NEAppProxyFlow+Extensions.swift

import Foundation
import NetworkExtension

// Simulate a "Connection refused" error
fileprivate let connectionRefusedError = NSError(domain: NSPOSIXErrorDomain, code: Int(ECONNREFUSED), userInfo: nil)

// Implement the shortcuts
extension NEAppProxyFlow: Flow {
    // Kill a flow
    func closeReadAndWrite() {
        self.closeReadWithError(connectionRefusedError)
        self.closeWriteWithError(connectionRefusedError)
    }

    // Open a flow
    func openFlow(completionHandler: @escaping (Error?) -> Void) {
        if #available(macOS 15.0, *) {
            open(withLocalFlowEndpoint: nil, completionHandler: completionHandler)
        } else {
            open(withLocalEndpoint: nil, completionHandler: completionHandler)
        }
    }

    // Flow metadata
    var sourceAppSigningIdentifier: String { self.metaData.sourceAppSigningIdentifier }
    var sourceAppAuditToken: Data? { self.metaData.sourceAppAuditToken }
}

// Enforce Flow protocol conformance for NEAppProxyTCPFlow and NEAppProxyUDPFlow subclasses.
// This approach allows using Flow protocols universally instead of specific NEAppProxyFlow classes,
// facilitating easier stubbing/mocking in tests as Flow protocols are simpler to satisfy.
extension NEAppProxyTCPFlow: FlowTCP {
    var flowEndpoint: NWEndpoint {
        if #available(macOS 15.0, *) {
            self.remoteFlowEndpoint
        } else {
            self.remoteEndpoint
        }
    }
}
extension NEAppProxyUDPFlow: FlowUDP {}