converted ProgressResponseBody to Kt

usecases/src/main/java/com/zeyad/usecases/network/ProgressInterceptor.kt

@@ -12,7 +12,7 @@ abstract class ProgressInterceptor(private val progressListener: ProgressListene
         val originalResponse = chain.proceed(chain.request())
         val responseBuilder = originalResponse.newBuilder()
         if (isFileIO(originalResponse)) {
-            responseBuilder.body(ProgressResponseBody(originalResponse.body(), progressListener))
+            responseBuilder.body(originalResponse.body()?.let { ProgressResponseBody(it, progressListener) })
         } else {
             responseBuilder.body(originalResponse.body())
         }

usecases/src/main/java/com/zeyad/usecases/network/ProgressResponseBody.kt

@@ -0,0 +1,44 @@
+package com.zeyad.usecases.network
+
+import okhttp3.MediaType
+import okhttp3.ResponseBody
+import okio.*
+import java.io.IOException
+
+/**
+ * @author by ZIaDo on 7/11/17.
+ */
+internal class ProgressResponseBody(private val responseBody: ResponseBody, private val progressListener: ProgressListener) : ResponseBody() {
+    private lateinit var bufferedSource: BufferedSource
+
+    override fun contentType(): MediaType? {
+        return responseBody.contentType()
+    }
+
+    override fun contentLength(): Long {
+        return responseBody.contentLength()
+    }
+
+    override fun source(): BufferedSource {
+        if (!::bufferedSource.isInitialized) {
+            bufferedSource = Okio.buffer(source(responseBody.source()))
+        }
+        return bufferedSource
+    }
+
+    private fun source(source: Source): Source {
+        return object : ForwardingSource(source) {
+            var totalBytesRead = 0L
+
+            @Throws(IOException::class)
+            override fun read(sink: Buffer, byteCount: Long): Long {
+                val bytesRead = super.read(sink, byteCount)
+                // read() returns the number of bytes read, or -1 if this source is exhausted.
+                totalBytesRead += if (bytesRead != -1L) bytesRead else 0
+                progressListener.update(totalBytesRead, responseBody.contentLength(),
+                        bytesRead == -1L)
+                return bytesRead
+            }
+        }
+    }
+}