PalacePal/Pal.Client/Net/JwtClaims.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace Pal.Client.Net;

internal sealed class JwtClaims
{
    [JsonPropertyName("nameid")]
    public Guid NameId { get; set; }

    [JsonPropertyName("role")]
    [JsonConverter(typeof(JwtRoleConverter))]
    public List<string> Roles { get; set; } = new();

    [JsonPropertyName("nbf")]
    [JsonConverter(typeof(JwtDateConverter))]
    public DateTimeOffset NotBefore { get; set; }

    [JsonPropertyName("exp")]
    [JsonConverter(typeof(JwtDateConverter))]
    public DateTimeOffset ExpiresAt { get; set; }

    public static JwtClaims FromAuthToken(string authToken)
    {
        if (string.IsNullOrEmpty(authToken))
            throw new ArgumentException("Server sent no auth token", nameof(authToken));

        string[] parts = authToken.Split('.');
        if (parts.Length != 3)
            throw new ArgumentException("Unsupported token type", nameof(authToken));

        // fix padding manually
        string payload = parts[1].Replace(",", "=").Replace("-", "+").Replace("/", "_");
        if (payload.Length % 4 == 2)
            payload += "==";
        else if (payload.Length % 4 == 3)
            payload += "=";

        string content = Encoding.UTF8.GetString(Convert.FromBase64String(payload));
        return JsonSerializer.Deserialize<JwtClaims>(content) ?? throw new InvalidOperationException("token deserialization returned null");
    }
}

internal sealed class JwtRoleConverter : JsonConverter<List<string>>
{
    public override List<string> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        if (reader.TokenType == JsonTokenType.String)
            return new List<string> { reader.GetString() ?? throw new JsonException("no value present") };
        else if (reader.TokenType == JsonTokenType.StartArray)
        {
            List<string> result = new();
            while (reader.Read())
            {
                if (reader.TokenType == JsonTokenType.EndArray)
                {
                    result.Sort();
                    return result;
                }

                if (reader.TokenType != JsonTokenType.String)
                    throw new JsonException("string expected");

                result.Add(reader.GetString() ?? throw new JsonException("no value present"));
            }

            throw new JsonException("read to end of document");
        }
        else
            throw new JsonException("bad token type");
    }

    public override void Write(Utf8JsonWriter writer, List<string> value, JsonSerializerOptions options) => throw new NotImplementedException();
}