// Copyright IHY. Vertical Partition Streaming plugin (editor module).
//
// Editor-only conversion pipeline: scan -> validate -> assign -> generate
// descriptor -> generate HLOD proxies -> (optionally) bake streaming sub-levels.
#pragma once

#include "CoreMinimal.h"
#include "UObject/Object.h"
#include "VerticalPartitionTypes.h"
#include "VerticalPartitionBuilder.generated.h"

class AVerticalPartitionVolume;
class UVerticalPartitionDescriptor;
class UWorld;
class AActor;

/** One actor's analysed placement, shared between Analyze and Build. */
struct FVerticalActorAssignment
{
	TWeakObjectPtr<AActor> Actor;
	/** The renderable static-decor leaf actors this unit streams. For a normal actor this
	 *  is just [Actor]; for a Level Instance it is its (recursively flattened) static child
	 *  actors; for a Packed Level Actor it is [Actor] (its baked HISM live on it). */
	TArray<TWeakObjectPtr<AActor>> LeafActors;
	FVerticalCellId Cell;
	FBox Bounds = FBox(ForceInit);
	bool bCrossesMultiple = false;
	bool bExcluded = false;
	bool bLargeKeepPersistent = false;
};

UCLASS()
class UVerticalPartitionBuilder : public UObject
{
	GENERATED_BODY()

public:
	/** Scan the level, classify every actor, return a report without writing anything. */
	static FVerticalPartitionBuildReport AnalyzeCurrentLevel(AVerticalPartitionVolume* Volume);

	/** Full build: analyze -> create/refresh descriptor -> generate HLOD proxies ->
	 *  (DestructiveCommit only) bake streaming sub-levels + remove source actors.
	 *  Returns the report; writes the descriptor asset. */
	static bool Build(AVerticalPartitionVolume* Volume, FVerticalPartitionBuildReport& OutReport);

	/** Re-run only cells whose source content hash changed since the last build. */
	static bool RebuildChangedCells(AVerticalPartitionVolume* Volume, FVerticalPartitionBuildReport& OutReport);

	/** (Re)generate HLOD proxy meshes for all cells. */
	static bool RebuildHLOD(AVerticalPartitionVolume* Volume, FVerticalPartitionBuildReport& OutReport);

	/** Re-run analysis against the existing descriptor and flag drift / problems. */
	static FVerticalPartitionBuildReport ValidateCells(AVerticalPartitionVolume* Volume);

	/** Promote a NonDestructive descriptor to baked streaming sub-levels. */
	static bool CommitConversion(AVerticalPartitionVolume* Volume, FVerticalPartitionBuildReport& OutReport);

	static bool CreateBackup(UWorld* World, FString& OutBackupPath);
	static bool RestoreFromBackup(UWorld* World);

	/** Delete generated descriptor / cell maps / proxies under the output root. */
	static void ClearGenerated(AVerticalPartitionVolume* Volume);

	/** Write the report to Saved/VerticalPartition/<Map>_Report.txt and log it. */
	static FString DumpReport(const FVerticalPartitionBuildReport& Report, const FString& MapName);

private:
	// ---- pipeline steps ----
	static void GatherActors(AVerticalPartitionVolume* Volume, const FBox& VolumeBounds,
		TArray<FVerticalActorAssignment>& OutAssignments, FVerticalPartitionBuildReport& Report);

	static void ClassifyActorWarnings(const FVerticalActorAssignment& A, const FVerticalPartitionSettings& S,
		FVerticalPartitionBuildReport& Report);

	static UVerticalPartitionDescriptor* CreateOrLoadDescriptor(AVerticalPartitionVolume* Volume);

	static void BuildCells(AVerticalPartitionVolume* Volume, const FBox& VolumeBounds,
		const TArray<FVerticalActorAssignment>& Assignments,
		UVerticalPartitionDescriptor* Descriptor, FVerticalPartitionBuildReport& Report);

	/** Generate one proxy mesh for a cell from its static-mesh actors. Returns the
	 *  asset path or an empty path (with a warning) on failure / unavailable API. */
	static FSoftObjectPath GenerateHLODProxyForCell(const FVerticalCellId& Cell,
		const TArray<AActor*>& CellActors, const FVerticalPartitionSettings& S,
		const FString& PackageRoot, FVerticalPartitionBuildReport& Report);

	static int64 ComputeContentHash(const TArray<FVerticalActorAssignment>& Assignments);
	static bool SaveAsset(UObject* Asset);
};