import Foundation

// MARK: - 用户意图与收敛（命令面）

extension ProxyRuntimeController {
  // MARK: - 用户意图

  /// 激活一个服务器或分组目标（目录 UI 工单复用入口）：持久化目标；agent
  /// 意图开启时立即把新档推到运行时。激活原子失败时目标与运行时完全不动；
  /// 点名原因进 `lastActivationFailure` 并随 `.rejectedActivation` 自含返回；
  /// 意外错误 throws 并进入 `serviceFailed`。
  @discardableResult
  func activate(_ target: NodeID) async throws -> ActivationCommandOutcome {
    guard catalogSnapshotReader.isCatalogAvailable else { throw ServerLibraryError.notLoaded }
    refreshPluginSecurityFacts()
    let catalog = catalogSnapshotReader.catalogSnapshot
    do {
      let configuration = try machine.activate(
        target, in: catalog, plugins: plugins,
        options: settings.runtimeDocumentOptions)
      activeTargetID = target
      skippedServers = configuration.skippedServers
      lastActivationFailure = nil
      do {
        try activationFileStore.save(activeTargetID: target)
      } catch {
        state = .serviceFailed(.persistence)
        throw error
      }
      if settings.agentEnabled {
        await deploy(configuration.document)
      }
      return .activated(skippedInvalid: configuration.skippedServers.count)
    } catch let failure as ActivationFailure {
      lastActivationFailure = failure
      return .rejectedActivation(failure)
    } catch {
      state = .serviceFailed(.unknown)
      throw error
    }
  }

  /// Agent 开关：先持久化意图（显式关闭在 GUI 重启后仍生效），
  /// 再收敛运行时。UserDefaults 不提供同步落盘失败信号。意图已
  /// 开启时的开启命令仅在未达健康态时重收敛——它是启动失败/重置后的显式
  /// 重试入口；健康运行中不做无谓的注销重拉。关闭时级联：系统代理意图仍
  /// 开启则一并持久化为关闭，该 on→off 迁移触发清理，清理后才停止本地监听；
  /// 系统代理意图本就关闭则不做任何系统设置操作。
  func setAgentEnabled(_ enabled: Bool) async {
    let retryingFailure = enabled && runtimeFileStore.readFailure() != nil
    if enabled {
      do { try runtimeFileStore.clearFailure() } catch {
        state = .serviceFailed(.runtimeFile)
        return
      }
    }
    guard enabled != settings.agentEnabled else {
      await handleUnchangedAgentIntent(enabled, retryingFailure: retryingFailure)
      return
    }
    controlPreferences.agentEnabled = enabled
    settings.agentEnabled = enabled
    if enabled {
      await enableAgentAfterIntent()
    } else {
      await disableAgentAfterIntent()
    }
  }

  private func handleUnchangedAgentIntent(_ enabled: Bool, retryingFailure: Bool) async {
    guard enabled else { return }
    if retryingFailure {
      await convergeAgent()
      return
    }
    if ruleApplicationFailure != nil {
      scheduleRuleApplication()
      return
    }
    switch state {
    case .off, .launchFailed, .serviceFailed: await convergeAgent()
    case .starting, .running, .firewallBlocked, .requiresApproval: break
    }
  }

  private func enableAgentAfterIntent() async {
    await convergeAgent()
    if settings.systemProxyEnabled { systemProxyObserver.startEnabledSystemProxyObservation() }
  }

  private func disableAgentAfterIntent() async {
    let cleanupOutcome = await cascadeSystemProxyOffForAgentOff()
    await stopAgent()
    if let cleanupOutcome {
      systemProxyObserver.presentCleanupOutcome(cleanupOutcome)
    } else {
      systemProxyObserver.updateSystemProxyActions()
    }
  }

  /// 关闭 agent 时的系统代理级联：意图仍开启则一并持久化为
  /// 关闭并请求清理（返回清理结果），不依赖监听文件保存。
  private func cascadeSystemProxyOffForAgentOff() async -> SystemProxyControlState? {
    guard settings.systemProxyEnabled else { return nil }
    controlPreferences.systemProxyEnabled = false
    settings.systemProxyEnabled = false
    // 持久化的 on→off 迁移才触发清理；先清后停本地监听。
    return await systemProxyObserver.clearAndStopSystemProxyObservation()
  }

  /// 系统代理开关：先持久化意图。开启时经 helper 注册门禁收敛
  /// 应用；关闭即一次 on→off 意图迁移——请求一次无条件清理（临时观察网络
  /// 变化直至安静，失败也不后台重试），不影响 agent 注册与本地监听。
  func setSystemProxyEnabled(_ enabled: Bool) async {
    guard enabled != settings.systemProxyEnabled else { return }
    controlPreferences.systemProxyEnabled = enabled
    settings.systemProxyEnabled = enabled
    if enabled {
      await systemProxyObserver.enableSystemProxyIntent()
    } else {
      await systemProxyObserver.disableSystemProxyIntent()
    }
  }

  /// GUI startup restores the Agent. Healthy proxy intent only inspects; unhealthy
  /// proxy intent suspends; disabled intent never writes SystemConfiguration.
  func resyncOnLaunch() async {
    guard !settingsUnreadable else {
      state = .launchFailed(.unreadableSettings)
      return
    }
    guard catalogSnapshotReader.isCatalogAvailable else { return }
    refreshPluginSecurityFacts()
    systemProxyObserver.beginStartupResync()
    guard settings.agentEnabled else {
      await stopAgent()
      await systemProxyObserver.settleLaunchWithAgentOff()
      return
    }
    let catalog = catalogSnapshotReader.catalogSnapshot
    await convergeToReexpanded(catalog)
    await systemProxyObserver.settleLaunchAfterAgentConverged()
  }

  // MARK: - 动作执行

  /// Agent 意图开启的收敛：注册态不是事实来源，意图才是——未注册也会注册，
  /// 已注册则重校验目标并部署。偏好重置后也走此路径，把运行时收敛到出厂设置。
  func convergeAgent() async {
    await convergeToReexpanded(catalogSnapshotReader.catalogSnapshot)
  }

  /// Agent 意图关闭的收敛：只停止本地监听，不做系统代理清理。
  /// 系统代理状态按意图事实收尾——级联后意图已关闭为空闲；残留的「意图开
  /// 启 + agent 关闭」组合保持待应用（不静默清理，也无需网络观察）。
  func stopAgent() async {
    systemProxyObserver.agentDidStop()
    let outcome = await execute(.stop, document: nil)
    guard outcome.succeeded else { return }
    state = .off
    runtimeObservation = nil
    skippedServers = []
    lastActivationFailure = nil
  }

  /// 无活动目标时 agent 仍提供本地监听：空服务器列表文档，
  /// SOCKS/HTTP 端点照常绑定；系统代理门禁会因缺少可用出口保持待应用。
  @discardableResult
  func deployListeningWithoutTarget() async -> ConvergenceResult {
    let document = SslocalRuntimeDocument(
      servers: [],
      listen: settings.listen)
    return await deploy(document)
  }

  /// 普通部署意图；配置派生、执行与失败呈现由运行状态收敛 module 拥有。
  @discardableResult
  func deploy(_ sourceDocument: SslocalRuntimeDocument) async -> ConvergenceResult {
    refreshPluginSecurityFacts()
    let result = await convergeRuntime(.deployment(sourceDocument))
    if case .failed = result { refreshPluginSecurityFacts() }
    return result
  }

  /// 活动目标失效：清除并持久化 nil，点名原因独立呈现；agent
  /// 继续以空服务器列表监听；系统代理清理后保留意图，条件恢复后自动
  /// 收敛），不悄悄选择其他服务器。
  @discardableResult
  func handleCleared(_ failure: ActivationFailure) async -> ConvergenceResult {
    RuntimeLog.emit(.activationFailed(reason: String(describing: failure)))
    do {
      try activationFileStore.save(activeTargetID: nil)
    } catch {
      // 清目标失败不阻断收敛：下次重同步会再次收敛（目标已不在状态机中）。
      RuntimeLog.emit(.runtimePersistFailed(detail: String(describing: error)))
    }
    lastActivationFailure = failure
    skippedServers = []
    await systemProxyObserver.holdSystemProxyIntent()
    if settings.agentEnabled {
      return await deployListeningWithoutTarget()
    } else {
      // 会话内意图已被关闭的残余：按关闭语义收敛。
      let outcome = await execute(.stop, document: nil)
      guard outcome.succeeded else { return .failed }
      state = .off
      runtimeObservation = nil
      return .applied
    }
  }
}

// MARK: - 计划动作执行

extension ProxyRuntimeController {
  /// 把「运行定义档」意图推到运行时：计划动作 → 顺序执行。返回全部动作
  /// 是否成功与本次占用的并发流代际。
  func execute(
    _ intent: RuntimeIntent, document: SslocalRuntimeDocument?,
    preparedContract: PreparedRuntimeContract? = nil
  ) async -> RuntimeExecutionOutcome {
    cancelFirewallObservation()
    flowGeneration += 1
    let flow = flowGeneration
    let succeeded = await performPlannedActions(
      intent, document: document, preparedContract: preparedContract, flow: flow)
    return RuntimeExecutionOutcome(flow: flow, succeeded: succeeded)
  }

  /// 按计划顺序执行动作；返回 false 表示中途失败、状态已呈现（后续动作与
  /// 健康探测都不应继续）。
  private func performPlannedActions(
    _ intent: RuntimeIntent, document: SslocalRuntimeDocument?,
    preparedContract: PreparedRuntimeContract?, flow: Int
  ) async -> Bool {
    let preparation = runtimePreparationGeneration
    let contract: PreparedRuntimeContract?
    if case .run(let desired) = intent {
      guard let prepared = preparedContract ?? (try? PreparedRuntimeContract(desired)),
        prepared.document == desired, document == desired
      else {
        state = .serviceFailed(document == nil ? .missingDocument : .runtimeFile)
        return false
      }
      contract = prepared
    } else {
      contract = nil
    }
    let actions = ProxyRuntimePlan.actions(
      intent: intent,
      agentStatus: agent.status,
      wrapper: wrapperState(),
      configurationIsCurrent: contract.map { runtimeFileStore.contains($0) } ?? false)
    if case .run = intent, actions.isEmpty {
      RuntimeLog.emit(.contractUnchanged)
    }
    for action in actions {
      guard flow == flowGeneration, preparation == runtimePreparationGeneration,
        await perform(action, preparedContract: contract)
      else { return false }
    }
    return flow == flowGeneration && preparation == runtimePreparationGeneration
  }

  /// 执行单个动作；返回 false 表示应终止后续动作（状态已呈现）。
  private func perform(
    _ action: RuntimeAction, preparedContract: PreparedRuntimeContract?
  ) async -> Bool {
    switch action {
    case .writeContract:
      return performWriteContract(preparedContract)
    case .registerAgent:
      return performAgentRegistration()
    case .unregisterAgent:
      return await performAgentUnregistration()
    case .signalReload(let pid):
      return performSignalReload(pid)
    case .deleteRuntimeFiles:
      do { try runtimeFileStore.deleteRuntimeFiles() } catch {
        state = .serviceFailed(.runtimeFile)
        return false
      }
      RuntimeLog.emit(.runtimeFilesDeleted)
      return true
    }
  }

  /// 原子写契约文件；缺文档或写失败即终止。
  private func performWriteContract(_ contract: PreparedRuntimeContract?) -> Bool {
    guard let contract else {
      state = .serviceFailed(.missingDocument)
      return false
    }
    do {
      try runtimeFileStore.write(contract)
      RuntimeLog.emit(.contractWritten(serverCount: contract.document.servers.count))
      return true
    } catch {
      state = .serviceFailed(.runtimeFile)
      return false
    }
  }

  /// 注册 LaunchAgent；需用户批准或注册失败即终止并呈现对应状态。
  private func performAgentRegistration() -> Bool {
    do {
      try agent.register()
    } catch {
      RuntimeLog.emit(.agentRegisterFailed(detail: describe(error)))
      if agent.status == .requiresApproval {
        // 注册请求已被系统接收，等待用户在登录项中批准。
        state = .requiresApproval
        return false
      }
      if agent.status != .registered {
        state = .serviceFailed(.agent)
        return false
      }
      // 注册与状态读取之间的竞态：已注册即达意图，不视为失败。
    }
    RuntimeLog.emit(.agentRegistered)
    if agent.status == .requiresApproval {
      state = .requiresApproval
      return false
    }
    return true
  }

  /// 注销 LaunchAgent 并等待 wrapper 退出；未注册竞态可忽略（尽力而为）。
  private func performAgentUnregistration() async -> Bool {
    do {
      try agent.unregister()
    } catch {
      RuntimeLog.emit(.agentUnregisterFailed(detail: describe(error)))
    }
    RuntimeLog.emit(.agentUnregistered)
    await waitForWrapperExit()
    guard wrapperState() == .notRunning, !runtimeFileStore.hasUnconfirmedChild else {
      state = .serviceFailed(.agent)
      return false
    }
    return true
  }

  private func performSignalReload(_ pid: Int32) -> Bool {
    guard sendSignal(pid, SIGUSR1) == 0 else {
      state = .serviceFailed(.agent)
      return false
    }
    return true
  }
}