decePubClient/Helpers/SUtility.cs

using System.Net;
using System.Net.Http.Json;
using System.Text.Json;
using System.Text.Json.Serialization;

using decePubClient.Models;
using decePubClient.Services;

using PrivaPub.ClientModels;

namespace decePubClient.Helpers
{
	public static class SUtility
	{
		public const string dateTimeFormat = "dd/MM/yyyy";
		public const string timeFormat = "HH:mm";
		public const string dateTimeFormatExt = "dd/MM/yyyy HH:mm";

		/// <summary>Marks a response HttpService made up itself (a classified failure), not one the server sent.</summary>
		public const string FailureHeader = "X-DecePub-Failure";

		/// <summary>
		/// The JSON options for /clientapi payloads and localStorage: web defaults, enums by name as PrivaPub writes them
		/// (numbers still read), ClientJsonContext first, then PrivaPub.ClientModels' own context.
		/// </summary>
		public static JsonSerializerOptions DefaultSerializer { get; } = new(JsonSerializerDefaults.Web)
		{
			DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
			Converters = { new JsonStringEnumConverter() },
			TypeInfoResolverChain = { ClientJsonContext.Default, ClientModelsJsonContext.Default, UnregisteredJson.Instance }
		};

		/// <summary>The JSON options for PrivaPub's Mastodon API and /oauth: snake_case, MastodonJsonContext first.</summary>
		public static JsonSerializerOptions MastodonSerializer { get; } = new(JsonSerializerDefaults.Web)
		{
			PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
			DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
			IgnoreReadOnlyProperties = true,
			TypeInfoResolverChain = { MastodonJsonContext.Default, UnregisteredJson.Instance }
		};

		/// <summary>What a cancelled request turns into: HTTP 410, which AddResponseError ignores.</summary>
		public static WebResult DefaultTaskCancelledResult =>
			new WebResult().Invalidate("Request cancelled, not an error.", (int)HttpStatusCode.Gone, FailureCodes.Cancelled);

		public static HttpResponseMessage DefaultTaskCancelled() =>
			ClassifiedFailure(FailureCodes.Cancelled, DefaultTaskCancelledResult.ErrorMessage, HttpStatusCode.Gone);

		public static HttpResponseMessage DefaultUnauthorized(string message) =>
			ClassifiedFailure(FailureCodes.Unauthorized, message, HttpStatusCode.Unauthorized);

		/// <summary>A response carrying an invalid WebResult, tagged with FailureHeader so ReadWebResult reads it as is.</summary>
		public static HttpResponseMessage ClassifiedFailure(string failureCode, string message, HttpStatusCode statusCode)
		{
			var content = JsonContent.Create(new WebResult().Invalidate(message, (int)statusCode, failureCode), options: DefaultSerializer);
			content.Headers.Add(FailureHeader, failureCode);
			return new(statusCode) { Content = content };
		}

		/// <summary>The value a cancelled read returns: default for value types, an empty list for list interfaces.</summary>
		public static T CancellationDefault<T>()
		{
			var type = typeof(T);
			if (type.IsValueType)
				return default;
			if (type.IsInterface && type.IsGenericType &&
				type.GetGenericTypeDefinition() is var definition &&
				(definition == typeof(IEnumerable<>) || definition == typeof(ICollection<>) || definition == typeof(IList<>) ||
				 definition == typeof(IReadOnlyCollection<>) || definition == typeof(IReadOnlyList<>)))
				return (T)Activator.CreateInstance(typeof(List<>).MakeGenericType(type.GetGenericArguments()[0]));
			if (type.IsInterface || type.IsAbstract || type.GetConstructor(Type.EmptyTypes) is null)
				return default;
			return Activator.CreateInstance<T>();
		}

		#region Toasts

		/// <summary>Shows a failed result: connectivity failures as warnings, the rest as errors; cancellations not at all.</summary>
		public static void AddResponseError(this ToastService toast, WebResult result)
		{
			if (result.StatusCode is (int)HttpStatusCode.Gone)
				return;

			if (FailureCodes.IsConnectivity(result.ErrorCode))
			{
				toast.Add(ToastSeverity.Warning, result.ErrorMessage);
				return;
			}

			toast.Add(ToastSeverity.Error, $"{result.StatusCode} - {result.ErrorMessage}");
		}

		public static void AddResponseError(this ToastService toast, string message) =>
			toast.Add(ToastSeverity.Error, message);

		public static void AddResponseSuccess(this ToastService toast, string message) =>
			toast.Add(ToastSeverity.Success, message, TimeSpan.FromSeconds(5));

		public static void AddWarning(this ToastService toast, string message) =>
			toast.Add(ToastSeverity.Warning, message);

		public static void AddException(this ToastService toast, Exception exception) =>
			toast.Add(ToastSeverity.Error, exception.Message);

		#endregion

		public static T IfTrueThen<T>(bool conditionIsTrue, T ifTrue, T ifFalse = default) =>
			conditionIsTrue ? ifTrue : ifFalse;
	}
}