Custom promotion - Buy at least X items from catalog entries and get a discount on related catalog entries.

Problem: Buy at least X items from catalog entries and get related catalog entries at a discount that satisfy the below formula.

 or

Create a custom promotion to ‘Buy Products for Discount from Other Selections’ and apply the below formula to get a discount on other selections.

Formula = m x n,  then get the discounts on n items.

m = Spend at least X items

n = Multiplier

e.g.

m = 2

n = 1, 2,3……

If you notice the above table ‘Other Selection SKU Qty.’ column, customer added more than the eligible discounted qty in the cart. So, we need to make sure the discount is only eligible for 'Eligible Discount Qty.' not for all ‘Other Selection SKU Qty.’.

Solution:

1. Create a custom entry promotion

   [ContentType(
        GUID = "CB99C622-A170-4EF6-B28D-077B18BAFD81",
        GroupName = "Custom - Promotions",
        DisplayName = "Custom - Buy products for discount from other selection",
        Description = "Buy at least X items from catalog entries and get related catalog entries at a discount e.g. (2 + 1),  (4 + 2),  (6 + 3) ... ",
        Order = 30000)]
    [PromotionSettings(FixedRedemptionsPerOrder = 1)]
    [ImageUrl("~/Static/Img/CustomBuyQuantityGetItemDiscount.png")]
    public class CustomBuyQuantityGetItemDiscount : EntryPromotion, IMonetaryDiscount
    {
        [Display(Order = 10)]
        [PromotionRegion("Condition")]
        public virtual PurchaseQuantity Condition { get; set; }

        [Display(Order = 20)]
        [PromotionRegion("Reward")]
        public virtual DiscountItems DiscountTarget { get; set; }

        [Display(Order = 30)]
        [PromotionRegion("Discount")]
        public virtual MonetaryReward Discount { get; set; }
    }

2. Create custom discount processor and override following methods:

• GetPromotionItems
  • Return promotion conditions and reward items.
• RewardDescription
  • Read all discounted SKUs with the max eligible qty for discounts.
  • Create Redemption Description into GetRedemptions.

public class CustomBuyQuantityGetItemDiscountProcessor : EntryPromotionProcessorBase<CustomBuyQuantityGetItemDiscount>
{
        private readonly IContentLoader _contentLoader;

        public CustomBuyQuantityGetItemDiscountProcessor(
            RedemptionDescriptionFactory redemptionDescriptionFactory,
            IContentLoader contentLoader)
            : base(redemptionDescriptionFactory)
        {
            _contentLoader = contentLoader ?? throw new ArgumentNullException(nameof(contentLoader));
        }

        protected override PromotionItems GetPromotionItems(CustomBuyQuantityGetItemDiscount promotionData)
        {
            return new PromotionItems(
                promotionData,
                new CatalogItemSelection(promotionData.Condition.Items, CatalogItemSelectionType.Specific, true),
                new CatalogItemSelection(promotionData.DiscountTarget.Items, CatalogItemSelectionType.Specific, true));
        }

        protected override RewardDescription Evaluate(
            CustomBuyQuantityGetItemDiscount promotionData,
            PromotionProcessorContext context)
        {
            var allLineItems = this.GetLineItems(context.OrderForm)?
                .Where(x => !x.IsGift)?
                .ToList();

            if (promotionData?.DiscountTarget?.Items == null ||
                promotionData?.Condition?.Items == null ||
                promotionData?.Condition?.RequiredQuantity == 0 ||
                allLineItems.Count() == 0)
            {
                return
                    RewardDescription.CreateNotFulfilledDescription(
                    promotionData,
                    FulfillmentStatus.NotFulfilled);
            }

            //Read all excluded variants 
            var excludedVariants = new List<string>() { };
            if (promotionData.ExcludedItems != null && promotionData.ExcludedItems.Count > 0)
            {
                foreach (ContentReference item in promotionData.ExcludedItems)
                {
                    if (_contentLoader.TryGet(item, out NodeContent content))
                    {
                        excludedVariants.AddRange(
                            _contentLoader.GetDescendantsOfType<VariationContent>(content.ContentLink)
                            .Select(x => x.Code)
                            .ToList());
                    }
                    else if (_contentLoader.TryGet(item, out ProductContent productContent))
                    {
                        excludedVariants.AddRange(
                            _contentLoader.GetDescendantsOfType<VariationContent>(productContent.ContentLink)
                            .Select(x => x.Code)
                            .ToList());
                    }
                    else
                    {
                        excludedVariants.Add(_contentLoader.TryGet<VariationContent>(item)?.Code);
                    }
                }
            }
          
           //Read all condition variants
            var conditionSkus = new List<string>() { };
            foreach (ContentReference item in promotionData.Condition.Items)
            {
                if (_contentLoader.TryGet(item, out NodeContent content))
                {
                    conditionSkus.AddRange(
                        _contentLoader.GetDescendantsOfType<VariationContent>(content.ContentLink)
                        .Select(x => x.Code)
                        .ToList());
                }
                else if (_contentLoader.TryGet(item, out ProductContent productContent))
                {
                    conditionSkus.AddRange(
                        _contentLoader.GetDescendantsOfType<VariationContent>(productContent.ContentLink)
                        .Select(x => x.Code)
                        .ToList());
                }
                else
                {
                    conditionSkus.Add(_contentLoader.TryGet<VariationContent>(item)?.Code);
                }
            }
            //Read all discounted variants
            var discountSkus = new List<string>() { };
            foreach (ContentReference item in promotionData.DiscountTarget.Items)
            {
                if (_contentLoader.TryGet(item, out NodeContent content))
                {
                    discountSkus.AddRange(
                        _contentLoader.GetDescendantsOfType<VariationContent>(content.ContentLink)
                        .Select(x => x.Code)
                        .ToList());
                }
                else if (_contentLoader.TryGet(item, out ProductContent productContent))
                {
                    discountSkus.AddRange(
                        _contentLoader.GetDescendantsOfType<VariationContent>(productContent.ContentLink)
                        .Select(x => x.Code)
                        .ToList());
                }
                else
                {
                    discountSkus.Add(_contentLoader.TryGet<VariationContent>(item)?.Code);
                }
            }

            //remove the discounted SKUs if exist in the excluded list.
            if (excludedVariants.Count() > 0)
            {
                discountSkus = discountSkus.Where(x => !excludedVariants.Contains(x)).ToList();
                conditionSkus = conditionSkus.Where(x => !excludedVariants.Contains(x)).ToList();
            }

            var totalPurchasedQty = allLineItems.Where(x => conditionSkus.Contains(x.Code)).Sum(x => x.Quantity);
            var maxDiscountedQty = Math.Floor(totalPurchasedQty / promotionData.Condition.RequiredQuantity);
            if (promotionData.DiscountTarget.MaxQuantity != null &&
                maxDiscountedQty > promotionData.DiscountTarget.MaxQuantity)
            {
                maxDiscountedQty = (decimal)promotionData.DiscountTarget.MaxQuantity;
            }

            if (maxDiscountedQty == decimal.Zero)
            {
                return RewardDescription.CreateNotFulfilledDescription(
                       promotionData,
                       FulfillmentStatus.InvalidCoupon);
            }

            var discountedLineItems = allLineItems
                .Where(x => discountSkus.Contains(x.Code))
                .OrderByDescending(x => x.PlacedPrice)
                .ThenBy(x => x.Quantity)
                .ToList();

            return
                RewardDescription.CreateMoneyOrPercentageRewardDescription(
                         FulfillmentStatus.Fulfilled,
                         GetRedemptions(promotionData, context, discountedLineItems, maxDiscountedQty),
                         promotionData,
                         promotionData.Discount,
                         context.OrderGroup.Currency,
                         promotionData.Name);
        }

        private IEnumerable<RedemptionDescription> GetRedemptions(
          CustomBuyQuantityGetItemDiscount promotionData,
          PromotionProcessorContext context,
          List<ILineItem> discountedLineItems,
          decimal maxQty)
        {
            List<RedemptionDescription> redemptionDescriptionList = new List<RedemptionDescription>();
            var applicableCodes = discountedLineItems.Select(x => x.Code);
            decimal val2 = GetLineItems(context.OrderForm).Where(li => applicableCodes.Contains(li.Code)).Sum(li => li.Quantity);
            decimal num = Math.Min(GetMaxRedemptions(promotionData.RedemptionLimits), val2);

            for (int index = 0; index < num; ++index)
            {
                AffectedEntries entries = context.EntryPrices.ExtractEntries(applicableCodes, Math.Min(maxQty, val2), promotionData);
                if (entries != null)
                {
                    redemptionDescriptionList.Add(this.CreateRedemptionDescription(affectedEntries: entries));
                }
            }

            return redemptionDescriptionList;
        }
    }

Wishing you a year full of blessing and filled with a new adventure.

Happy new year 2023!

Cheers🥂