Add multipart machines system (#35969)

Content.Shared/Machines/EntitySystems/SharedMultipartMachineSystem.cs

@@ -0,0 +1,115 @@
+using System.Diagnostics.CodeAnalysis;
+using Content.Shared.Machines.Components;
+
+namespace Content.Shared.Machines.EntitySystems;
+
+/// <summary>
+/// Shared handling of multipart machines.
+/// </summary>
+public abstract class SharedMultipartMachineSystem : EntitySystem
+{
+    protected EntityQuery<TransformComponent> XformQuery;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        XformQuery = GetEntityQuery<TransformComponent>();
+    }
+
+    /// <summary>
+    /// Returns whether each non-optional part of the machine has a matched entity
+    /// </summary>
+    /// <param name="ent">Entity to check the assembled state of.</param>
+    /// <returns>True if all non-optional parts have a matching entity, false otherwise.</returns>
+    public bool IsAssembled(Entity<MultipartMachineComponent?> ent)
+    {
+        if (!Resolve(ent, ref ent.Comp))
+            return false;
+
+        foreach (var part in ent.Comp.Parts.Values)
+        {
+            if (!part.Entity.HasValue && !part.Optional)
+                return false;
+        }
+
+        return true;
+    }
+
+    /// <summary>
+    /// Returns whether a machine has a specifed EntityUid bound to one of its parts.
+    /// </summary>
+    /// <param name="machine">Entity, which might have a multpart machine attached, to use for the query.</param>
+    /// <param name="entity">EntityUid to search for.</param>
+    /// <returns>True if any part has the specified EntityUid, false otherwise.</returns>
+    public bool HasPartEntity(Entity<MultipartMachineComponent?> machine, EntityUid entity)
+    {
+        if (!Resolve(machine, ref machine.Comp))
+            return false;
+
+        foreach (var part in machine.Comp.Parts.Values)
+        {
+            if (part.Entity.HasValue && part.Entity.Value == entity)
+                return true;
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// Get the EntityUid for the entity bound to a specific part, if one exists.
+    /// </summary>
+    /// <param name="ent">Entity, which might have a multipart machine attached, to use for the query.</param>
+    /// <param name="part">Enum value for the part to find, must match the value specified in YAML.</param>
+    /// <returns>May contain the resolved EntityUid for the specified part, null otherwise.</returns>
+    public EntityUid? GetPartEntity(Entity<MultipartMachineComponent?> ent, Enum part)
+    {
+        if (!TryGetPartEntity(ent, part, out var entity))
+            return null;
+
+        return entity;
+    }
+
+    /// <summary>
+    /// Get the EntityUid for the entity bound to a specific part, if one exists.
+    /// </summary>
+    /// <param name="ent">Entity, which might have a multipart machine attached, to use for the query.</param>
+    /// <param name="part">Enum for the part to find, must match the value specified in YAML.</param>
+    /// <param name="entity">Out var which may contain the matched EntityUid for the specified part.</param>
+    /// <returns>True if the part is found and has a matched entity, false otherwise.</returns>
+    public bool TryGetPartEntity(
+        Entity<MultipartMachineComponent?> ent,
+        Enum part,
+        [NotNullWhen(true)] out EntityUid? entity
+    )
+    {
+        entity = null;
+        if (!Resolve(ent, ref ent.Comp))
+            return false;
+
+        if (ent.Comp.Parts.TryGetValue(part, out var value) && value.Entity.HasValue)
+        {
+            entity = value.Entity.Value;
+            return true;
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// Check if a machine has an entity bound to a specific part
+    /// </summary>
+    /// <param name="ent">Entity, which might have a multipart machine attached, to use for the query.</param>
+    /// <param name="part">Enum for the part to find.</param>
+    /// <returns>True if the specific part has a entity bound to it, false otherwise.</returns>
+    public bool HasPart(Entity<MultipartMachineComponent?> ent, Enum part)
+    {
+        if (!Resolve(ent, ref ent.Comp))
+            return false;
+
+        if (!ent.Comp.Parts.TryGetValue(part, out var value))
+            return false;
+
+        return value.Entity != null;
+    }
+}