Background HTTP fetcher and JSON parser example. (#2177)

samples/objc/src/main/kotlin/Window.kt

@@ -1,9 +1,27 @@
-import kotlin.native.concurrent.*
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
 import kotlinx.cinterop.*
 import platform.AppKit.*
 import platform.Foundation.*
-import platform.darwin.*
-import platform.posix.*
+import platform.darwin.NSObject
+import platform.darwin.dispatch_async_f
+import kotlin.native.concurrent.DetachedObjectGraph
+import kotlin.native.concurrent.attach
+import kotlin.native.concurrent.freeze
+
+inline fun <reified T> executeAsync(queue: NSOperationQueue, crossinline producerConsumer: () -> Pair<T, (T) -> Unit>) {
+    dispatch_async_f(queue.underlyingQueue, DetachedObjectGraph {
+        producerConsumer()
+    }.asCPointer(), staticCFunction { it ->
+        val result = DetachedObjectGraph<Pair<T, (T) -> Unit>>(it).attach()
+        result.second(result.first)
+    })
+}
+
+data class QueryResult(val json: Map<String, *>?, val error: String?)
 
 fun main(args: Array<String>) {
     autoreleasepool {
@@ -11,53 +29,97 @@ fun main(args: Array<String>) {
     }
 }
 
+val appDelegate = MyAppDelegate()
+
 private fun runApp() {
     val app = NSApplication.sharedApplication()
 
-    app.delegate = MyAppDelegate()
+    app.delegate = appDelegate
     app.setActivationPolicy(NSApplicationActivationPolicy.NSApplicationActivationPolicyRegular)
     app.activateIgnoringOtherApps(true)
 
     app.run()
 }
 
-data class Data(val stamp: ULong)
-
-private class Controller : NSObject() {
-    private val asyncQueue = dispatch_queue_create("com.jetbrains.CustomQueue", null)
+class Controller : NSObject() {
+    private var index = 1
+    private var httpDelegate = HttpDelegate()
 
     @ObjCAction
     fun onClick() {
-        // Execute some async action on button click.
-        dispatch_async_f(asyncQueue, DetachedObjectGraph {
-            Data(clock_gettime_nsec_np(CLOCK_REALTIME))
-        }.asCPointer(), staticCFunction {
-                it ->
-            initRuntimeIfNeeded()
-            val data = DetachedObjectGraph<Data>(it).attach()
-            println("in async: $data")
-        })
+        if (!appDelegate.canClick) {
+            appDelegate.contentText.string = "Another load in progress..."
+            return
+        }
+        appDelegate.canClick = false
+        // Fetch URL in the background on the button click.
+        httpDelegate.fetchUrl("https://jsonplaceholder.typicode.com/todos/${index++}")
     }
 
     @ObjCAction
     fun onQuit() {
         NSApplication.sharedApplication().stop(this)
     }
+
+    class HttpDelegate: NSObject(), NSURLSessionDataDelegateProtocol {
+        private val asyncQueue = NSOperationQueue()
+        internal val receivedData = NSMutableData()
+
+        init {
+            freeze()
+        }
+
+        fun fetchUrl(url: String) {
+            receivedData.setLength(0)
+            val session = NSURLSession.sessionWithConfiguration(
+                    NSURLSessionConfiguration.defaultSessionConfiguration(),
+                    this,
+                    delegateQueue = asyncQueue
+            )
+            session.dataTaskWithURL(NSURL(string = url)).resume()
+        }
+
+        override fun URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveData: NSData) {
+            initRuntimeIfNeeded()
+            receivedData.appendData(didReceiveData)
+        }
+
+        override fun URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError: NSError?) {
+            initRuntimeIfNeeded()
+
+            executeAsync(NSOperationQueue.mainQueue) {
+                val response = task.response as? NSHTTPURLResponse
+                Pair(when {
+                    response == null -> QueryResult(null, didCompleteWithError?.localizedDescription)
+                    response.statusCode.toInt() != 200 -> QueryResult(null, "${response.statusCode.toInt()})")
+                    else -> QueryResult(
+                            NSJSONSerialization.JSONObjectWithData(receivedData, 0, null) as? Map<String, *>,
+                            null
+                    )
+                }, { result: QueryResult ->
+                    appDelegate.contentText.string = result.json?.toString() ?: "Error: ${result.error}"
+                    appDelegate.canClick = true
+                })
+            }
+        }
+    }
 }
 
-private class MyAppDelegate() : NSObject(), NSApplicationDelegateProtocol {
+class MyAppDelegate() : NSObject(), NSApplicationDelegateProtocol {
 
     private val window: NSWindow
     private val controller = Controller()
+    val contentText: NSText
+    var canClick = true
 
     init {
         val mainDisplayRect = NSScreen.mainScreen()!!.frame
         val windowRect = mainDisplayRect.useContents {
             NSMakeRect(
-                origin.x + size.width * 0.25,
-                origin.y + size.height * 0.25,
-                size.width * 0.5,
-                size.height * 0.5
+                    origin.x + size.width * 0.25,
+                    origin.y + size.height * 0.25,
+                    size.width * 0.5,
+                    size.height * 0.5
             )
 
         }
@@ -66,7 +128,7 @@ private class MyAppDelegate() : NSObject(), NSApplicationDelegateProtocol {
                 NSWindowStyleMaskClosable or NSWindowStyleMaskResizable
 
         window = NSWindow(windowRect, windowStyle, NSBackingStoreBuffered, false).apply {
-            title = "Окошко Konan"
+            title = "URL async fetcher"
             opaque = true
             hasShadow = true
             preferredBackingLocation = NSWindowBackingLocationVideoMemory
@@ -83,7 +145,7 @@ private class MyAppDelegate() : NSObject(), NSApplicationDelegateProtocol {
         }
 
         val buttonPress = NSButton(NSMakeRect(10.0, 10.0, 100.0, 40.0)).apply {
-            title = "Press me"
+            title = "Click"
             target = controller
             action = NSSelectorFromString("onClick")
         }
@@ -94,11 +156,16 @@ private class MyAppDelegate() : NSObject(), NSApplicationDelegateProtocol {
             action = NSSelectorFromString("onQuit")
         }
         window.contentView!!.addSubview(buttonQuit)
+        contentText = NSText(NSMakeRect(10.0, 80.0, 600.0, 350.0)).apply {
+            string = "Press 'Click' to start fetching"
+            verticallyResizable = false
+            horizontallyResizable = false
 
+        }
+        window.contentView!!.addSubview(contentText)
     }
 
     override fun applicationWillFinishLaunching(notification: NSNotification) {
         window.makeKeyAndOrderFront(this)
     }
 }
-