Add mediator examples

src/MediatorPattern/StockExchange/Buyer.cs

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+namespace MediatorPattern.StockExchange
+{
+    public class Buyer : Trader
+    {
+        IStockExchange stockExchange;
+        public Buyer(string name, string symbol, int count, double price, IStockExchange stockExchange) : base(name, symbol, count, price)
+        {
+            this.stockExchange = stockExchange;            
+        }
+
+        public bool BuyFromStockExchange()
+        {
+            return stockExchange.Buy(this, new StockRequest { Count = Count, Price = Price, Symbol = Symbol, Requester = Name });
+        }
+    }
+}

src/MediatorPattern/StockExchange/IStockExchange.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MediatorPattern.StockExchange
+{
+    /// <summary>
+    /// Mediator
+    /// </summary>
+    public interface IStockExchange
+    {
+        bool Buy(Trader trader, StockRequest request);
+
+        bool Sell(Trader trader, StockRequest request);
+    }    
+}

src/MediatorPattern/StockExchange/Seller.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MediatorPattern.StockExchange
+{
+    public class Seller : Trader
+    {
+        IStockExchange stockExchange;
+        public Seller(string name, string symbol, int count, double price, IStockExchange stockExchange) : base(name, symbol, count, price)
+        {
+            this.stockExchange = stockExchange;
+        }
+
+        public bool SellFromStockExchange()
+        {
+            return stockExchange.Sell(this, new StockRequest { Count = Count, Price = Price, Symbol = Symbol, Requester = Name });
+        }
+    }
+}

src/MediatorPattern/StockExchange/StockExchange.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MediatorPattern.StockExchange
+{
+    public class StockExchange : IStockExchange
+    {
+        Dictionary<string, List<Trader>> sellers;
+        Dictionary<string, List<Trader>> buyers;
+
+        public StockExchange()
+        {
+            sellers = new Dictionary<string, List<Trader>>();
+            buyers = new Dictionary<string, List<Trader>>();
+            
+        }
+        protected void AddSeller(Trader trader)
+        {
+            AddTrader(trader, sellers);
+        }
+
+        protected void AddBuyer(Trader trader)
+        {
+            AddTrader(trader, buyers);
+        }        
+
+        public bool Buy(Trader trader, StockRequest request)
+        {
+            if (!sellers.ContainsKey(request.Symbol))
+            {
+                AddBuyer(trader);
+                Console.WriteLine("There are no sellers for {0}", request.Symbol);
+                return false;
+            }
+
+            List<Trader> sellersOfStock = sellers[request.Symbol];
+
+            var couldBuyStocks = sellersOfStock.Any(s => s.AcceptSell(request));
+
+            if (!couldBuyStocks)
+            {
+                AddBuyer(trader);
+                Console.WriteLine("No one seller sells it at this price, try a higher price");
+            }
+            else
+            {
+                Console.WriteLine("Actions bought");
+            }
+
+            return couldBuyStocks;
+        }
+
+        public bool Sell(Trader trader, StockRequest request)
+        {
+            if (!buyers.ContainsKey(request.Symbol))
+            {
+                AddSeller(trader);
+                Console.WriteLine("There are no buyers for {0}", request.Symbol);
+                return false;
+            }
+
+            var couldSellStocks = buyers[request.Symbol].Any(b => b.AcceptBuy(request));
+
+            if (!couldSellStocks)
+            {
+                AddSeller(trader);
+                Console.WriteLine("No one seller buys it at this price, try a lower price");
+            }
+                
+
+            return couldSellStocks;
+        }
+
+        private void AddTrader(Trader trader, Dictionary<string, List<Trader>> traderList)
+        {
+            if (!traderList.ContainsKey(trader.Symbol))
+            {
+                traderList.Add(trader.Symbol, new List<Trader> { trader });
+            }
+            else
+            {
+                traderList[trader.Symbol].Add(trader);
+            }
+        }
+    }
+}
+

src/MediatorPattern/StockExchange/StockExchangeExample.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MediatorPattern.StockExchange
+{
+    public class StockExchangeExample
+    {
+        public void Run()
+        {
+            IStockExchange stockExchange = new StockExchange();
+            Buyer aaplBuyer = new Buyer("El Ciupi AAPL", "AAPL", 100, 15.0, stockExchange);
+            var buyResult = aaplBuyer.BuyFromStockExchange();
+
+            Seller aaplSeller = new Seller("capo di APPL", "AAPL", 100, 16.0, stockExchange);
+            var sellResult = aaplSeller.SellFromStockExchange();
+
+            aaplSeller = new Seller("capo di APPL", "AAPL", 100, 14.0, stockExchange);
+            sellResult = aaplSeller.SellFromStockExchange();
+
+        }
+    }
+}

src/MediatorPattern/StockExchange/StockRequest.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace MediatorPattern.StockExchange
+{
+    public class StockRequest
+    {
+        public string Symbol { get; set; }
+
+        public int Count { get; set; }
+
+        public double Price { get; set; }
+
+        public string Requester { get; set; }
+    }
+}

src/MediatorPattern/StockExchange/Trader.cs

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+using System;
+
+namespace MediatorPattern.StockExchange
+{
+    /// <summary>
+    /// Colleague
+    /// </summary>
+    public class Trader
+    {
+        public string Name { get; private set; }
+        public Trader(string name, string symbol, int count, double price)
+        {
+            Name = name;
+            Symbol = symbol;
+            Count = count;
+            Price = price;
+        }
+        public string Symbol { get; private set; }
+
+        public int Count { get; private set; }
+
+        public double Price { get; private set; }
+
+        public virtual bool AcceptSell(StockRequest request)
+        {
+            if(request.Price >= Price)
+            {
+                Console.WriteLine("{0} will sell {1} actions of {2} at the price of {3} to {4}",
+                    Name, request.Count, request.Symbol, request.Price, request.Requester);
+                return true;
+            }
+            return false;
+        }
+
+        public virtual bool AcceptBuy(StockRequest request)
+        {
+            if(request.Price <= Price)
+            {
+                Console.WriteLine("{0} will buy {1} actions of {2} at the price of {3} from {4}",
+                    Name, request.Count, request.Symbol, request.Price, request.Requester);
+                return true;
+            }
+
+            return false;
+        }
+    }
+}