import Foundation
import Network
#if os(macOS)
import AppKit
#endif

private let networkChanged = Notification.Name("run.fc.byre.networkChanged")

@MainActor
final class NetworkWatch {
    static let shared = NetworkWatch()

    private let monitor = NWPathMonitor()
    private var seen = false

    private init() {
        monitor.pathUpdateHandler = { [weak self] path in
            let summary = "\(path.status) \(path.availableInterfaces.map(\.name).joined(separator: " "))"
            Task { @MainActor in
                self?.pathChanged(summary)
            }
        }
        monitor.start(queue: .main)
        #if os(macOS)
        NSWorkspace.shared.notificationCenter.addObserver(forName: NSWorkspace.didWakeNotification, object: nil, queue: .main) { [weak self] _ in
            Task { @MainActor in
                log.notice("woke from sleep, reconnecting")
                self?.post()
            }
        }
        #endif
    }

    func observe(_ handler: @escaping @MainActor () -> Void) -> any NSObjectProtocol {
        NotificationCenter.default.addObserver(forName: networkChanged, object: self, queue: .main) { _ in
            MainActor.assumeIsolated {
                handler()
            }
        }
    }

    private func pathChanged(_ summary: String) {
        guard seen else {
            seen = true
            return
        }
        log.notice("network changed (\(summary, privacy: .public)), reconnecting")
        post()
    }

    private func post() {
        NotificationCenter.default.post(name: networkChanged, object: self)
    }
}