stevanfreeborn.atproto.identityresolver/tests/StevanFreeborn.Atproto.IdentityResolver.Tests/Unit/StringToCollectionConverterTests.cs

using System.Collections.ObjectModel;
using System.Text;
using System.Text.Json;

using StevanFreeborn.Atproto.IdentityResolver.Json;

namespace StevanFreeborn.Atproto.IdentityResolver.Tests.Unit;

public sealed class StringToCollectionConverterTests
{
  private readonly StringToCollectionConverter _converter = new();
  private readonly JsonSerializerOptions _options = new();

  private Collection<string>? ReadJson(string json)
  {
    var reader = new Utf8JsonReader(Encoding.UTF8.GetBytes(json));
    reader.Read();
    return _converter.Read(ref reader, typeof(Collection<string>), _options);
  }

  private string WriteJson(Collection<string> value)
  {
    using var stream = new MemoryStream();
    using var writer = new Utf8JsonWriter(stream);
    
    _converter.Write(writer, value, _options);
    
    return Encoding.UTF8.GetString(stream.ToArray());
  }

  [Fact]
  public void Read_WhenJsonTokenIsNull_ItShouldReturnEmptyCollection()
  {
    var result = ReadJson("null");

    result.Should().NotBeNull();
    result.Should().BeEmpty();
  }

  [Fact]
  public void Read_WhenJsonTokenIsString_ItShouldReturnCollectionWithSingleString()
  {
    var result = ReadJson("\"https://w3id.org/did/v1\"");

    result.Should().NotBeNull();
    result.Should().ContainSingle().Which.Should().Be("https://w3id.org/did/v1");
  }

  [Fact]
  public void Read_WhenJsonTokenIsEmptyString_ItShouldReturnCollectionWithEmptyString()
  {
    var result = ReadJson("\"\"");

    result.Should().NotBeNull();
    result.Should().ContainSingle().Which.Should().Be(string.Empty);
  }

  [Fact]
  public void Read_WhenJsonTokenIsArrayOfStrings_ItShouldReturnCollectionWithAllStrings()
  {
    var result = ReadJson("[\"https://w3id.org/did/v1\",\"https://w3id.org/security/suites/ed25519-2020/v1\"]");

    result.Should().NotBeNull();
    result.Should().HaveCount(2);
    result.Should().ContainInOrder("https://w3id.org/did/v1", "https://w3id.org/security/suites/ed25519-2020/v1");
  }

  [Fact]
  public void Read_WhenJsonTokenIsEmptyArray_ItShouldReturnEmptyCollection()
  {
    var result = ReadJson("[]");

    result.Should().NotBeNull();
    result.Should().BeEmpty();
  }

  [Theory]
  [InlineData("123", "Number")]
  [InlineData("true", "True")]
  [InlineData("false", "False")]
  [InlineData("{\"key\":\"value\"}", "StartObject")]
  public void Read_WhenJsonTokenIsUnexpectedType_ItShouldThrowJsonException(string json, string expectedToken)
  {
    var act = () => ReadJson(json);

    var e = act.Should().Throw<JsonException>();

    e.WithMessage($"Unexpected token type '{expectedToken}' when deserializing Collection.");
  }

  [Fact]
  public void Write_WhenCollectionContainsMultipleStrings_ItShouldSerializeAsJsonArray()
  {
    var collection = new Collection<string>
    {
      "https://w3id.org/did/v1",
      "https://w3id.org/security/suites/ed25519-2020/v1"
    };

    var json = WriteJson(collection);

    json.Should().Be("[\"https://w3id.org/did/v1\",\"https://w3id.org/security/suites/ed25519-2020/v1\"]");
  }

  [Fact]
  public void Write_WhenCollectionContainsSingleString_ItShouldSerializeAsJsonArray()
  {
    var collection = new Collection<string>
    {
      "https://w3id.org/did/v1"
    };

    var json = WriteJson(collection);

    json.Should().Be("[\"https://w3id.org/did/v1\"]");
  }

  [Fact]
  public void Write_WhenCollectionIsEmpty_ItShouldSerializeAsEmptyJsonArray()
  {
    var collection = new Collection<string>();

    var json = WriteJson(collection);

    json.Should().Be("[]");
  }
}