feat(installer): add ChecksumVerifier (SHA256 + checksums.txt parser)

src/ClaudeDo.Installer/Core/ChecksumVerifier.cs

@@ -0,0 +1,37 @@
+using System.IO;
+using System.Security.Cryptography;
+
+namespace ClaudeDo.Installer.Core;
+
+public static class ChecksumVerifier
+{
+    public static string ComputeSha256(string filePath)
+    {
+        using var stream = File.OpenRead(filePath);
+        using var sha = SHA256.Create();
+        var hash = sha.ComputeHash(stream);
+        return Convert.ToHexString(hash).ToLowerInvariant();
+    }
+
+    public static bool Verify(string filePath, string expectedSha256)
+    {
+        var actual = ComputeSha256(filePath);
+        return string.Equals(actual, expectedSha256.Trim(), StringComparison.OrdinalIgnoreCase);
+    }
+
+    public static IReadOnlyDictionary<string, string> ParseChecksumsFile(string content)
+    {
+        var map = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+        foreach (var rawLine in content.Split('\n'))
+        {
+            var line = rawLine.Trim();
+            if (line.Length == 0) continue;
+            var parts = line.Split(new[] { ' ', '\t' }, 2, StringSplitOptions.RemoveEmptyEntries);
+            if (parts.Length != 2) continue;
+            var hashPart = parts[0].Trim();
+            if (hashPart.Length != 64) continue;
+            map[parts[1].Trim()] = hashPart;
+        }
+        return map;
+    }
+}

tests/ClaudeDo.Installer.Tests/ChecksumVerifierTests.cs

@@ -0,0 +1,106 @@
+using System.IO;
+using ClaudeDo.Installer.Core;
+
+namespace ClaudeDo.Installer.Tests;
+
+public sealed class ChecksumVerifierTests : IDisposable
+{
+    private readonly string _tempDir;
+
+    public ChecksumVerifierTests()
+    {
+        _tempDir = Path.Combine(Path.GetTempPath(), "ClaudeDoChecksum-" + Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(_tempDir);
+    }
+
+    public void Dispose()
+    {
+        try { Directory.Delete(_tempDir, recursive: true); } catch { }
+    }
+
+    [Fact]
+    public void ComputeSha256_KnownVector_EmptyFile()
+    {
+        var path = Path.Combine(_tempDir, "empty.bin");
+        File.WriteAllBytes(path, Array.Empty<byte>());
+
+        var hash = ChecksumVerifier.ComputeSha256(path);
+
+        Assert.Equal("e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855", hash);
+    }
+
+    [Fact]
+    public void ComputeSha256_KnownVector_Hello()
+    {
+        var path = Path.Combine(_tempDir, "hello.bin");
+        File.WriteAllText(path, "hello");
+
+        var hash = ChecksumVerifier.ComputeSha256(path);
+
+        Assert.Equal("2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824", hash);
+    }
+
+    [Fact]
+    public void Verify_ReturnsTrue_WhenHashMatches()
+    {
+        var path = Path.Combine(_tempDir, "x.bin");
+        File.WriteAllText(path, "hello");
+
+        Assert.True(ChecksumVerifier.Verify(path,
+            "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"));
+    }
+
+    [Fact]
+    public void Verify_IsCaseInsensitive()
+    {
+        var path = Path.Combine(_tempDir, "x.bin");
+        File.WriteAllText(path, "hello");
+
+        Assert.True(ChecksumVerifier.Verify(path,
+            "2CF24DBA5FB0A30E26E83B2AC5B9E29E1B161E5C1FA7425E73043362938B9824"));
+    }
+
+    [Fact]
+    public void Verify_ReturnsFalse_OnMismatch()
+    {
+        var path = Path.Combine(_tempDir, "x.bin");
+        File.WriteAllText(path, "hello");
+
+        Assert.False(ChecksumVerifier.Verify(path, new string('0', 64)));
+    }
+
+    [Fact]
+    public void ParseChecksumsFile_ReadsTwoLines()
+    {
+        var content = """
+            e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  ClaudeDo-0.2.0-win-x64.zip
+            2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824  ClaudeDo.Installer-0.2.0.exe
+            """;
+
+        var map = ChecksumVerifier.ParseChecksumsFile(content);
+
+        Assert.Equal(2, map.Count);
+        Assert.Equal(
+            "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+            map["ClaudeDo-0.2.0-win-x64.zip"]);
+        Assert.Equal(
+            "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824",
+            map["ClaudeDo.Installer-0.2.0.exe"]);
+    }
+
+    [Fact]
+    public void ParseChecksumsFile_SkipsBlankAndMalformedLines()
+    {
+        var content = """
+
+            not a line
+            e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  file.zip
+
+            """;
+
+        var map = ChecksumVerifier.ParseChecksumsFile(content);
+
+        Assert.Single(map);
+        Assert.True(map.ContainsKey("file.zip"));
+    }
+}