Export: Refactor interfaces and classes

Elwig/Helpers/Export/Csv.cs

@@ -1,4 +1,50 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using System.Threading.Tasks;
+
 namespace Elwig.Helpers.Export {
-    public class Csv {
+    public abstract class Csv<T> : IExporter<T> {
+        public static string FileExtension => "csv";
+
+        protected readonly StreamWriter Writer;
+        protected readonly char Separator;
+        protected string? Header;
+
+        public Csv(string filename, char separator = ';') : this(filename, separator, Encoding.UTF8) { }
+
+        public Csv(string filename, char separator, Encoding encoding) {
+            Writer = new StreamWriter(filename, false, encoding);
+            Separator = separator;
+        }
+
+        public void Dispose() {
+            GC.SuppressFinalize(this);
+            Writer.Dispose();
+        }
+
+        public ValueTask DisposeAsync() {
+            GC.SuppressFinalize(this);
+            return Writer.DisposeAsync();
+        }
+
+        public async Task ExportAsync(IEnumerable<T> data) {
+            if (Header != null) await Writer.WriteLineAsync(Header);
+            foreach (var row in data) {
+                await Writer.WriteLineAsync(FormatRow(row));
+            }
+        }
+
+        public void Export(IEnumerable<T> data) {
+            ExportAsync(data).GetAwaiter().GetResult();
+        }
+
+        public string FormatRow(IEnumerable row) {
+            return string.Join(Separator, row);
+        }
+
+        public abstract string FormatRow(T row);
     }
 }