Add destructible component threshold triggers (#3080)

* WIP changes

* Fix tests, merge conflict and trigger once behavior

* Update yml

* Change test strings to be consts

* Fix total damage types and classes triggers

* Simplify damage trigger logic, move state to Threshold

* Update outdated code and docs

* Change the name of IBehavior back to IThresholdBehavior

* Change human gibbing to trigger at 400 brute damage

* Change gibbing from brute to blunt damage

* Fix one (1) typo

* Add damage class trigger test

* Add missing nullable enable to thresholds

Content.IntegrationTests/Tests/Destructible/DestructibleDestructionTest.cs

@@ -0,0 +1,95 @@
+using System.Linq;
+using System.Threading.Tasks;
+using Content.Server.GameObjects.Components.Destructible.Thresholds;
+using Content.Server.GameObjects.Components.Destructible.Thresholds.Behaviors;
+using Content.Shared.Damage;
+using Content.Shared.GameObjects.Components.Damage;
+using NUnit.Framework;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Interfaces.Map;
+using Robust.Shared.IoC;
+using Robust.Shared.Map;
+using static Content.IntegrationTests.Tests.Destructible.DestructibleTestPrototypes;
+
+namespace Content.IntegrationTests.Tests.Destructible
+{
+    public class DestructibleDestructionTest : ContentIntegrationTest
+    {
+        [Test]
+        public async Task Test()
+        {
+            var server = StartServerDummyTicker(new ServerContentIntegrationOption
+            {
+                ExtraPrototypes = Prototypes,
+                ContentBeforeIoC = () =>
+                {
+                    IoCManager.Resolve<IComponentFactory>().Register<TestThresholdListenerComponent>();
+                }
+            });
+
+            await server.WaitIdleAsync();
+
+            var sEntityManager = server.ResolveDependency<IEntityManager>();
+            var sMapManager = server.ResolveDependency<IMapManager>();
+
+            IEntity sDestructibleEntity = null;
+            IDamageableComponent sDamageableComponent = null;
+            TestThresholdListenerComponent sThresholdListenerComponent = null;
+
+            await server.WaitPost(() =>
+            {
+                var mapId = new MapId(1);
+                var coordinates = new MapCoordinates(0, 0, mapId);
+                sMapManager.CreateMap(mapId);
+
+                sDestructibleEntity = sEntityManager.SpawnEntity(DestructibleDestructionEntityId, coordinates);
+                sDamageableComponent = sDestructibleEntity.GetComponent<IDamageableComponent>();
+                sThresholdListenerComponent = sDestructibleEntity.GetComponent<TestThresholdListenerComponent>();
+            });
+
+            await server.WaitAssertion(() =>
+            {
+                var coordinates = sDestructibleEntity.Transform.Coordinates;
+
+                Assert.DoesNotThrow(() =>
+                {
+                    Assert.True(sDamageableComponent.ChangeDamage(DamageClass.Brute, 50, true));
+                });
+
+                Assert.That(sThresholdListenerComponent.ThresholdsReached.Count, Is.EqualTo(1));
+
+                var threshold = sThresholdListenerComponent.ThresholdsReached[0].Threshold;
+
+                Assert.That(threshold.Triggered, Is.True);
+                Assert.That(threshold.Behaviors.Count, Is.EqualTo(3));
+
+                var spawnEntitiesBehavior = (SpawnEntitiesBehavior) threshold.Behaviors.Single(b => b is SpawnEntitiesBehavior);
+
+                Assert.That(spawnEntitiesBehavior.Spawn.Count, Is.EqualTo(1));
+                Assert.That(spawnEntitiesBehavior.Spawn.Keys.Single(), Is.EqualTo(SpawnedEntityId));
+                Assert.That(spawnEntitiesBehavior.Spawn.Values.Single(), Is.EqualTo(new MinMax {Min = 1, Max = 1}));
+
+                var entitiesInRange = sEntityManager.GetEntitiesInRange(coordinates, 2);
+                var found = false;
+
+                foreach (var entity in entitiesInRange)
+                {
+                    if (entity.Prototype == null)
+                    {
+                        continue;
+                    }
+
+                    if (entity.Prototype.Name != SpawnedEntityId)
+                    {
+                        continue;
+                    }
+
+                    found = true;
+                    break;
+                }
+
+                Assert.That(found, Is.True);
+            });
+        }
+    }
+}