Add basic chemical reactions (#376)

* Add basic chemical reaction system

What it adds:
- Reactions defined in yaml with an arbitrary amount of reactants (can be catalysts), products, and effects.

What it doesn't add:
- Temperature dependent reactions
- Metabolism or other medical/health effects

* Add many common SS13 chemicals and reactions

Added many of the common SS13 medicines and other chemicals, and their chemical reactions. Note that many of them are lacking their effects since we don't have medical yet.

* Add ExplosiveReactionEffect

Shows how IReactionEffect can be implemented to have effects that occur with a reaction by adding ExplosionReactionEffect and the potassium + water explosion reaction.

* Move ReactionSystem logic into SolutionComponent

No need for this to be a system currently so the behavior for reaction checking has been moved into SolutionComponent. Now it only checks for reactions when a reagent or solution is added to a solution. Also fixed a bug with SolutionValidReaction incorrectly returning true.

* Move explosion logic out of ExplosiveComponent

Allows you to create explosions without needing to add an ExplosiveComponent to an entity first.

* Add SolutionComponent.SolutionChanged event. Trigger dispenser ui updates with it.

This removes the need for SolutionComponent having a reference to the dispenser it's in. Instead the dispenser subscribes to the event and updates it's UI whenever the event is triggered.

* Add forgotten checks

`SolutionComponent.TryAddReagent` and `SolutionComponent.TryAddSolution` now check to see if `skipReactionCheck` is false before checking for a chemical reaction to avoid unnecessarily checking themselves for a reaction again when `SolutionComponent.PerformReaction` calls either of them.

* Change SolutionComponent.SolutionChanged to an Action

The arguments for event handler have no use here, and any class that can access SolutionChanged can access the SolutionComponent so it can just be an Action with no arguments instead.

Content.Server/GameObjects/Components/Chemistry/SolutionComponent.cs

@@ -1,7 +1,10 @@
 using System;
+using System.Collections.Generic;
+using Content.Server.Chemistry;
 using Content.Server.GameObjects.EntitySystems;
 using Content.Shared.Chemistry;
 using Content.Shared.GameObjects;
+using Robust.Server.GameObjects.EntitySystems;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Interfaces.GameObjects;
 using Robust.Shared.IoC;
@@ -20,14 +23,26 @@ namespace Content.Server.GameObjects.Components.Chemistry
 #pragma warning disable 649
         [Dependency] private readonly IPrototypeManager _prototypeManager;
         [Dependency] private readonly ILocalizationManager _localizationManager;
+        [Dependency] private readonly IEntitySystemManager _entitySystemManager;
 #pragma warning restore 649
 
+        private IEnumerable<ReactionPrototype> _reactions;
+        private AudioSystem _audioSystem;
+
+        protected override void Startup()
+        {
+            base.Startup();
+
+            _reactions = _prototypeManager.EnumeratePrototypes<ReactionPrototype>();
+            _audioSystem = _entitySystemManager.GetEntitySystem<AudioSystem>();
+        }
+
         /// <summary>
         ///     Transfers solution from the held container to the target container.
         /// </summary>
         [Verb]
         private sealed class FillTargetVerb : Verb<SolutionComponent>
-        {
+        { 
             protected override string GetText(IEntity user, SolutionComponent component)
             {
                 if(!user.TryGetComponent<HandsComponent>(out var hands))
@@ -164,5 +179,116 @@ namespace Content.Server.GameObjects.Components.Chemistry
                 handSolutionComp.TryAddSolution(transferSolution);
             }
         }
+
+        private void CheckForReaction()
+        {
+            //Check the solution for every reaction
+            foreach (var reaction in _reactions)
+            {
+                if (SolutionValidReaction(reaction, out int unitReactions))
+                {
+                    PerformReaction(reaction, unitReactions);
+                    break; //Only perform one reaction per solution per update.
+                }
+            }
+        }
+
+        public bool TryAddReagent(string reagentId, int quantity, out int acceptedQuantity, bool skipReactionCheck = false)
+        {
+            if (quantity > _maxVolume - _containedSolution.TotalVolume)
+            {
+                acceptedQuantity = _maxVolume - _containedSolution.TotalVolume;
+                if (acceptedQuantity == 0) return false;
+            }
+            else
+            {
+                acceptedQuantity = quantity;
+            }
+
+            _containedSolution.AddReagent(reagentId, acceptedQuantity);
+            RecalculateColor();
+            if(!skipReactionCheck)
+                CheckForReaction();
+            OnSolutionChanged();
+            return true;
+        }
+
+        public bool TryAddSolution(Solution solution, bool skipReactionCheck = false)
+        {
+            if (solution.TotalVolume > (_maxVolume - _containedSolution.TotalVolume))
+                return false;
+
+            _containedSolution.AddSolution(solution);
+            RecalculateColor();
+            if(!skipReactionCheck)
+                CheckForReaction();
+            OnSolutionChanged();
+            return true;
+        }
+
+        /// <summary>
+        /// Checks if a solution has the reactants required to cause a specified reaction.
+        /// </summary>
+        /// <param name="solution">The solution to check for reaction conditions.</param>
+        /// <param name="reaction">The reaction whose reactants will be checked for in the solution.</param>
+        /// <param name="unitReactions">The number of times the reaction can occur with the given solution.</param>
+        /// <returns></returns>
+        private bool SolutionValidReaction(ReactionPrototype reaction, out int unitReactions)
+        {
+            unitReactions = int.MaxValue; //Set to some impossibly large number initially
+            foreach (var reactant in reaction.Reactants)
+            {
+                if (!ContainsReagent(reactant.Key, out int reagentQuantity))
+                {
+                    return false;
+                }
+                int currentUnitReactions = reagentQuantity / reactant.Value.Amount;
+                if (currentUnitReactions < unitReactions)
+                {
+                    unitReactions = currentUnitReactions;
+                }
+            }
+
+            if (unitReactions == 0)
+            {
+                return false;
+            }
+            else
+            {
+                return true;
+            }
+        }
+
+        /// <summary>
+        /// Perform a reaction on a solution. This assumes all reaction criteria have already been checked and are met.
+        /// </summary>
+        /// <param name="solution">Solution to be reacted.</param>
+        /// <param name="reaction">Reaction to occur.</param>
+        /// <param name="unitReactions">The number of times to cause this reaction.</param>
+        private void PerformReaction(ReactionPrototype reaction, int unitReactions)
+        {
+            //Remove non-catalysts
+            foreach (var reactant in reaction.Reactants)
+            {
+                if (!reactant.Value.Catalyst)
+                {
+                    int amountToRemove = unitReactions * reactant.Value.Amount;
+                    TryRemoveReagent(reactant.Key, amountToRemove);
+                }
+            }
+            //Add products
+            foreach (var product in reaction.Products)
+            {
+                TryAddReagent(product.Key, (int)(unitReactions * product.Value), out int acceptedQuantity, true);
+            }
+            //Trigger reaction effects
+            foreach (var effect in reaction.Effects)
+            {
+                effect.React(Owner, unitReactions);
+            }
+
+            //Play reaction sound client-side
+            _audioSystem.Play("/Audio/effects/chemistry/bubbles.ogg", Owner.Transform.GridPosition);
+        }
     }
 }