Options.cs

//
// Options.cs
//
// Authors:
//  Jonathan Pryor <jpryor@novell.com>
//
// Copyright (C) 2008 Novell (https://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
//
// The NUnit version of this file introduces conditional compilation for
// building under .NET Standard
//
// 11/5/2015 -
// Change namespace to avoid conflict with user code use of mono.options

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;

// Missing XML Docs
#pragma warning disable 1591

namespace NUnit.Options
{
    public class OptionValueCollection : IList, IList<string>
    {
        private readonly List<string> _values = new List<string>();
        private readonly OptionContext _c;

        internal OptionValueCollection(OptionContext c)
        {
            _c = c;
        }

        #region ICollection
        void ICollection.CopyTo(Array array, int index)
        {
            (_values as ICollection).CopyTo(array, index);
        }
        bool ICollection.IsSynchronized => (_values as ICollection).IsSynchronized;
        object ICollection.SyncRoot => (_values as ICollection).SyncRoot;

        #endregion

        #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 => _values.Count;
        public bool IsReadOnly => false;

        #endregion

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

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

        #region IList
        int IList.Add(object value)
        {
            return (_values as IList).Add(value);
        }
        bool IList.Contains(object value)
        {
            return (_values as IList).Contains(value);
        }
        int IList.IndexOf(object value)
        {
            return (_values as IList).IndexOf(value);
        }
        void IList.Insert(int index, object value)
        {
            (_values as IList).Insert(index, value);
        }
        void IList.Remove(object value)
        {
            (_values as IList).Remove(value);
        }
        void IList.RemoveAt(int index)
        {
            (_values as IList).RemoveAt(index);
        }
        bool IList.IsFixedSize => false;
        object IList.this[int index]
        {
            get => this[index];
            set => (_values as IList)[index] = value;
        }
        #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);
        }

        private void AssertValid(int index)
        {
            if (_c.Option is null)
                throw new InvalidOperationException("OptionContext.Option is null.");
            if (index >= _c.Option.MaxValueCount)
                throw new ArgumentOutOfRangeException(nameof(index));
            if (_c.Option.OptionValueType == OptionValueType.Required &&
                    index >= _values.Count)
            {
                throw new OptionException(string.Format(
                            _c.OptionSet.MessageLocalizer("Missing required value for option '{0}'."), _c.OptionName),
                        _c.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
    {
        private Option _option;
        private string _name;
        private int _index;
        private readonly OptionSet _set;
        private readonly OptionValueCollection _c;

        public OptionContext(OptionSet set)
        {
            _set = set;
            _c = new OptionValueCollection(this);
        }

        public Option Option
        {
            get => _option;
            set => _option = value;
        }

        public string OptionName
        {
            get => _name;
            set => _name = value;
        }

        public int OptionIndex
        {
            get => _index;
            set => _index = value;
        }

        public OptionSet OptionSet => _set;

        public OptionValueCollection OptionValues => _c;
    }

    public enum OptionValueType
    {
        None,
        Optional,
        Required,
    }

    public abstract class Option
    {
        private readonly string _prototype;
        private readonly string _description;
        private readonly string[] _names;
        private readonly OptionValueType _type;
        private readonly int _count;
        private string[] _separators;

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

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

            _prototype = prototype;
            _names = prototype.Split('|');
            _description = description;
            _count = maxValueCount;
            _type = ParsePrototype();

            if (_count == 0 && _type != OptionValueType.None)
            {
                throw new ArgumentException(
                        "Cannot provide maxValueCount of 0 for OptionValueType.Required or " +
                            "OptionValueType.Optional.",
                        nameof(maxValueCount));
            }

            if (_type == OptionValueType.None && maxValueCount > 1)
            {
                throw new ArgumentException(
                    $"Cannot provide maxValueCount of {maxValueCount} for OptionValueType.None.",
                    nameof(maxValueCount));
            }

            if (Array.IndexOf(_names, "<>") >= 0 &&
                    ((_names.Length == 1 && _type != OptionValueType.None) ||
                     (_names.Length > 1 && MaxValueCount > 1)))
            {
                throw new ArgumentException(
                        "The default option handler '<>' cannot require values.",
                        nameof(prototype));
            }
        }

        public string Prototype => _prototype;
        public string Description => _description;
        public OptionValueType OptionValueType => _type;
        public int MaxValueCount => _count;

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

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

        protected static T Parse<T>(string value, OptionContext c)
        {
            Type tt = typeof(T);
            bool nullable = tt.IsValueType && tt.IsGenericType &&
                !tt.IsGenericTypeDefinition &&
                tt.GetGenericTypeDefinition() == typeof(Nullable<>);
            Type targetType = nullable ? tt.GetGenericArguments()[0] : typeof(T);

            TypeConverter conv = TypeDescriptor.GetConverter(targetType);
            T t = default(T);
            try
            {
                if (value is not 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, targetType.Name, c.OptionName),
                        c.OptionName, e);
            }
            return t;
        }

        internal string[] Names => _names;
        internal string[] ValueSeparators => _separators;

        private static readonly char[] NameTerminator = new[] { '=', ':' };

        private OptionValueType ParsePrototype()
        {
            char type = '\0';
            List<string> 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.", "prototype");

                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(
                        $"Conflicting option types: '{type}' vs. '{name[end]}'.",
                        "prototype");
                }

                AddSeparators(name, end, seps);
            }

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

            if (_count <= 1 && seps.Count != 0)
            {
                throw new ArgumentException(
                    $"Cannot provide key/value separators for Options taking {_count} value(s).",
                    "prototype");
            }

            if (_count > 1)
            {
                if (seps.Count == 0)
                    _separators = new[] { ":", "=" };
                else if (seps.Count == 1 && seps[0].Length == 0)
                    _separators = null;
                else
                    _separators = seps.ToArray();
            }

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

        private 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(
                                $"Ill-formed name/value separator found in \"{name}\".",
                                "prototype");
                        }

                        start = i + 1;
                        break;
                    case '}':
                        if (start == -1)
                        {
                            throw new ArgumentException(
                                $"Ill-formed name/value separator found in \"{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(
                    $"Ill-formed name/value separator found in \"{name}\".",
                    "prototype");
            }
        }

        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
    {
        private readonly string _option;

        public OptionException()
        {
        }

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

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

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

        public string OptionName => _option;

#if !NET6_0_OR_GREATER
        [SecurityPermission(SecurityAction.LinkDemand, SerializationFormatter = true)]
#endif
        public override void GetObjectData(SerializationInfo info, StreamingContext context)
        {
            base.GetObjectData(info, context);
            info.AddValue("OptionName", _option);
        }
    }

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

    public class OptionSet : KeyedCollection<string, Option>
    {
        private string Localizer(string msg)
        {
            return msg;
        }

        public string MessageLocalizer(string msg)
        {
            return msg;
        }

        protected override string GetKeyForItem(Option item)
        {
            if (item is null)
                throw new ArgumentNullException(nameof(item));
            if (item.Names is not 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);
            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);
        }

        private void AddImpl(Option option)
        {
            if (option is null)
                throw new ArgumentNullException(nameof(option));
            List<string> 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;
        }

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

            public ActionOption(string prototype, string description, int count, Action<OptionValueCollection> action)
                : base(prototype, description, count)
            {
                if (action is null)
                    throw new ArgumentNullException(nameof(action));
                _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 is null)
                throw new ArgumentNullException(nameof(action));
            Option p = new ActionOption(prototype, description, 1,
                    delegate(OptionValueCollection 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 is null)
                throw new ArgumentNullException(nameof(action));
            Option p = new ActionOption(prototype, description, 2,
                    delegate(OptionValueCollection v) { action(v[0], v[1]); });
            base.Add(p);
            return this;
        }

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

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

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

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

            public ActionOption(string prototype, string description, OptionAction<TKey, TValue> action)
                : base(prototype, description, 2)
            {
                if (action is null)
                    throw new ArgumentNullException(nameof(action));
                _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;
            List<string> 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);
            }

            c.Option?.Invoke(c);
            return unprocessed;
        }

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

        private static 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 is null)
                throw new ArgumentNullException(nameof(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 is not null)
            {
                ParseValue(argument, c);
                return true;
            }

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

            Option p;
            if (Contains(n))
            {
                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;
        }

        private void ParseValue(string option, OptionContext c)
        {
            if (option is not null)
            {
                foreach (string o in c.Option.ValueSeparators is not 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(Localizer($"Error: Found {c.OptionValues.Count} option values when expecting {c.Option.MaxValueCount}."),
                        c.OptionName);
            }
        }

        private bool ParseBool(string option, string n, OptionContext c)
        {
            Option p;
            string rn;
            if (n.Length >= 1 && (n[n.Length - 1] == '+' || n[n.Length - 1] == '-') &&
                    Contains((rn = n.Substring(0, n.Length - 1))))
            {
                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;
        }

        private bool ParseBundledValue(string f, string n, OptionContext c)
        {
            if (f != "-")
                return false;
            for (int i = 0; i < n.Length; ++i)
            {
                Option p;
                string opt = f + n[i];
                string rn = n[i].ToString();
                if (!Contains(rn))
                {
                    if (i == 0)
                        return false;
                    throw new OptionException(string.Format(Localizer(
                                    "Cannot bundle unregistered option '{0}'."), opt), opt);
                }
                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;
        }

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

        private const int OptionWidth = 29;

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

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

                bool indent = false;
                string prefix = new string(' ', OptionWidth + 2);
                foreach (string line in GetLines(Localizer(GetDescription(p.Description))))
                {
                    if (indent)
                        o.Write(prefix);
                    o.WriteLine(line);
                    indent = true;
                }
            }
        }

        private 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, Localizer("["));
                }
                Write(o, ref written, Localizer("=" + GetArgumentName(0, p.MaxValueCount, p.Description)));
                string sep = p.ValueSeparators is not null && p.ValueSeparators.Length > 0
                    ? p.ValueSeparators[0]
                    : " ";
                for (int c = 1; c < p.MaxValueCount; ++c)
                {
                    Write(o, ref written, Localizer(sep + GetArgumentName(c, p.MaxValueCount, p.Description)));
                }
                if (p.OptionValueType == OptionValueType.Optional)
                {
                    Write(o, ref written, Localizer("]"));
                }
            }
            return true;
        }

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

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

        private static string GetArgumentName(int index, int maxIndex, string description)
        {
            if (description is null)
                return maxIndex == 1 ? "VALUE" : "VALUE" + (index + 1);
            string[] nameStart;
            if (maxIndex == 1)
                nameStart = new[] { "{0:", "{" };
            else
                nameStart = new[] { "{" + index + ":" };
            for (int i = 0; i < nameStart.Length; ++i)
            {
                int start, j = 0;
                do
                {
                    start = description.IndexOf(nameStart[i], j);
                }
                while (start >= 0 && j != 0 ? description[j++ - 1] == '{' : false);
                if (start == -1)
                    continue;
                int end = description.IndexOf("}", start);
                if (end == -1)
                    continue;
                return description.Substring(start + nameStart[i].Length, end - start - nameStart[i].Length);
            }
            return maxIndex == 1 ? "VALUE" : "VALUE" + (index + 1);
        }

        private static string GetDescription(string description)
        {
            if (description is null)
                return string.Empty;
            StringBuilder 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();
        }

        private static IEnumerable<string> GetLines(string description)
        {
            if (string.IsNullOrEmpty(description))
            {
                yield return string.Empty;
                yield break;
            }
            int length = 80 - OptionWidth - 1;
            int start = 0, end;
            do
            {
                end = GetLineEnd(start, length, description);
                char c = description[end - 1];
                if (char.IsWhiteSpace(c))
                    --end;
                bool writeContinuation = end != description.Length && !IsEolChar(c);
                string line = description.Substring(start, end - start) +
                        (writeContinuation ? "-" : string.Empty);
                yield return line;
                start = end;
                if (char.IsWhiteSpace(c))
                    ++start;
                length = 80 - OptionWidth - 2 - 1;
            }
            while (end < description.Length);
        }

        private static bool IsEolChar(char c)
        {
            return !char.IsLetterOrDigit(c);
        }

        private static int GetLineEnd(int start, int length, string description)
        {
            int end = System.Math.Min(start + length, description.Length);
            int sep = -1;
            for (int i = start + 1; i < end; ++i)
            {
                if (description[i] == '\n')
                    return i + 1;
                if (IsEolChar(description[i]))
                    sep = i + 1;
            }
            if (sep == -1 || end == description.Length)
                return end;
            return sep;
        }
    }
}