audiotee/Sources/Permissions/AudioRecordingPermission.swift

import OSLog
import Observation
import SwiftUI

// Adapted with a huge debt of gratitude from https://github.com/insidegui/AudioCap/blob/main/AudioCap/ProcessTap/AudioRecordingPermission.swift

/// Uses TCC SPI in order to check/request system audio recording permission.
@Observable
final class AudioRecordingPermission {
  // private let logger = Logger(subsystem: kAppSubsystem, category: String(describing: AudioRecordingPermission.self))

  enum Status: String {
    case unknown
    case denied
    case authorized
  }

  private(set) var status: Status = .unknown

  init() {
    #if ENABLE_TCC_SPI
      NotificationCenter.default.addObserver(
        forName: NSApplication.didBecomeActiveNotification, object: nil, queue: .main
      ) { [weak self] _ in
        guard let self else { return }
        self.updateStatus()
      }

      updateStatus()
    #else
      status = .authorized
    #endif  // ENABLE_TCC_SPI
  }

  func request() {
    #if ENABLE_TCC_SPI
      // logger.debug(#function)

      guard let request = Self.requestSPI else {
        // logger.fault("Request SPI missing")
        return
      }

      request("kTCCServiceAudioCapture" as CFString, nil) { [weak self] granted in
        guard let self else { return }

        // self.logger.info("Request finished with result: \(granted, privacy: .public)")

        DispatchQueue.main.async {
          if granted {
            self.status = .authorized
          } else {
            self.status = .denied
          }
        }
      }
    #endif  // ENABLE_TCC_SPI
  }

  private func updateStatus() {
    #if ENABLE_TCC_SPI
      // logger.debug(#function)

      guard let preflight = Self.preflightSPI else {
        // logger.fault("Preflight SPI missing")
        return
      }

      let result = preflight("kTCCServiceAudioCapture" as CFString, nil)

      if result == 1 {
        status = .denied
      } else if result == 0 {
        status = .authorized
      } else {
        status = .unknown
      }
    #endif  // ENABLE_TCC_SPI
  }

  #if ENABLE_TCC_SPI
    private typealias PreflightFuncType = @convention(c) (CFString, CFDictionary?) -> Int
    private typealias RequestFuncType = @convention(c) (
      CFString, CFDictionary?, @escaping (Bool) -> Void
    ) -> Void

    /// `dlopen` handle to the TCC framework.
    private static let apiHandle: UnsafeMutableRawPointer? = {
      let tccPath = "/System/Library/PrivateFrameworks/TCC.framework/Versions/A/TCC"

      guard let handle = dlopen(tccPath, RTLD_NOW) else {
        assertionFailure("dlopen failed")
        return nil
      }

      return handle
    }()

    /// `dlsym` function handle for `TCCAccessPreflight`.
    private static let preflightSPI: PreflightFuncType? = {
      guard let apiHandle else { return nil }

      let fnName = "TCCAccessPreflight"

      guard let funcSym = dlsym(apiHandle, fnName) else {
        assertionFailure("Couldn't find symbol")
        return nil
      }

      let fn = unsafeBitCast(funcSym, to: PreflightFuncType.self)

      return fn
    }()

    /// `dlsym` function handle for `TCCAccessRequest`.
    private static let requestSPI: RequestFuncType? = {
      guard let apiHandle else { return nil }

      let fnName = "TCCAccessRequest"

      guard let funcSym = dlsym(apiHandle, fnName) else {
        assertionFailure("Couldn't find symbol")
        return nil
      }

      let fn = unsafeBitCast(funcSym, to: RequestFuncType.self)

      return fn
    }()
  #endif  // ENABLE_TCC_SPI
}