Conditions now can be used by other plugins

To make other plugins to be able extend you need 

1) Define class that is marked [ConditionModule]

2) Add method in that class is marked by [Condition("name", helpText: "tooltip")]

3) Method should return bool, and accept MyCubeGrid. It may also accept 1 extra param (string, double, int ...)

Essentials/Conditions/Condition.cs

@@ -0,0 +1,66 @@
+using System;
+using System.Reflection;
+using Sandbox.Game.Entities;
+using Torch.Commands;
+
+namespace Essentials.Conditions
+{
+    public class Condition
+    {
+        public string Command;
+        public string InvertCommand;
+        public string HelpText;
+        private MethodInfo _method;
+        public readonly ParameterInfo Parameter;
+
+        public Condition(MethodInfo evalMethod, ConditionAttribute attribute)
+        {
+            Command = attribute.Command;
+            InvertCommand = attribute.InvertCommand;
+            HelpText = attribute.HelpText;
+            _method = evalMethod;
+            if (_method.ReturnType != typeof(bool))
+                throw new TypeLoadException("Condition does not return a bool!");
+            var p = _method.GetParameters();
+            if (p.Length < 1 || p[0].ParameterType != typeof(MyCubeGrid))
+                throw new TypeLoadException("Condition does not accept MyCubeGrid as first parameter");
+            if (p.Length > 2)
+                throw new TypeLoadException("Condition can only have two parameters");
+            if (p.Length == 1)
+                Parameter = null;
+            else
+                Parameter = p[1];
+        }
+
+        public bool? Evaluate(MyCubeGrid grid, string arg, bool invert, CommandContext context)
+        {
+            bool result;
+            if (!string.IsNullOrEmpty(arg) && Parameter == null)
+            {
+                context.Respond($"Condition does not accept an argument. Cannot continue!");
+                return null;
+            }
+            if (string.IsNullOrEmpty(arg) && Parameter != null && !Parameter.HasDefaultValue)
+            {
+                context.Respond($"Condition requires an argument! {Parameter.ParameterType.Name}: {Parameter.Name} Not supplied, cannot continue!");
+                return null;
+            }
+            if (Parameter != null && !string.IsNullOrEmpty(arg))
+            {
+                if (!arg.TryConvert(Parameter.ParameterType, out object val))
+                {
+                    context.Respond($"Could not parse argument!");
+                    return null;
+                }
+
+                result = (bool)_method.Invoke(null, new[] { grid, val });
+            }
+            else
+            {
+                result = (bool)_method.Invoke(null, new object[] { grid });
+            }
+
+            return result != invert;
+        }
+    }
+}

Essentials/Conditions/ConditionAttribute.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace Essentials
+{
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+    public sealed class ConditionAttribute : Attribute
+    {
+        public string Command;
+        public string InvertCommand;
+        public string HelpText;
+
+        public ConditionAttribute(string command, string invertCommand = null, string helpText = null)
+        {
+            Command = command;
+            InvertCommand = invertCommand;
+            HelpText = helpText;
+        }
+    }
+}

Essentials/Conditions/ConditionModule.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace Essentials
+{
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
+    public sealed class ConditionModule : Attribute
+    {
+
+    }
+}

Essentials/Conditions/ConditionsChecker.cs

@@ -0,0 +1,143 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using Essentials.Conditions;
+using ParallelTasks;
+using Sandbox.Game.Entities;
+using Torch.Commands;
+
+namespace Essentials.Commands
+{
+    public static class ConditionsChecker
+    {
+        private static List<Condition> _conditionLookup;
+
+        public static void Init()
+        {
+            _conditionLookup = new List<Condition>();
+
+            var types = AppDomain.CurrentDomain.GetAssemblies()
+                .SelectMany((x) =>
+                {
+                    try
+                    {
+                        return x.GetTypes();
+                    }
+                    catch (Exception e) // ignored 
+                    {
+                        return new Type[0];
+                    }
+                }).Where(t => t.IsDefined(typeof(ConditionModule)));
+
+            foreach (var type in types)
+            {
+                var methods = type.GetMethods(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static);
+                foreach (var m in methods)
+                {
+                    var a = m.GetCustomAttribute<ConditionAttribute>();
+                    if (a == null)
+                        continue;
+
+                    var c = new Condition(m, a);
+
+                    _conditionLookup.Add(c);
+                }
+            }
+        }
+
+        public static List<Condition> GetAllConditions()
+        {
+            return _conditionLookup;
+        }
+
+        public static IEnumerable<MyCubeGrid> ScanConditions(CommandContext context, IReadOnlyList<string> args)
+        {
+            var conditions = new List<Func<MyCubeGrid, bool?>>();
+
+            for (var i = 0; i < args.Count; i++)
+            {
+                string parameter;
+                if (i + 1 >= args.Count)
+                {
+                    parameter = null;
+                }
+                else
+                {
+                    parameter = args[i + 1];
+                }
+
+                var arg = args[i];
+
+                if (parameter != null)
+                {
+                    //parameter is the name of a command. Assume this command requires no parameters
+                    if (_conditionLookup.Any(c => parameter.Equals(c.Command, StringComparison.CurrentCultureIgnoreCase) || parameter.Equals(c.InvertCommand, StringComparison.CurrentCultureIgnoreCase)))
+                    {
+                        parameter = null;
+                    }
+                    //next string is a parameter, so pass it to the condition and skip it next loop
+                    else
+                        i++;
+                }
+
+                bool found = false;
+
+                foreach (var condition in _conditionLookup)
+                {
+                    if (arg.Equals(condition.Command, StringComparison.CurrentCultureIgnoreCase))
+                    {
+                        conditions.Add(g => condition.Evaluate(g, parameter, false, context));
+                        found = true;
+                        break;
+                    }
+                    else if (arg.Equals(condition.InvertCommand, StringComparison.CurrentCultureIgnoreCase))
+                    {
+                        conditions.Add(g => condition.Evaluate(g, parameter, true, context));
+                        found = true;
+                        break;
+                    }
+                }
+                if (!found)
+                {
+                    context.Respond($"Unknown argument '{arg}'");
+                    yield break;
+                }
+            }
+
+            //default scan to find grids without pilots
+            if (!args.Contains("haspilot", StringComparer.CurrentCultureIgnoreCase))
+                conditions.Add(g => !ConditionsImplementations.Piloted(g));
+
+            foreach (var group in MyCubeGridGroups.Static.Logical.Groups)
+            {
+                //if (group.Nodes.All(grid => conditions.TrueForAll(func => func(grid.NodeData))))
+                bool res = true;
+                foreach (var node in group.Nodes)
+                {
+                    if (node.NodeData.Projector != null)
+                        continue;
+
+                    foreach (var c in conditions)
+                    {
+                        bool? r = c.Invoke(node.NodeData);
+                        if (r == null)
+                            yield break;
+                        if (r == true)
+                            continue;
+
+                        res = false;
+                        break;
+                    }
+                    if (!res)
+                        break;
+                }
+
+                if (res)
+                    foreach (var grid in group.Nodes.Where(x => x.NodeData.Projector == null))
+                        yield return grid.NodeData;
+            }
+        }
+
+    }
+}