = this[rn];
  				switch (p.OptionValueType)
  				{
  					case OptionValueType.None:
  						Invoke(c, opt, n, p);
  						break;
  					case OptionValueType.Optional:
  					case OptionValueType.Required:
  						{
  							var v = n.Substring(i + 1);
  							c.Option = p;
  							c.OptionName = opt;
                              this.ParseValue(v.Length != 0 ? v : null, c);
  							return true;
  						}
  					default:
  						throw new InvalidOperationException("Unknown OptionValueType: " + p.OptionValueType);
  				}
  			}
  
  			return true;
  		}
  
  		/// <exception cref="OptionException"><c>OptionException</c>.</exception>
  		private void ParseValue(string option, OptionContext c)
  		{
  			if (option != null)
  			{
  				foreach (var o in c.Option.ValueSeparators != null
  					? option.Split(c.Option.ValueSeparators, StringSplitOptions.None)
  					: new[] {option})
  				{
  					c.OptionValues.Add(o);
  				}
  			}
  			
  			if (c.OptionValues.Count == c.Option.MaxValueCount ||
  				c.Option.OptionValueType == OptionValueType.Optional)
  			{
  				c.Option.Invoke(c);
  			}
  			else if (c.OptionValues.Count > c.Option.MaxValueCount)
  			{
  				throw new OptionException(this.MessageLocalizer(string.Format(
  					"Error: Found {0} option values when expecting {1}.",
  					c.OptionValues.Count, c.Option.MaxValueCount)),
  					c.OptionName);
  			}
  		}
  
  		private bool WriteOptionPrototype(TextWriter o, Option p, ref int written)
  		{
  			var names = p.Names;
  
  			var i = GetNextOptionIndex(names, 0);
  			if (i == names.Length)
  			{
  				return false;
  			}
  
  			if (names[i].Length == 1)
  			{
  				Write(o, ref written, "  -");
  				Write(o, ref written, names[0]);
  			}
  			else
  			{
  				Write(o, ref written, "      --");
  				Write(o, ref written, names[0]);
  			}
  
  			for (i = GetNextOptionIndex(names, i + 1);
  				i < names.Length;
  				i = GetNextOptionIndex(names, i + 1))
  			{
  				Write(o, ref written, ", ");
  				Write(o, ref written, names[i].Length == 1 ? "-" : "--");
  				Write(o, ref written, names[i]);
  			}
  
  			if (p.OptionValueType == OptionValueType.Optional ||
  				p.OptionValueType == OptionValueType.Required)
  			{
  				if (p.OptionValueType == OptionValueType.Optional)
  				{
  					Write(o, ref written, this.MessageLocalizer("["));
  				}
  				
  				Write(o, ref written, this.MessageLocalizer("=" + GetArgumentName(0, p.MaxValueCount, p.Description)));
  				var sep = p.ValueSeparators != null && p.ValueSeparators.Length > 0
  					? p.ValueSeparators[0]
  					: " ";
  				
  				for (var c = 1; c < p.MaxValueCount; ++c)
  				{
  					Write(o, ref written, this.MessageLocalizer(sep + GetArgumentName(c, p.MaxValueCount, p.Description)));
  				}
  				
  				if (p.OptionValueType == OptionValueType.Optional)
  				{
  					Write(o, ref written, this.MessageLocalizer("]"));
  				}
  			}
  			return true;
  		}
  
  		#endregion
  
  		#region Class Methods
  
  		private static string GetArgumentName(int index, int maxIndex, string description)
  		{
  			if (description == null)
  			{
  				return maxIndex == 1 ? "VALUE" : "VALUE" + (index + 1);
  			}
  
  			var nameStart = maxIndex == 1 ? new[] {"{0:", "{"} : new[] {"{" + index + ":"};
  			foreach (var t in nameStart)
  			{
  				int start, j = 0;
  				do
  				{
  
gt: 					start = description.IndexOf(t, j);