Refactor (#94)

CliFx.Demo/Domain/LibraryProvider.cs

@@ -0,0 +1,41 @@
+using System.IO;
+using System.Linq;
+using Newtonsoft.Json;
+
+namespace CliFx.Demo.Domain
+{
+    public class LibraryProvider
+    {
+        private static string StorageFilePath { get; } = Path.Combine(Directory.GetCurrentDirectory(), "Library.json");
+
+        private void StoreLibrary(Library library)
+        {
+            var data = JsonConvert.SerializeObject(library);
+            File.WriteAllText(StorageFilePath, data);
+        }
+
+        public Library GetLibrary()
+        {
+            if (!File.Exists(StorageFilePath))
+                return Library.Empty;
+
+            var data = File.ReadAllText(StorageFilePath);
+
+            return JsonConvert.DeserializeObject<Library>(data);
+        }
+
+        public Book? TryGetBook(string title) => GetLibrary().Books.FirstOrDefault(b => b.Title == title);
+
+        public void AddBook(Book book)
+        {
+            var updatedLibrary = GetLibrary().WithBook(book);
+            StoreLibrary(updatedLibrary);
+        }
+
+        public void RemoveBook(Book book)
+        {
+            var updatedLibrary = GetLibrary().WithoutBook(book);
+            StoreLibrary(updatedLibrary);
+        }
+    }
+}