From 6029dd30607b98b2c01466dee7f6e530bc949cad Mon Sep 17 00:00:00 2001
From: Zane Shannon <z@zcs.me>
Date: Wed, 1 Aug 2018 12:55:32 -0700
Subject: [PATCH 1/4] added TaskQueueStatus struct. added collection of
 callbacks. added execution of callbacks following each task execution.

---
 Sources/TaskQueue.swift | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Sources/TaskQueue.swift b/Sources/TaskQueue.swift
index 93d969c..34e606d 100644
--- a/Sources/TaskQueue.swift
+++ b/Sources/TaskQueue.swift
@@ -14,6 +14,13 @@
 
 import Foundation
 
+public struct TaskQueueStatus {
+  var activeTaskCount: Int
+  var maximumActiveTaskCount: Int
+  var queuedTaskCount: Int
+  var running: Bool
+}
+
 // MARK: TaskQueue class
 
 open class TaskQueue: CustomStringConvertible {
@@ -23,12 +30,14 @@ open class TaskQueue: CustomStringConvertible {
     //
     public typealias ClosureNoResultNext = () -> Void
     public typealias ClosureWithResultNext = (Any? , @escaping (Any?) -> Void) -> Void
+    public typealias ClosureWithTaskQueueStatus = (TaskQueueStatus) -> Void
 
     //
     // tasks and completions storage
     //
     open var tasks = [ClosureWithResultNext]()
     open lazy var completions = [ClosureNoResultNext]()
+    open var callbacks = [ClosureWithTaskQueueStatus]()
 
     //
     // concurrency
@@ -126,6 +135,13 @@ open class TaskQueue: CustomStringConvertible {
                 self.numberOfActiveTasks -= 1
                 self._runNextTask(nextResult)
             }
+          self.callbacks.forEach({ (callback) in
+            callback(TaskQueueStatus(activeTaskCount: self.numberOfActiveTasks,
+                                     maximumActiveTaskCount: self.maximumNumberOfActiveTasks,
+                                     queuedTaskCount: self.tasks.count,
+                                     running: self.running)
+            )
+          })
         }
 
         if maximumNumberOfActiveTasks > 1 {

From 85ebdfab987299779a14651e509247b86e3711b6 Mon Sep 17 00:00:00 2001
From: Zane Shannon <z@zcs.me>
Date: Wed, 1 Aug 2018 13:04:33 -0700
Subject: [PATCH 2/4] document callbacks with an example.

---
 README.md | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/README.md b/README.md
index 62e6e76..c9309db 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,8 @@
 * [Serial and Concurrent Tasks](#serial-and-concurrent-tasks)
 * [GCD Queue Control](#gcd-queue-control)
 * [Extensive Example](#extensive-example)
+* [Callbacks](#callbacks)
+* [Callbacks Example](#callbacks-example)
 * [Credit](#credit)
 * [License](#license)
 
@@ -293,6 +295,48 @@ queue.run { result in
 
 Run the included demo app to see some of these examples above in action.
 
+## Callbacks
+
+You can register closures to receive status updates on the queue after each task executes.
+
+```swift
+typealias ClosureWithTaskQueueStatus = (TaskQueueStatus) -> Void
+```
+
+They will receive a status object:
+
+```swift
+struct TaskQueueStatus {
+  var activeTaskCount: Int
+  var maximumActiveTaskCount: Int
+  var queuedTaskCount: Int
+  var running: Bool
+}
+```
+
+## Callbacks example
+
+```swift
+let queue = TaskQueue()
+
+//
+// Simple sync task, just prints to console
+//
+queue.tasks += {
+    print("====== tasks ======")
+    print("task #1: run")
+}
+
+//
+// Simple callback, just prints to console
+//
+queue.callbacks.append({ (status) in
+  print("task queue status", status)
+})
+
+
+queue.run()
+```
 
 ## Credit
 

From 1230e86d590f740d869ef1ad23228c45ec7294ca Mon Sep 17 00:00:00 2001
From: Zane Shannon <z@zcs.me>
Date: Thu, 2 Aug 2018 12:16:00 -0700
Subject: [PATCH 3/4] derp, need to publicize these properties.

---
 Sources/TaskQueue.swift | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Sources/TaskQueue.swift b/Sources/TaskQueue.swift
index 34e606d..da48eb5 100644
--- a/Sources/TaskQueue.swift
+++ b/Sources/TaskQueue.swift
@@ -15,10 +15,10 @@
 import Foundation
 
 public struct TaskQueueStatus {
-  var activeTaskCount: Int
-  var maximumActiveTaskCount: Int
-  var queuedTaskCount: Int
-  var running: Bool
+  public var activeTaskCount: Int
+  public var maximumActiveTaskCount: Int
+  public var queuedTaskCount: Int
+  public var running: Bool
 }
 
 // MARK: TaskQueue class

From 39b5407953ed042637a8791c6cd9223369342c4c Mon Sep 17 00:00:00 2001
From: Zane Shannon <z@zcs.me>
Date: Thu, 2 Aug 2018 13:25:11 -0700
Subject: [PATCH 4/4] relocate callbacks.

---
 Sources/TaskQueue.swift | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/Sources/TaskQueue.swift b/Sources/TaskQueue.swift
index da48eb5..f90bdcc 100644
--- a/Sources/TaskQueue.swift
+++ b/Sources/TaskQueue.swift
@@ -134,14 +134,14 @@ open class TaskQueue: CustomStringConvertible {
             task!(self.maximumNumberOfActiveTasks > 1 ? nil : result) { nextResult in
                 self.numberOfActiveTasks -= 1
                 self._runNextTask(nextResult)
+                self.callbacks.forEach({ (callback) in
+                  callback(TaskQueueStatus(activeTaskCount: self.numberOfActiveTasks,
+                                           maximumActiveTaskCount: self.maximumNumberOfActiveTasks,
+                                           queuedTaskCount: self.tasks.count,
+                                           running: self.running)
+                  )
+                })
             }
-          self.callbacks.forEach({ (callback) in
-            callback(TaskQueueStatus(activeTaskCount: self.numberOfActiveTasks,
-                                     maximumActiveTaskCount: self.maximumNumberOfActiveTasks,
-                                     queuedTaskCount: self.tasks.count,
-                                     running: self.running)
-            )
-          })
         }
 
         if maximumNumberOfActiveTasks > 1 {