//
//  PhoneStatusCollector.swift
//  QuickLocation
//

import AVFoundation
import CoreTelephony
import Foundation
import Network
import UIKit

struct PhoneStatusSnapshot: Equatable {
    let model: String
    let batteryPercent: Int?
    let batteryText: String
    let isCharging: Bool
    let network: String
    let brightnessPercent: Int
    let brightnessText: String
    let volumePercent: Int
    let volumeText: String
    let memoryUsed: String?
    let memoryTotal: String?
    let storageRatio: CGFloat
    let storageText: String
}

final class PhoneStatusCollector: NSObject {

    static let shared = PhoneStatusCollector()

    private let networkMonitor = PhoneNetworkStatusMonitor()
    private var volumeObservation: NSKeyValueObservation?
    private var pendingNotify: DispatchWorkItem?
    private var started = false

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

    func start() {
        guard !started else { return }
        started = true
        UIDevice.current.isBatteryMonitoringEnabled = true
        networkMonitor.start { [weak self] in
            self?.emitChange()
        }

        let center = NotificationCenter.default
        center.addObserver(
            self,
            selector: #selector(handleChange),
            name: UIDevice.batteryLevelDidChangeNotification,
            object: nil
        )
        center.addObserver(
            self,
            selector: #selector(handleChange),
            name: UIDevice.batteryStateDidChangeNotification,
            object: nil
        )
        center.addObserver(
            self,
            selector: #selector(handleChange),
            name: UIScreen.brightnessDidChangeNotification,
            object: nil
        )
        center.addObserver(
            self,
            selector: #selector(handleChange),
            name: UIApplication.didBecomeActiveNotification,
            object: nil
        )
        volumeObservation = AVAudioSession.sharedInstance().observe(\.outputVolume, options: [.new]) { [weak self] _, _ in
            self?.emitChange()
        }
    }

    func snapshot() -> PhoneStatusSnapshot {
        start()
        let batteryPercent = UIDevice.batteryPercent
        let brightnessPercent = Int((UIScreen.main.brightness * 100).rounded())
        let volumePercent = Int((AVAudioSession.sharedInstance().outputVolume * 100).rounded())
        let storage = Self.storageInfo()
        let used = storage?.used
        let total = storage?.total
        let ratio: CGFloat
        if let usedValue = Self.firstNumber(in: used),
           let totalValue = Self.firstNumber(in: total),
           totalValue > 0 {
            ratio = CGFloat(max(0, min(1, usedValue / totalValue)))
        } else {
            ratio = 0
        }
        let storageText: String
        if let used, let total {
            storageText = "\(used)/\(total)"
        } else {
            storageText = "**"
        }
        return PhoneStatusSnapshot(
            model: UIDevice.modelName,
            batteryPercent: batteryPercent,
            batteryText: batteryPercent.map { "\($0)%" } ?? "未知",
            isCharging: UIDevice.isBatteryCharging,
            network: networkMonitor.statusText,
            brightnessPercent: brightnessPercent,
            brightnessText: "\(brightnessPercent)%",
            volumePercent: volumePercent,
            volumeText: "\(volumePercent)%",
            memoryUsed: used,
            memoryTotal: total,
            storageRatio: ratio,
            storageText: storageText
        )
    }

    @objc private func handleChange() {
        emitChange()
    }

    private func emitChange() {
        let work = {
            self.pendingNotify?.cancel()
            let item = DispatchWorkItem {
                NotificationCenter.default.post(name: .phoneStatusDidChange, object: nil)
            }
            self.pendingNotify = item
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.25, execute: item)
        }
        if Thread.isMainThread {
            work()
        } else {
            DispatchQueue.main.async(execute: work)
        }
    }

    static func storageInfo() -> (used: String, total: String)? {
        let url = URL(fileURLWithPath: NSHomeDirectory())
        let keys: Set<URLResourceKey> = [
            .volumeTotalCapacityKey,
            .volumeAvailableCapacityForImportantUsageKey
        ]
        guard let values = try? url.resourceValues(forKeys: keys),
              let total = values.volumeTotalCapacity,
              let available = values.volumeAvailableCapacityForImportantUsage,
              total > 0 else { return nil }

        let totalBytes = Int64(total)
        let usedBytes = max(0, totalBytes - available)
        return (
            used: String(format: "%.1fGB", Double(usedBytes) / 1_000_000_000),
            total: String(format: "%.0fGB", Double(totalBytes) / 1_000_000_000)
        )
    }

    private static func firstNumber(in value: String?) -> Double? {
        guard let value,
              let range = value.range(of: #"\d+(?:\.\d+)?"#, options: .regularExpression) else { return nil }
        return Double(value[range])
    }
}

private final class PhoneNetworkStatusMonitor {

    private let monitor = NWPathMonitor()
    private let queue = DispatchQueue(label: "com.quicklocation.phone.network")
    private let lock = NSLock()
    private let telephonyInfo = CTTelephonyNetworkInfo()
    private var path: NWPath?
    private var onChange: (() -> Void)?

    func start(onChange: @escaping () -> Void) {
        self.onChange = onChange
        monitor.pathUpdateHandler = { [weak self] path in
            self?.lock.lock()
            self?.path = path
            self?.lock.unlock()
            onChange()
        }
        monitor.start(queue: queue)
    }

    var statusText: String {
        lock.lock()
        let currentPath = path
        lock.unlock()

        guard let currentPath, currentPath.status == .satisfied else {
            return "无网络"
        }
        if currentPath.usesInterfaceType(.wifi) {
            return "Wi-Fi"
        }
        guard currentPath.usesInterfaceType(.cellular) else {
            return "无网络"
        }
        return cellularGeneration
    }

    private var cellularGeneration: String {
        let technologies = telephonyInfo.serviceCurrentRadioAccessTechnology
            .map { Array($0.values) } ?? []
        guard let technology = technologies.first else { return "蜂窝" }
        switch technology {
        case CTRadioAccessTechnologyNR, CTRadioAccessTechnologyNRNSA:
            return "5G"
        case CTRadioAccessTechnologyLTE:
            return "4G"
        case CTRadioAccessTechnologyWCDMA,
             CTRadioAccessTechnologyHSDPA,
             CTRadioAccessTechnologyHSUPA,
             CTRadioAccessTechnologyCDMAEVDORev0,
             CTRadioAccessTechnologyCDMAEVDORevA,
             CTRadioAccessTechnologyCDMAEVDORevB,
             CTRadioAccessTechnologyeHRPD:
            return "3G"
        case CTRadioAccessTechnologyGPRS,
             CTRadioAccessTechnologyEdge,
             CTRadioAccessTechnologyCDMA1x:
            return "2G"
        default:
            return "蜂窝"
        }
    }
}