FlurSchnaps-Server/Sources/App/APNSInterface.swift

import Foundation
import APNSwift
import NIO
import Crypto

struct APNSInterface {
    
    private struct Payload: Codable {}

    private var apnsConfiguration: APNSClientConfiguration!
    private let title: String
    private let messages: [String]
    private let topic: String
    private let apnsEventGroup = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount)
    private let apnsRequestEncoder = JSONEncoder()
    private let apnsResponseDecoder = JSONDecoder()
    
    init?(_ config: ServerConfiguration) {
        guard let key = load(keyAtPath: config.privateKeyFilePath) else {
            return nil
        }
        let authentication = APNSClientConfiguration.AuthenticationMethod.jwt(
            privateKey: key,
            keyIdentifier: config.keyIdentifier,
            teamIdentifier: config.teamIdentifier)


        apnsConfiguration = APNSClientConfiguration(
            authenticationMethod: authentication,
            environment: .sandbox)
        title = config.messageTitle
        messages = config.messages
        topic = config.topic
    }
    
    func sendPush(to tokens: Set<String>) async {
        let client = APNSClient(
            configuration: apnsConfiguration,
            eventLoopGroupProvider: .shared(apnsEventGroup),
            responseDecoder: apnsResponseDecoder,
            requestEncoder: apnsRequestEncoder)
        log(info: "Client created")
        let alert = APNSAlertNotificationContent(
            title: .raw(title),
            body: .raw(messages.randomElement()!))

        let apnsNotification = APNSAlertNotification(
            alert: alert,
            expiration: .none,
            priority: .immediately,
            topic: topic,
            payload: Payload(),
            sound: .default)
        do {
            for token in tokenStorage.tokens {
                log(info: "Sending push to \(token.prefix(6))...")
                try await client.sendAlertNotification(
                    apnsNotification,
                    deviceToken: token,
                    deadline: .now() + .seconds(10))
                log(info: "Sent push to \(token.prefix(6))...")
            }
        } catch let error as APNSError {
            print(error)
        } catch {
            log(error: error.localizedDescription)
        }
        do {
            log("Closing client")
            try client.syncShutdown()
        } catch {
            log(error: error.localizedDescription)
        }
    }
}

private func load(keyAtPath path: String) -> P256.Signing.PrivateKey? {
    do {
        guard let key = try P256.Signing.PrivateKey.loadFrom(filePath: path) else {
            print("Failed to read key \(path)")
            return nil
        }
        return key
    } catch {
        print("Failed to load key \(error)")
        return nil
    }
}