decePubClient/Services/PublicNoticeService.cs

using Blazored.LocalStorage;

using decePubClient.Models;

namespace decePubClient.Services
{
	/// <summary>
	/// Asks a persona, once, before its first reaction or poll vote, and once before it first joins an event, to accept
	/// that these are public and visible as that persona (an owner decision); and this device, once, before its first Web
	/// Push subscription, to accept that the browser's push service learns when notifications arrive (PublicAct.Push, told
	/// once for the device whichever persona asks). PublicNoticeHost shows the question; Confirm returns true at once for
	/// what was accepted already, and false when the reader declines.
	/// </summary>
	public class PublicNoticeService(ILocalStorageService localStorage)
	{
		TaskCompletionSource<bool> pending;

		public event Action Changed;

		public bool IsAsking => pending is not null;

		/// <summary>What the persona is being told about.</summary>
		public PublicAct Act { get; private set; } = PublicAct.Reaction;

		public async Task<bool> Confirm(string personaId, PublicAct act = PublicAct.Reaction, CancellationToken cancellationToken = default)
		{
			if (string.IsNullOrEmpty(personaId) && act != PublicAct.Push)
				return false;
			var seen = await localStorage.GetItemAsync<PublicActionNotices>(nameof(PublicActionNotices), cancellationToken) ?? new();
			var told = act == PublicAct.Participation ? seen.EventPersonaIds : seen.PersonaIds;
			if (act == PublicAct.Push ? seen.PushTold : told.Contains(personaId))
				return true;

			Act = act;
			pending = new TaskCompletionSource<bool>();
			Changed?.Invoke();
			var accepted = await pending.Task;
			pending = null;
			Changed?.Invoke();
			if (!accepted)
				return false;

			if (act == PublicAct.Push)
				seen.PushTold = true;
			else
				told.Add(personaId);
			await localStorage.SetItemAsync(nameof(PublicActionNotices), seen, cancellationToken);
			return true;
		}

		public void Answer(bool accepted) => pending?.TrySetResult(accepted);
	}
}