docs(CommandHookModSystem): add XML doc comments to Register/Unregister and internal comments to Rebuild, FireBefore, FireAfter, CommandListEquals

CommandHook/CommandHookModSystem.cs

@@ -7,6 +7,20 @@ using Vintagestory.API.Server;
 
 namespace CommandHook;
 
+/// <summary>
+/// Server-side event bus for chat commands. Other mods register an
+/// <see cref="ICommandHookListener"/> here to get Before/After callbacks on
+/// specific command names, namespaced by <see cref="ICommandHookListener.ModId"/>
+/// so multiple mods can watch the same command without stepping on each other.
+/// </summary>
+/// <remarks>
+/// Patches <c>ChatCommandApi.Execute</c> via Harmony. Server only, see
+/// <see cref="ShouldLoad"/>. A listener's <see cref="ICommandHookListener.Commands"/>
+/// and <see cref="ICommandHookListener.Registration"/> are read at registration
+/// time and cached in a <see cref="System.Collections.Frozen.FrozenDictionary{TKey,TValue}"/>
+/// for fast lookup on the command dispatch path. If you change which commands a
+/// listener watches, call <see cref="Register"/> again with the updated list.
+/// </remarks>
 public class CommandHookModSystem : ModSystem
 {
     internal static CommandHookModSystem? Instance;
@@ -38,6 +52,17 @@ public class CommandHookModSystem : ModSystem
         Instance = null;
     }
 
+    /// <summary>
+    /// Registers a listener for the commands it returns from <see cref="ICommandHookListener.Commands"/>.
+    /// </summary>
+    /// <remarks>
+    /// Calling this again for a <see cref="ICommandHookListener.ModId"/> that is already
+    /// registered replaces its previous registration. If the new <see cref="ICommandHookListener.Commands"/>
+    /// list is identical to the existing one this is a no-op, no rebuild happens.
+    /// If <paramref name="listener"/> has a null or empty <see cref="ICommandHookListener.Commands"/>
+    /// list, this just calls <see cref="Unregister"/> instead.
+    /// </remarks>
+    /// <param name="listener">The listener to register or update.</param>
     public void Register(ICommandHookListener listener)
     {
         var commands = listener.Commands;
@@ -66,6 +91,11 @@ public class CommandHookModSystem : ModSystem
             Rebuild();
     }
 
+    /// <summary>
+    /// Removes a listener's registration entirely. Safe to call on a listener
+    /// that was never registered, this is a no-op in that case.
+    /// </summary>
+    /// <param name="listener">The listener to remove, matched by <see cref="ICommandHookListener.ModId"/>.</param>
     public void Unregister(ICommandHookListener listener)
     {
         int index = listeners.FindIndex(l => l.ModId == listener.ModId);
@@ -77,6 +107,14 @@ public class CommandHookModSystem : ModSystem
         Rebuild();
     }
 
+    // Rebuilds the dispatch table from listeners. Runs unconditionally and
+    // immediately whenever Register/Unregister actually changes something,
+    // no batching or startup-phase awareness. Command list sizes here are
+    // small (a handful of mods, a handful of commands each), so the realloc
+    // on every change is cheap and not worth the complexity of an incremental
+    // update. The two-level structure (command -> ModId -> registration) is
+    // what FireBefore/FireAfter walk on the hot path, so it's built once here
+    // instead of being derived per-dispatch.
     private void Rebuild()
     {
         var builder = new Dictionary<string, Dictionary<string, CommandRegistration>>();
@@ -108,6 +146,13 @@ public class CommandHookModSystem : ModSystem
         registrations = pruned.ToFrozenDictionary();
     }
 
+    // Called from ChatCommandApiPatch.Prefix before the real command executes.
+    // CommandData is passed by ref the whole way down, no allocation here.
+    // Each listener's Before is isolated in its own try/catch so one mod
+    // throwing doesn't stop the rest from running or break command dispatch
+    // for the server. If a listener sets data.Cancel, we stop walking the
+    // rest of the listeners immediately rather than letting them all run
+    // against an already-cancelled command.
     internal bool FireBefore(string commandName, ref CommandData data)
     {
         if (registrations.TryGetValue(commandName, out var mods))
@@ -131,6 +176,11 @@ public class CommandHookModSystem : ModSystem
         return data.Cancel;
     }
 
+    // Called from the wrapped onCommandComplete in ChatCommandApiPatch.Prefix,
+    // only on the path where the command actually ran (Before didn't cancel).
+    // Same per-listener try/catch as FireBefore, but there's no early-out here
+    // since cancelling after the fact doesn't mean anything, the command
+    // already ran.
     internal void FireAfter(string commandName, ref CommandData data, TextCommandResult result)
     {
         if (registrations.TryGetValue(commandName, out var mods))
@@ -149,6 +199,10 @@ public class CommandHookModSystem : ModSystem
         }
     }
 
+    // Order-sensitive on purpose. Register only treats an update as a no-op
+    // if the list is identical in order and content, a reordered list still
+    // triggers a rebuild. Cheap to check (just an index walk, no allocation)
+    // and correctness here matters more than being lenient about ordering.
     private static bool CommandListEquals(IReadOnlyList<string> a, IReadOnlyList<string> b)
     {
         if (a.Count != b.Count)