Added backend skeleton, models and services

DemoApplication.csproj

@@ -7,4 +7,9 @@
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="CsvHelper" Version="30.0.1" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.2" />
+  </ItemGroup>
+
 </Project>

Program.cs

@@ -1,10 +1,29 @@
-namespace OrderParser
+using Configuration;
+using DTO;
+using static Configuration.DemoApplicationConfiguration;
+
+namespace OrderParser
 {
     class Program
     {
         static void Main(string[] args)
         {
-            Console.WriteLine(string.Join(" ", args));
+            try
+            {
+                var filesInfoConfig = DemoApplicationConfiguration.InitializeFrom(args);
+                var csvFileWriter = new CsvFileWriter(filesInfoConfig.OutputFile);
+
+                foreach (var jsonFile in filesInfoConfig.JsonFilesInfo)
+                {
+                    var orderModel = new OrderModel(Newtonsoft.Json.JsonConvert.DeserializeObject<OrderDto>(File.ReadAllText(jsonFile.FullName)));
+
+                    csvFileWriter.writeOutRow(orderModel);
+                }
+            }
+            catch (DemoApplicationConfigurationException e)
+            {
+                Console.WriteLine(e.Message);
+            }
         }
     }
 }

assets/input2.json

@@ -6,13 +6,13 @@
 			"ProductId": "PID3",
 			"Description": "pid3 description",
 			"Amount": 1.5,
-			"price": 19.5
+			"price": 42.0
 		},
 		{
 			"ProductId": "PID4",
 			"Description": "pid4 description",
 			"Amount": 2.5,
-			"price": 12.1
+			"price": 169.0
 		}
 	]
 }

data/dtos/order_dto.cs

@@ -0,0 +1,34 @@
+namespace DTO
+{
+    using Newtonsoft.Json;
+
+    public partial class OrderDto
+    {
+        [JsonProperty("OrderId")]
+        public virtual long OrderId { get; set; }
+
+        [JsonProperty("Description")]
+        public virtual string Description { get; set; }
+
+        [JsonProperty("customer ID")]
+        public virtual long CustomerId { get; set; }
+
+        [JsonProperty("products")]
+        public virtual Product[] Products { get; set; }
+    }
+
+    public partial class Product
+    {
+        [JsonProperty("ProductId")]
+        public virtual string ProductId { get; set; }
+
+        [JsonProperty("Description")]
+        public virtual string Description { get; set; }
+
+        [JsonProperty("Amount")]
+        public virtual double Amount { get; set; }
+
+        [JsonProperty("price")]
+        public virtual double Price { get; set; }
+    }
+}

models/OrderModel.cs

@@ -0,0 +1,17 @@
+using DTO;
+
+public sealed class OrderModel {
+    public long OrderId { get; set; }
+    public string OrderDescription { get; set; }
+
+    public long CustomerId { get; set; }
+
+    public double TotalPrice { get; set; }
+
+    public OrderModel(OrderDto orderDTO) {
+        OrderId = orderDTO.OrderId;
+        OrderDescription = orderDTO.Description;
+        CustomerId = orderDTO.CustomerId;
+        TotalPrice = orderDTO.Products.Select(product => product.Price).Sum();
+    }
+}

services/CsvWriter.cs

@@ -0,0 +1,22 @@
+using System.Globalization;
+using CsvHelper;
+
+class CsvFileWriter
+{
+    private TextWriter textWriter; 
+    private CsvWriter csvWriter;
+
+    public CsvFileWriter(FileInfo fileInfo) {
+        textWriter = new StreamWriter(fileInfo.FullName);
+        csvWriter = new CsvWriter(textWriter, CultureInfo.InvariantCulture);
+    }
+
+    public void writeOutRow(OrderModel orderModel) {
+        csvWriter.WriteField(orderModel.OrderId);
+        csvWriter.WriteField(orderModel.OrderDescription);
+        csvWriter.WriteField(orderModel.CustomerId);
+        csvWriter.WriteField(orderModel.TotalPrice);
+
+        csvWriter.NextRecord();
+    }
+}

services/DemoApplicationConfiguration.cs

@@ -0,0 +1,92 @@
+namespace Configuration
+{
+    public sealed class DemoApplicationConfiguration
+    {        
+        private FileInfo[] jsonFiles;
+        public FileInfo[] JsonFilesInfo
+        {
+            get { return jsonFiles; }
+            private set
+            {
+                jsonFiles = value.Reverse().ToArray();
+            }
+        }
+        private FileInfo outputFile;
+        public FileInfo OutputFile{
+            get {return outputFile;}
+            private set
+            {
+                if (!canCreateFile(value.FullName))
+                    throw new DemoApplicationConfigurationException($"Given output name '{value.FullName}' cannot be used");
+                outputFile = value;
+            }
+        }
+
+        public static DemoApplicationConfiguration InitializeFrom(string[] args)
+        {
+            if (args.Length < 3)
+                throw new DemoApplicationConfigurationException("Must have atleast: 1 flag, 1 path, 1 output filename");
+
+            var outputFileName = new FileInfo(args.Last());
+
+            // Remove last file-name arg, to get a more consistent array
+            args = args.SkipLast(1).ToArray();
+
+
+            string[] givenFlags = args.Where((value, index) => index % 2 == 0).ToArray();
+            string[] givenFilePaths = args.Where((value, index) => index % 2 != 0).ToArray();
+            
+            try
+            {
+                if ( givenFlags.Length == 1 && givenFlags[0].Equals("-d") ) {
+                string[] filesInDirectory = Directory.GetFiles(givenFilePaths[0]);
+                return new DemoApplicationConfiguration {
+                    OutputFile = outputFileName,
+                    JsonFilesInfo = filesInDirectory.Select(name => new FileInfo(name)).ToArray(),
+                };
+            }
+                else if (givenFlags.All((string flag) => flag.Equals("-f"))) {
+                    return new DemoApplicationConfiguration {
+                        OutputFile = outputFileName,
+                        JsonFilesInfo = givenFilePaths.Select(name => new FileInfo(name)).ToArray(),
+                    };
+                }
+                else {
+                    throw new DemoApplicationConfigurationException("Must have either 1 flag that is '-d', of all flags must be '-f");
+                }
+            }
+            catch (System.Exception e)
+            {
+                Console.WriteLine("Something else went wrong");
+                throw;
+            }
+        }
+
+
+        private static bool canCreateFile(string filename) {
+            try
+            {
+                using (File.Create(filename)) {
+                    File.Delete(filename);
+                    return true;
+                }            
+            }
+            catch
+            {
+                return false;
+            }
+        }
+
+        [Serializable]
+        internal sealed class DemoApplicationConfigurationException : Exception
+        {
+            public DemoApplicationConfigurationException()
+            {
+            }
+
+            public DemoApplicationConfigurationException(string? message) : base(message)
+            {
+            }
+        }
+    }
+}