From 5b3394b7216f4234619d88afc993b433cc3070b0 Mon Sep 17 00:00:00 2001
From: Guy Elsmore-Paddock <guy.paddock@gmail.com>
Date: Mon, 18 Dec 2023 00:48:20 -0500
Subject: [PATCH] [#9] [#53] Implement `FindChildTag` Utility Method

---
 .../Private/Libraries/PF2TagLibrary.cpp       | 37 ++++++++++++++
 .../Public/Libraries/PF2TagLibrary.h          | 51 +++++++++++++++++++
 2 files changed, 88 insertions(+)
 create mode 100644 Source/OpenPF2Core/Private/Libraries/PF2TagLibrary.cpp
 create mode 100644 Source/OpenPF2Core/Public/Libraries/PF2TagLibrary.h

diff --git a/Source/OpenPF2Core/Private/Libraries/PF2TagLibrary.cpp b/Source/OpenPF2Core/Private/Libraries/PF2TagLibrary.cpp
new file mode 100644
index 000000000..90e7a0cfe
--- /dev/null
+++ b/Source/OpenPF2Core/Private/Libraries/PF2TagLibrary.cpp
@@ -0,0 +1,37 @@
+// OpenPF2 for UE Game Logic, Copyright 2023, Guy Elsmore-Paddock. All Rights Reserved.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not
+// distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#include "Libraries/PF2TagLibrary.h"
+
+FGameplayTag UPF2TagLibrary::FindChildTag(const FGameplayTagContainer& AllTags,
+                                          const FGameplayTag&          ParentTag,
+                                          bool&                        bMatchFound)
+{
+	FGameplayTag                Result;
+	const FGameplayTagContainer AllChildren = AllTags.Filter(FGameplayTagContainer(ParentTag));
+
+	if (AllChildren.IsEmpty())
+	{
+		bMatchFound = false;
+	}
+	else
+	{
+		Result      = AllChildren.First();
+		bMatchFound = true;
+
+		if (AllChildren.Num() > 1)
+		{
+			UE_LOG(
+				LogPf2Core,
+				Warning,
+				TEXT("More than one child tag ('%s') matched parent tag ('%s')."),
+				*(AllChildren.ToStringSimple()),
+				*(ParentTag.ToString())
+			);
+		}
+	}
+
+	return Result;
+}
diff --git a/Source/OpenPF2Core/Public/Libraries/PF2TagLibrary.h b/Source/OpenPF2Core/Public/Libraries/PF2TagLibrary.h
new file mode 100644
index 000000000..be051ce96
--- /dev/null
+++ b/Source/OpenPF2Core/Public/Libraries/PF2TagLibrary.h
@@ -0,0 +1,51 @@
+// OpenPF2 for UE Game Logic, Copyright 2023, Guy Elsmore-Paddock. All Rights Reserved.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not
+// distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+// ReSharper disable CppUEBlueprintCallableFunctionUnused
+#pragma once
+
+#include <GameplayTagContainer.h>
+
+#include <Kismet/BlueprintFunctionLibrary.h>
+
+#include "PF2TagLibrary.generated.h"
+
+// =====================================================================================================================
+// Forward Declarations (to minimize header dependencies)
+// =====================================================================================================================
+
+// =====================================================================================================================
+// Normal Declarations
+// =====================================================================================================================
+/**
+ * Function library for working with gameplay abilities in OpenPF2.
+ */
+UCLASS()
+class OPENPF2CORE_API UPF2TagLibrary final : public UBlueprintFunctionLibrary
+{
+	GENERATED_BODY()
+
+public:
+	/**
+	 * Locates the tag within the specified tag container that is a child of another tag.
+	 *
+	 * If there are multiple tags in the container that are children or grandchildren of the given tag, only the first
+	 * one gets returned.
+	 *
+	 * @param [in] AllTags
+	 *	The tags to search.
+	 * @param [in] ParentTag
+	 *	The parent (or grandparent) tag of the desired tag.
+	 * @param [out] bMatchFound
+	 *	Whether a tag was found that is a child of the specified tag.
+	 *
+	 * @return
+	 *	Either the matching tag; or a gameplay tag that is not valid if there is no tag that matches.
+	 */
+	UFUNCTION(BlueprintCallable, BlueprintPure, meta=(AutoCreateRefTerm="ParentTag"), Category="OpenPF2|Gameplay Tags")
+	static FGameplayTag FindChildTag(const FGameplayTagContainer& AllTags,
+	                                 const FGameplayTag&          ParentTag,
+	                                 bool&                        bMatchFound);
+};