Add API for injecting client mods

Torch.API/Session/ITorchSessionManager.cs

@@ -1,9 +1,11 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using Torch.API.Managers;
+using VRage.Game;
 
 namespace Torch.API.Session
 {
@@ -47,5 +49,29 @@ namespace Torch.API.Session
         /// <returns>true if removed, false if not present</returns>
         /// <exception cref="ArgumentNullException">If the factory is null</exception>
         bool RemoveFactory(SessionManagerFactoryDel factory);
+
+        /// <summary>
+        /// Add a mod to be injected into client's world download.
+        /// </summary>
+        /// <param name="modId"></param>
+        /// <returns></returns>
+        bool AddOverrideMod(ulong modId);
+        
+        /// <summary>
+        /// Removes a mod from the injected mod list.
+        /// </summary>
+        /// <param name="modId"></param>
+        /// <returns></returns>
+        bool RemoveOverrideMod(ulong modId);
+        
+        /// <summary>
+        /// List over mods that will be injected into client world downloads.
+        /// </summary>
+        IReadOnlyCollection<MyObjectBuilder_Checkpoint.ModItem> OverrideMods { get; }
+
+        /// <summary>
+        /// Event raised when injected mod list changes.
+        /// </summary>
+        event Action<CollectionChangeEventArgs> OverrideModsChanged;
     }
 }

Torch/Patches/SessionDownloadPatch.cs

@@ -7,6 +7,8 @@ using System.Text;
 using System.Threading.Tasks;
 using NLog;
 using Sandbox.Game.World;
+using Torch.API.Session;
+using Torch.API.Managers;
 using Torch.Managers.PatchManager;
 using Torch.Mod;
 using VRage.Game;
@@ -16,6 +18,10 @@ namespace Torch.Patches
     [PatchShim]
     internal static class SessionDownloadPatch
     {
+        private static ITorchSessionManager _sessionManager;
+        private static ITorchSessionManager SessionManager => _sessionManager ?? (_sessionManager = TorchBase.Instance.Managers.GetManager<ITorchSessionManager>());
+
+
         internal static void Patch(PatchContext context)
         {
             context.GetPattern(typeof(MySession).GetMethod(nameof(MySession.GetWorld))).Suffixes.Add(typeof(SessionDownloadPatch).GetMethod(nameof(SuffixGetWorld), BindingFlags.Static | BindingFlags.NonPublic));
@@ -27,7 +33,7 @@ namespace Torch.Patches
             //copy this list so mods added here don't propagate up to the real session
             __result.Checkpoint.Mods = __result.Checkpoint.Mods.ToList();
             
-            __result.Checkpoint.Mods.Add(new MyObjectBuilder_Checkpoint.ModItem(TorchModCore.MOD_ID));
+            __result.Checkpoint.Mods.AddRange(SessionManager.OverrideMods);
         }
     }
 }

Torch/Session/TorchSessionManager.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
@@ -9,7 +10,9 @@ using Torch.API;
 using Torch.API.Managers;
 using Torch.API.Session;
 using Torch.Managers;
+using Torch.Mod;
 using Torch.Session;
+using VRage.Game;
 
 namespace Torch.Session
 {
@@ -21,6 +24,15 @@ namespace Torch.Session
         private static readonly Logger _log = LogManager.GetCurrentClassLogger();
         private TorchSession _currentSession;
 
+        private readonly Dictionary<ulong, MyObjectBuilder_Checkpoint.ModItem> _overrideMods;
+
+        public event Action<CollectionChangeEventArgs> OverrideModsChanged;
+
+        /// <summary>
+        /// List of mods that will be injected into client world downloads.
+        /// </summary>
+        public IReadOnlyCollection<MyObjectBuilder_Checkpoint.ModItem> OverrideMods => _overrideMods.Values;
+
         /// <inheritdoc />
         public event TorchSessionStateChangedDel SessionStateChanged;
 
@@ -31,6 +43,8 @@ namespace Torch.Session
 
         public TorchSessionManager(ITorchBase torchInstance) : base(torchInstance)
         {
+            _overrideMods = new Dictionary<ulong, MyObjectBuilder_Checkpoint.ModItem>();
+            _overrideMods.Add(TorchModCore.MOD_ID, new MyObjectBuilder_Checkpoint.ModItem(TorchModCore.MOD_ID));
         }
 
         /// <inheritdoc/>
@@ -49,6 +63,27 @@ namespace Torch.Session
             return _factories.Remove(factory);
         }
 
+        /// <inheritdoc/>
+        public bool AddOverrideMod(ulong modId)
+        {
+            if (_overrideMods.ContainsKey(modId))
+                return false;
+            var item = new MyObjectBuilder_Checkpoint.ModItem();
+            _overrideMods.Add(modId, item);
+
+            OverrideModsChanged?.Invoke(new CollectionChangeEventArgs(CollectionChangeAction.Add, item));
+            return true;
+        }
+
+        /// <inheritdoc/>
+        public bool RemoveOverrideMod(ulong modId)
+        {
+            if(_overrideMods.TryGetValue(modId, out var item))
+                OverrideModsChanged?.Invoke(new CollectionChangeEventArgs(CollectionChangeAction.Remove, item));
+
+            return _overrideMods.Remove(modId);
+        }
+
         #region Session events
 
         private void SetState(TorchSessionState state)