feat: Consuming Item Event (#805)

* one shot

* fix doc

* d

Author: MS-crew

EXILED/Exiled.Events/EventArgs/Interfaces/IConsumableEvent.cs

@@ -0,0 +1,22 @@
+// -----------------------------------------------------------------------
+// <copyright file="IConsumableEvent.cs" company="ExMod Team">
+// Copyright (c) ExMod Team. All rights reserved.
+// Licensed under the CC BY-SA 3.0 license.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Exiled.Events.EventArgs.Interfaces
+{
+    using Exiled.API.Features.Items;
+
+    /// <summary>
+    /// Event args used for all <see cref="API.Features.Items.Consumable" /> related events.
+    /// </summary>
+    public interface IConsumableEvent : IItemEvent
+    {
+        /// <summary>
+        /// Gets the <see cref="API.Features.Items.Consumable" /> triggering the event.
+        /// </summary>
+        public Consumable Consumable { get; }
+    }
+}

EXILED/Exiled.Events/EventArgs/Player/ConsumingItemEventArgs.cs

@@ -0,0 +1,49 @@
+// -----------------------------------------------------------------------
+// <copyright file="ConsumingItemEventArgs.cs" company="ExMod Team">
+// Copyright (c) ExMod Team. All rights reserved.
+// Licensed under the CC BY-SA 3.0 license.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Exiled.Events.EventArgs.Player
+{
+    using API.Features;
+    using API.Features.Items;
+
+    using Exiled.Events.EventArgs.Interfaces;
+
+    /// <summary>
+    /// Contains all information before a player's consumable item effects are applied.
+    /// </summary>
+    public class ConsumingItemEventArgs : IPlayerEvent, IDeniableEvent, IConsumableEvent
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ConsumingItemEventArgs" /> class.
+        /// </summary>
+        /// <param name="hub">The player who is consuming the item.</param>
+        /// <param name="item">The consumable item to be consumed.</param>
+        public ConsumingItemEventArgs(ReferenceHub hub, InventorySystem.Items.Usables.Consumable item)
+        {
+            Player = Player.Get(hub);
+            Consumable = Item.Get(item) as Consumable;
+        }
+
+        /// <summary>
+        /// Gets the consumable item to be consumed.
+        /// </summary>
+        public Consumable Consumable { get; }
+
+        /// <inheritdoc/>
+        public Item Item => Consumable;
+
+        /// <summary>
+        /// Gets the player who is consuming the item.
+        /// </summary>
+        public Player Player { get; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether the item's being consumed should be allowed or not.
+        /// </summary>
+        public bool IsAllowed { get; set; } = true;
+    }
+}

EXILED/Exiled.Events/Handlers/Player.cs

@@ -98,6 +98,11 @@ public class Player
         /// </remarks>
         public static Event<UsedItemEventArgs> UsedItem { get; set; } = new();
 
+        /// <summary>
+        /// Invoked before a <see cref="API.Features.Player"/> consumes an <see cref="API.Features.Items.Consumable"/>. In other words, it is invoked before the consumable item logic are applied.
+        /// </summary>
+        public static Event<ConsumingItemEventArgs> ConsumingItem { get; set; } = new();
+
         /// <summary>
         /// Invoked before a <see cref="API.Features.Player"/> has stopped the use of a <see cref="API.Features.Items.Usable"/>.
         /// </summary>
@@ -723,6 +728,12 @@ public class Player
         /// <param name="ev">The <see cref="UsedItemEventArgs"/> instance.</param>
         public static void OnUsedItem(UsedItemEventArgs ev) => UsedItem.InvokeSafely(ev);
 
+        /// <summary>
+        /// Called before a <see cref="API.Features.Player"/> consumes a <see cref="API.Features.Items.Consumable"/> item.
+        /// </summary>
+        /// <param name="ev">The <see cref="ConsumingItemEventArgs"/> instance.</param>
+        public static void OnConsumingItem(ConsumingItemEventArgs ev) => ConsumingItem.InvokeSafely(ev);
+
         /// <summary>
         /// Called before a <see cref="API.Features.Player"/> has stopped the use of a <see cref="API.Features.Items.Usable"/> item.
         /// </summary>

EXILED/Exiled.Events/Patches/Events/Player/ConsumingItem.cs

@@ -0,0 +1,78 @@
+// -----------------------------------------------------------------------
+// <copyright file="ConsumingItem.cs" company="ExMod Team">
+// Copyright (c) ExMod Team. All rights reserved.
+// Licensed under the CC BY-SA 3.0 license.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Exiled.Events.Patches.Events.Player
+{
+    using System.Collections.Generic;
+    using System.Reflection.Emit;
+
+    using Exiled.API.Features.Pools;
+    using Exiled.Events.Attributes;
+    using Exiled.Events.EventArgs.Player;
+
+    using HarmonyLib;
+
+    using InventorySystem.Items.Usables;
+
+    using static HarmonyLib.AccessTools;
+
+    /// <summary>
+    /// Patches <see cref="Consumable.ActivateEffects" />.
+    /// Adds the <see cref="Handlers.Player.ConsumingItem" /> event.
+    /// </summary>
+    [EventPatch(typeof(Handlers.Player), nameof(Handlers.Player.ConsumingItem))]
+    [HarmonyPatch(typeof(Consumable), nameof(Consumable.ActivateEffects))]
+    internal static class ConsumingItem
+    {
+        private static IEnumerable<CodeInstruction> Transpiler(IEnumerable<CodeInstruction> instructions, ILGenerator generator)
+        {
+            List<CodeInstruction> newInstructions = ListPool<CodeInstruction>.Pool.Get(instructions);
+
+            Label skip = generator.DefineLabel();
+
+            int offset = -1;
+            int index = newInstructions.FindIndex(instruction => instruction.Calls(Method(typeof(Consumable), nameof(Consumable.OnEffectsActivated)))) + offset;
+
+            List<Label> mainLabels = newInstructions[index].ExtractLabels();
+            newInstructions[index].WithLabels(skip);
+
+            newInstructions.InsertRange(0, new CodeInstruction[]
+            {
+                // this.Owner;
+                new CodeInstruction(OpCodes.Ldarg_0).WithLabels(mainLabels),
+                new(OpCodes.Callvirt, PropertyGetter(typeof(Consumable), nameof(Consumable.Owner))),
+
+                // this;
+                new(OpCodes.Ldarg_0),
+
+                // ConsumingItemEventArgs ev = new(this.Owner, this);
+                new(OpCodes.Newobj, GetDeclaredConstructors(typeof(ConsumingItemEventArgs))[0]),
+                new(OpCodes.Dup),
+
+                // Player.OnConsumingItem(ev);
+                new(OpCodes.Call, Method(typeof(Handlers.Player), nameof(Handlers.Player.OnConsumingItem))),
+
+                // if (!ev.IsAllowed)
+                //   this._alreadyActivated = true;
+                //   return;
+                new(OpCodes.Callvirt, PropertyGetter(typeof(ConsumingItemEventArgs), nameof(ConsumingItemEventArgs.IsAllowed))),
+                new(OpCodes.Brtrue_S, skip),
+
+                new(OpCodes.Ldarg_0),
+                new(OpCodes.Ldc_I4_1),
+                new(OpCodes.Stfld, Field(typeof(Consumable), nameof(Consumable._alreadyActivated))),
+
+                new(OpCodes.Ret),
+            });
+
+            for (int z = 0; z < newInstructions.Count; z++)
+                yield return newInstructions[z];
+
+            ListPool<CodeInstruction>.Pool.Return(newInstructions);
+        }
+    }
+}