import webpush from "web-push";
import type { PushProvider, PushSendResult, SendPushParams } from "./push-provider";

/**
 * Standards-based Web Push (RFC 8030 + VAPID) via the `web-push` package —
 * works against any browser's push service (Chrome/FCM, Firefox, Safari)
 * without a vendor-specific SDK. Nothing here is Brevo-specific; push and
 * email are unrelated delivery channels with unrelated providers.
 */
export interface WebPushProviderConfig {
  publicKey: string;
  privateKey: string;
  subject: string;
}

export function loadWebPushProviderConfigFromEnv(): WebPushProviderConfig {
  const publicKey = process.env.VAPID_PUBLIC_KEY;
  const privateKey = process.env.VAPID_PRIVATE_KEY;
  const subject = process.env.VAPID_SUBJECT;
  if (!publicKey || !privateKey || !subject) {
    throw new Error("Web Push is not configured — VAPID_PUBLIC_KEY, VAPID_PRIVATE_KEY, and VAPID_SUBJECT must all be set. See .env.example.");
  }
  return { publicKey, privateKey, subject };
}

interface WebPushError {
  statusCode?: number;
  message?: string;
}

export class WebPushProvider implements PushProvider {
  readonly name = "web-push";

  constructor(config: WebPushProviderConfig) {
    webpush.setVapidDetails(config.subject, config.publicKey, config.privateKey);
  }

  async sendPush(params: SendPushParams): Promise<PushSendResult> {
    try {
      await webpush.sendNotification(
        {
          endpoint: params.subscription.endpoint,
          keys: { p256dh: params.subscription.p256dhKey, auth: params.subscription.authKey },
        },
        JSON.stringify({ title: params.title, body: params.body, url: params.deepLinkPath }),
      );
      return { status: "sent" };
    } catch (error) {
      const webPushError = error as WebPushError;
      // 404/410: the push service itself says this subscription no longer
      // exists (browser data cleared, permission revoked, uninstalled) —
      // never retryable, and the caller should revoke the row.
      if (webPushError.statusCode === 404 || webPushError.statusCode === 410) {
        return { status: "failed", retryable: false, subscriptionInvalid: true, reason: "Subscription is no longer valid." };
      }
      if (typeof webPushError.statusCode === "number" && webPushError.statusCode >= 500) {
        return { status: "failed", retryable: true, reason: webPushError.message ?? "Push service error." };
      }
      return { status: "failed", retryable: false, reason: webPushError.message ?? "Unknown push error." };
    }
  }
}