refactoring and adding clamav scanning backend

MalwareMultiScan.Backends/Backends/Implementations/ClamavScanBackend.cs

@@ -0,0 +1,32 @@
+using System;
+using System.IO;
+using System.Text.RegularExpressions;
+using MalwareMultiScan.Backends.Backends.Abstracts;
+using Microsoft.Extensions.Logging;
+
+namespace MalwareMultiScan.Backends.Backends.Implementations
+{
+    public class ClamavScanBackend : AbstractLocalProcessScanBackend
+    {
+        public ClamavScanBackend(ILogger logger) : base(logger)
+        {
+        }
+        
+        public override string Name { get; } = "Clamav";
+        
+        public override DateTime DatabaseLastUpdate =>
+            File.GetLastWriteTime("/var/lib/clamav/daily.cvd");
+
+        protected override string BackendPath { get; } = "/usr/bin/clamscan";
+        
+        protected override Regex MatchRegex { get; } =
+            new Regex(@"(\S+): (?<threat>[\S]+) FOUND", RegexOptions.Compiled | RegexOptions.Multiline);
+        
+        protected override bool ParseStdErr { get; } = false;
+        
+        protected override string GetBackendArguments(string path)
+        {
+            return $"--no-summary {path}";
+        }
+    }
+}