hrynco-notification-service/HrynCo.NotificationService.Worker.Services/Push/PushChannelTestService.cs

using System.Security.Cryptography;
using System.Text.Json;
using HrynCo.NotificationService.DAL.Abstract.Push;
using HrynCo.NotificationService.DAL.Abstract.PushChannels;

namespace HrynCo.NotificationService.Worker.Services.Push;

public sealed class PushChannelTestService(IPushChannelRepository channels, IFirebasePushClient firebase)
{
    public async Task<PushDeliveryOutcome> TestAsync(PushChannelTestSettings settings, bool send, CancellationToken ct)
    {
        if (send && !ValidToken(settings.RecipientToken))
            return new PushDeliveryOutcome("Enter a valid recipient FCM token.");
        var project = settings.FirebaseProjectId?.Trim() ?? "";
        var json = await ResolveCredentialsAsync(settings, project, ct);
        if (string.IsNullOrWhiteSpace(json))
            return new PushDeliveryOutcome("Provide credentials for this project. Saved credentials can only be used with the unchanged project.");
        return await ExecuteAsync(json, project, settings.RecipientToken, send, ct);
    }

    private async Task<string?> ResolveCredentialsAsync(PushChannelTestSettings settings, string project, CancellationToken ct)
    {
        if (!string.IsNullOrWhiteSpace(settings.CredentialsJson)) return settings.CredentialsJson;
        if (settings.ChannelId is not Guid id) return null;
        var saved = await channels.GetByIdAsync(id, ct);
        return saved?.FirebaseProjectId == project ? await channels.GetCredentialsAsync(id, ct) : null;
    }

    private async Task<PushDeliveryOutcome> ExecuteAsync(string json, string project, string? token, bool send, CancellationToken ct)
    {
        try
        {
            var credentials = FirebaseServiceAccountCredentials.Parse(json, project);
            return send ? await firebase.SendTestAsync(token!.Trim(), credentials, ct)
                : await firebase.CheckAuthorizationAsync(credentials, ct);
        }
        catch (Exception error) when (error is JsonException or FormatException or ArgumentException or CryptographicException)
        {
            return new PushDeliveryOutcome("Provide a valid Firebase service account JSON for this project.");
        }
        catch (PushRetryException)
        {
            return new PushDeliveryOutcome("Firebase is temporarily unavailable or throttled. Try again later; acceptance was not confirmed.");
        }
    }

    private static bool ValidToken(string? token) => !string.IsNullOrWhiteSpace(token)
        && token.Trim().Length <= 4096 && !token.Trim().Any(char.IsWhiteSpace);
}