Initial commit: Item Interaction Ecosystem plugin (UE5.7)

Server-authoritative, data-driven item/inventory/interaction/carry/equipment/
world-slot/placement/crafting framework. 8 modules, compiles against UE 5.7.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Source/ItemPlacement/Public/PlacementPreviewComponent.h

@@ -0,0 +1,82 @@
+// Copyright ExByte Studios. Item Interaction Ecosystem.
+
+#pragma once
+
+#include "CoreMinimal.h"
+#include "Components/ActorComponent.h"
+#include "ItemPlacementRules.h"
+#include "PlacementPreviewComponent.generated.h"
+
+class UStaticMeshComponent;
+struct FItemDefinitionRow;
+
+DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnPlacementStateChanged, bool, bIsValid);
+
+/**
+ * Drives the local ghost-mesh preview and the server-validated confirm for
+ * placeable items (section 13). The client shows a green/red ghost; the server
+ * re-runs every rule before committing (collision, slope, distance, surface).
+ */
+UCLASS(ClassGroup = (Placement), meta = (BlueprintSpawnableComponent))
+class ITEMPLACEMENT_API UPlacementPreviewComponent : public UActorComponent
+{
+	GENERATED_BODY()
+
+public:
+	UPlacementPreviewComponent();
+
+	virtual void TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction) override;
+	virtual void EndPlay(const EEndPlayReason::Type EndPlayReason) override;
+
+	UPROPERTY(BlueprintReadOnly, Category = "Placement")
+	bool bIsPlacing = false;
+
+	UPROPERTY(BlueprintReadOnly, Category = "Placement")
+	FName ItemId;
+
+	UPROPERTY(BlueprintReadOnly, Category = "Placement")
+	FGuid ItemInstanceId;
+
+	UPROPERTY(BlueprintReadOnly, Category = "Placement")
+	FTransform PreviewTransform = FTransform::Identity;
+
+	UPROPERTY(BlueprintReadOnly, Category = "Placement")
+	bool bCurrentValid = false;
+
+	UPROPERTY(BlueprintAssignable, Category = "Placement")
+	FOnPlacementStateChanged OnPlacementStateChanged;
+
+	/** Client: begin placing an inventory item. */
+	UFUNCTION(BlueprintCallable, Category = "Placement")
+	void StartPlacement(FGuid InstanceId);
+
+	/** Client: confirm at the current preview transform (sends a server request). */
+	UFUNCTION(BlueprintCallable, Category = "Placement")
+	void ConfirmPlacement();
+
+	/** Client: abort placement. */
+	UFUNCTION(BlueprintCallable, Category = "Placement")
+	void CancelPlacement();
+
+	UFUNCTION(BlueprintCallable, Category = "Placement")
+	void RotatePreview(float DeltaYawDegrees);
+
+	/** Pure rule check used by both the client preview and the server (section 13.3). */
+	static bool ValidatePlacement(const UObject* WorldContext, const FItemDefinitionRow& Def,
+		const FTransform& Transform, AActor* Instigator, FString& OutReason);
+
+protected:
+	UFUNCTION(Server, Reliable)
+	void Server_ConfirmPlacement(FGuid InstanceId, FTransform Transform);
+
+private:
+	UPROPERTY(Transient)
+	TObjectPtr<UStaticMeshComponent> Ghost = nullptr;
+
+	float PreviewYaw = 0.f;
+
+	bool ComputePreviewTransform(FTransform& OutTransform) const;
+	void DestroyGhost();
+	void SetValidity(bool bNewValid);
+	bool GetViewPoint(FVector& OutLoc, FRotator& OutRot) const;
+};