ADD GrantConditionOnAttack Trait

Useful for making Gattling weapons (Yuri's Revenge and C&C Generals) or
Boris (RA2) / Natasha (RA3) call for airstrike.

OpenRA.Mods.Common/Traits/Conditions/GrantConditionOnAttack.cs

@@ -0,0 +1,168 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2017 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Collections.Generic;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits
+{
+	public class GrantConditionOnAttackInfo : ITraitInfo
+	{
+		[FieldLoader.Require]
+		[GrantedConditionReference]
+		[Desc("The condition type to grant.")]
+		public readonly string Condition = null;
+
+		[Desc("Name of the armaments that grant this condition.")]
+		public readonly HashSet<string> ArmamentNames = new HashSet<string>() { "primary" };
+
+		[Desc("Shots required to apply an instance of the condition. If there are more instances of the condition granted than values listed,",
+			"the last value is used for all following instances beyond the defined range.")]
+		public readonly int[] RequiredShotsPerInstance = { 1 };
+
+		[Desc("Maximum instances of the condition to grant.")]
+		public readonly int MaximumInstances = 1;
+
+		[Desc("Should all instances reset if the actor passes the final stage?")]
+		public readonly bool IsCyclic = false;
+
+		[Desc("Amount of ticks required to pass without firing to revoke an instance.")]
+		public readonly int RevokeDelay = 15;
+
+		[Desc("Should an instance be revoked if the actor changes target?")]
+		public readonly bool RevokeOnNewTarget = false;
+
+		[Desc("Should all instances be revoked instead of only one?")]
+		public readonly bool RevokeAll = false;
+
+		public object Create(ActorInitializer init) { return new GrantConditionOnAttack(init, this); }
+	}
+
+	public class GrantConditionOnAttack : INotifyCreated, ITick, INotifyAttack
+	{
+		readonly GrantConditionOnAttackInfo info;
+		readonly Stack<int> tokens = new Stack<int>();
+
+		int cooldown = 0;
+		int shotsFired = 0;
+		ConditionManager manager;
+
+		// Only tracked when RevokeOnNewTarget is true.
+		Target lastTarget = Target.Invalid;
+
+		public GrantConditionOnAttack(ActorInitializer init, GrantConditionOnAttackInfo info)
+		{
+			this.info = info;
+		}
+
+		void INotifyCreated.Created(Actor self)
+		{
+			manager = self.TraitOrDefault<ConditionManager>();
+		}
+
+		void GrantInstance(Actor self, string cond)
+		{
+			if (manager == null || string.IsNullOrEmpty(cond))
+				return;
+
+			tokens.Push(manager.GrantCondition(self, cond));
+		}
+
+		void RevokeInstance(Actor self, bool revokeAll)
+		{
+			shotsFired = 0;
+
+			if (manager == null || tokens.Count == 0)
+				return;
+
+			if (!revokeAll)
+				manager.RevokeCondition(self, tokens.Pop());
+			else
+				while (tokens.Count > 0)
+					manager.RevokeCondition(self, tokens.Pop());
+		}
+
+		void ITick.Tick(Actor self)
+		{
+			if (tokens.Count > 0 && --cooldown == 0)
+			{
+				cooldown = info.RevokeDelay;
+				RevokeInstance(self, info.RevokeAll);
+			}
+		}
+
+		bool TargetChanged(Target lastTarget, Target target)
+		{
+			// Invalidate reveal changing the target.
+			if (lastTarget.Type == TargetType.FrozenActor && target.Type == TargetType.Actor)
+				if (lastTarget.FrozenActor.Actor == target.Actor)
+					return false;
+
+			if (lastTarget.Type == TargetType.Actor && target.Type == TargetType.FrozenActor)
+				if (target.FrozenActor.Actor == lastTarget.Actor)
+					return false;
+
+			if (lastTarget.Type != target.Type)
+				return true;
+
+			// Invalidate attacking different targets with shared target types.
+			if (lastTarget.Type == TargetType.Actor && target.Type == TargetType.Actor)
+				if (lastTarget.Actor != target.Actor)
+					return true;
+
+			if (lastTarget.Type == TargetType.FrozenActor && target.Type == TargetType.FrozenActor)
+				if (lastTarget.FrozenActor != target.FrozenActor)
+					return true;
+
+			if (lastTarget.Type == TargetType.Terrain && target.Type == TargetType.Terrain)
+				if (lastTarget.CenterPosition != target.CenterPosition)
+					return true;
+
+			return false;
+		}
+
+		void INotifyAttack.Attacking(Actor self, Target target, Armament a, Barrel barrel)
+		{
+			if (!info.ArmamentNames.Contains(a.Info.Name))
+				return;
+
+			if (info.RevokeOnNewTarget)
+			{
+				if (TargetChanged(lastTarget, target))
+					RevokeInstance(self, info.RevokeAll);
+
+				lastTarget = target;
+			}
+
+			cooldown = info.RevokeDelay;
+
+			if (!info.IsCyclic && tokens.Count >= info.MaximumInstances)
+				return;
+
+			shotsFired++;
+			var requiredShots = tokens.Count < info.RequiredShotsPerInstance.Length
+				? info.RequiredShotsPerInstance[tokens.Count]
+				: info.RequiredShotsPerInstance[info.RequiredShotsPerInstance.Length - 1];
+
+			if (shotsFired >= requiredShots)
+			{
+				if (info.IsCyclic && tokens.Count == info.MaximumInstances)
+					RevokeInstance(self, true);
+				else
+					GrantInstance(self, info.Condition);
+
+				shotsFired = 0;
+			}
+		}
+
+		void INotifyAttack.PreparingAttack(Actor self, Target target, Armament a, Barrel barrel) { }
+	}
+}