Refactoring file filter; fixing docs

Author: thiagosgarcia

src/Serilog.Sinks.File/FileLoggerConfigurationExtensions.cs

@@ -138,7 +138,6 @@ public static LoggerConfiguration File(
         /// including the current log file. For unlimited retention, pass null. The default is 31.</param>
         /// <param name="encoding">Character encoding used to write the text file. The default is UTF-8 without BOM.</param>
         /// <returns>Configuration object allowing method chaining.</returns>
-        /// <remarks>The file will be written using the UTF-8 character set.</remarks>
         [Obsolete("New code should not be compiled against this obsolete overload"), EditorBrowsable(EditorBrowsableState.Never)]
         public static LoggerConfiguration File(
             this LoggerSinkConfiguration sinkConfiguration,
@@ -239,7 +238,6 @@ public static LoggerConfiguration File(
         /// Ignored if <paramref see="rollingInterval"/> is <see cref="RollingInterval.Infinite"/>.
         /// The default is to retain files indefinitely.</param>
         /// <returns>Configuration object allowing method chaining.</returns>
-        /// <remarks>The file will be written using the UTF-8 character set.</remarks>
         public static LoggerConfiguration File(
             this LoggerSinkConfiguration sinkConfiguration,
             string path,

src/Serilog.Sinks.File/Sinks/File/RollingFileSink.cs

@@ -191,15 +191,11 @@ void ApplyRetentionPolicy(string currentFilePath)
             var newestFirst = _roller
                 .SelectMatches(potentialMatches)
                 .OrderByDescending(m => m.DateTime)
-                .ThenByDescending(m => m.SequenceNumber)
-                .Select(m => new { m.Filename, m.DateTime });
+                .ThenByDescending(m => m.SequenceNumber);
 
             var toRemove = newestFirst
                 .Where(n => StringComparer.OrdinalIgnoreCase.Compare(currentFileName, n.Filename) != 0)
-                .SkipWhile((x, i) => (i < (_retainedFileCountLimit - 1 ?? 0)) &&
-                                     (!_retainedFileTimeLimit.HasValue ||
-                                          x.DateTime.HasValue &&
-                                          DateTime.Now.Subtract(_retainedFileTimeLimit.Value).CompareTo(x.DateTime.Value) <= 0))
+                .SkipWhile(FilterFiles)
                 .Select(x => x.Filename)
                 .ToList();
 
@@ -217,6 +213,17 @@ void ApplyRetentionPolicy(string currentFilePath)
             }
         }
 
+        private bool FilterFiles(RollingLogFile file, int index)
+        {
+            var isInCountLimit = index < (_retainedFileCountLimit - 1 ?? 0);
+
+            var isInTimeLimit = !_retainedFileTimeLimit.HasValue;
+            if (_retainedFileTimeLimit.HasValue && file.DateTime.HasValue)
+                isInTimeLimit = DateTime.Now.Subtract(_retainedFileTimeLimit.Value).CompareTo(file.DateTime.Value) <= 0;
+
+            return isInCountLimit && isInTimeLimit;
+        }
+
         public void Dispose()
         {
             lock (_syncRoot)