Add latest url to the response to make detection of a redirect possible

Will be latest one in this commit because there's need to check the
history of redirects as of now.

extractor/src/main/java/org/schabi/newpipe/extractor/downloader/Response.java

@@ -15,12 +15,16 @@ public class Response {
     private final Map<String, List<String>> responseHeaders;
     private final String responseBody;
 
-    public Response(int responseCode, String responseMessage, Map<String, List<String>> responseHeaders, @Nullable String responseBody) {
+    private final String latestUrl;
+
+    public Response(int responseCode, String responseMessage, Map<String, List<String>> responseHeaders,
+                    @Nullable String responseBody, @Nullable String latestUrl) {
         this.responseCode = responseCode;
         this.responseMessage = responseMessage;
         this.responseHeaders = responseHeaders != null ? responseHeaders : Collections.<String, List<String>>emptyMap();
 
         this.responseBody = responseBody == null ? "" : responseBody;
+        this.latestUrl = latestUrl;
     }
 
     public int responseCode() {
@@ -40,6 +44,16 @@ public class Response {
         return responseBody;
     }
 
+    /**
+     * Used for detecting a possible redirection, limited to the latest one.
+     *
+     * @return latest url known right before this response object was created
+     */
+    @Nonnull
+    public String latestUrl() {
+        return latestUrl;
+    }
+
     /*//////////////////////////////////////////////////////////////////////////
     // Utils
     //////////////////////////////////////////////////////////////////////////*/

extractor/src/test/java/org/schabi/newpipe/DownloaderTestImpl.java

@@ -99,8 +99,9 @@ public class DownloaderTestImpl extends Downloader {
             final int responseCode = connection.getResponseCode();
             final String responseMessage = connection.getResponseMessage();
             final Map<String, List<String>> responseHeaders = connection.getHeaderFields();
+            final String latestUrl = connection.getURL().toString();
 
-            return new Response(responseCode, responseMessage, responseHeaders, response.toString());
+            return new Response(responseCode, responseMessage, responseHeaders, response.toString(), latestUrl);
         } catch (Exception e) {
             final int responseCode = connection.getResponseCode();
 
@@ -112,7 +113,8 @@ public class DownloaderTestImpl extends Downloader {
             if (responseCode == 429) {
                 throw new ReCaptchaException("reCaptcha Challenge requested", url);
             } else if (responseCode != -1) {
-                return new Response(responseCode, connection.getResponseMessage(), connection.getHeaderFields(), null);
+                final String latestUrl = connection.getURL().toString();
+                return new Response(responseCode, connection.getResponseMessage(), connection.getHeaderFields(), null, latestUrl);
             }
 
             throw new IOException("Error occurred while fetching the content", e);