/// <summary>
/// Creates a new character group with the given sub-expressions.
/// </summary>
/// <param name="isNegated">Indicates whether the character group should be negated.</param>
/// <param name="expressions">The sub-expressions to add to the character group.</param>
/// <returns>The character group.</returns>
public static ICharacterGroup From(CharacterGroupOptions options, IEnumerable <ICharacterGroupMember> expressions)
{
if (expressions == null)
{
throw new ArgumentNullException(nameof(expressions));
}
var group = new CharacterGroup()
{
IsNegated = options?.IsNegated ?? false,
Exclusions = options?.Exclusions
};
foreach (var expression in expressions)
{
group.Add(expression);
}
return(group);
}
private ICharacterGroup ParseCharacterGroupInternal()
{
++index; // swallow '['
var members = new List <ICharacterGroupMember>();
bool isNegated = regex[index] == '^';
if (isNegated)
{
++index; // swallow '^'
}
bool isDone = false;
ICharacterGroup exclusions = null;
while (!isDone)
{
var nextChar = regex[index];
switch (nextChar)
{
case ']':
isDone = true;
++index; // swallow ']'
break;
case '-':
++index; // swallow '-'
if (index == regex.Length)
{
// The Regex constructor should prevent this
throw new InvalidOperationException();
}
else if (regex[index] == '[')
{
exclusions = ParseCharacterGroupInternal();
}
else if (members.Count == 0 || regex[index] == ']')
{
// If '-' is the first or last character, add it literally
members.Add(Literal.For('-'));
}
else
{
var lastMember = members[members.Count - 1];
var range = ParseRange(lastMember);
members.RemoveAt(members.Count - 1);
members.Add(range);
}
break;
default:
var member = ParseCharacterGroupMember();
members.Add(member);
break;
}
}
var options = new CharacterGroupOptions()
{
IsNegated = isNegated, Exclusions = exclusions
};
return(CharacterGroup.From(options, members));
}