// ── Location Trigger Manager ──────────────────────────────────
// CoreLocation geofencing for location-based timer triggers
// Privacy-first: all processing on-device, no server tracking

import Foundation
import CoreLocation
import Combine

@MainActor
final class LocationTriggerManager: NSObject, ObservableObject {
    static let shared = LocationTriggerManager()

    @Published var authorizationStatus: CLAuthorizationStatus = .notDetermined
    @Published var savedLocations: [SavedLocation] = []
    @Published var locationTriggers: [LocationTrigger] = []

    private let locationManager = CLLocationManager()
    private let locationsKey = "chronomind-saved-locations"
    private let triggersKey = "chronomind-location-triggers"

    override private init() {
        super.init()
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters
        authorizationStatus = locationManager.authorizationStatus
        loadData()
    }

    // MARK: - Authorization

    func requestAlwaysAuthorization() {
        locationManager.requestAlwaysAuthorization()
    }

    func requestWhenInUseAuthorization() {
        locationManager.requestWhenInUseAuthorization()
    }

    // MARK: - Saved Locations

    func addLocation(_ location: SavedLocation) {
        savedLocations.append(location)
        saveData()
    }

    func removeLocation(_ id: String) {
        // Remove associated triggers first
        let triggerIds = locationTriggers.filter { $0.locationId == id }.map(\.id)
        for triggerId in triggerIds {
            removeTrigger(triggerId)
        }
        savedLocations.removeAll { $0.id == id }
        saveData()
    }

    func updateLocation(_ location: SavedLocation) {
        if let index = savedLocations.firstIndex(where: { $0.id == location.id }) {
            savedLocations[index] = location
            saveData()
        }
    }

    // MARK: - Triggers

    func addTrigger(_ trigger: LocationTrigger) {
        locationTriggers.append(trigger)
        startMonitoring(trigger)
        saveData()
    }

    func removeTrigger(_ id: String) {
        if let trigger = locationTriggers.first(where: { $0.id == id }),
           let location = savedLocations.first(where: { $0.id == trigger.locationId }) {
            let region = CLCircularRegion(
                center: CLLocationCoordinate2D(latitude: location.latitude, longitude: location.longitude),
                radius: location.radius,
                identifier: trigger.id
            )
            locationManager.stopMonitoring(for: region)
        }
        locationTriggers.removeAll { $0.id == id }
        saveData()
    }

    // MARK: - Monitoring

    private func startMonitoring(_ trigger: LocationTrigger) {
        guard let location = savedLocations.first(where: { $0.id == trigger.locationId }) else { return }

        let region = CLCircularRegion(
            center: CLLocationCoordinate2D(latitude: location.latitude, longitude: location.longitude),
            radius: location.radius,
            identifier: trigger.id
        )
        region.notifyOnEntry = trigger.triggerType == .enter
        region.notifyOnExit = trigger.triggerType == .exit

        locationManager.startMonitoring(for: region)
    }

    func startAllMonitoring() {
        for trigger in locationTriggers where trigger.enabled {
            startMonitoring(trigger)
        }
    }

    func stopAllMonitoring() {
        for region in locationManager.monitoredRegions {
            locationManager.stopMonitoring(for: region)
        }
    }

    // MARK: - Current Location

    func getCurrentLocation() async -> CLLocation? {
        return await withCheckedContinuation { continuation in
            let delegate = SingleLocationDelegate { location in
                continuation.resume(returning: location)
            }
            let tempManager = CLLocationManager()
            tempManager.delegate = delegate
            tempManager.desiredAccuracy = kCLLocationAccuracyBest
            tempManager.requestLocation()
            // Hold reference
            objc_setAssociatedObject(tempManager, "delegate", delegate, .OBJC_ASSOCIATION_RETAIN)
        }
    }

    // MARK: - Persistence

    private func loadData() {
        if let data = UserDefaults.standard.data(forKey: locationsKey),
           let decoded = try? JSONDecoder().decode([SavedLocation].self, from: data) {
            savedLocations = decoded
        }
        if let data = UserDefaults.standard.data(forKey: triggersKey),
           let decoded = try? JSONDecoder().decode([LocationTrigger].self, from: data) {
            locationTriggers = decoded
        }
    }

    private func saveData() {
        if let data = try? JSONEncoder().encode(savedLocations) {
            UserDefaults.standard.set(data, forKey: locationsKey)
        }
        if let data = try? JSONEncoder().encode(locationTriggers) {
            UserDefaults.standard.set(data, forKey: triggersKey)
        }
    }
}

// MARK: - CLLocationManagerDelegate

extension LocationTriggerManager: CLLocationManagerDelegate {
    nonisolated func locationManagerDidChangeAuthorization(_ manager: CLLocationManager) {
        Task { @MainActor in
            authorizationStatus = manager.authorizationStatus
            if manager.authorizationStatus == .authorizedAlways {
                startAllMonitoring()
            }
        }
    }

    nonisolated func locationManager(_ manager: CLLocationManager, didEnterRegion region: CLRegion) {
        Task { @MainActor in
            handleRegionEvent(region.identifier, type: .enter)
        }
    }

    nonisolated func locationManager(_ manager: CLLocationManager, didExitRegion region: CLRegion) {
        Task { @MainActor in
            handleRegionEvent(region.identifier, type: .exit)
        }
    }

    nonisolated func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        // Silently handle — location is best-effort
    }

    private func handleRegionEvent(_ triggerId: String, type: LocationTriggerType) {
        guard let trigger = locationTriggers.first(where: { $0.id == triggerId }),
              trigger.enabled,
              trigger.triggerType == type else { return }

        // Post notification for TimerStore to handle
        NotificationCenter.default.post(
            name: .chronoMindLocationTriggerFired,
            object: nil,
            userInfo: [
                "triggerId": triggerId,
                "triggerType": type.rawValue,
                "timerLabel": trigger.timerLabel,
                "timerDuration": trigger.timerDurationSeconds ?? 0,
            ]
        )
    }
}

// MARK: - Single Location Delegate Helper

private class SingleLocationDelegate: NSObject, CLLocationManagerDelegate {
    let completion: (CLLocation?) -> Void
    init(completion: @escaping (CLLocation?) -> Void) {
        self.completion = completion
    }
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        completion(locations.first)
    }
    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        completion(nil)
    }
}

// MARK: - Models

struct SavedLocation: Codable, Identifiable {
    let id: String
    var name: String
    var latitude: Double
    var longitude: Double
    var radius: Double // meters, default 100
    var icon: String // SF Symbol name

    init(name: String, latitude: Double, longitude: Double, radius: Double = 100, icon: String = "mappin.circle.fill") {
        self.id = UUID().uuidString
        self.name = name
        self.latitude = latitude
        self.longitude = longitude
        self.radius = radius
        self.icon = icon
    }

    static let presets: [(name: String, icon: String)] = [
        ("Home", "house.fill"),
        ("Work", "building.2.fill"),
        ("Gym", "figure.run"),
        ("School", "graduationcap.fill"),
    ]
}

enum LocationTriggerType: String, Codable, CaseIterable, Identifiable {
    case enter = "enter"
    case exit = "exit"
    var id: String { rawValue }

    var label: String {
        switch self {
        case .enter: return "Arrive"
        case .exit: return "Leave"
        }
    }
}

struct LocationTrigger: Codable, Identifiable {
    let id: String
    let locationId: String
    let triggerType: LocationTriggerType
    let timerLabel: String
    let timerDurationSeconds: TimeInterval?
    let timerUrgency: UrgencyLevel
    var enabled: Bool

    init(
        locationId: String,
        triggerType: LocationTriggerType,
        timerLabel: String,
        timerDurationSeconds: TimeInterval? = nil,
        timerUrgency: UrgencyLevel = .standard,
        enabled: Bool = true
    ) {
        self.id = UUID().uuidString
        self.locationId = locationId
        self.triggerType = triggerType
        self.timerLabel = timerLabel
        self.timerDurationSeconds = timerDurationSeconds
        self.timerUrgency = timerUrgency
        self.enabled = enabled
    }
}

// MARK: - Notification Names

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