UnrealEngineUWP/Engine/Source/Runtime/SkillSystem/Private/SkillSystemTestAttributeSet.cpp

// Copyright 1998-2014 Epic Games, Inc. All Rights Reserved.

#include "SkillSystemModulePrivatePCH.h"
#include "GameplayTagsModule.h"

USkillSystemTestAttributeSet::USkillSystemTestAttributeSet(const class FPostConstructInitializeProperties& PCIP)
: Super(PCIP)
{
	Health = MaxHealth = 100.f;
	Mana = MaxMana = 100.f;
	
	Damage = 0.f;
	CritChance = 0.f;
	SpellDamage = 0.f;
	PhysicalDamage = 0.f;
	Strength = 0.f;
	StackingAttribute1 = 0.f;
	StackingAttribute2 = 0.f;
	NoStackAttribute = 0.f;
}

void USkillSystemTestAttributeSet::PreAttributeModify(struct FGameplayEffectModCallbackData &Data)
{
	static UProperty *HealthProperty = FindFieldChecked<UProperty>(USkillSystemTestAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(USkillSystemTestAttributeSet, Health));
	static UProperty *DamageProperty = FindFieldChecked<UProperty>(USkillSystemTestAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(USkillSystemTestAttributeSet, Damage));

	// In this function, our GameplayEffect mod has been evaluated. We have a magnitude and a Tags collection that we can still modify before it is applied.
	// We also still have the Aggregation data that calculated Data.EvaluatedData. If we really needed to, we could look at this, remove or change things at the aggregator level, and reevaluate ourselves.
	// But that would be considered very advanced/rare.

	UProperty *ModifiedProperty = Data.ModifierSpec.Info.Attribute.GetUProperty();

	// Is Damage about to be applied?
	if (DamageProperty == ModifiedProperty)
	{
		// Can the target dodge this completely?
		if (DodgeChance > 0.f)
		{
			if (FMath::FRand() <= DodgeChance)
			{
				// Dodge!
				Data.EvaluatedData.Magnitude = 0.f;
				Data.EvaluatedData.Tags.AddTag(IGameplayTagsModule::RequestGameplayTag(FName(TEXT("Dodged"))));

				// How dodge is handled will be game dependant. There are a few options I think of:
				// -We still apply 0 damage, but tag it as Dodged. The GameplayCue system could pick up on this and play a visual effect. The combat log could pick up in and print it out too.
				// -We throw out this GameplayEffect right here, and apply another GameplayEffect for 'Dodge' it wouldn't modify an attribute but could trigger gameplay cues, it could serve as a 'cooldown' for dodge
				//		if the game wanted rules like 'you can't dodge more than once every .5 seconds', etc.
			}
		}		
		
		if (Data.EvaluatedData.Magnitude > 0.f)
		{
			// Check the source - does he have Crit?
			USkillSystemTestAttributeSet * SourceAttributes = Data.EffectSpec.InstigatorStack.GetOriginInstigatorAttributeComponent()->GetSet<USkillSystemTestAttributeSet>();
			if (SourceAttributes && SourceAttributes->CritChance > 0.f)
			{
				if (FMath::FRand() <= SourceAttributes->CritChance)
				{
					// Crit!
					Data.EvaluatedData.Magnitude *= SourceAttributes->CritMultiplier;
					Data.EvaluatedData.Tags.AddTag(IGameplayTagsModule::RequestGameplayTag(FName(TEXT("Damage.Crit"))));
				}
			}

			// Now apply armor reduction
			if (Data.EvaluatedData.Tags.HasTag(IGameplayTagsModule::RequestGameplayTag(FName(TEXT("Damage.Physical"))), EGameplayTagMatchType::IncludeParentTags, EGameplayTagMatchType::Explicit))
			{
				// This is a trivial/naive implementation of armor. It assumes the rmorDamageReduction is an actual % to reduce physics damage by.
				// Real games would probably use armor rating as an attribute and calculate a % here based on the damage source's level, etc.
				Data.EvaluatedData.Magnitude *= (1.f - ArmorDamageReduction);
				Data.EvaluatedData.Tags.AddTag(IGameplayTagsModule::RequestGameplayTag(FName(TEXT("Damage.Mitigatd.Armor"))));
			}
		}

		// At this point, the Magnitude of the applied damage may have been modified by us. We still do the translation to Health in USkillSystemTestAttributeSet::PostAttributeModify.
	}
}

void USkillSystemTestAttributeSet::PostAttributeModify(const struct FGameplayEffectModCallbackData &Data)
{
	static UProperty *HealthProperty = FindFieldChecked<UProperty>(USkillSystemTestAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(USkillSystemTestAttributeSet, Health));
	static UProperty *DamageProperty = FindFieldChecked<UProperty>(USkillSystemTestAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(USkillSystemTestAttributeSet, Damage));

	UProperty *ModifiedProperty = Data.ModifierSpec.Info.Attribute.GetUProperty();

	// What property was modified?
	if (DamageProperty == ModifiedProperty)
	{
		// Anytime Damage is applied with 'Damage.Fire' tag, there is a chance to apply a burning DOT
		if (Data.EvaluatedData.Tags.HasTag( IGameplayTagsModule::RequestGameplayTag(FName(TEXT("FireDamage"))), EGameplayTagMatchType::IncludeParentTags, EGameplayTagMatchType::Explicit))
		{
			// Logic to rand() a burning DOT, if successful, apply DOT GameplayEffect to the target
		}

		// Treat damage as minus health
		Health -= Damage;
		Damage = 0.f;

		// Check for Death?
		//  -This could be defined here or at the actor level.
		//  -Doing it here makes a lot of sense to me, but we have legacy code in ::TakeDamage function, so some games may just want to punt to that pipeline from here.
	}
}


void USkillSystemTestAttributeSet::GetLifetimeReplicatedProps(TArray< FLifetimeProperty > & OutLifetimeProps) const
{
	/*
	DOREPLIFETIME( USkillSystemTestAttributeSet, MaxHealth);
	DOREPLIFETIME( USkillSystemTestAttributeSet, Health);
	DOREPLIFETIME( USkillSystemTestAttributeSet, Mana);
	DOREPLIFETIME( USkillSystemTestAttributeSet, MaxMana);

	DOREPLIFETIME( USkillSystemTestAttributeSet, SpellDamage);
	DOREPLIFETIME( USkillSystemTestAttributeSet, PhysicalDamage);

	DOREPLIFETIME( USkillSystemTestAttributeSet, CritChance);
	DOREPLIFETIME( USkillSystemTestAttributeSet, CritMultiplier);
	DOREPLIFETIME( USkillSystemTestAttributeSet, ArmorDamageReduction);

	DOREPLIFETIME( USkillSystemTestAttributeSet, DodgeChance);
	DOREPLIFETIME( USkillSystemTestAttributeSet, LifeSteal);

	DOREPLIFETIME( USkillSystemTestAttributeSet, Strength);
	*/
}