Support recurrence for TimeWindowFilter

src/Microsoft.FeatureManagement/FeatureFilters/Recurrence/Recurrence.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+namespace Microsoft.FeatureManagement.FeatureFilters
+{
+    /// <summary>
+    /// A recurrence definition describing how time window recurs
+    /// </summary>
+    public class Recurrence
+    {
+        /// <summary>
+        /// The recurrence pattern specifying how often the time window repeats
+        /// </summary>
+        public RecurrencePattern Pattern { get; set; }
+
+        /// <summary>
+        /// The recurrence range specifying how long the recurrence pattern repeats
+        /// </summary>
+        public RecurrenceRange Range { get; set; }
+    }
+}

src/Microsoft.FeatureManagement/FeatureFilters/Recurrence/RecurrencePattern.cs

@@ -0,0 +1,48 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using System.Collections.Generic;
+
+namespace Microsoft.FeatureManagement.FeatureFilters
+{
+    /// <summary>
+    /// The recurrence pattern specifying how often the time window repeats
+    /// </summary>
+    public class RecurrencePattern
+    {
+        /// <summary>
+        /// The recurrence pattern type
+        /// </summary>
+        public string Type { get; set; }
+
+        /// <summary>
+        /// The number of units between occurrences, where units can be in days, weeks, months, or years, depending on the pattern type
+        /// </summary>
+        public int Interval { get; set; } = 1;
+
+        /// <summary>
+        /// The days of the week on which the time window occurs
+        /// </summary>
+        public IEnumerable<string> DaysOfWeek { get; set; }
+
+        /// <summary>
+        /// The first day of the week.
+        /// </summary>
+        public string FirstDayOfWeek { get; set; } = "Sunday";
+
+        /// <summary>
+        /// Specifies on which instance of the allowed days specified in DaysOfWeek the time window occurs, counted from the first instance in the month
+        /// </summary>
+        public string Index { get; set; } = "First";
+
+        /// <summary>
+        /// The day of the month on which the time window occurs
+        /// </summary>
+        public int? DayOfMonth { get; set; }
+
+        /// <summary>
+        /// The month on which the time window occurs
+        /// </summary>
+        public int? Month { get; set; }
+    }
+}

src/Microsoft.FeatureManagement/FeatureFilters/Recurrence/RecurrenceRange.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using System;
+
+namespace Microsoft.FeatureManagement.FeatureFilters
+{
+    /// <summary>
+    /// The recurrence range specifying how long the recurrence pattern repeats
+    /// </summary>
+    public class RecurrenceRange
+    {
+        /// <summary>
+        /// The recurrence range type
+        /// </summary>
+        public string Type { get; set; } = "NoEnd";
+
+        /// <summary>
+        /// The date to stop applying the recurrence pattern
+        /// </summary>
+        public DateTimeOffset? EndDate { get; set; }
+
+        /// <summary>
+        /// The number of times to repeat the time window
+        /// </summary>
+        public int? NumberOfOccurrences { get; set; }
+
+        /// <summary>
+        /// Time zone for recurrence settings, e.g. UTC+08:00
+        /// </summary>
+        public string RecurrenceTimeZone { get; set; }
+    }
+}

src/Microsoft.FeatureManagement/FeatureFilters/TimeWindowFilter.cs

@@ -10,6 +10,7 @@ namespace Microsoft.FeatureManagement.FeatureFilters
 {
     /// <summary>
     /// A feature filter that can be used to activate a feature based on a time window.
+    /// The time window filter supports recurrence settings. The time window can occur repeatedly.
     /// </summary>
     [FilterAlias(Alias)]
     public class TimeWindowFilter : IFeatureFilter, IFilterParametersBinder
@@ -23,7 +24,7 @@ public class TimeWindowFilter : IFeatureFilter, IFilterParametersBinder
         /// <param name="loggerFactory">A logger factory for creating loggers.</param>
         public TimeWindowFilter(ILoggerFactory loggerFactory)
         {
-            _logger = loggerFactory.CreateLogger<TimeWindowFilter>();
+            _logger = loggerFactory?.CreateLogger<TimeWindowFilter>() ?? throw new ArgumentNullException(nameof(loggerFactory));
         }
 
         /// <summary>
@@ -37,7 +38,7 @@ public object BindParameters(IConfiguration filterParameters)
         }
 
         /// <summary>
-        /// Evaluates whether a feature is enabled based on a configurable time window.
+        /// Evaluates whether a feature is enabled based on a configurable fixed time window or recurring time windows.
         /// </summary>
         /// <param name="context">The feature evaluation context.</param>
         /// <returns>True if the feature is enabled, false otherwise.</returns>
@@ -56,7 +57,19 @@ public Task<bool> EvaluateAsync(FeatureFilterEvaluationContext context)
                 return Task.FromResult(false);
             }
 
-            return Task.FromResult((!settings.Start.HasValue || now >= settings.Start.Value) && (!settings.End.HasValue || now < settings.End.Value));
+            //
+            // Hit the first occurrence of the time window
+            if ((!settings.Start.HasValue || now >= settings.Start.Value) && (!settings.End.HasValue || now < settings.End.Value))
+            {
+                return Task.FromResult(true);
+            }
+
+            if (settings.Recurrence != null)
+            {
+                return Task.FromResult(RecurrenceEvaluator.MatchRecurrence(now, settings));
+            }
+
+            return Task.FromResult(false);
         }
     }
 }

src/Microsoft.FeatureManagement/FeatureFilters/TimeWindowFilterSettings.cs

@@ -14,12 +14,18 @@ public class TimeWindowFilterSettings
         /// An optional start time used to determine when a feature configured to use the <see cref="TimeWindowFilter"/> feature filter should be enabled.
         /// If no start time is specified the time window is considered to have already started.
         /// </summary>
-        public DateTimeOffset? Start { get; set; } // E.g. "Wed, 01 May 2019 22:59:30 GMT"
+        public DateTimeOffset? Start { get; set; }
 
         /// <summary>
         /// An optional end time used to determine when a feature configured to use the <see cref="TimeWindowFilter"/> feature filter should be enabled.
         /// If no end time is specified the time window is considered to never end.
         /// </summary>
-        public DateTimeOffset? End { get; set; } // E.g. "Wed, 01 May 2019 23:00:00 GMT"
+        public DateTimeOffset? End { get; set; }
+
+        /// <summary>
+        /// Add-on recurrence rule allows the time window defined by Start and End to recur.
+        /// The rule specifies both how often the time window repeats and for how long.
+        /// </summary>
+        public Recurrence Recurrence { get; set; }
     }
 }

tests/Tests.FeatureManagement/FeatureManagement.cs

@@ -226,6 +226,8 @@ public async Task TimeWindow()
             const string feature2 = "feature2";
             const string feature3 = "feature3";
             const string feature4 = "feature4";
+            const string feature5 = "feature5";
+            const string feature6 = "feature6";
 
             Environment.SetEnvironmentVariable($"FeatureManagement:{feature1}:EnabledFor:0:Name", "TimeWindow");
             Environment.SetEnvironmentVariable($"FeatureManagement:{feature1}:EnabledFor:0:Parameters:End", DateTimeOffset.UtcNow.AddDays(1).ToString("r"));
@@ -239,6 +241,19 @@ public async Task TimeWindow()
             Environment.SetEnvironmentVariable($"FeatureManagement:{feature4}:EnabledFor:0:Name", "TimeWindow");
             Environment.SetEnvironmentVariable($"FeatureManagement:{feature4}:EnabledFor:0:Parameters:Start", DateTimeOffset.UtcNow.AddDays(1).ToString("r"));
 
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature5}:EnabledFor:0:Name", "TimeWindow");
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature5}:EnabledFor:0:Parameters:Start", DateTimeOffset.UtcNow.AddDays(-2).ToString("r"));
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature5}:EnabledFor:0:Parameters:End", DateTimeOffset.UtcNow.AddDays(-1).ToString("r"));
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature5}:EnabledFor:0:Parameters:Recurrence:Pattern:Type", "Daily");
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature5}:EnabledFor:0:Parameters:Recurrence:Range:Type", "NoEnd");
+
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature6}:EnabledFor:0:Name", "TimeWindow");
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature6}:EnabledFor:0:Parameters:Start", DateTimeOffset.UtcNow.AddDays(-2).ToString("r"));
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature6}:EnabledFor:0:Parameters:End", DateTimeOffset.UtcNow.AddDays(-1).ToString("r"));
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature6}:EnabledFor:0:Parameters:Recurrence:Pattern:Type", "Daily");
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature6}:EnabledFor:0:Parameters:Recurrence:Pattern:Interval", "3");
+            Environment.SetEnvironmentVariable($"FeatureManagement:{feature6}:EnabledFor:0:Parameters:Recurrence:Range:Type", "NoEnd");
+
             IConfiguration config = new ConfigurationBuilder().AddEnvironmentVariables().Build();
 
             var serviceCollection = new ServiceCollection();
@@ -254,6 +269,8 @@ public async Task TimeWindow()
             Assert.False(await featureManager.IsEnabledAsync(feature2));
             Assert.True(await featureManager.IsEnabledAsync(feature3));
             Assert.False(await featureManager.IsEnabledAsync(feature4));
+            Assert.True(await featureManager.IsEnabledAsync(feature5));
+            Assert.False(await featureManager.IsEnabledAsync(feature6));
         }
 
         [Fact]