// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "Engine/DataAsset.h"
#include "StateTreeTypes.h"
#include "StateTreeSchema.h"
#include "InstancedStruct.h"
#include "InstancedStructArray.h"
#include "StateTreePropertyBindings.h"
#include "StateTreeInstanceData.h"
#include "StateTree.generated.h"


/** Custom serialization version for StateTree Asset */
struct STATETREEMODULE_API FStateTreeCustomVersion
{
	enum Type
	{
		// Before any version changes were made in the plugin
		BeforeCustomVersionWasAdded = 0,
		// Separated conditions to shared instance data.
		SharedInstanceData,
		// Moved evaluators to be global.
		GlobalEvaluators,
		// Moved instance data to arrays.
		InstanceDataArrays,
		// Added index types.
		IndexTypes,

		// -----<new versions can be added above this line>-------------------------------------------------
		VersionPlusOne,
		LatestVersion = VersionPlusOne - 1
	};

	/** The GUID for this custom version number */
	const static FGuid GUID;

private:
	FStateTreeCustomVersion() {}
};


#if WITH_EDITOR
/** Struct containing information about the StateTree runtime memory usage. */
struct FStateTreeMemoryUsage
{
	FStateTreeMemoryUsage() = default;
	FStateTreeMemoryUsage(const FString InName, const FStateTreeStateHandle InHandle = FStateTreeStateHandle::Invalid)
		: Name(InName)
		, Handle(InHandle)
	{
	}
	
	void AddUsage(FConstStructView View);
	void AddUsage(const UObject* Object);

	FString Name;
	FStateTreeStateHandle Handle;
	int32 NodeCount = 0;
	int32 EstimatedMemoryUsage = 0;
	int32 ChildNodeCount = 0;
	int32 EstimatedChildMemoryUsage = 0;
};
#endif


/**
 * StateTree asset. Contains the StateTree definition in both editor and runtime (baked) formats.
 */
UCLASS(BlueprintType)
class STATETREEMODULE_API UStateTree : public UDataAsset
{
	GENERATED_BODY()

public:

	/**
	 * @todo: This should return different data for each thread.
	 * @return Shared instance data.
	 */
	const FStateTreeInstanceData& GetSharedInstanceData() const { return SharedInstanceData; }

	/** @return Number of data views required for StateTree execution (Evaluators, Tasks, Conditions, External data). */
	int32 GetNumDataViews() const { return NumDataViews; }

	/** @return List of external data required by the state tree */
	TConstArrayView<FStateTreeExternalDataDesc> GetExternalDataDescs() const { return ExternalDataDescs; }

	/** @return List of named external data enforced by the schema that must be provided through the execution context. */
	TConstArrayView<FStateTreeExternalDataDesc> GetNamedExternalDataDescs() const { return NamedExternalDataDescs; }

	/** @return List of default parameters of the state tree. Default parameter values can be overridden at runtime by the execution context. */
	const FInstancedPropertyBag& GetDefaultParameters() const { return Parameters; }

	/** @return true if the tree asset can be used at runtime. */
	bool IsReadyToRun() const;

#if WITH_EDITOR
	/** Resets the compiled data to empty. */
	void ResetCompiled();

	/** Calculates runtime memory usage for different sections of the tree. */
	TArray<FStateTreeMemoryUsage> CalculateEstimatedMemoryUsage() const;
#endif

#if WITH_EDITORONLY_DATA
	/** Edit time data for the StateTree, instance of UStateTreeEditorData */
	UPROPERTY()
	TObjectPtr<UObject> EditorData;

	/** Hash of the editor data from last compile. */
	UPROPERTY()
	uint32 LastCompiledEditorDataHash = 0;
#endif

protected:
	
	/**
	 * Resolves references between data in the StateTree.
	 * @return true if all references to internal and external data are resolved properly, false otherwise.
	 */
	[[nodiscard]] bool Link();

	virtual void PostLoad() override;
	virtual void Serialize(FStructuredArchiveRecord Record) override;
	
#if WITH_EDITOR
	virtual void GetAssetRegistryTags(TArray<FAssetRegistryTag>& OutTags) const override;
	virtual void PostLoadAssetRegistryTags(const FAssetData& InAssetData, TArray<FAssetRegistryTag>& OutTagsAndValuesToUpdate) const;
#endif

private:

	/**
     * Reset the data generated by Link(), this in turn will cause IsReadyToRun() to return false.
     * Used during linking, or to invalidate the linked data when data version is old (requires recompile). 
	 */
	void ResetLinked();

	// Data created during compilation, source data in EditorData.
	
	/** Schema used to compile the StateTree. */
	UPROPERTY(Instanced)
	TObjectPtr<UStateTreeSchema> Schema = nullptr;

	/** Runtime states, root state at index 0 */
	UPROPERTY()
	TArray<FCompactStateTreeState> States;

	/** Runtime transitions. */
	UPROPERTY()
	TArray<FCompactStateTransition> Transitions;

	/** Evaluators, Tasks, and Condition nodes. */
	UPROPERTY()
	FInstancedStructArray Nodes;

	/** Default node instance data (e.g. evaluators, tasks). */
	UPROPERTY()
	FStateTreeInstanceData DefaultInstanceData;

	/** Shared node instance data (e.g. conditions). */
	UPROPERTY()
	FStateTreeInstanceData SharedInstanceData;

	/** List of names external data enforced by the schema, created at compilation. */
	UPROPERTY()
	TArray<FStateTreeExternalDataDesc> NamedExternalDataDescs;

	UPROPERTY()
	FStateTreePropertyBindings PropertyBindings;

	/**
	 * Parameters that could be used for bindings within the Tree.
	 * Default values are stored within the asset but StateTreeReference can be used to parameterized the tree.
	 * @see FStateTreeReference
	 */
	UPROPERTY()
	FInstancedPropertyBag Parameters;

	/** Data view index of the tree Parameters */
	UPROPERTY()
	FStateTreeIndex8 ParametersDataViewIndex = FStateTreeIndex8::Invalid;

	/** Index of first evaluator in Nodes. */
	UPROPERTY()
	uint16 EvaluatorsBegin = 0;

	/** Number of evaluators. */
	UPROPERTY()
	uint16 EvaluatorsNum = 0;

	// Data created during linking.
	
	/** List of external data required by the state tree, created during linking. */
	UPROPERTY(Transient)
	TArray<FStateTreeExternalDataDesc> ExternalDataDescs;

	/** Base index of external data, created during linking. */
	UPROPERTY(Transient)
	int32 ExternalDataBaseIndex = 0;

	/** Total number of data views, created during linking. */
	UPROPERTY(Transient)
	int32 NumDataViews = 0;

	/** True if the StateTree was linked successfully. */
	bool bIsLinked = false;

	friend struct FStateTreeInstance;
	friend struct FStateTreeExecutionContext;
#if WITH_EDITORONLY_DATA
	friend struct FStateTreeCompiler;
#endif
};