PluginCommandManager.cs

using Dalamud.Game.Command;
using Dalamud.Plugin;
using FATEAutoSync.Attributes;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using static Dalamud.Game.Command.CommandInfo;
// ReSharper disable ForCanBeConvertedToForeach

namespace FATEAutoSync
{
  public class PluginCommandManager<THost> : IDisposable
  {
    private readonly CommandManager commandManager;
    private readonly (string, CommandInfo)[] pluginCommands;
    private readonly THost host;

    public PluginCommandManager(THost host, CommandManager commands)
    {
      this.commandManager = commands;
      this.host = host;

      this.pluginCommands = host.GetType().GetMethods(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance)
        .Where(method => method.GetCustomAttribute<CommandAttribute>() != null)
        .SelectMany(GetCommandInfoTuple)
        .ToArray();

      AddCommandHandlers();
    }

    // http://codebetter.com/patricksmacchia/2008/11/19/an-easy-and-efficient-way-to-improve-net-code-performances/
    // Benchmarking this myself gave similar results, so I'm doing this to somewhat counteract using reflection to access command attributes.
    // I like the convenience of attributes, but in principle it's a bit slower to use them as opposed to just initializing CommandInfos directly.
    // It's usually sub-1 millisecond anyways, though. It probably doesn't matter at all.
    private void AddCommandHandlers()
    {
      for (var i = 0; i < this.pluginCommands.Length; i++)
      {
        var (command, commandInfo) = this.pluginCommands[i];
        this.commandManager.AddHandler(command, commandInfo);
      }
    }

    private void RemoveCommandHandlers()
    {
      for (var i = 0; i < this.pluginCommands.Length; i++)
      {
        var (command, _) = this.pluginCommands[i];
        this.commandManager.RemoveHandler(command);
      }
    }

    private IEnumerable<(string, CommandInfo)> GetCommandInfoTuple(MethodInfo method)
    {
      var handlerDelegate = (HandlerDelegate)Delegate.CreateDelegate(typeof(HandlerDelegate), this.host, method);

      var command = handlerDelegate.Method.GetCustomAttribute<CommandAttribute>();
      var aliases = handlerDelegate.Method.GetCustomAttribute<AliasesAttribute>();
      var helpMessage = handlerDelegate.Method.GetCustomAttribute<HelpMessageAttribute>();
      var doNotShowInHelp = handlerDelegate.Method.GetCustomAttribute<DoNotShowInHelpAttribute>();

      var commandInfo = new CommandInfo(handlerDelegate)
      {
        HelpMessage = helpMessage?.HelpMessage ?? string.Empty,
        ShowInHelp = doNotShowInHelp == null,
      };

      // Create list of tuples that will be filled with one tuple per alias, in addition to the base command tuple.
      var commandInfoTuples = new List<(string, CommandInfo)> { (command.Command, commandInfo) };
      if (aliases != null)
      {
        // ReSharper disable once LoopCanBeConvertedToQuery
        for (var i = 0; i < aliases.Aliases.Length; i++)
        {
          commandInfoTuples.Add((aliases.Aliases[i], commandInfo));
        }
      }

      return commandInfoTuples;
    }

    public void Dispose()
    {
      RemoveCommandHandlers();
    }
  }
}