Stop a short imported hash crashing every Search

ImageDescriber.Test/SearchTests.cs

@@ -0,0 +1,86 @@
+// Copyright (c) 2023-2026 ktsu-dev contributors
+
+namespace ktsu.ImageDescriber.Tests;
+
+using ktsu.ImageDescriber.Verbs;
+using ktsu.Semantics.Paths;
+using ktsu.Semantics.Strings;
+
+[TestClass]
+public class SearchTests
+{
+	private PersistentState? originalSettings;
+
+	[TestInitialize]
+	public void Initialize() => originalSettings = Program.Settings;
+
+	[TestCleanup]
+	public void Cleanup() => Program.Settings = originalSettings!;
+
+	[TestMethod]
+	public void SearchPrintsEntryWhoseHashIsShorterThanTwelveCharacters()
+	{
+		Program.Settings = new PersistentState();
+		Program.Settings.Descriptions["abc123"] = new ImageDescription
+		{
+			Hash = "abc123",
+			Description = "a dog on a beach",
+			SuggestedFileName = "dog.jpg".As<FileName>(),
+		};
+
+		string output = CaptureConsole(() => new Search().Run(new Search { Query = "dog" }));
+
+		StringAssert.Contains(output, "Hash: abc123...");
+		StringAssert.Contains(output, "Description: a dog on a beach");
+	}
+
+	[TestMethod]
+	public void MergeEntriesSkipsEntriesWhoseHashIsNotSha256Hex()
+	{
+		Program.Settings = new PersistentState();
+		string validHash = new('a', ImageHasher.HashLength);
+		List<ImageDescription> entries =
+		[
+			new() { Hash = "abc123" },
+			new() { Hash = new string('z', ImageHasher.HashLength) },
+			new() { Hash = validHash },
+		];
+
+		(int NewCount, int UpdatedCount, int SkippedCount) result = default;
+		CaptureConsole(() => result = Import.MergeEntries(entries));
+
+		Assert.AreEqual(1, result.NewCount);
+		Assert.AreEqual(2, result.SkippedCount);
+		string[] expectedKeys = [validHash];
+		CollectionAssert.AreEquivalent(expectedKeys, Program.Settings.Descriptions.Keys.ToArray());
+	}
+
+	[TestMethod]
+	public void IsValidHashAcceptsOnlySha256HexStrings()
+	{
+		Assert.IsTrue(ImageHasher.IsValidHash(new string('0', 64)));
+		Assert.IsTrue(ImageHasher.IsValidHash(string.Concat(Enumerable.Repeat("0123456789abcdefABCDEF", 3))[..64]));
+		Assert.IsFalse(ImageHasher.IsValidHash(null));
+		Assert.IsFalse(ImageHasher.IsValidHash(string.Empty));
+		Assert.IsFalse(ImageHasher.IsValidHash("abc123"));
+		Assert.IsFalse(ImageHasher.IsValidHash(new string('0', 65)));
+		Assert.IsFalse(ImageHasher.IsValidHash(new string('g', 64)));
+	}
+
+	private static string CaptureConsole(Action action)
+	{
+		TextWriter original = Console.Out;
+		using StringWriter writer = new();
+		Console.SetOut(writer);
+		try
+		{
+			action();
+		}
+		finally
+		{
+			Console.SetOut(original);
+		}
+
+		return writer.ToString();
+	}
+}

ImageDescriber/ImageHasher.cs

@@ -5,6 +5,7 @@ namespace ktsu.ImageDescriber;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Security.Cryptography;
 
 using ktsu.Semantics.Paths;
@@ -31,6 +32,13 @@ internal static Dictionary<AbsoluteFilePath, string> HashFiles(IReadOnlyList<Abs
 		return new Dictionary<AbsoluteFilePath, string>(results);
 	}
 
+	internal const int HashLength = 64;
+
+	internal static bool IsValidHash(string? hash) =>
+		hash is { Length: HashLength } && hash.All(char.IsAsciiHexDigit);
+
+	internal static string ShortHash(string hash) => hash[..Math.Min(12, hash.Length)];
+
 	internal static string ComputeHash(AbsoluteFilePath filePath)
 	{
 		using FileStream stream = File.OpenRead(filePath.WeakString);

ImageDescriber/Verbs/Import.cs

@@ -85,7 +85,7 @@ internal override void Run(Import options)
 		}
 	}
 
-	private static (int NewCount, int UpdatedCount, int SkippedCount) MergeEntries(List<ImageDescription> entries)
+	internal static (int NewCount, int UpdatedCount, int SkippedCount) MergeEntries(List<ImageDescription> entries)
 	{
 		int newCount = 0;
 		int updatedCount = 0;
@@ -99,6 +99,15 @@ private static (int NewCount, int UpdatedCount, int SkippedCount) MergeEntries(L
 				continue;
 			}
 
+			// Every stored hash is a SHA-256 hex string, and Search and Scan both slice it, so a
+			// malformed one would crash them on every later run rather than just this import.
+			if (!ImageHasher.IsValidHash(entry.Hash))
+			{
+				Console.WriteLine($"  Skipping entry with invalid hash \"{entry.Hash}\" ({entry.SuggestedFileName}): expected {ImageHasher.HashLength} hex characters.");
+				skippedCount++;
+				continue;
+			}
+
 			if (Program.Settings.Descriptions.TryGetValue(entry.Hash, out ImageDescription? existing))
 			{
 				if (MergeKnownPaths(entry, existing))

ImageDescriber/Verbs/Search.cs

@@ -37,7 +37,7 @@ internal override void Run(Search options)
 		foreach (ImageDescription desc in matches)
 		{
 			Console.WriteLine($"  Suggested: {desc.SuggestedFileName}");
-			Console.WriteLine($"  Hash: {desc.Hash[..12]}...");
+			Console.WriteLine($"  Hash: {ImageHasher.ShortHash(desc.Hash)}...");
 			Console.WriteLine($"  Date: {desc.DescribedAt:yyyy-MM-dd HH:mm:ss} UTC");
 			Console.WriteLine($"  Paths ({desc.KnownPaths.Count}):");
 			foreach (AbsoluteFilePath path in desc.KnownPaths)