An async stream wrapper for NWBrowser events

NWBrowserStream.swift

//
//  NWBrowserStream.swift
//  AsyncNetwork
//
//  Created by Helge Heß on 14.04.24.
//

import OSLog
import Network

public extension NWBrowser {
  
  typealias Stream =
    AsyncThrowingStream<Set<NWBrowser.Result.Change>, any Error>

  func makeStream(queue: DispatchQueue = .main) -> Stream {
    let logger =
      Logger(subsystem: "de.zeezide.async.nw", category: "browser")
    
    return AsyncThrowingStream(Stream.Element.self) { continuation in
      
      continuation.onTermination = { [weak self] termination in
        logger.debug("Browser stream terminated.")
        self?.cancel()
      }
      
      self.browseResultsChangedHandler = { newResults, changes in
        logger.debug("Browser stream got results: #\(changes.count).")
        continuation.yield(changes)
      }

      self.stateUpdateHandler = { [weak self] newState in
        switch newState {
          case .setup: // created but not started
            logger.debug("Browser has setup as new state?")
            
          case .cancelled:
            logger.debug("Browser stream got cancelled.")
            continuation.finish()
          case .failed(let error):
            logger.error("Browser stream failed: \(error)")
            continuation.finish(throwing: error)
            
          case .ready: // started
            // Yield initial results add "added"
            guard let self else {
              logger.error("Browser stream ready, but self is gone?")
              continuation.finish()
              return
            }
            let initial = self.browseResults
            assert(initial.isEmpty, "There are browse results on startup?")
            if !initial.isEmpty {
              logger.debug("Browser stream, initial results: #\(initial.count)")
              continuation.yield(
                Set(initial.map { NWBrowser.Result.Change.added($0) }))
            }
            

          case .waiting(let error):
            logger.warning("Browser waiting \(error)")
          @unknown default:
            logger.error(
              "Unexpected State Change: \(String(describing: newState))")
        }
      }
      
      self.start(queue: queue)
    }
  }
}