//
//  HomeLocationProvider.swift
//  suixinkan
//

import CoreLocation

/// 首页位置采集结果。
struct HomeLocationSnapshot: Sendable {
    let latitude: Double
    let longitude: Double
    let address: String
}

/// 首页位置采集，基于 CoreLocation 并提供可选逆地理。
final class HomeLocationProvider: NSObject, CLLocationManagerDelegate {

    private let manager = CLLocationManager()
    private var coordinateContinuation: CheckedContinuation<CLLocationCoordinate2D, Error>?

    override init() {
        super.init()
        manager.delegate = self
        manager.desiredAccuracy = kCLLocationAccuracyBest
    }

    /// 请求当前位置与地址。
    func requestSnapshot() async throws -> HomeLocationSnapshot {
        let status = manager.authorizationStatus
        if status == .notDetermined {
            manager.requestWhenInUseAuthorization()
            try await Task.sleep(nanoseconds: 300_000_000)
        }

        let resolvedStatus = manager.authorizationStatus
        guard resolvedStatus == .authorizedWhenInUse || resolvedStatus == .authorizedAlways else {
            throw HomeLocationProviderError.permissionDenied
        }

        let coordinate = try await requestCoordinate()
        let address = await reverseGeocode(latitude: coordinate.latitude, longitude: coordinate.longitude)
        return HomeLocationSnapshot(
            latitude: coordinate.latitude,
            longitude: coordinate.longitude,
            address: address
        )
    }

    private func requestCoordinate() async throws -> CLLocationCoordinate2D {
        try await withCheckedThrowingContinuation { continuation in
            self.coordinateContinuation = continuation
            manager.requestLocation()
        }
    }

    private func reverseGeocode(latitude: Double, longitude: Double) async -> String {
        let location = CLLocation(latitude: latitude, longitude: longitude)
        let geocoder = CLGeocoder()
        do {
            let placemarks = try await geocoder.reverseGeocodeLocation(location)
            return placemarks.first?.formattedAddress ?? ""
        } catch {
            return ""
        }
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        guard let location = locations.last else { return }
        coordinateContinuation?.resume(returning: location.coordinate)
        coordinateContinuation = nil
    }

    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        coordinateContinuation?.resume(throwing: error)
        coordinateContinuation = nil
    }
}

/// 首页定位错误。
enum HomeLocationProviderError: LocalizedError {
    case permissionDenied

    var errorDescription: String? {
        switch self {
        case .permissionDenied: "需要位置权限才能上线"
        }
    }
}

private extension CLPlacemark {
    var formattedAddress: String {
        [subLocality, locality, administrativeArea]
            .compactMap { $0?.trimmingCharacters(in: .whitespacesAndNewlines) }
            .filter { !$0.isEmpty }
            .joined(separator: "")
    }
}