AsyncAction implementation for Suas that write to disk in the background

DiskWriteAsyncAction.swift

/// Callback called when Disk IO write operation completes
public typealias DiskWriteActionCompletionBlock = (Bool, DispatchFunction) -> Void


/// Disk Write `AsyncAction` implementation to write data to the disk asynchronously. Requires `AsyncMiddleware` to be added to the store.
///
/// # Example
///
/// ```
/// let action = DiskWriteAsyncAction(path: ..., data: ...) { succeeded, dispatch in
///   // After data is written, dispatch an action
///   dispatch(DataWrittenToDisk(succeeded))
/// }
/// ```
public struct DiskWriteAsyncAction: AsyncAction {
  static let defaultDispatchQueue = DispatchQueue(label: "DISK_WRITE_ASYNC_ACTION")

  private let path: String
  private let data: Data
  private let fileManager: FileManager
  private let dispatchQueue: DispatchQueue
  private let completionBlock: DiskWriteActionCompletionBlock

  /// Create a Write DiskIO AsyncAction
  ///
  /// - Parameters:
  ///   - path: path to write to disk
  ///   - data: data to write to disk
  ///   - fileManager: (optional) the file manager to use. When not passed it defaults to `FileManager.default`
  ///   - dispatchQueue: (optional) the dispatch queue to use when accessing disk. When not passed it defaults to `DispatchQueue(label: "IOMIDDLEWARE_IO_QUEUE")
  ///   - completionBlock: callback to call when data is read from disk. In this block `dispatch` is used to dispatch new actions
  /// - Returns: an async action to dispatch
  public init(path: String,
              data: Data,
              fileManager: FileManager = .default,
              dispatchQueue: DispatchQueue = defaultDispatchQueue,
              completionBlock: @escaping DiskWriteActionCompletionBlock) {

    self.path = path
    self.data = data
    self.fileManager = fileManager
    self.dispatchQueue = dispatchQueue
    self.completionBlock = completionBlock
  }

  public func execute(getState: @escaping GetStateFunction, dispatch: @escaping DispatchFunction) {
    // Perform action on a background thread
    dispatchQueue.async {
      
      // When data is written call the block
      let result = self.fileManager.createFile(atPath: self.path, contents: self.data, attributes: nil)
      self.completionBlock(result, dispatch)
    }
  }
}