pipe Process (NSTask) in swift

ProcessPipe.swift

//
//  ProcessPipe.swift
//
//  Created by Eldon on 8/10/18.
//  Copyright © 2018 Big Club Digital. All rights reserved.
//  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

/**
 ## Pipeable Process
 
 ### Usage Examples:
 
 #### Example 1
 
 ```
 let ls = Process("/bin/ls", ["-al"])
 let grep = Process("/usr/bin/grep", ["com"])
 let cut = Process("/usr/bin/awk", ["{print $3}"])
 
 ls.pipe(grep).pipe(cut).complete {
    message, status in
    print("P1 \(message) \(status)")
 }
 ls.launch()
 ```
 
 #### Example 2, the | infix operator (Very Shell)
 
 ```
 let ls = Process("/bin/ls", ["-al"])
 let grep = Process("/usr/bin/grep", ["com"])
 let cut = Process("/usr/bin/awk", ["{print $1}"])
 
 ls | grep | cut.complete {
     message, status in
     print("P2 \(message) \(status)")
 }
 ls.launch()
 ```
 */


import Foundation

public typealias PipeProcessTerminationHandler = ((_ out: String, _ status: OSStatus) -> Void)
typealias ProcessTerminationHandler = ((_ process: Process) -> Void)

protocol Pipeable {
    func pipe(_ process: Self, _ complete:PipeProcessTerminationHandler) -> Self
}


infix operator |

/// Shorthand For Piping one process to another, very shell
///
/// - Parameters:
///   - left: One Process
///   - right: The Other Process
/// - Returns: The Other Process (To Further chain)
func | ( left: Process, right: Process) -> Process {
    return left.pipe(right)
}


// MARK: - Process Extension For Piping
public extension Process {
    
    
    /// Initalize a process with the command and some args
    ///
    /// - Parameters:
    ///   - launchPath: Sets the receiver’s executable.
    ///   - arguments: Sets the command arguments that should be used to launch the executable.
    convenience init(_ launchPath: String, _ arguments: [String]?=nil) {
        self.init()
        self.launchPath = launchPath
        self.arguments = arguments
    }
    
    
    /// Handler for converting the pipable processs termination handler to one that returns the text
    ///
    /// - Parameter complete: ((_ process: Process) -> Void)
    /// - Returns: ((_ out: String, _ status: OSStatus) -> Void)
    internal func pipeTerminationAdapter( _ complete: PipeProcessTerminationHandler?)->ProcessTerminationHandler {
        return {
            task in
            guard
                let data = (task.standardOutput as? Pipe)?.fileHandleForReading.availableData,
                let string = String(data: data, encoding: .utf8)
            else {
                complete?("", task.terminationStatus)
                return
            }
            complete?(string, task.terminationStatus)
        }
    }
    
    
    /// Called When The Pipeable task finishes
    ///
    /// - Parameter complete: ((_ out: String, _ status: OSStatus) -> Void)
    /// - Returns: Self
    func complete( _ complete:@escaping PipeProcessTerminationHandler) -> Process {
        self.terminationHandler = pipeTerminationAdapter(complete)
        return self
    }
    
    
    /// Create a process pipe
    ///
    /// - Parameters:
    ///   - launchPath: Sets the receiver’s executable.
    ///   - arguments: Sets the command arguments that should be used to launch the executable.
    ///   - complete: ((_ process: Process) -> Void) called when the chained process completes _NOTE: this should only be on the final process in the pipe_
    /// - Returns: The chained process
    func pipe(_ launchPath: String, _ arguments: [String]?=nil, _ complete:PipeProcessTerminationHandler?=nil) -> Process {
        let process = Process(launchPath, arguments)
        return self.pipe(process, complete)
    }
    
    
    /// Create a process pipe
    ///
    /// - Parameters:
    ///   - process: Process the process to chain
    ///   - complete: ((_ process: Process) -> Void) called when the chained process completes _NOTE: this should only be on the final process in the pipe_
    /// - Returns: the process to chain
    func pipe(_ process: Process, _ complete:PipeProcessTerminationHandler?=nil) -> Process {
        let command = Pipe()
        let target = Pipe()
        
        self.standardOutput = command
        process.standardInput = command
        process.standardOutput = target
        
        self.terminationHandler = {
            _ in
            process.launch()
        }
        
        if let _ = complete {
            process.terminationHandler = self.pipeTerminationAdapter(complete)
        }

        return process
    }
}

Good job. Thank you.