Prevent duplicate user email

backend/LexBoxApi/GraphQL/UserMutations.cs

@@ -8,6 +8,7 @@
 using LexCore.Exceptions;
 using LexData;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
 using Microsoft.IdentityModel.Tokens;
 
 namespace LexBoxApi.GraphQL;
@@ -21,7 +22,7 @@ public record ChangeUserAccountByAdminInput(Guid UserId, string Email, string Na
 
     [Error<NotFoundException>]
     [Error<DbError>]
-    [Error<InvalidFormatException>]
+    [Error<UniqueValueException>]
     [UseMutationConvention]
     [RefreshJwt]
     public Task<User> ChangeUserAccountData(
@@ -38,7 +39,7 @@ LexAuthService lexAuthService
 
     [Error<NotFoundException>]
     [Error<DbError>]
-    [Error<InvalidFormatException>]
+    [Error<UniqueValueException>]
     [AdminRequired]
     public Task<User> ChangeUserAccountByAdmin(
         LoggedInContext loggedInContext,
@@ -78,21 +79,22 @@ LexAuthService lexAuthService
 
         await dbContext.SaveChangesAsync();
 
-        if (!input.Email.IsNullOrEmpty() && !input.Email.Equals(user.Email))
+        if (!input.Email.IsNullOrEmpty() && !input.Email.Equals(user.Email, StringComparison.InvariantCultureIgnoreCase))
         {
-            await SendVerifyNewAddressEmail(user, emailService, lexAuthService, input.Email);
+            await SendVerifyNewAddressEmail(user, emailService, lexAuthService, dbContext, input.Email);
         }
 
         return user;
     }
 
-    private static async Task SendVerifyNewAddressEmail(
-        User user,
+    private static async Task SendVerifyNewAddressEmail(User user,
         EmailService emailService,
         LexAuthService lexAuthService,
-        string newEmail
-    )
+        LexBoxDbContext lexBoxDbContext,
+        string newEmail)
     {
+        var emailInUse = await lexBoxDbContext.Users.AnyAsync(u => u.Email == newEmail);
+        if (emailInUse) throw new UniqueValueException("Email");
         var (jwt, _) = lexAuthService.GenerateJwt(new LexAuthUser(user)
         {
             EmailVerificationRequired = null,

backend/LexCore/Exceptions/UniqueValueException.cs

@@ -0,0 +1,8 @@
+namespace LexCore.Exceptions;
+
+public class UniqueValueException: Exception
+{
+    public UniqueValueException(string field) : base($"The value for {field} is not unique")
+    {
+    }
+}

backend/LexData/Entities/UserEntityConfiguration.cs

@@ -11,13 +11,16 @@ public override void Configure(EntityTypeBuilder<User> builder)
     {
         base.Configure(builder);
         builder.Property(u => u.LocalizationCode).HasDefaultValue(User.DefaultLocalizationCode);
+        builder.Property(u => u.Email).UseCollation(LexBoxDbContext.CaseInsensitiveCollation);
+        builder.HasIndex(u => u.Email).IsUnique();
         builder.HasMany(user => user.Projects)
             .WithOne(projectUser => projectUser.User)
             .HasForeignKey(projectUser => projectUser.UserId)
             .OnDelete(DeleteBehavior.Cascade);
     }
 }
 
+
 public static class UserEntityExtensions
 {
     public static IQueryable<User> FilterByEmail(this IQueryable<User> users, string email)

backend/LexData/LexBoxDbContext.cs

@@ -6,12 +6,14 @@ namespace LexData;
 
 public class LexBoxDbContext : DbContext
 {
+    public const string CaseInsensitiveCollation = "case_insensitive";
     public LexBoxDbContext(DbContextOptions<LexBoxDbContext> options) : base(options)
     {
     }
 
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
+        modelBuilder.HasCollation(CaseInsensitiveCollation, locale: "und-u-ks-level2", provider: "icu", deterministic: false);
         modelBuilder.ApplyConfigurationsFromAssembly(typeof(EntityBaseConfiguration<>).Assembly);
     }
 

backend/LexData/Migrations/20230904060630_AddEmailCaseInsenstiveCollation.cs

@@ -0,0 +1,52 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace LexData.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddEmailCaseInsenstiveCollation : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AlterDatabase()
+                .Annotation("Npgsql:CollationDefinition:case_insensitive", "und-u-ks-level2,und-u-ks-level2,icu,False");
+
+            migrationBuilder.AlterColumn<string>(
+                name: "Email",
+                table: "Users",
+                type: "text",
+                nullable: false,
+                collation: "case_insensitive",
+                oldClrType: typeof(string),
+                oldType: "text");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Users_Email",
+                table: "Users",
+                column: "Email",
+                unique: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_Users_Email",
+                table: "Users");
+
+            migrationBuilder.AlterDatabase()
+                .OldAnnotation("Npgsql:CollationDefinition:case_insensitive", "und-u-ks-level2,und-u-ks-level2,icu,False");
+
+            migrationBuilder.AlterColumn<string>(
+                name: "Email",
+                table: "Users",
+                type: "text",
+                nullable: false,
+                oldClrType: typeof(string),
+                oldType: "text",
+                oldCollation: "case_insensitive");
+        }
+    }
+}