add plugin loading and game modes

Assets/Prefabs/GameManager.prefab

@@ -27,6 +27,8 @@ GameObject:
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   m_Layer: 0
   m_Name: GameManager
   m_TagString: Untagged
@@ -352,3 +354,27 @@ MonoBehaviour:
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Assets/Scripts/Behaviours/GameModeManager.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace SanAndreasUnity.Behaviours
+{
+    public class GameModeManager : MonoBehaviour
+    {
+        public static GameModeManager Instance { get; private set; }
+
+        public class GameModeInfo
+        {
+            public string Name { get; }
+            public string Description { get; }
+            public System.Action ActivationCallback { get; }
+
+            public GameModeInfo(string name, string description, Action activationCallback)
+            {
+                Name = name;
+                Description = description;
+                ActivationCallback = activationCallback;
+            }
+        }
+
+        List<GameModeInfo> m_gameModes = new List<GameModeInfo>();
+        public IReadOnlyList<GameModeInfo> GameModes => m_gameModes;
+
+        private GameModeInfo m_activeGameMode;
+
+
+        void Awake()
+        {
+            Instance = this;
+        }
+
+        public void RegisterGameMode(GameModeInfo gameModeInfo)
+        {
+            m_gameModes.Add(gameModeInfo);
+        }
+
+        public void ActivateGameMode(GameModeInfo gameModeInfo)
+        {
+            if (m_activeGameMode != null)
+            {
+                if (m_activeGameMode == gameModeInfo)
+                    throw new Exception($"Can not activate game mode '{gameModeInfo.Name}' because it is already activated");
+                throw new Exception($"Can not activate game mode '{gameModeInfo.Name}' because another one ('{m_activeGameMode.Name}') is already activated");
+            }
+
+            m_activeGameMode = gameModeInfo;
+            gameModeInfo.ActivationCallback();
+        }
+    }
+}

Assets/Scripts/Behaviours/GameModeManager.cs.meta

@@ -0,0 +1,11 @@
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+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Assets/Scripts/Behaviours/PluginManager.cs

@@ -0,0 +1,66 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Reflection;
+using SanAndreasUnity.Utilities;
+using UnityEngine;
+
+namespace SanAndreasUnity.Behaviours
+{
+    public class PluginManager : MonoBehaviour
+    {
+
+        public static string[] PluginDirectories => new []
+        {
+            #if UNITY_EDITOR
+            Path.Combine(Application.dataPath, "../SAU_Plugins"),
+            #else
+            Path.Combine(Application.dataPath, "Plugins"),
+            #endif
+        };
+
+        void Awake()
+        {
+            F.RunExceptionSafe(LoadPlugins, $"Error while loading plugins: ");
+        }
+
+        void LoadPlugins()
+        {
+            // find all plugins
+
+            var allFiles = new List<string>();
+            foreach (string pluginsDirectory in PluginDirectories)
+            {
+                if (!Directory.Exists(pluginsDirectory))
+                    continue;
+
+                var filePaths = Directory.GetFiles(pluginsDirectory, "*.dll", SearchOption.TopDirectoryOnly);
+
+                // sort files manually to prevent undefined behavior
+                Array.Sort(filePaths);
+
+                allFiles.AddRange(filePaths);
+            }
+
+            //allFiles.RemoveAll(path => !path.EndsWith(".json", StringComparison.InvariantCultureIgnoreCase) || !path.EndsWith(".dll", StringComparison.InvariantCultureIgnoreCase));
+
+
+            int numLoaded = 0;
+            foreach (string pluginFilePath in allFiles)
+            {
+                if (LoadPlugin(pluginFilePath))
+                    numLoaded++;
+            }
+
+            if (allFiles.Count > 0)
+                Debug.Log($"Loaded {numLoaded}/{allFiles.Count} plugins");
+        }
+
+        bool LoadPlugin(string pluginFilePath)
+        {
+            return F.RunExceptionSafe(
+                () => Assembly.LoadFrom(pluginFilePath),
+                $"error loading plugin from '{pluginFilePath}': ");
+        }
+    }
+}

Assets/Scripts/Behaviours/PluginManager.cs.meta

@@ -0,0 +1,11 @@
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+MonoImporter:
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+  defaultReferences: []
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+  userData: 
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Assets/Scripts/UI/StartGameWindow.cs

@@ -1,4 +1,6 @@
 using System.Collections.Generic;
+using System.Linq;
+using SanAndreasUnity.Behaviours;
 using UnityEngine;
 using SanAndreasUnity.Utilities;
 using SanAndreasUnity.Net;
@@ -13,7 +15,7 @@ namespace SanAndreasUnity.UI
 		bool m_dedicatedServer = false;
 		string m_maxNumPlayersStr = "40";
 		[SerializeField] string[] m_availableScenes = new string[0];
-		int m_selectedSceneIndex = 0;
+		int m_selectedModeIndex = 0;
 	    bool m_registerAtMasterServer = false;
 
 		public int width = 550;
@@ -60,8 +62,12 @@ namespace SanAndreasUnity.UI
 			GUILayout.Label("Max num players:");
 			m_maxNumPlayersStr = GUILayout.TextField(m_maxNumPlayersStr, GUILayout.Width(100));
 
-			GUILayout.Label("Map:");
-			m_selectedSceneIndex = GUILayout.SelectionGrid(m_selectedSceneIndex, m_availableScenes, this.mapSelectionGridXCount, GUILayout.MinHeight(this.minMapButtonHeight));
+			GUILayout.Label("Game mode:");
+			m_selectedModeIndex = GUILayout.SelectionGrid(
+				m_selectedModeIndex,
+				m_availableScenes.Concat(GameModeManager.Instance.GameModes.Select(gm => gm.Name)).ToArray(),
+				this.mapSelectionGridXCount,
+				GUILayout.MinHeight(this.minMapButtonHeight));
 			GUILayout.Space(5);
 
 			m_registerAtMasterServer = GUILayout.Toggle(m_registerAtMasterServer, "Register at master server");
@@ -86,13 +92,24 @@ namespace SanAndreasUnity.UI
 			try
 			{
 				ushort port = ushort.Parse(m_portStr);
-				string scene = m_availableScenes[m_selectedSceneIndex];
+				string scene = m_selectedModeIndex < m_availableScenes.Length
+					? m_availableScenes[m_selectedModeIndex]
+					: m_availableScenes[0];
 				ushort maxNumPlayers = ushort.Parse(m_maxNumPlayersStr);
 
 				MasterServerClient.Instance.IsServerRegistrationEnabled = m_registerAtMasterServer;
 
 				NetManager.StartServer(port, scene, maxNumPlayers, m_dedicatedServer, m_dontListen);
 
+				// activate game mode if it is selected
+				if (m_selectedModeIndex >= m_availableScenes.Length)
+				{
+					var gm = GameModeManager.Instance.GameModes[m_availableScenes.Length - m_selectedModeIndex];
+					F.RunExceptionSafe(
+						() => GameModeManager.Instance.ActivateGameMode(gm),
+						$"Error while activating game mode '{gm.Name}': ");
+				}
+
 			}
 			catch (System.Exception ex)
 			{

Assets/Scripts/Utilities/F.cs

@@ -396,6 +396,20 @@ namespace SanAndreasUnity.Utilities
 		}
 
 
+		public static bool RunExceptionSafe (System.Action function, string errorMessagePrefix)
+		{
+			try {
+				function();
+				return true;
+			} catch(System.Exception ex) {
+				try {
+					Debug.LogError (errorMessagePrefix + ex);
+				} catch {}
+			}
+
+			return false;
+		}
+
 		public static void RunExceptionSafe (System.Action function)
 		{
 			try {