Allow caching by minutes and seconds.

Author: JimBobSquarePants

src/ImageSharp.Web/Middleware/ImageSharpMiddleware.cs

@@ -71,6 +71,12 @@ public class ImageSharpMiddleware
         /// </summary>
         private readonly ICacheHash cacheHash;
 
+        /// <summary>
+        /// The minimum allowable last write time for source files.
+        /// Used to determine whether a file has expired its cache duration.
+        /// </summary>
+        private readonly DateTimeOffset minCacheLastWriteTimeUtc;
+
         /// <summary>
         /// The collection of known commands gathered from the processors.
         /// </summary>
@@ -121,6 +127,7 @@ public ImageSharpMiddleware(
             this.processors = processors as IImageWebProcessor[] ?? processors.ToArray();
             this.cache = cache;
             this.cacheHash = cacheHash;
+            this.minCacheLastWriteTimeUtc = this.GetMaxCacheDateTimeOffset();
 
             var commands = new HashSet<string>();
             foreach (IImageWebProcessor processor in this.processors)
@@ -329,7 +336,7 @@ private async Task<ValueTuple<bool, ImageMetadata>> IsNewOrUpdatedAsync(
                     {
                         // Has the cached image expired or has the source image been updated?
                         if (cachedImageMetadata.SourceLastWriteTimeUtc == sourceImageMetadata.LastWriteTimeUtc
-                            && cachedImageMetadata.CacheLastWriteTimeUtc > DateTimeOffset.UtcNow.AddDays(-this.options.MaxCacheDays))
+                            && cachedImageMetadata.CacheLastWriteTimeUtc > this.minCacheLastWriteTimeUtc)
                         {
                             // We're pulling the image from the cache.
                             using Stream cachedBuffer = await cachedImageResolver.OpenReadAsync();
@@ -401,5 +408,13 @@ private static string GetUri(HttpContext context, IDictionary<string, string> co
 
             return sb.ToString().ToLowerInvariant();
         }
+
+        private DateTimeOffset GetMaxCacheDateTimeOffset()
+        {
+            return DateTimeOffset.UtcNow
+                .AddDays(-this.options.MaxCacheDays)
+                .AddMinutes(-this.options.MaxCacheMinutes)
+                .AddSeconds(-this.options.MaxCacheSeconds);
+        }
     }
 }

src/ImageSharp.Web/Middleware/ImageSharpMiddlewareOptions.cs

@@ -36,6 +36,16 @@ public class ImageSharpMiddlewareOptions
         /// </summary>
         public int MaxCacheDays { get; set; } = 365;
 
+        /// <summary>
+        /// Gets or sets the number of seconds to store images in the image cache.
+        /// </summary>
+        public int MaxCacheMinutes { get; set; }
+
+        /// <summary>
+        /// Gets or sets the number of minutes to store images in the image cache.
+        /// </summary>
+        public int MaxCacheSeconds { get; set; }
+
         /// <summary>
         /// Gets or sets the length of the filename to use (minus the extension) when storing images in the image cache.
         /// </summary>