Add user agent string

PolyFeed/FeedBuilder.cs

@@ -30,7 +30,10 @@ namespace PolyFeed
 
 		public async Task AddSource(FeedSource source) {
 			await Console.Error.WriteLineAsync("[Builder] Downloading content");
-			WebResponse response = await WebRequest.Create(source.Feed.Url).GetResponseAsync();
+			HttpWebRequest request = (HttpWebRequest)WebRequest.Create(source.Feed.Url);
+
+			request.UserAgent = UserAgentHelper.UserAgent;
+			WebResponse response = await request.GetResponseAsync();
 
 			await Console.Error.WriteLineAsync("[Builder] Generating feed header");
 

PolyFeed/Helpers/UserAgentHelper.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Reflection;
+
+namespace PolyFeed.Helpers
+{
+	public static class UserAgentHelper
+	{
+		public static string UserAgent {
+			get {
+				return $"PolyFeed/{version} ({os_name} {cpu_arch}; +https://github.com/sbrl/PolyFeed) .NET-CLR/{clr_version} {mono_info}";
+			}
+		}
+
+		private static string version => Program.GetProgramVersion();
+		private static string os_name => Environment.OSVersion.Platform.ToString().Replace("Unix", "Linux");
+		private static string cpu_arch => System.Runtime.InteropServices.RuntimeInformation.ProcessArchitecture.ToString();
+
+		private static string clr_version => Environment.Version.ToString();
+
+		private static string mono_info {
+			get {
+				Type type = Type.GetType("Mono.Runtime");
+				if (type == null)
+					return string.Empty;
+
+				MethodInfo displayName = type.GetMethod("GetDisplayName", BindingFlags.NonPublic | BindingFlags.Static);
+				if (displayName != null)
+					return $"Mono/{(string)displayName.Invoke(null, null)}";
+				
+				return string.Empty;
+			}
+		}
+	}
+}

PolyFeed/PolyFeed.csproj

@@ -149,6 +149,7 @@
     <Compile Include="ReferenceSubstitutor.cs" />
     <Compile Include="SnakeCasePropertySelector.cs" />
     <Compile Include="Helpers\HtmlHelpers.cs" />
+    <Compile Include="Helpers\UserAgentHelper.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="packages.config" />