All items with a specific item template set price

CartAllItemsWithTemplateSpecifyAmountAction.cs

namespace Plugin.Pricing.Action
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Runtime.CompilerServices;

    using Sitecore.Commerce.Core;
    using Sitecore.Commerce.Plugin.Carts;
    using Sitecore.Commerce.Plugin.Pricing;
    using Sitecore.Framework.Rules;

    [EntityIdentifier("All items with a specific item template set price")]
    public class CartAllItemsWithTemplateSpecifyAmountAction : ICartLineAction
    {
        public void Execute(IRuleExecutionContext context)
        {
            var commerceContext = context.Fact<CommerceContext>();

            if (commerceContext == null)
            {
                return;
            }

            var cart = (commerceContext.Objects.OfType<Cart>()).FirstOrDefault();
            var totals = (commerceContext.Objects.OfType<CartTotals>()).FirstOrDefault();

            if ((cart != null) && cart.Lines.Any() && ((totals != null) && totals.Lines.Any()) == false)
            {
                return;
            }

            // This the code that decides which lines to discount
            var source = new List<CartLineComponent>();
            foreach (var cartLine in cart.Lines.Where(x => x.HasComponent<CartProductComponent>()))
            {
                if(cartLine.GetComponent<CartProductComponent>().ItemTemplate == this.Template.Yield(context))
                {
                    source.Add(cartLine);
                }
            }

            if (!source.Any())
            {
                return;
            }

            var model = commerceContext.Objects.OfType<PropertiesModel>().FirstOrDefault();
            if (model == null)
            {
                return;
            }

            foreach (var line in source) 
            {
                if (!totals.Lines.ContainsKey(line.Id))
                {
                    continue;
                }

                var discount = commerceContext.GetPolicy<KnownCartAdjustmentTypesPolicy>().Discount;
                var d = this.Price.Yield(context);
                if (commerceContext.GetPolicy<GlobalPricingPolicy>().ShouldRoundPriceCalc)
                {
                    d = decimal.Round(d, commerceContext.GetPolicy<GlobalPricingPolicy>().RoundDigits, commerceContext.GetPolicy<GlobalPricingPolicy>().MidPointRoundUp ? MidpointRounding.AwayFromZero : MidpointRounding.ToEven);
                }

                decimal amount;
                
                var currentAmount = totals.Lines[line.Id].SubTotal.Amount;
                if (currentAmount <= d)
                {
                    amount = d - currentAmount;
                    totals.Lines[line.Id].SubTotal.Amount += amount;
                }
                else
                {
                    amount = currentAmount - d;
                    amount = amount * decimal.MinusOne;
                    totals.Lines[line.Id].SubTotal.Amount += amount;
                }
                
                var item = new CartLineLevelAwardedAdjustment
                {
                    Name = (string) model.GetPropertyValue("PromotionText"),
                    DisplayName = (string) model.GetPropertyValue("PromotionCartText"),
                    Adjustment = new Money(commerceContext.CurrentCurrency(), amount), 
                    AdjustmentType = discount, 
                    IsTaxable = false, 
                    AwardingBlock = "CartAllItemsWithProductDefinitionSpecifyAmountAction"
                };
                line.Adjustments.Add(item);
               
                line.GetComponent<MessagesComponent>().AddMessage(commerceContext.GetPolicy<KnownMessageCodePolicy>().Promotions, $"PromotionApplied: {model.GetPropertyValue("PromotionId")}");
            }
        }

        public IRuleValue<decimal> Price { get; set; }

        public IRuleValue<string> Template { get; set; }
    }
}