// Copyright (c) 2026 GiantAccel, LLC
// XStats modifications Copyright (C) 2026 ysicing
// SPDX-License-Identifier: AGPL-3.0-or-later AND MIT
// See LICENSE, LICENSING.md and LICENSES/OpenStats-MIT.txt.

import Foundation
import HelperShared
import Localization
import Observation
import ServiceManagement

/// 与 root 辅助工具的连接。安装通过 SMAppService.daemon，用户需在“登录项”中批准一次。
@MainActor
@Observable
public final class HelperClient {
    public enum Status: Equatable {
        case notInstalled
        case requiresApproval
        case enabled
        case unavailable(String)

        var title: String {
            switch self {
            case .notInstalled: tr("未安装")
            case .requiresApproval: tr("等待批准")
            case .enabled: tr("已启用")
            case .unavailable: tr("不可用")
            }
        }
    }

    public private(set) var status: Status = .notInstalled
    public private(set) var isWorking = false
    public private(set) var lastError: String?
    /// 正在运行的辅助工具比应用旧：登记的是另一份应用包里的辅助工具，或替换应用后旧进程还没退出
    public private(set) var isOutdated = false

    /// 连接中断后重新连上时回调，用于重新下发风扇 / 防休眠状态
    @ObservationIgnored var onReconnect: (() -> Void)?

    @ObservationIgnored private var connection: NSXPCConnection?
    @ObservationIgnored private let service: any HelperRegistration
    @ObservationIgnored private let teamIdentifier: String?
    @ObservationIgnored private let versionProbe: (@MainActor () async -> Int?)?
    private var isCheckingVersion = false
    private var hasVerifiedConnection = false

    public convenience init() {
        self.init(teamIdentifier: CodeSigningInfo.currentTeamIdentifier(), service: SystemHelperRegistration())
    }

    init(teamIdentifier: String?, service: any HelperRegistration,
         versionProbe: (@MainActor () async -> Int?)? = nil) {
        self.teamIdentifier = teamIdentifier
        self.service = service
        self.versionProbe = versionProbe
    }

    public var canInstall: Bool { HelperConstants.clientRequirement(teamIdentifier: teamIdentifier) != nil }
    public var isReady: Bool { canInstall && status == .enabled && hasVerifiedConnection && !isOutdated && !isWorking && !isCheckingVersion }
    static var signingMessage: String {
        L10n.helperSigningMessage
    }

    static var outdatedMessage: String { tr("辅助工具版本比应用旧，部分功能可能无法使用，请重新安装一次（需要管理员授权）。") }

    /// 未安装、待批准或版本过旧，需要用户处理
    var needsAttention: Bool { !isReady || isOutdated }

    public func refreshStatus() {
        guard canInstall else { status = .unavailable(Self.signingMessage); return }
        switch service.status {
        case .enabled: status = .enabled
        case .requiresApproval: status = .requiresApproval
        case .notRegistered: status = .notInstalled
        case .notFound:
            // 首次注册前系统同样返回 notFound，需结合包内文件判断
            let plist = Bundle.main.bundleURL
                .appendingPathComponent("Contents/Library/LaunchDaemons/\(HelperConstants.launchdPlistName)")
            status = FileManager.default.fileExists(atPath: plist.path)
                ? .notInstalled
                : .unavailable(tr("应用包内未找到辅助工具，请使用完整构建的 XStats.app"))
        @unknown default: status = .unavailable(tr("未知状态"))
        }
        if status == .enabled, !hasVerifiedConnection, !isCheckingVersion, !isWorking, !isOutdated {
            Task {
                guard !hasVerifiedConnection, !isOutdated else { return }
                await verifyVersion()
            }
        }
    }

    public func install() {
        guard canInstall, !isWorking else {
            if !canInstall { status = .unavailable(Self.signingMessage); lastError = Self.signingMessage }
            return
        }
        isWorking = true
        defer { isWorking = false }
        lastError = nil
        do {
            try service.register()
        } catch {
            lastError = tr("安装失败：\(error.localizedDescription)")
            Log.helper.error("安装失败：\(error.localizedDescription, privacy: .public)")
        }
        refreshStatus()
        if status == .requiresApproval {
            SMAppService.openSystemSettingsLoginItems()
        } else if status == .enabled, !isCheckingVersion {
            Task { await verifyVersion() }
        }
    }

    public func uninstall() async {
        isWorking = true
        defer { isWorking = false }
        lastError = nil
        connection?.invalidate()
        connection = nil
        hasVerifiedConnection = false
        do {
            // 使用回调版本：不把非 Sendable 的 SMAppService 跨隔离域传递
            try await service.unregister()
        } catch {
            lastError = tr("卸载失败：\(error.localizedDescription)")
            Log.helper.error("卸载失败：\(error.localizedDescription, privacy: .public)")
        }
        refreshStatus()
    }

    /// 卸载后重新登记，让 launchd 运行当前应用包里的辅助工具
    public func reinstall() async {
        guard !isWorking else { return }
        await uninstall()
        guard lastError == nil, canInstall else { return }
        install()
        await verifyVersion(allowRestart: false)
    }

    /// 注册状态不等于可安全调用。版本 5 之前必须注销旧服务，再注册并核对当前版本。
    func verifyVersion(allowRestart: Bool = true) async {
        guard !isCheckingVersion, !isWorking else { return }
        isCheckingVersion = true
        defer { isCheckingVersion = false }
        // 没有团队签名时不连接旧 daemon，注销已注册服务以关闭旧的宽松鉴权进程。
        guard canInstall else {
            if service.status == .enabled || service.status == .requiresApproval { await uninstall() }
            refreshStatus()
            return
        }
        let remote = await remoteProtocolVersion()
        guard let version = remote else { hasVerifiedConnection = false; isOutdated = service.status == .enabled; return }
        guard !HelperConstants.isCompatible(version: version) else {
            hasVerifiedConnection = true
            isOutdated = false
            return
        }
        isOutdated = true
        connection?.invalidate()
        connection = nil
        // 不能等待旧进程“自行空闲退出”：其他连接可能一直让它存活。
        // 注销失败时保留过期状态，禁止后续特权调用，也不继续注册。
        await uninstall()
        guard lastError == nil, allowRestart else { return }
        install()
        guard lastError == nil, service.status == .enabled else { return }
        isOutdated = !HelperConstants.isCompatible(version: await remoteProtocolVersion())
        hasVerifiedConnection = !isOutdated
    }

    public func openLoginItemsSettings() {
        SMAppService.openSystemSettingsLoginItems()
    }

    // MARK: 远程调用

    func setFanTarget(fan: Int, rpm: Double) async -> String? {
        await call { proxy, reply in proxy.setFanTarget(fan: fan, rpm: rpm, reply: reply) }
    }

    func setFanAutomatic(fan: Int) async -> String? {
        await call { proxy, reply in proxy.setFanAutomatic(fan: fan, reply: reply) }
    }

    func resetAllFans() async -> String? {
        await call { proxy, reply in proxy.resetAllFans(reply: reply) }
    }

    func setSleepDisabled(_ disabled: Bool) async -> String? {
        await call { proxy, reply in proxy.setSleepDisabled(disabled, reply: reply) }
    }

    func run(_ command: MaintenanceCommand) async -> String? {
        switch command {
        case .flushDNS: await call { proxy, reply in proxy.flushDNSCache(reply: reply) }
        case .purgeMemory: await call { proxy, reply in proxy.purgeMemory(reply: reply) }
        }
    }

    func setDNSServers(service: String, servers: [String]) async -> String? {
        await call { proxy, reply in proxy.setDNSServers(service: service, servers: servers, reply: reply) }
    }

    func deleteLocalSnapshots(identifiers: [String]) async -> String? {
        await call { proxy, reply in proxy.deleteLocalSnapshots(identifiers: identifiers, reply: reply) }
    }

    /// 已安装的辅助工具的协议版本；旧版本不认识新增的方法，调用前先确认
    func remoteProtocolVersion() async -> Int? {
        refreshStatus()
        guard canInstall, status == .enabled else { return nil }
        if let versionProbe { return await versionProbe() }
        let connection = ensureConnection()
        return await withCheckedContinuation { (continuation: CheckedContinuation<Int?, Never>) in
            let once = ResumeOnceValue<Int?>(continuation)
            let proxy = connection.remoteObjectProxyWithErrorHandler { _ in once.resume(nil) } as? XStatsHelperProtocol
            guard let proxy else { return once.resume(nil) }
            proxy.protocolVersion { once.resume($0) }
        }
    }

    /// 退出应用时使用：同步恢复风扇与睡眠设置。
    ///
    /// 在主线程上阻塞，因此总等待时间设上限；每一步互相独立——取代理失败只跳过当前这步，
    /// 不能提前 return，否则第一步失败就会连带跳过“恢复睡眠设置”，让 Mac 保持禁止睡眠。
    func restoreDefaultsSynchronously() {
        guard isReady else { return }
        let connection = ensureConnection()
        let steps: [(XStatsHelperProtocol, @escaping @Sendable (String?) -> Void) -> Void] = [
            { proxy, reply in proxy.resetAllFans(reply: reply) },
            { proxy, reply in proxy.setSleepDisabled(false, reply: reply) },
        ]
        let deadline = DispatchTime.now() + Self.restoreBudget
        for step in steps {
            let semaphore = DispatchSemaphore(value: 0)
            guard let proxy = connection.remoteObjectProxyWithErrorHandler({ _ in semaphore.signal() })
                    as? XStatsHelperProtocol else { continue }
            step(proxy) { _ in semaphore.signal() }
            _ = semaphore.wait(timeout: deadline)
        }
    }

    /// 退出时为恢复操作预留的总时长；辅助工具无响应时不让退出卡住超过这个值
    private static let restoreBudget: DispatchTimeInterval = .milliseconds(1500)

    private func call(_ body: (XStatsHelperProtocol, @escaping @Sendable (String?) -> Void) -> Void) async -> String? {
        refreshStatus()
        if canInstall { await verifyVersion() }
        guard isReady else { return tr("辅助工具未启用") }
        let connection = ensureConnection()
        return await withCheckedContinuation { (continuation: CheckedContinuation<String?, Never>) in
            let once = ResumeOnce(continuation)
            let proxy = connection.remoteObjectProxyWithErrorHandler { error in
                Log.helper.error("XPC 调用失败：\(error.localizedDescription, privacy: .public)")
                once.resume(tr("无法连接辅助工具：\(error.localizedDescription)"))
            } as? XStatsHelperProtocol
            guard let proxy else {
                once.resume(tr("无法连接辅助工具"))
                return
            }
            body(proxy) { once.resume($0) }
        }
    }

    private func ensureConnection() -> NSXPCConnection {
        if let connection { return connection }
        let connection = NSXPCConnection(machServiceName: HelperConstants.machServiceName, options: .privileged)
        connection.remoteObjectInterface = NSXPCInterface(with: XStatsHelperProtocol.self)
        connection.interruptionHandler = { [weak self, weak connection] in
            Task { @MainActor in
                guard let self, self.connection === connection else { return }
                self.hasVerifiedConnection = false
                await self.verifyVersion()
                if self.isReady { self.onReconnect?() }
            }
        }
        connection.invalidationHandler = { [weak self, weak connection] in
            Task { @MainActor in
                guard let self, self.connection === connection else { return }
                self.connection = nil
                self.hasVerifiedConnection = false
            }
        }
        connection.resume()
        self.connection = connection
        return connection
    }
}

private typealias ResumeOnce = ResumeOnceValue<String?>

/// XPC 的错误回调和正常回调可能都会触发，保证 continuation 只恢复一次
private final class ResumeOnceValue<Value: Sendable>: @unchecked Sendable {
    private let lock = NSLock()
    private var continuation: CheckedContinuation<Value, Never>?

    init(_ continuation: CheckedContinuation<Value, Never>) {
        self.continuation = continuation
    }

    func resume(_ value: Value) {
        lock.lock()
        let pending = continuation
        continuation = nil
        lock.unlock()
        pending?.resume(returning: value)
    }
}