From 8bcb891089ce314c0e790b5b1b4e8bb9ea5139b7 Mon Sep 17 00:00:00 2001
From: Mark Knapp <makman99@gmail.com>
Date: Thu, 22 Jan 2026 17:03:24 -0500
Subject: [PATCH] Stop todo evaluation at given datetime

Fixes #913
---
 Ical.Net.Tests/TodoTest.cs           | 27 ++++++++++++++++++++++++++-
 Ical.Net/Evaluation/TodoEvaluator.cs |  2 +-
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/Ical.Net.Tests/TodoTest.cs b/Ical.Net.Tests/TodoTest.cs
index 239b98cf8..608bde0f3 100644
--- a/Ical.Net.Tests/TodoTest.cs
+++ b/Ical.Net.Tests/TodoTest.cs
@@ -3,7 +3,6 @@
 // Licensed under the MIT license.
 //
 
-using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
@@ -240,4 +239,30 @@ public void Todo_WithFutureStart_AndNoDuration_ShouldSucceed()
         Assert.That(firstOccurrence.Period.StartTime, Is.Not.Null);
         Assert.That(firstOccurrence.Period.Duration, Is.Null);
     }
+
+    [Test, Category("Todo")]
+    public void Todo_RecurrenceWithNoEnd_IsCompletedUntilNextOccurrence()
+    {
+        var start = new CalDateTime(2026, 1, 15, 0, 0, 0, "UTC");
+
+        var todo = new Todo
+        {
+            Start = start,
+            RecurrenceRules = [new("FREQ=DAILY;BYDAY=TH")],
+        };
+
+        todo.Status = "COMPLETED";
+        todo.Completed = new CalDateTime(2026, 1, 16, 0, 0, 0, "UTC");
+
+        var results = Enumerable.Range(14, 10)
+            .Select(x => new CalDateTime(2026, 1, x, 0, 0, 0, "UTC"))
+            .Select(todo.IsCompleted)
+            .ToList();
+
+        // Jan 14-21: true (8 days) - TODO is considered completed
+        // Jan 22-23: false (2 days) - TODO is NOT completed
+        List<bool> expected = [true, true, true, true, true, true, true, true, false, false];
+
+        Assert.That(results, Is.EquivalentTo(expected));
+    }
 }
diff --git a/Ical.Net/Evaluation/TodoEvaluator.cs b/Ical.Net/Evaluation/TodoEvaluator.cs
index 25f4fe5ca..05427ab01 100644
--- a/Ical.Net/Evaluation/TodoEvaluator.cs
+++ b/Ical.Net/Evaluation/TodoEvaluator.cs
@@ -48,7 +48,7 @@ internal IEnumerable<Period> EvaluateToPreviousOccurrence(CalDateTime completedD
         }
 
         return Evaluate(Todo.Start, beginningDate, options)
-            .Where(p => p.StartTime <= currDt);
+            .TakeWhile(p => p.StartTime <= currDt);
     }
 
     private static void DetermineStartingRecurrence(IEnumerable<Period> rdate, ref CalDateTime referenceDateTime)