Expose TMultiMap to Blueprint

// Developer Bastian © 2024
// License Creative Commons DEED 4.0 (https://creativecommons.org/licenses/by-sa/4.0/deed.en)
// Tutorial video how to use this at https://youtu.be/HffUZPG_-vQ
// Part of an Unreal Basics video tutorial series at: https://bit.ly/Unreal_Basics_en


#pragma once

#include "CoreMinimal.h"
#include "UObject/NoExportTypes.h"
#include "Templates/SharedPointer.h"
#include "Containers/Map.h"
#include "Misc/Guid.h"

#include "TMultiMap.generated.h"

/**
 * Struct to showcase the TMultiMap.
 */
USTRUCT(BlueprintType)
struct FTMultiMapTestStruct
{
public:
    GENERATED_USTRUCT_BODY()

    UPROPERTY(VisibleAnywhere, BlueprintReadWrite, Category = "Test Struct")
    FGuid Guid;

    UPROPERTY(VisibleAnywhere, BlueprintReadWrite, Category = "Test Struct")
    FString Name;

    UPROPERTY(VisibleAnywhere, BlueprintReadWrite, Category = "Test Struct")
    int32 Number;

    FTMultiMapTestStruct() : Guid(FGuid()), Name(""), Number(0)
    {
    }

    // define a value that acts as comparison between two struct
    // THIS IS MANDATORY FOR THE RemoveSingle Function to work
    FORCEINLINE bool operator==(const FTMultiMapTestStruct& StructToCompare) const
    {
        return Number == StructToCompare.Number;
    }
};

/**
 * Delegates to indicate queue changes
 */
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnMultiMapChanged, FGuid, ChangedKey);


/**
 * Class to encapsulate TMultiMap
 * A TMapBase specialization that allows multiple values to be associated with each key.
 */
UCLASS(BlueprintType, Transient)
class UTMultiMap : public UObject
{
    GENERATED_BODY()

public:

    UTMultiMap()
    {

    }

    #pragma region Delegates

    UPROPERTY(BlueprintAssignable, Category = "BA Container - Queue"
        , meta = (ToolTip = "Delegate to indicate enqueue event on queue"))
    FOnMultiMapChanged OnMultiMapAddKey_Delegate;

    UPROPERTY(BlueprintAssignable, Category = "BA Container - Queue"
        , meta = (ToolTip = "Delegate to indicate dequeue event on queue"))
    FOnMultiMapChanged OnMultiMapRemoveFromKey_Delegate;

#pragma endregion Delegates

private:
    TMultiMap<FGuid, FTMultiMapTestStruct> BA_MultiMap;

public:

    #pragma region Public Functions

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "Add key-value pair"
            , ToolTip = "Add a key-value association to the multi map."))
    FORCEINLINE void MM_Add(UPARAM(ref) FGuid& Key, UPARAM(ref) FTMultiMapTestStruct& Value)
    {
        this->BA_MultiMap.Add(Key, Value);
        this->OnMultiMapAddKey_Delegate.Broadcast(Key);
    }

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "Number of values"
            , ToolTip = "Returns the number of values within this multi map associated with the specified key"))
    FORCEINLINE int32 MM_NumberOfValues(UPARAM(ref) FGuid& Key)
    {
        return this->BA_MultiMap.Num(Key);
    }

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "Multi Find"
            , ToolTip = "Finds all values associated with the specified key"))
    FORCEINLINE TArray<FTMultiMapTestStruct> MM_MultiFind(UPARAM(ref) FGuid& Key)
    {
        TArray<FTMultiMapTestStruct> FoundValues;
        this->BA_MultiMap.MultiFind(Key, FoundValues);
        return FoundValues;
    }

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "Remove All"
            , ToolTip = "Remove all associations between the specified key and value from the multi map"))
    FORCEINLINE int32 MM_RemoveAll(UPARAM(ref) FGuid& Key)
    {
        this->OnMultiMapRemoveFromKey_Delegate.Broadcast(Key);
        return this->BA_MultiMap.Remove(Key);
    }

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "Remove First"
            , ToolTip = "Remove the first association between the specified key and value from the map"))
    FORCEINLINE int32 MM_RemoveFirst(UPARAM(ref) FGuid& Key, UPARAM(ref) FTMultiMapTestStruct& Value)
    {
        this->OnMultiMapRemoveFromKey_Delegate.Broadcast(Key);
        return this->BA_MultiMap.RemoveSingle(Key, Value);
        return 1;
    }

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "Get Keys"
            , ToolTip = "Gets all keys of the multi map"))
    FORCEINLINE TArray<FGuid> MM_GetKeys()
    {
        TArray<FGuid> keys;
        this->BA_MultiMap.GetKeys(keys);
        return keys;
    }

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "Empty"
            , ToolTip = "Empties the multi map - set NewCapacity to zero if you dont need to reserve space for new content, otherwise provide the expected capacity"))
    FORCEINLINE void MM_Empty(int32 NewCapacity)
    {
        this->BA_MultiMap.Empty(NewCapacity);
    }

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "KvP Exists"
            , ToolTip = "Check if a given key-value pair exists"))
    FORCEINLINE bool MM_KeyValueExist(UPARAM(ref) FGuid& Key, UPARAM(ref) FTMultiMapTestStruct& Value)
    {
        const FTMultiMapTestStruct* FoundValuePtr = this->BA_MultiMap.FindPair(Key, Value);
        if (FoundValuePtr == nullptr)
            return false;
        else
            return true;
    }

    UFUNCTION(BlueprintCallable, Category = "BA Container - MultiMap"
        , meta = (CompactNodeTitle = "Get All Values"
            , ToolTip = "Gets all values of the multi map"))
    FORCEINLINE TArray<FTMultiMapTestStruct> MM_GetAllValues()
    {
        TSet<FGuid> keys;
        TArray<FTMultiMapTestStruct> values;
        // get all keys from multi map and iterate
        this->BA_MultiMap.GetKeys(keys);
        for (auto& guid : keys)
        {
            // find all values per key
            TArray<FTMultiMapTestStruct> FoundValues;
            this->BA_MultiMap.MultiFind(guid, FoundValues);
            // add all values to return array
            for (auto& value: FoundValues)
                values.Add(value);
        }
        return values;
    }

#pragma endregion Public Functions
};