Merge pull request #160 from ktsu-dev/fix/151-stream-glob-regex-filter

Author: matt-edmondson

TextFilter.Test/TextFilterTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) 2023-2026 ktsu-dev contributors
+// Copyright (c) 2023-2026 ktsu-dev contributors
 
 namespace TextFilter.Test;
 
@@ -1167,4 +1167,67 @@ public void FuzzyFilterIgnoresFilterPadding(string paddedFilter)
 		CollectionAssert.AreEquivalent(HelMatches, result,
 			$"Padding in '{paddedFilter}' should not hide items that 'hel' matches.");
 	}
+
+	[TestMethod]
+	[DataRow(TextFilterType.Glob, "*.cs")]
+	[DataRow(TextFilterType.Regex, "\\.cs$")]
+	public void FilterTakeStopsReadingOnceEnoughGlobOrRegexItemsMatch(TextFilterType filterType, string filter)
+	{
+		IEnumerable<string> items = Enumerable.Range(0, 10_000).Select(i => $"File{i}.cs");
+		int calls = 0;
+		string CountingKey(string s)
+		{
+			calls++;
+			return s;
+		}
+
+		List<string> page = [.. TextFilter.Filter(items, CountingKey, filter, filterType).Take(10)];
+
+		CollectionAssert.AreEqual(items.Take(10).ToList(), page);
+		Assert.AreEqual(10, calls, "Only the items needed for the first page should be matched.");
+	}
+
+	[TestMethod]
+	public void FilterGlobFirstDoesNotReadPastTheFirstMatch()
+	{
+		// Stands in for an endless or streaming source: reading past the first page fails the test
+		// rather than hanging it.
+		static IEnumerable<string> StreamingLines()
+		{
+			for (int i = 0; i < 1_000; i++)
+			{
+				yield return i % 3 == 2 ? $"line{i}.log" : $"line{i}.txt";
+			}
+
+			throw new InvalidOperationException("Filter read the whole source before yielding its first match.");
+		}
+
+		Assert.AreEqual("line2.log", TextFilter.Filter(StreamingLines(), "*.log").First());
+	}
+
+	[TestMethod]
+	[DataRow(TextFilterType.Glob, "b* a*")]
+	[DataRow(TextFilterType.Regex, "^(b|a)")]
+	public void FilterGlobOrRegexKeepsInputOrder(TextFilterType filterType, string filter)
+	{
+		List<string> strings = ["banana", "cherry", "apple", "blueberry", "avocado"];
+		List<string> result = [.. TextFilter.Filter(strings, filter, filterType)];
+		CollectionAssert.AreEqual(new List<string> { "banana", "apple", "blueberry", "avocado" }, result);
+	}
+
+	[TestMethod]
+	public void FilterFuzzyStillSortsByDescendingScore()
+	{
+		List<string> strings = ["hello world", "yellow", "hello", "help"];
+		List<string> result = [.. TextFilter.Filter(strings, "hello", TextFilterType.Fuzzy)];
+		static int ScoreOf(string s)
+		{
+			TextFilter.IsMatch(s, "hello", out int score, TextFilterType.Fuzzy);
+			return score;
+		}
+
+		List<int> scores = [.. result.Select(ScoreOf)];
+		CollectionAssert.AreEqual(scores.OrderByDescending(s => s).ToList(), scores);
+		Assert.IsNotEmpty(result);
+	}
 }

TextFilter/TextFilter.cs

@@ -1,4 +1,4 @@
-// Copyright (c) 2023-2026 ktsu-dev contributors
+// Copyright (c) 2023-2026 ktsu-dev contributors
 
 namespace ktsu.TextFilter;
 
@@ -181,14 +181,22 @@ public static IEnumerable<TItem> Filter<TItem>(IEnumerable<TItem> items, Func<TI
 		Ensure.NotNull(keySelector);
 		Ensure.NotNull(filter);
 
-		return items.Select(item =>
+		IEnumerable<(TItem item, bool isMatch, int score)> matches = items.Select(item =>
 		{
 			bool isMatch = IsMatch(keySelector(item), filter, out int score, filterType, textFilterMatchOptions, caseSensitivity);
 			return (item, isMatch, score);
 		})
-		.Where(t => t.isMatch)
-		.OrderByDescending(t => t.score)
-		.Select(t => t.item);
+		.Where(t => t.isMatch);
+
+		// Only a non-blank fuzzy filter sets a score, so sorting anything else would reorder nothing
+		// while still reading the whole source before yielding the first item. Skipping it lets glob
+		// and regex results stream, so Take(n) or First() stops as soon as it has enough matches.
+		if (filterType is TextFilterType.Fuzzy && !string.IsNullOrWhiteSpace(filter))
+		{
+			matches = matches.OrderByDescending(t => t.score);
+		}
+
+		return matches.Select(t => t.item);
 	}
 
 	/// <summary>