feat: Add validation, that IdentificationDateTime is German midnight

MaLoIdentModels/MaLoIdentModels/Validation/GermanMidnightValidationAttribute.cs

@@ -0,0 +1,34 @@
+namespace MaLoIdentModels.Validation;
+
+using System;
+using System.ComponentModel.DataAnnotations;
+
+/// <summary>
+/// an attribute that checks that a datetimeoffset is 00:00 Uhr in German local time
+/// </summary>
+public class GermanMidnightValidationAttribute : ValidationAttribute
+{
+    public const string GermanTimeZoneSerializedAsString =
+        "Central Europe Standard Time;60;(UTC+01:00) Belgrad, Bratislava (Pressburg), Budapest, Ljubljana, Prag (Praha);Mitteleuropäische Zeit ;Mitteleuropäische Sommerzeit ;[01:01:0001;12:31:9999;60;[0;02:00:00;3;5;0;];[0;03:00:00;10;5;0;];];";
+
+    private static TimeZoneInfo GermanTimeZoneInfo =>
+        TimeZoneInfo.FromSerializedString(GermanTimeZoneSerializedAsString);
+
+    protected override ValidationResult? IsValid(object? value, ValidationContext validationContext)
+    {
+        if (value is not DateTimeOffset dto)
+        {
+            return new ValidationResult("Invalid datetime format.");
+        }
+
+        var germanLocalTime = TimeZoneInfo.ConvertTime(dto, GermanTimeZoneInfo);
+
+        if (germanLocalTime.Hour != 0 || germanLocalTime.Minute != 0 || germanLocalTime.Second != 0)
+        {
+            return new ValidationResult(
+                $"The date must be at 00:00 (midnight) German time but was '{dto:o}'."
+            );
+        }
+        return ValidationResult.Success;
+    }
+}

MaLoIdentModels/MaLoIdentModels/v1/IdentificationParameter.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Text.Json.Serialization;
 using MaLoIdentModels.JsonSettings;
+using MaLoIdentModels.Validation;
 
 namespace MaLoIdentModels.v1;
 
@@ -10,6 +11,16 @@ public class IdentificationParameter
     [System.ComponentModel.DataAnnotations.Key]
     public Guid? Id { get; set; }
 
+    /// <summary>
+    ///
+    /// </summary>
+    /// <remarks>
+    /// Has to be midnight in German local time.
+    /// See Seite 6 von 111
+    /// 1.1.2 SD: Ermittlung der MaLo-ID der Marktlokation
+    /// https://www.bundesnetzagentur.de/DE/Beschlusskammern/1_GZ/BK6-GZ/2022/BK6-22-024/Beschluss/Anlage1b_GPKE_Teil2.pdf?__blob=publicationFile&v=1
+    /// </remarks>
+    [GermanMidnightValidation]
     [JsonConverter(typeof(DateTimeOffsetWithTrailingZConverter))]
     [JsonPropertyName("identificationDateTime")]
     public DateTimeOffset IdentificationDateTime { get; set; }

MaLoIdentModels/MaLoIdentModelsTests/v1Tests/DateTimeOffsetDeserializationTests.cs

@@ -1,3 +1,4 @@
+using System.ComponentModel.DataAnnotations;
 using System.Text.Json;
 using FluentAssertions;
 using MaLoIdentModels.v1;
@@ -80,4 +81,24 @@ string dateTimeOffsetString
             .IdentificationDateTime.Should()
             .Be(new DateTimeOffset(2023, 8, 2, 22, 0, 0, 0, TimeSpan.Zero));
     }
+
+    [Theory]
+    [InlineData("2025-01-01T00:00:00Z", false)]
+    [InlineData("2024-12-31T23:00:00Z", true)]
+    [InlineData("2025-06-30T22:00:00Z", true)]
+    [InlineData("2025-06-30T23:00:00Z", false)]
+    public void Validation_Of_German_Midnight_Works(
+        string dateTimeOffsetString,
+        bool isValidExpected
+    )
+    {
+        var parameter = new IdentificationParameter
+        {
+            IdentificationDateTime = DateTimeOffset.Parse(dateTimeOffsetString),
+        };
+        var context = new ValidationContext(parameter);
+        var results = new List<ValidationResult>();
+        var isValidActual = Validator.TryValidateObject(parameter, context, results, true);
+        isValidActual.Should().Be(isValidExpected);
+    }
 }

MaLoIdentModels/MaLoIdentModelsTests/v1Tests/SerializeGermanTimezoneInfo.cs

@@ -0,0 +1,35 @@
+using FluentAssertions;
+using MaLoIdentModels.Validation;
+
+namespace MaLoIdentModelsTests.v1Tests;
+
+public class CreateTimeZoneFile
+{
+    /// <summary>
+    /// saves the German timezone to a serialized string: https://learn.microsoft.com/en-us/dotnet/standard/datetime/save-time-zones-to-an-embedded-resource#example
+    /// </summary>
+    [Fact]
+    public void Serialized_Timezoneinfo_Is_Actual_German_Timezone()
+    {
+        TimeZoneInfo tzi;
+        try
+        {
+            tzi = TimeZoneInfo.FindSystemTimeZoneById("Central Europe Standard Time");
+        }
+        catch (TimeZoneNotFoundException)
+        {
+            //Assert.IsTrue(false, "You cannot use this method on your machine."); // this occurs in github actions. it's ok.
+            return;
+        }
+
+        tzi.SupportsDaylightSavingTime.Should().BeTrue();
+        var expected = tzi.ToSerializedString();
+        GermanMidnightValidationAttribute.GermanTimeZoneSerializedAsString.Should().Be(expected);
+        TimeZoneInfo
+            .FromSerializedString(
+                GermanMidnightValidationAttribute.GermanTimeZoneSerializedAsString
+            )
+            .Should()
+            .BeEquivalentTo(tzi);
+    }
+}