//
// 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.
//

//
// 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 a != null
//      p.Parse (new string[]{"-a+"});  // sets a != null
//      p.Parse (new string[]{"-a-"});  // sets a == null
//

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.IO;
using System.Runtime.Serialization;
using System.Security.Permissions;
using System.Text;
using System.Text.RegularExpressions;

namespace NDesk.Options {

	public class OptionValueCollection : IList<string> {
		readonly List<string> values = new List<string> ();
		readonly OptionContext context;

		internal OptionValueCollection (OptionContext context)
		{
			this.context = context;
		}

		#region ICollection<T>
		public void Add (string item)                       {values.Add (item);}
		public void Clear ()                                {values.Clear ();}
		public bool Contains (string item)                  {return values.Contains (item);}
		public void CopyTo (string[] array, int arrayIndex) {values.CopyTo (array, arrayIndex);}
		public bool Remove (string item)                    {return values.Remove (item);}
		public int Count                                    {get {return values.Count;}}
		public bool IsReadOnly                              {get {return false;}}
		#endregion

		#region IEnumerable
		IEnumerator IEnumerable.GetEnumerator () {return values.GetEnumerator ();}
		#endregion

		#region IEnumerable<T>
		public IEnumerator<string> GetEnumerator () {return values.GetEnumerator ();}
		#endregion

		#region IList<T>
		public int IndexOf (string item)            {return values.IndexOf (item);}
		public void Insert (int index, string item) {values.Insert (index, item);}
		public void RemoveAt (int index)            {values.RemoveAt (index);}

		void AssertValid (int index)
		{
			if (context.Option == null)
				throw new InvalidOperationException ("OptionContext.Option is null.");
			if (index >= context.Option.MaxValueCount)
				throw new ArgumentOutOfRangeException ("index");
			if (context.Option.OptionValueType == OptionValueType.Required &&
					index >= values.Count)
				throw new OptionException (String.Format (
							context.OptionSet.MessageLocalizer ("Missing required value for option '{0}'."), context.OptionName), 
						context.OptionName);
		}

		public string this [int index] {
			get {
				AssertValid (index);
				return index >= values.Count ? null : values [index];
			}
			set {
				values [index] = value;
			}
		}
		#endregion

		public List<string> ToList ()
		{
			return new List<string> (values);
		}

		public string[] ToArray ()
		{
			return values.ToArray ();
		}

		public override string ToString ()
		{
			return String.Join (", ", values.ToArray ());
		}
	}

	public class OptionContext {
		public OptionContext (OptionSet set)
		{
			OptionSet = set;
			OptionValues = new OptionValueCollection (this);
		}

		public Option Option { get; set; }

		public string OptionName { get; set; }

		public int OptionIndex { get; set; }

		public OptionSet OptionSet { get; private set; }

		public OptionValueCollection OptionValues { get; private set; }
	}

	public enum OptionValueType {
		None, 
		Optional,
		Required,
	}

	public abstract class Option {
		protected Option (string prototype, string description)
			: this (prototype, description, 1)
		{
		}

		protected Option (string prototype, string description, int maxValueCount)
		{
			if (prototype == null)
				throw new ArgumentNullException ("prototype");
			if (prototype.Length == 0)
				throw new ArgumentException ("Cannot be the empty string.", "prototype");
			if (maxValueCount < 0)
				throw new ArgumentOutOfRangeException ("maxValueCount");

			Prototype       = prototype;
			Description     = description;
			Names           = prototype.Split ('|');
			MaxValueCount   = maxValueCount;
			OptionValueType = ParsePrototype ();

			if (MaxValueCount == 0 && OptionValueType != OptionValueType.None)
				throw new ArgumentException (
						"Cannot provide maxValueCount of 0 for OptionValueType.Required or " +
							"OptionValueType.Optional.",
						"maxValueCount");
			if (OptionValueType == OptionValueType.None && maxValueCount > 1)
				throw new ArgumentException (
						String.Format ("Cannot provide maxValueCount of {0} for OptionValueType.None.", maxValueCount),
						"maxValueCount");
			if (Array.IndexOf (Names, "<>") >= 0 && 
					((Names.Length == 1 && OptionValueType != OptionValueType.None) ||
					 (Names.Length > 1 && MaxValueCount > 1)))
				throw new ArgumentException (
						"The default option handler '<>' cannot require values.",
						"prototype");
		}

		public string Prototype { get; private set; }
		public string Description { get; private set; }
		public OptionValueType OptionValueType { get; private set; }
		public int MaxValueCount { get; private set; }

		public string[] GetNames ()
		{
			return (string[]) Names.Clone ();
		}

		public string[] GetValueSeparators ()
		{
			if (ValueSeparators == null)
				return new string [0];
			return (string[]) ValueSeparators.Clone ();
		}

		protected static T Parse<T> (string value, OptionContext c)
		{
			TypeConverter conv = TypeDescriptor.GetConverter (typeof (T));
			T t = default (T);
			try {
				if (value != 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;
		}

		internal string[] Names { get; private set; }
		internal string[] ValueSeparators { get; private set; }

		static readonly char[] nameTerminator = {'=', ':'};

		OptionValueType ParsePrototype ()
		{
			char type = '\0';
			var seps = new List<string> ();
			for (int i = 0; i < Names.Length; ++i) {
				string name = Names [i];
				if (name.Length == 0)
					throw new ArgumentException ("Empty option names are not supported.");

				int end = name.IndexOfAny (nameTerminator);
				if (end == -1)
					continue;
				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]));
				AddSeparators (name, end, seps);
			}

			if (type == '\0')
				return OptionValueType.None;

			if (MaxValueCount <= 1 && seps.Count != 0)
				throw new ArgumentException (
						String.Format ("Cannot provide key/value separators for Options taking {0} value(s).", MaxValueCount));
			if (MaxValueCount > 1) {
				if (seps.Count == 0)
					ValueSeparators = new[]{":", "="};
				else if (seps.Count == 1 && seps [0].Length == 0)
					ValueSeparators = null;
				else
					ValueSeparators = seps.ToArray ();
			}

			return type == '=' ? OptionValueType.Required : OptionValueType.Optional;
		}

		static void AddSeparators (string name, int end, ICollection<string> seps)
		{
			int start = -1;
			for (int 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),
									"name");
						start = i+1;
						break;
					case '}':
						if (start == -1)
							throw new ArgumentException (
									String.Format ("Ill-formed name/value separator found in \"{0}\".", name),
									"name");
						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),
						"name");
		}

		public void Invoke (OptionContext c)
		{
			OnParseComplete (c);
			c.OptionName  = null;
			c.Option      = null;
			c.OptionValues.Clear ();
		}

		protected abstract void OnParseComplete (OptionContext c);

		public override string ToString ()
		{
			return Prototype;
		}
	}

	[Serializable]
	public class OptionException : Exception {
		public OptionException ()
		{
		}

		public OptionException (string message, string optionName)
			: base (message)
		{
			OptionName = optionName;
		}

		public OptionException (string message, string optionName, Exception innerException)
			: base (message, innerException)
		{
			OptionName = optionName;
		}

		protected OptionException (SerializationInfo info, StreamingContext context)
			: base (info, context)
		{
			OptionName = info.GetString ("OptionName");
		}

		public string OptionName { get; private set; }

		[SecurityPermission (SecurityAction.LinkDemand, SerializationFormatter = true)]
		public override void GetObjectData (SerializationInfo info, StreamingContext context)
		{
			base.GetObjectData (info, context);
			info.AddValue ("OptionName", OptionName);
		}
	}

	public delegate void OptionAction<in TKey, in TValue> (TKey key, TValue value);

	public class OptionSet : KeyedCollection<string, Option>
	{
		public OptionSet ()
			: this (f => f)
		{
		}

		public OptionSet (Converter<string, string> localizer)
		{
			MessageLocalizer = localizer;
		}

		public Converter<string, string> MessageLocalizer { get; private set; }

		protected override string GetKeyForItem (Option item)
		{
			if (item == null)
				throw new ArgumentNullException ("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!");
		}

		[Obsolete ("Use KeyedCollection.this[string]")]
		protected Option GetOptionForName (string option)
		{
			if (option == null)
				throw new ArgumentNullException ("option");
			try {
				return base [option];
			}
			catch (KeyNotFoundException) {
				return null;
			}
		}

		protected override void InsertItem (int index, Option item)
		{
			base.InsertItem (index, item);
			AddImpl (item);
		}

		protected override void RemoveItem (int index)
		{
			base.RemoveItem (index);
			Option p = Items [index];
			// KeyedCollection.RemoveItem() handles the 0th item
			for (int i = 1; i < p.Names.Length; ++i) {
				Dictionary.Remove (p.Names [i]);
			}
		}

		protected override void SetItem (int index, Option item)
		{
			base.SetItem (index, item);
			RemoveItem (index);
			AddImpl (item);
		}

		void AddImpl (Option option)
		{
			if (option == null)
				throw new ArgumentNullException ("option");
			var added = new List<string> (option.Names.Length);
			try {
				// KeyedCollection.InsertItem/SetItem handle the 0th name.
				for (int i = 1; i < option.Names.Length; ++i) {
					Dictionary.Add (option.Names [i], option);
					added.Add (option.Names [i]);
				}
			}
			catch (Exception) {
				foreach (string name in added)
					Dictionary.Remove (name);
				throw;
			}
		}

		public new OptionSet Add (Option option)
		{
			base.Add (option);
			return this;
		}

		sealed class ActionOption : Option {
			readonly Action<OptionValueCollection> action;

			public ActionOption (string prototype, string description, int count, Action<OptionValueCollection> action)
				: base (prototype, description, count)
			{
				if (action == null)
					throw new ArgumentNullException ("action");
				this.action = action;
			}

			protected override void OnParseComplete (OptionContext c)
			{
				action (c.OptionValues);
			}
		}

		public OptionSet Add (string prototype, Action<string> action)
		{
			return Add (prototype, null, action);
		}

		public OptionSet Add (string prototype, string description, Action<string> action)
		{
			if (action == null)
				throw new ArgumentNullException ("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 Add (prototype, null, action);
		}

		public OptionSet Add (string prototype, string description, OptionAction<string, string> action)
		{
			if (action == null)
				throw new ArgumentNullException ("action");
			Option p = new ActionOption (prototype, description, 2,
				v => action (v [0], v [1]));
			base.Add (p);
			return this;
		}

		sealed class ActionOption<T> : Option {
			readonly Action<T> action;

			public ActionOption (string prototype, string description, Action<T> action)
				: base (prototype, description, 1)
			{
				if (action == null)
					throw new ArgumentNullException ("action");
				this.action = action;
			}

			protected override void OnParseComplete (OptionContext c)
			{
				action (Parse<T> (c.OptionValues [0], c));
			}
		}

		sealed class ActionOption<TKey, TValue> : Option {
			readonly OptionAction<TKey, TValue> action;

			public ActionOption (string prototype, string description, OptionAction<TKey, TValue> action)
				: base (prototype, description, 2)
			{
				if (action == null)
					throw new ArgumentNullException ("action");
				this.action = action;
			}

			protected override void OnParseComplete (OptionContext c)
			{
				action (
					Parse<TKey> (c.OptionValues [0], c),
					Parse<TValue> (c.OptionValues [1], c));
			}
		}

		public OptionSet Add<T> (string prototype, Action<T> action)
		{
			return Add (prototype, null, action);
		}

		public OptionSet Add<T> (string prototype, string description, Action<T> action)
		{
			return Add (new ActionOption<T> (prototype, description, action));
		}

		public OptionSet Add<TKey, TValue> (string prototype, OptionAction<TKey, TValue> action)
		{
			return Add (prototype, null, action);
		}

		public OptionSet Add<TKey, TValue> (string prototype, string description, OptionAction<TKey, TValue> action)
		{
			return Add (new ActionOption<TKey, TValue> (prototype, description, action));
		}

		protected virtual OptionContext CreateOptionContext ()
		{
			return new OptionContext (this);
		}

		public List<string> Parse (IEnumerable<string> arguments)
		{
			OptionContext c = CreateOptionContext ();
			c.OptionIndex = -1;
			bool process = true;
			var unprocessed = new List<string> ();
			Option def = Contains ("<>") ? this ["<>"] : null;
			foreach (string argument in arguments) {
				++c.OptionIndex;
				if (argument == "--") {
					process = false;
					continue;
				}
				if (!process) {
					Unprocessed (unprocessed, def, c, argument);
					continue;
				}
				if (!Parse (argument, c))
					Unprocessed (unprocessed, def, c, argument);
			}
			if (c.Option != null)
				c.Option.Invoke (c);
			return unprocessed;
		}

		static void Unprocessed (ICollection<string> extra, Option def, OptionContext c, string argument)
		{
			if (def == null) {
				extra.Add (argument);
				return;
			}
			c.OptionValues.Add (argument);
			c.Option = def;
			c.Option.Invoke (c);
		}

		readonly Regex valueOption = new Regex (
			@"^(?<flag>--|-|/)(?<name>[^:=]+)((?<sep>[:=])(?<value>.*))?$");

		protected bool GetOptionParts (string argument, out string flag, out string name, out string sep, out string value)
		{
			if (argument == null)
				throw new ArgumentNullException ("argument");

			flag = name = sep = value = null;
			Match 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;
		}

		protected virtual bool Parse (string argument, OptionContext c)
		{
			if (c.Option != null) {
				ParseValue (argument, c);
				return true;
			}

			string f, n, s, v;
			if (!GetOptionParts (argument, out f, out n, out s, out v))
				return false;

			if (Contains (n)) {
				Option 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: 
						ParseValue (v, c);
						break;
				}
				return true;
			}
			// no match; is it a bool option?
			if (ParseBool (argument, n, c))
				return true;
			// is it a bundled option?
			if (ParseBundledValue (f, String.Concat (n, s, v), c))
				return true;

			return false;
		}

		void ParseValue (string option, OptionContext c)
		{
			if (option != null)
				foreach (string 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 (MessageLocalizer (String.Format (
								"Error: Found {0} option values when expecting {1}.", 
								c.OptionValues.Count, c.Option.MaxValueCount)),
						c.OptionName);
			}
		}

		bool ParseBool (string option, string n, OptionContext c)
		{
			string rn;
			if (n.Length >= 1 && (n [n.Length-1] == '+' || n [n.Length-1] == '-') &&
					Contains ((rn = n.Substring (0, n.Length-1)))) {
				Option p = this [rn];
				string v = n [n.Length-1] == '+' ? option : null;
				c.OptionName  = option;
				c.Option      = p;
				c.OptionValues.Add (v);
				p.Invoke (c);
				return true;
			}
			return false;
		}

		bool ParseBundledValue (string f, string n, OptionContext c)
		{
			if (f != "-")
				return false;
			for (int i = 0; i < n.Length; ++i) {
				string opt = f + n [i];
				string rn = n [i].ToString ();
				if (!Contains (rn)) {
					if (i == 0)
						return false;
					throw new OptionException (String.Format (MessageLocalizer (
									"Cannot bundle unregistered option '{0}'."), opt), opt);
				}
				Option p = this [rn];
				switch (p.OptionValueType) {
					case OptionValueType.None:
						Invoke (c, opt, n, p);
						break;
					case OptionValueType.Optional:
					case OptionValueType.Required: {
						string v     = n.Substring (i+1);
						c.Option     = p;
						c.OptionName = opt;
						ParseValue (v.Length != 0 ? v : null, c);
						return true;
					}
					default:
						throw new InvalidOperationException ("Unknown OptionValueType: " + p.OptionValueType);
				}
			}
			return true;
		}

		static void Invoke (OptionContext c, string name, string value, Option option)
		{
			c.OptionName  = name;
			c.Option      = option;
			c.OptionValues.Add (value);
			option.Invoke (c);
		}

		const int OPTION_WIDTH = 29;

		public void WriteOptionDescriptions (TextWriter o)
		{
			foreach (Option p in this) {
				int written = 0;
				if (!WriteOptionPrototype (o, p, ref written))
					continue;

				if (written < OPTION_WIDTH)
					o.Write (new string (' ', OPTION_WIDTH - written));
				else {
					o.WriteLine ();
					o.Write (new string (' ', OPTION_WIDTH));
				}

				List<string> lines = GetLines (MessageLocalizer (GetDescription (p.Description)));
				o.WriteLine (lines [0]);
				var prefix = new string (' ', OPTION_WIDTH+2);
				for (int i = 1; i < lines.Count; ++i) {
					o.Write (prefix);
					o.WriteLine (lines [i]);
				}
			}
		}

		bool WriteOptionPrototype (TextWriter o, Option p, ref int written)
		{
			string[] names = p.Names;

			int 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, MessageLocalizer ("["));
				}
				Write (o, ref written, MessageLocalizer ("=" + GetArgumentName (0, p.MaxValueCount, p.Description)));
				string sep = p.ValueSeparators != null && p.ValueSeparators.Length > 0 
					? p.ValueSeparators [0]
					: " ";
				for (int c = 1; c < p.MaxValueCount; ++c) {
					Write (o, ref written, MessageLocalizer (sep + GetArgumentName (c, p.MaxValueCount, p.Description)));
				}
				if (p.OptionValueType == OptionValueType.Optional) {
					Write (o, ref written, MessageLocalizer ("]"));
				}
			}
			return true;
		}

		static int GetNextOptionIndex (string[] names, int i)
		{
			while (i < names.Length && names [i] == "<>") {
				++i;
			}
			return i;
		}

		static void Write (TextWriter o, ref int n, string s)
		{
			n += s.Length;
			o.Write (s);
		}

		static string GetArgumentName (int index, int maxIndex, string description)
		{
			if (String.IsNullOrEmpty (description))
				return maxIndex == 1 ? "VALUE" : "VALUE" + (index + 1);
			string[] nameStart = maxIndex == 1
				? new[] { "{0:", "{" }
				: new[] { "{" + index + ":" };
			foreach (string name in nameStart) {
				int start, j = 0;
				do {
					start = description.IndexOf (name, j);
				} while (start >= 0 && j != 0 && description [j++ - 1] == '{');
				if (start == -1)
					continue;
				int end = description.IndexOf ("}", start);
				if (end == -1)
					continue;
				return description.Substring (start + name.Length, end - start - name.Length);
			}
			return maxIndex == 1 ? "VALUE" : "VALUE" + (index + 1);
		}

		static string GetDescription (string description)
		{
			if (String.IsNullOrEmpty (description))
				return String.Empty;
			var sb = new StringBuilder (description.Length);
			int start = -1;
			for (int i = 0; i < description.Length; ++i) {
				switch (description [i]) {
					case '{':
						if (i == start) {
							sb.Append ('{');
							start = -1;
						}
						else if (start < 0)
							start = i + 1;
						break;
					case '}':
						if (start < 0) {
							if ((i+1) == description.Length || description [i+1] != '}')
								throw new InvalidOperationException ("Invalid option description: " + description);
							++i;
							sb.Append ("}");
						}
						else {
							sb.Append (description.Substring (start, i - start));
							start = -1;
						}
						break;
					case ':':
						if (start < 0)
							goto default;
						start = i + 1;
						break;
					default:
						if (start < 0)
							sb.Append (description [i]);
						break;
				}
			}
			return sb.ToString ();
		}

		static List<string> GetLines (string description)
		{
			var lines = new List<string> ();
			if (String.IsNullOrEmpty (description)) {
				lines.Add (String.Empty);
				return lines;
			}
			const int length = 80 - OPTION_WIDTH - 2;
			int start = 0, end;
			do {
				end = GetLineEnd (start, length, description);
				bool cont = false;
				if (end < description.Length) {
					char c = description [end];
					if (c == '-' || (char.IsWhiteSpace (c) && c != '\n'))
						++end;
					else if (c != '\n') {
						cont = true;
						--end;
					}
				}
				lines.Add (description.Substring (start, end - start));
				if (cont) {
					lines [lines.Count-1] += "-";
				}
				start = end;
				if (start < description.Length && description [start] == '\n')
					++start;
			} while (end < description.Length);
			return lines;
		}

		static int GetLineEnd (int start, int length, string description)
		{
			int end = Math.Min (start + length, description.Length);
			int sep = -1;
			for (int i = start; i < end; ++i) {
				switch (description [i]) {
					case ' ':
					case '\t':
					case '\v':
					case '-':
					case ',':
					case '.':
					case ';':
						sep = i;
						break;
					case '\n':
						return i;
				}
			}
			if (sep == -1 || end == description.Length)
				return end;
			return sep;
		}
	}
}