import Foundation
import Combine

private func ud<T: Decodable>(_ type: T.Type, key: String) -> T? {
    guard let data = UserDefaults.standard.data(forKey: key) else { return nil }
    return try? JSONDecoder().decode(type, from: data)
}

private func saveUD<T: Encodable>(_ value: T?, key: String) {
    guard let value else { UserDefaults.standard.removeObject(forKey: key); return }
    if let data = try? JSONEncoder().encode(value) { UserDefaults.standard.set(data, forKey: key) }
}

final class ConnectionStore: ObservableObject {
    static let shared = ConnectionStore()

    @Published var savedConnection: NASConnection? {
        didSet {
            if let conn = savedConnection { SavedConnections.save(conn) }
            else { SavedConnections.delete() }
        }
    }
    @Published var backupFilter: BackupFilter {
        didSet { saveUD(backupFilter, key: "backupFilter") }
    }
    @Published var trustedSSIDs: [String] {
        didSet { UserDefaults.standard.set(trustedSSIDs, forKey: "trustedSSIDs") }
    }
    @Published var lanTriggerEnabled: Bool {
        didSet { UserDefaults.standard.set(lanTriggerEnabled, forKey: "lanTriggerEnabled") }
    }
    @Published var startDelaySeconds: Int {
        didSet { UserDefaults.standard.set(startDelaySeconds, forKey: "startDelaySeconds") }
    }
    @Published var chargingOnlyMode: Bool {
        didSet { UserDefaults.standard.set(chargingOnlyMode, forKey: "chargingOnlyMode") }
    }
    @Published var quietHoursEnabled: Bool {
        didSet { UserDefaults.standard.set(quietHoursEnabled, forKey: "quietHoursEnabled") }
    }
    @Published var quietHoursStart: Int {
        didSet { UserDefaults.standard.set(quietHoursStart, forKey: "quietHoursStart") }
    }
    @Published var quietHoursEnd: Int {
        didSet { UserDefaults.standard.set(quietHoursEnd, forKey: "quietHoursEnd") }
    }

    // Session — not persisted, resets on every app launch
    @Published var isSessionActive = false

    // Onboarding — persisted so we only show each step once
    @Published var onboardingPhotoShown: Bool {
        didSet { UserDefaults.standard.set(onboardingPhotoShown, forKey: "onboardingPhotoShown") }
    }

    // Appearance
    @Published var appearanceMode: AppearanceMode {
        didSet { UserDefaults.standard.set(appearanceMode.rawValue, forKey: "appearanceMode") }
    }

    // Local retention: 0 = never delete, 60/90/365 = days after backup
    @Published var localRetentionDays: Int {
        didSet { UserDefaults.standard.set(localRetentionDays, forKey: "localRetentionDays") }
    }

    // Auto-backup: default on after first destination is configured
    @Published var autoBackupEnabled: Bool {
        didSet { UserDefaults.standard.set(autoBackupEnabled, forKey: "autoBackupEnabled") }
    }

    // Cellular & remote access
    @Published var allowCellularBackup: Bool {
        didSet { UserDefaults.standard.set(allowCellularBackup, forKey: "allowCellularBackup") }
    }
    @Published var useTailscaleWhenRemote: Bool {
        didSet { UserDefaults.standard.set(useTailscaleWhenRemote, forKey: "useTailscaleWhenRemote") }
    }
    @Published var tailscaleHost: String {
        didSet { UserDefaults.standard.set(tailscaleHost, forKey: "tailscaleHost") }
    }

    @Published private(set) var historyEntries: [BackupHistoryEntry] = []

    private init() {
        savedConnection        = SavedConnections.load()
        backupFilter           = ud(BackupFilter.self, key: "backupFilter") ?? BackupFilter()
        trustedSSIDs           = UserDefaults.standard.stringArray(forKey: "trustedSSIDs") ?? []
        lanTriggerEnabled      = UserDefaults.standard.object(forKey: "lanTriggerEnabled") as? Bool ?? true
        startDelaySeconds      = UserDefaults.standard.object(forKey: "startDelaySeconds") as? Int ?? 30
        chargingOnlyMode       = UserDefaults.standard.object(forKey: "chargingOnlyMode") as? Bool ?? true
        quietHoursEnabled      = UserDefaults.standard.object(forKey: "quietHoursEnabled") as? Bool ?? false
        quietHoursStart        = UserDefaults.standard.object(forKey: "quietHoursStart") as? Int ?? 23
        quietHoursEnd          = UserDefaults.standard.object(forKey: "quietHoursEnd") as? Int ?? 7
        onboardingPhotoShown   = UserDefaults.standard.bool(forKey: "onboardingPhotoShown")
        appearanceMode         = AppearanceMode(rawValue: UserDefaults.standard.string(forKey: "appearanceMode") ?? "") ?? .system
        localRetentionDays     = UserDefaults.standard.object(forKey: "localRetentionDays") as? Int ?? 0
        autoBackupEnabled      = UserDefaults.standard.object(forKey: "autoBackupEnabled") as? Bool ?? true
        allowCellularBackup    = UserDefaults.standard.object(forKey: "allowCellularBackup") as? Bool ?? false
        useTailscaleWhenRemote = UserDefaults.standard.object(forKey: "useTailscaleWhenRemote") as? Bool ?? false
        tailscaleHost          = UserDefaults.standard.string(forKey: "tailscaleHost") ?? ""
        historyEntries         = ud([BackupHistoryEntry].self, key: "historyEntries") ?? []
    }

    func appendHistoryEntry(_ entry: BackupHistoryEntry) {
        historyEntries.insert(entry, at: 0)
        saveUD(historyEntries, key: "historyEntries")
    }

    func removeHistoryEntries(at offsets: IndexSet) {
        historyEntries.remove(atOffsets: offsets)
        saveUD(historyEntries, key: "historyEntries")
    }

    func clearHistory() {
        historyEntries = []
        UserDefaults.standard.removeObject(forKey: "historyEntries")
    }

    func clearCompletedHistory() {
        historyEntries.removeAll { $0.failedCount == 0 }
        saveUD(historyEntries, key: "historyEntries")
    }

    func clearErrorHistory() {
        historyEntries.removeAll { $0.failedCount > 0 }
        saveUD(historyEntries, key: "historyEntries")
    }

    /// Locks the screen — keeps the saved connection but requires Face ID again.
    func lock() {
        isSessionActive = false
    }

    /// Clears everything: connection, session, and onboarding state. Returns to ConnectView.
    func signOut() {
        isSessionActive = false
        onboardingPhotoShown = false
        savedConnection = nil
    }

    var isInQuietHours: Bool {
        guard quietHoursEnabled else { return false }
        let hour = Calendar.current.component(.hour, from: Date())
        if quietHoursStart > quietHoursEnd {
            return hour >= quietHoursStart || hour < quietHoursEnd
        }
        return hour >= quietHoursStart && hour < quietHoursEnd
    }
}