ModernUO/Projects/Scripts/Commands/Generic/Extensions/DistinctExtension.cs

using System;
using System.Collections.Generic;

namespace Server.Commands.Generic
{
  public sealed class DistinctExtension : BaseExtension
  {
    public static ExtensionInfo ExtInfo =
      new ExtensionInfo(30, "Distinct", -1, () => new DistinctExtension());

    private IComparer<object> m_Comparer;

    private List<Property> m_Properties;

    public DistinctExtension() => m_Properties = new List<Property>();

    public override ExtensionInfo Info => ExtInfo;

    public static void Initialize()
    {
      ExtensionInfo.Register(ExtInfo);
    }

    public override void Optimize(Mobile from, Type baseType, ref AssemblyEmitter assembly)
    {
      if (baseType == null)
        throw new Exception("Distinct extension may only be used in combination with an object conditional.");

      foreach (Property prop in m_Properties)
      {
        prop.BindTo(baseType, PropertyAccess.Read);
        prop.CheckAccess(from);
      }

      assembly ??= new AssemblyEmitter("__dynamic");

      m_Comparer = DistinctCompiler.Compile<object>(assembly, baseType, m_Properties.ToArray());
    }

    public override void Parse(Mobile from, string[] arguments, int offset, int size)
    {
      if (size < 1)
        throw new Exception("Invalid distinction syntax.");

      int end = offset + size;

      while (offset < end)
      {
        string binding = arguments[offset++];

        m_Properties.Add(new Property(binding));
      }
    }

    public override void Filter(List<object> list)
    {
      if (m_Comparer == null)
        throw new InvalidOperationException("The extension must first be optimized.");

      List<object> copy = new List<object>(list);

      copy.Sort(m_Comparer);

      list.Clear();

      object last = null;

      for (int i = 0; i < copy.Count; ++i)
      {
        object obj = copy[i];

        if (last == null || m_Comparer.Compare(obj, last) != 0)
        {
          list.Add(obj);
          last = obj;
        }
      }
    }
  }
}