Add RuleEngine sample

Behavioral/ChainOfResponsibility/RuleEngine/Dto/PriceDto.cs

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+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+
+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Dto
+{
+    public record PriceModel
+    {
+        public decimal Price { get; set; }
+
+        public Source Source { get; set; }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Entity/Product.cs

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+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity
+{
+    public class Product
+    {
+        public Product()
+        {
+            Sources=new List<ProductSource>();
+        }
+        public int Id { get; set; }
+
+        public decimal Price { get; set; }
+        public decimal SalePrice { get; set; }
+
+        public ICollection<ProductSource> Sources { get; set; }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Entity/ProductSource.cs

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+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity
+{
+    public class ProductSource
+    {
+        public Source Source { get; set; }
+
+        public Product Product { get; set; }
+
+        public string Url { get; set; }
+
+        public DateTime LastUpdatedOn { get; set; }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Entity/Source.cs

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+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity
+{
+    public enum Source
+    {
+        Amazon,
+        Decathlon,
+        DigiKala,
+        Torob,
+        Trendyol
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Infra/PriceRuleEngine.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Dto;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Interface;
+
+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Infra
+{
+    public class PriceRuleEngine
+    {
+        private readonly IEnumerable<IPriceRule> _rules;
+
+        public PriceRuleEngine(IEnumerable<IPriceRule> rules)
+        {
+            _rules=rules;
+        }
+
+        public PriceModel CalculatePrice(Product product)
+        {
+            var price=new PriceModel();
+            foreach (var rule in _rules)
+            {
+                price = rule.Calculate(product, price);
+            }
+
+            return price;
+        }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Infra/PriceRules/AmazonRule.cs

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+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Dto;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Interface;
+
+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Infra.PriceRules
+{
+    public class AmazonRule : IPriceRule
+    {
+        public int Priority { get; set; } = 1;
+        public PriceModel Calculate(Product product, PriceModel price)
+        {
+            //fetch the price from Amazon and get the lower price
+            return new PriceModel
+            {
+                Source = Source.Amazon,
+                Price = 19_000
+            };
+        }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Infra/PriceRules/DecathlonRule.cs

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+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Dto;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Interface;
+
+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Infra.PriceRules
+{
+    public class DecathlonRule : IPriceRule
+    {
+        public int Priority { get; set; } = 2;
+        public PriceModel Calculate(Product product, PriceModel price)
+        {
+            //fetch the price from Decathlon and get the lower price
+            return new PriceModel
+            {
+                Source = Source.Decathlon,
+                Price = 16_000
+            };
+        }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Infra/PriceRules/DigiKalaRule.cs

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+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Dto;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Interface;
+
+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Infra.PriceRules
+{
+    public class DigiKalaRule : IPriceRule
+    {
+        public int Priority { get; set; } = 3;
+        public PriceModel Calculate(Product product, PriceModel price)
+        {
+            //fetch the price from DigiKala and get the lower price
+            return new PriceModel
+            {
+                Source = Source.DigiKala,
+                Price = 15_000
+            };
+        }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Infra/PriceRules/TorobRule.cs

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+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Dto;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Interface;
+
+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Infra.PriceRules
+{
+    public class TorobRule : IPriceRule
+    {
+        public int Priority { get; set; } = 4;
+        public PriceModel Calculate(Product product, PriceModel price)
+        {
+            //fetch the price from Torob and get the lower price
+            return new PriceModel
+            {
+                Source = Source.Torob,
+                Price = 10_000
+            };
+        }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Infra/PriceRules/TrendyolRule.cs

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+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Dto;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Interface;
+
+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Infra.PriceRules
+{
+    public class TrendyolRule : IPriceRule
+    {
+        public int Priority { get; set; } = 2;
+        public PriceModel Calculate(Product product, PriceModel price)
+        {
+            //fetch the price from Trendyol and get the lower price
+            return new PriceModel
+            {
+                Source = Source.Trendyol,
+                Price = 8_000
+            };
+        }
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Interface/IPriceRule.cs

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+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Dto;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+
+namespace Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Interface
+{
+    public interface IPriceRule
+    {
+        public int Priority { get; set; }
+
+        PriceModel Calculate(Product product,PriceModel price);
+    }
+}

Behavioral/ChainOfResponsibility/RuleEngine/Program.cs

@@ -1,2 +1,40 @@
 // See https://aka.ms/new-console-template for more information
-Console.WriteLine("Hello, World!");
+
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Entity;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Infra;
+using Thisisnabi.DesignPattern.Behavioral.ChainOfResponsibility.RuleEngine.Interface;
+using System.Reflection;
+
+var product = new Product
+{
+    Sources = new List<ProductSource>
+    {
+        new()
+        {
+            Source = Source.Torob,
+            Url = "https://torob.com/.."
+        },
+        new ProductSource
+        {
+            Source = Source.DigiKala,
+            Url = "https://digikala.com/.."
+        },
+        new ProductSource
+        {
+            Source = Source.Amazon,
+            Url = "https://Amazon.com/.."
+        }
+    }
+};
+var ruleType = typeof(IPriceRule);
+
+var rules = Assembly.GetExecutingAssembly().GetTypes()
+    .Where(p => ruleType.IsAssignableFrom(p) && !p.IsInterface)
+    .Select(q => Activator.CreateInstance(q) as IPriceRule)
+    .OrderBy(p => p.Priority).ToList();
+
+var engine = new PriceRuleEngine(rules);
+
+var result = engine.CalculatePrice(product);
+
+Console.WriteLine($"The lowest price is :{result.Price} and available on :{result.Source} ");