using System.Net;
using WebPush;

namespace ROLAC.API.Services.Notifications;

/// <summary>
/// Sends one encrypted Web Push message via the WebPush library, signing with the VAPID keys from
/// the notification settings. Translates a "subscription gone" (404/410) response into
/// <see cref="WebPushSendResult.IsExpired"/> so the caller prunes the dead subscription.
/// </summary>
public sealed class WebPushSender : IWebPushSender
{
    private readonly INotificationSettingsService _settings;
    private readonly WebPushClient _client = new();

    public WebPushSender(INotificationSettingsService settings) => _settings = settings;

    public async Task<WebPushSendResult> SendAsync(
        WebPushTarget target, string payloadJson, CancellationToken ct = default)
    {
        var options = _settings.GetWebPush();
        if (string.IsNullOrWhiteSpace(options.PublicKey) || string.IsNullOrWhiteSpace(options.PrivateKey))
            return new WebPushSendResult(Success: false, IsExpired: false, Error: "Web Push is not configured (missing VAPID keys).");

        var subject = string.IsNullOrWhiteSpace(options.Subject) ? "mailto:admin@rolac.local" : options.Subject;
        var vapid = new VapidDetails(subject, options.PublicKey, options.PrivateKey);
        var subscription = new PushSubscription(target.Endpoint, target.P256dh, target.Auth);

        try
        {
            await _client.SendNotificationAsync(subscription, payloadJson, vapid, ct);
            return new WebPushSendResult(Success: true, IsExpired: false, Error: null);
        }
        catch (WebPushException ex)
        {
            var expired = ex.StatusCode is HttpStatusCode.NotFound or HttpStatusCode.Gone;
            return new WebPushSendResult(Success: false, IsExpired: expired, Error: ex.Message);
        }
    }
}