Merge pull request #803 from Injazz/bartending

Bartending tricks and some revamping on chemistry components

Content.Server/GameObjects/EntitySystems/ChemistrySystem.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Linq;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects.Systems;
+using Robust.Shared.Interfaces.GameObjects;
+
+namespace Content.Server.GameObjects.EntitySystems
+{
+    /// <summary>
+    /// This interface gives components behavior on whether entities solution (implying SolutionComponent is in place) is changed
+    /// </summary>
+    public interface ISolutionChange
+    {
+        /// <summary>
+        /// Called when solution is mixed with some other solution, or when some part of the solution is removed
+        /// </summary>
+        void SolutionChanged(SolutionChangeEventArgs eventArgs);
+    }
+
+    public class SolutionChangeEventArgs : EventArgs
+    {
+        public IEntity Owner { get; set; }
+    }
+
+    [UsedImplicitly]
+    public class ChemistrySystem : EntitySystem
+    {
+        public void HandleSolutionChange(IEntity owner)
+        {
+            var eventArgs = new SolutionChangeEventArgs
+            {
+                Owner = owner,
+            };
+            var solutionChangeArgs = owner.GetAllComponents<ISolutionChange>().ToList();
+
+            foreach (var solutionChangeArg in solutionChangeArgs)
+            {
+                solutionChangeArg.SolutionChanged(eventArgs);
+            }
+        }
+    }
+}