convert CopyTask to kotlin

app/src/main/java/com/simplemobiletools/filemanager/asynctasks/CopyTask.kt

@@ -0,0 +1,83 @@
+package com.simplemobiletools.filemanager.asynctasks
+
+import android.os.AsyncTask
+import android.support.v4.util.Pair
+import android.util.Log
+import java.io.File
+import java.io.FileInputStream
+import java.io.FileOutputStream
+import java.io.IOException
+import java.lang.ref.WeakReference
+
+class CopyTask(listener: CopyTask.CopyListener) : AsyncTask<Pair<List<File>, File>, Void, Boolean>() {
+    private val TAG = CopyTask::class.java.simpleName
+    private var mListener: WeakReference<CopyListener>? = null
+    private var destinationDir: File? = null
+
+    init {
+        mListener = WeakReference(listener)
+    }
+
+    override fun doInBackground(vararg params: Pair<List<File>, File>): Boolean? {
+        val pair = params[0]
+        val files = pair.first
+        for (file in files) {
+            try {
+                destinationDir = File(pair.second, file.name)
+                copy(file, destinationDir!!)
+                return true
+            } catch (e: Exception) {
+                Log.e(TAG, "copy " + e)
+            }
+
+        }
+        return false
+    }
+
+    @Throws(Exception::class)
+    private fun copy(source: File, destination: File) {
+        if (source.isDirectory) {
+            if (!destination.exists() && !destination.mkdirs()) {
+                throw IOException("Could not create dir " + destination.absolutePath)
+            }
+
+            val children = source.list()
+            for (child in children) {
+                copy(File(source, child), File(destination, child))
+            }
+        } else {
+            val directory = destination.parentFile
+            if (!directory.exists() && !directory.mkdirs()) {
+                throw IOException("Could not create dir " + directory.absolutePath)
+            }
+
+            val inputStream = FileInputStream(source)
+            val out = FileOutputStream(destination)
+
+            val buf = ByteArray(1024)
+            var len: Int
+            while (true) {
+                len = inputStream.read(buf)
+                if (len <= 0)
+                    break
+                out.write(buf, 0, len)
+            }
+        }
+    }
+
+    override fun onPostExecute(success: Boolean) {
+        val listener = mListener?.get() ?: return
+
+        if (success) {
+            listener.copySucceeded(destinationDir!!)
+        } else {
+            listener.copyFailed()
+        }
+    }
+
+    interface CopyListener {
+        fun copySucceeded(destinationDir: File)
+
+        fun copyFailed()
+    }
+}