import Vapor
import SwiftyGPIO
import APNSwift
import NIO
import Crypto

private struct Payload: Codable {}

private var apnsConfiguration: APNSClientConfiguration!
private var apnsNotification: APNSAlertNotification<Payload>!
private let apnsEventGroup = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount)
private let apnsRequestEncoder = JSONEncoder()
private let apnsResponseDecoder = JSONDecoder()

// configures your application
public func configure(_ app: Application) throws {
    
    let resourcesFolderUrl = URL(fileURLWithPath: app.directory.resourcesDirectory)
    let configUrl = resourcesFolderUrl.appendingPathComponent("config.json")
    
    let config: ServerConfiguration
    do {
        let data = try Data(contentsOf: configUrl)
        config = try JSONDecoder().decode(from: data)
    } catch {
        print("Failed to load config: \(error)")
        return
    }
    
    guard configureAPNS(config) else {
        return
    }
    
    configureGPIO(config)
    
    // register routes
    try routes(app)
    
    serverStatus = .running
}

private extension JSONDecoder {
    
    func decode<T>(from data: Data) throws -> T where T: Decodable {
        try self.decode(T.self, from: data)
    }
}

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
    }
}

private func configureAPNS(_ config: ServerConfiguration) -> Bool {
    guard let key = load(keyAtPath: config.privateKeyFilePath) else {
        return false
    }
    let authentication = APNSClientConfiguration.AuthenticationMethod.jwt(
        privateKey: key,
        keyIdentifier: config.keyIdentifier,
        teamIdentifier: config.teamIdentifier)


    apnsConfiguration = APNSClientConfiguration(
        authenticationMethod: authentication,
        environment: .sandbox)
    
    let alert = APNSAlertNotificationContent(
        title: .raw(config.messageTitle),
        body: .raw(config.messageBody))

    apnsNotification = APNSAlertNotification(
        alert: alert,
        expiration: .none,
        priority: .immediately,
        topic: config.topic,
        payload: Payload(),
        sound: .default)
    return true
}

private func configureGPIO(_ config: ServerConfiguration) {
    let gpio = RaspberryGPIO(
        name: "GPIO\(config.buttonPin)",
        id: config.buttonPin,
        baseAddr: 0x7E000000)

    gpio.direction = .IN
    gpio.pull = .down
    gpio.bounceTime = config.bounceTime
    gpio.onChange { _ in
        log(info: "Push detected")
        sendPush()
    }
    log(info: "GPIO \(config.buttonPin) configured")
}

private func sendPush() {
    Task(priority: .userInitiated) {
        let client = APNSClient(
            configuration: apnsConfiguration,
            eventLoopGroupProvider: .shared(apnsEventGroup),
            responseDecoder: apnsResponseDecoder,
            requestEncoder: apnsRequestEncoder)
        log(info: "Client created")
        do {
            for token in knownTokens {
                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)
        }
    }
}