import Foundation
import WatchConnectivity

extension Notification.Name {
    static let fuelBoardWatchDataDidUpdate = Notification.Name("FuelBoardWatchDataDidUpdate")
}

final class WatchSyncManager: NSObject, WCSessionDelegate {
    static let shared = WatchSyncManager()

    private let suiteName = "group.com.apt.fuelboard"
    private let snapshotRequestKey = "fuelboard.snapshotRequest"

    private override init() {
        super.init()
    }

    func activate() {
        guard WCSession.isSupported() else { return }
        let session = WCSession.default
        if session.delegate !== self {
            session.delegate = self
        }
        session.activate()
    }

    func requestRefresh(at date: Date = Date()) {
        guard WCSession.isSupported() else { return }
        let raw = String(date.timeIntervalSince1970)
        let payload = ["fuelboard.watchRefreshRequest": raw]
        let session = WCSession.default

        if session.isReachable {
            session.sendMessage(payload, replyHandler: nil, errorHandler: nil)
        } else {
            session.transferUserInfo(payload)
        }
    }

    func requestSnapshot() {
        guard WCSession.isSupported() else { return }
        let payload = [snapshotRequestKey: String(Date().timeIntervalSince1970)]
        let session = WCSession.default

        if session.isReachable {
            session.sendMessage(payload, replyHandler: nil, errorHandler: nil)
        } else {
            session.transferUserInfo(payload)
        }
    }

    private func sharedDefaults() -> UserDefaults? {
        UserDefaults(suiteName: suiteName)
    }

    private func storeSnapshot(_ payload: [String: Any]) {
        guard let defaults = sharedDefaults() else { return }

        if let favourites = payload["fuelboard.favourites"] as? Data {
            defaults.set(favourites, forKey: "fuelboard.favourites")
        }
        if let stations = payload["fuelboard.stations"] as? Data {
            defaults.set(stations, forKey: "fuelboard.stations")
        }
        if let fuel = payload["fuelboard.selectedFuel"] as? String {
            defaults.set(fuel, forKey: "fuelboard.selectedFuel")
        }
        if let distanceUnit = payload["fuelboard.distanceUnit"] as? String {
            defaults.set(distanceUnit, forKey: "fuelboard.distanceUnit")
        }
        if let priceStyle = payload["fuelboard.priceDisplayStyle"] as? String {
            defaults.set(priceStyle, forKey: "fuelboard.priceDisplayStyle")
        }
        if let location = payload["fuelboard.lastLocation"] as? String {
            defaults.set(location, forKey: "fuelboard.lastLocation")
        }
        if let lastRefresh = payload["fuelboard.lastRefresh"] as? String {
            defaults.set(lastRefresh, forKey: "fuelboard.lastRefresh")
        }
        if let handled = payload["fuelboard.watchRefreshHandled"] as? String {
            defaults.set(handled, forKey: "fuelboard.watchRefreshHandled")
        }

        NotificationCenter.default.post(name: .fuelBoardWatchDataDidUpdate, object: nil)
    }

    func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: (any Error)?) {
        if let error {
            print("WATCH-SYNC activation failed: \(error.localizedDescription)")
            return
        }
        if activationState == .activated {
            requestSnapshot()
        }
    }

    func session(_ session: WCSession, didReceiveApplicationContext applicationContext: [String : Any]) {
        storeSnapshot(applicationContext)
    }

    func session(_ session: WCSession, didReceiveUserInfo userInfo: [String : Any] = [:]) {
        storeSnapshot(userInfo)
    }
}