import Vapor
import Clairvoyant
import ClairvoyantVapor
import ClairvoyantBinaryCodable

var deviceManager: DeviceManager!

private var provider: VaporMetricProvider!
private var status: Metric<ServerStatus>!

private var asyncScheduler = MultiThreadedEventLoopGroup(numberOfThreads: 2)

private let df: DateFormatter = {
    let df = DateFormatter()
    df.dateStyle = .short
    df.timeStyle = .short
    return df
}()

enum ServerError: Error {
    case invalidAuthenticationFileContent
    case invalidAuthenticationToken
}

private func updateStatus(_ newStatus: ServerStatus) {
    asyncScheduler.schedule {
        do {
            try await status.update(newStatus)
        } catch {
            print("Failed to update server status: \(error)")
        }
    }
}

// configures your application
public func configure(_ app: Application) throws {
    let storageFolder = URL(fileURLWithPath: app.directory.resourcesDirectory)
    
    let configUrl = storageFolder.appendingPathComponent("config.json")
    let config = try Config(loadFrom: configUrl)
    
    let logFolder = config.logURL(possiblyRelativeTo: storageFolder)
    
    let monitor = MetricObserver(logFileFolder: logFolder, logMetricId: "sesame.log")
    MetricObserver.standard = monitor

    status = Metric<ServerStatus>("sesame.status")
    updateStatus(.initializing)

    app.http.server.configuration.port = config.port

    let keyFile = storageFolder.appendingPathComponent(config.keyFileName)

    let (deviceKey, remoteKey) = try loadKeys(at: keyFile)
    deviceManager = DeviceManager(deviceKey: deviceKey, remoteKey: remoteKey, deviceTimeout: config.deviceTimeout)
    
    try routes(app)

    provider = .init(observer: monitor, accessManager: config.authenticationTokens)
    provider.asyncScheduler = asyncScheduler
    provider.registerRoutes(app)
    monitor.saveCurrentListOfMetricsToLogFolder()
    
    updateStatus(.nominal)

    // Update the metric of the device status to ensure that it is accurate
    asyncScheduler.schedule {
        await deviceManager.updateDeviceConnectionMetric()
    }
    
    log("[\(df.string(from: Date()))] Server started")
}

public func shutdown() {
    print("[\(df.string(from: Date()))] Server shutdown")
    asyncScheduler.schedule {
        // Gracefully shut down by closing potentially open socket
        await deviceManager.removeDeviceConnection()
        do {
            try await asyncScheduler.shutdownGracefully()
        } catch {
            print("Failed to shut down MultiThreadedEventLoopGroup: \(error)")
        }
    }
}

private func loadKeys(at url: URL) throws -> (deviceKey: Data, remoteKey: Data) {
    let authContent: [Data] = try String(contentsOf: url)
        .trimmingCharacters(in: .whitespacesAndNewlines)
        .components(separatedBy: "\n")
        .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
        .map {
            guard let key = Data(fromHexEncodedString: $0) else {
                throw ServerError.invalidAuthenticationToken
            }
            guard key.count == SHA256.byteCount else {
                throw ServerError.invalidAuthenticationToken
            }
            return key
        }
    guard authContent.count == 2 else {
        throw ServerError.invalidAuthenticationFileContent
    }
    return (deviceKey: authContent[0], remoteKey: authContent[1])
}

func log(_ message: String) {
    guard let observer = MetricObserver.standard else {
        print(message)
        return
    }
    asyncScheduler.schedule {
        await observer.log(message)
    }
}