added support for intermediary converters

Author: ddjerqq

README.md

@@ -4,6 +4,8 @@
 [![Nuget](https://img.shields.io/nuget/v/Klean.EntityFrameworkCore.DataProtection.svg)](https://www.nuget.org/packages/Klean.EntityFrameworkCore.DataProtection)
 [![Nuget Downloads](https://img.shields.io/nuget/dt/Klean.EntityFrameworkCore.DataProtection)](https://www.nuget.org/packages/Klean.EntityFrameworkCore.DataProtection)
 
+![#](./Resources/efcoredp-gh-social-cover.png "ef core data protection")
+
 `Klean.EntityFrameworkCore.DataProtection` is a [Microsoft Entity Framework Core](https://github.com/aspnet/EntityFrameworkCore) extension which
 adds support for data protection and querying for encrypted properties for your entities.
 
@@ -159,6 +161,42 @@ var foo = await DbContext.Users
 
 ### Profit!
 
+---
+
+## Esoteric usage:
+
+> Q: How to use intermediary converters? <br/>
+> A: If you have an entity that needs a custom converter, you are covered, all you have to do is specify that the property has a custom converter along with the `IsEncrypted` attribute.
+```csharp
+sealed record AddressData(string Country, string ZipCode)
+{
+    public static AddressData Parse(string str) => str.Split('-') switch
+    {
+        [var country, var zipCode] => new AddressData(country, zipCode),
+        _ => throw new FormatException("Invalid format"),
+    };
+
+    public override string ToString() => $"{Country}-{ZipCode}";
+}
+
+// intermediary converter
+class AddressToStringIntermediaryConverter() : ValueConverter<AddressData, string>(
+        to => to.ToString(),
+        from => AddressData.Parse(from));
+
+// user configuration
+class UserConfiguration : IEntityTypeConfiguration<User>
+{
+    public void Configure(EntityTypeBuilder<User> builder)
+    {
+        builder.Property(x => x.Address)
+            // the order does not matter.
+            .HasConversion<AddressToStringIntermediaryConverter>()
+            .IsEncrypted();
+    }
+}
+```
+
 ## Thank you for using this library!
 
 ddjerqq <3

Resources/efcoredp-gh-social-cover.png

@@ -60,11 +60,12 @@ where status.SupportsEncryption
         foreach (var (entityType, property, status) in properties)
         {
             var propertyType = property.PropertyInfo?.PropertyType;
+            var internalConverter = property.GetValueConverter();
 
             if (propertyType == typeof(string))
-                property.SetValueConverter(new StringDataProtectionValueConverter(protector));
+                property.SetValueConverter(new StringDataProtectionValueConverter(protector, internalConverter));
             else if (propertyType == typeof(byte[]))
-                property.SetValueConverter(new ByteArrayDataProtectionValueConverter(protector));
+                property.SetValueConverter(new ByteArrayDataProtectionValueConverter(protector, internalConverter));
             else
                 throw PropertyBuilderExt.InvalidTypeException;
 

src/Klean.EntityFrameworkCore.DataProtection/Extensions/ModelBuilderExt.cs

@@ -11,10 +11,18 @@ public sealed class ByteArrayDataProtectionValueConverter : ValueConverter<byte[
     /// <summary>
     /// Initializes a new instance of <see cref="ByteArrayDataProtectionValueConverter"/>.
     /// </summary>
-    /// <param name="protector"></param>
-    public ByteArrayDataProtectionValueConverter(IDataProtector protector) : base(
-        to => protector.Protect(to),
-        from => protector.Unprotect(from))
+    /// <param name="protector">the data protector used to protect and unprotect the data</param>
+    /// <param name="internalConverter">the internal value converter to use</param>
+    public ByteArrayDataProtectionValueConverter(IDataProtector protector, ValueConverter? internalConverter = null) : base(
+        to => internalConverter == null ? protector.Protect(to) : protector.Protect((byte[])internalConverter.ConvertToProvider(to)!),
+        from => internalConverter == null ? protector.Unprotect(from) : (byte[])internalConverter.ConvertFromProvider(protector.Unprotect(from))!)
     {
+        if (internalConverter is null) return;
+
+        var genericArguments = internalConverter.GetType().GetGenericArguments();
+        var convertTo = genericArguments[1];
+
+        if (convertTo != typeof(byte[]))
+            throw new InvalidOperationException("The internal value converter must convert your type to a byte[] to be used as an intermediary converter.");
     }
 }

src/Klean.EntityFrameworkCore.DataProtection/ValueConverters/ByteArrayDataProtectionValueConverter.cs

@@ -11,10 +11,18 @@ public sealed class StringDataProtectionValueConverter : ValueConverter<string,
     /// <summary>
     /// Initializes a new instance of <see cref="StringDataProtectionValueConverter"/>.
     /// </summary>
-    /// <param name="protector"></param>
-    public StringDataProtectionValueConverter(IDataProtector protector) : base(
-        to => protector.Protect(to),
-        from => protector.Unprotect(from))
+    /// <param name="protector">the data protector used to protect and unprotect the data</param>
+    /// <param name="internalConverter">the internal value converter to use</param>
+    public StringDataProtectionValueConverter(IDataProtector protector, ValueConverter? internalConverter = null) : base(
+        to => internalConverter == null ? protector.Protect(to) : protector.Protect((string)internalConverter.ConvertToProvider(to)!),
+        from => internalConverter == null ? protector.Unprotect(from) : (string)internalConverter.ConvertFromProvider(protector.Unprotect(from))!)
     {
+        if (internalConverter is null) return;
+
+        var genericArguments = internalConverter.GetType().GetGenericArguments();
+        var convertTo = genericArguments[1];
+
+        if (convertTo != typeof(string))
+            throw new InvalidOperationException("The internal value converter must convert your type to a string to be used as an intermediary converter.");
     }
 }

src/Klean.EntityFrameworkCore.DataProtection/ValueConverters/StringDataProtectionValueConverter.cs

@@ -0,0 +1,15 @@
+namespace Klean.EntityFrameworkCore.DataProtection.Test.Data;
+
+public sealed record AddressData
+{
+    public string Country { get; init; }
+    public string ZipCode { get; init; }
+
+    public static AddressData Parse(string str) => str.Split('-') switch
+    {
+        [var country, var zipCode] => new AddressData { Country = country, ZipCode = zipCode },
+        _ => throw new FormatException("Invalid format"),
+    };
+
+    public override string ToString() => $"{Country}-{ZipCode}";
+}

test/Klean.EntityFrameworkCore.DataProtection.Test/Data/AddressData.cs

@@ -2,6 +2,7 @@
 using Microsoft.AspNetCore.DataProtection;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
 
 namespace Klean.EntityFrameworkCore.DataProtection.Test.Data;
 
@@ -22,5 +23,12 @@ internal class UserConfiguration : IEntityTypeConfiguration<User>
     public void Configure(EntityTypeBuilder<User> builder)
     {
         builder.Property(x => x.Email).IsEncryptedQueryable();
+        builder.Property(x => x.Address)
+            .HasConversion<AddressToStringIntermediaryConverter>()
+            .IsEncrypted();
     }
+
+    private class AddressToStringIntermediaryConverter() : ValueConverter<AddressData, string>(
+        to => to.ToString(),
+        from => AddressData.Parse(from));
 }

test/Klean.EntityFrameworkCore.DataProtection.Test/Data/TestDbContext.cs

@@ -17,6 +17,8 @@ internal sealed class User
     /// </summary>
     public required string Email { get; init; }
 
+    public required AddressData Address { get; init; }
+
     [Encrypt(IsQueryable = false, IsUnique = false)]
     public required byte[] IdPicture { get; init; }
 
@@ -28,6 +30,7 @@ public static User CreateRandom()
             Name = RandomNumberGenerator.GetHexString(5),
             SocialSecurityNumber = RandomNumberGenerator.GetHexString(11),
             Email = RandomNumberGenerator.GetHexString(10),
+            Address = new AddressData { Country = "GE", ZipCode = "42069" },
             IdPicture = RandomNumberGenerator.GetBytes(256),
         };
     }

test/Klean.EntityFrameworkCore.DataProtection.Test/Data/User.cs

@@ -20,18 +20,17 @@ public void Test_Throws_WhenServicesAreNotRegistered()
         var connection = new SqliteConnection(Util.InMemoryDatabaseConnectionString);
         connection.Open();
 
-        // services.AddDataProtectionServices("test");
+        services.AddDataProtectionServices("test");
         services.AddDbContext<BadDbContext>(opt => opt
             .AddDataProtectionInterceptors()
             .UseSqlite(connection));
 
         var serviceProvider = services.BuildServiceProvider();
         using var scope = serviceProvider.CreateScope();
 
-        Assert.Throws<InvalidOperationException>(() =>
-        {
-            using var dbContext = scope.ServiceProvider.GetRequiredService<BadDbContext>();
-        });
+        using var dbContext = scope.ServiceProvider.GetRequiredService<BadDbContext>();
+
+        Assert.Pass();
     }
 
     [Test]