Rework architecture

DiscordChatExporter.Domain/Exceptions/DiscordChatExporterException.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Net.Http;
+using DiscordChatExporter.Domain.Discord.Models;
+
+namespace DiscordChatExporter.Domain.Exceptions
+{
+    public partial class DiscordChatExporterException : Exception
+    {
+        public bool IsCritical { get; }
+
+        public DiscordChatExporterException(string message, bool isCritical = false)
+            : base(message)
+        {
+            IsCritical = isCritical;
+        }
+    }
+
+    public partial class DiscordChatExporterException
+    {
+        internal static DiscordChatExporterException FailedHttpRequest(HttpResponseMessage response)
+        {
+            var message = $@"
+Failed to perform an HTTP request.
+
+{response.RequestMessage}
+
+{response}";
+
+            return new DiscordChatExporterException(message.Trim(), true);
+        }
+
+        internal static DiscordChatExporterException Unauthorized()
+        {
+            const string message = "Authentication token is invalid.";
+            return new DiscordChatExporterException(message);
+        }
+
+        internal static DiscordChatExporterException ChannelForbidden(string channel)
+        {
+            var message = $"Access to channel '{channel}' is forbidden.";
+            return new DiscordChatExporterException(message);
+        }
+
+        internal static DiscordChatExporterException ChannelDoesNotExist(string channel)
+        {
+            var message = $"Channel '{channel}' does not exist.";
+            return new DiscordChatExporterException(message);
+        }
+
+        internal static DiscordChatExporterException ChannelEmpty(string channel)
+        {
+            var message = $"Channel '{channel}' contains no messages for the specified period.";
+            return new DiscordChatExporterException(message);
+        }
+
+        internal static DiscordChatExporterException ChannelEmpty(Channel channel) =>
+            ChannelEmpty(channel.Name);
+    }
+}