Add support for duplicate links

Support duplicate links [1] to handle better temporarily unavailable
mirrors.

[1] https://tools.ietf.org/html/rfc6249

Change-Id: If78fb4a90da68ef221294eed2c59063a14cf1f43

src/org/lineageos/updater/controller/UpdaterController.java

@@ -375,6 +375,7 @@ public class UpdaterController implements Controller {
                     .setDestination(update.getFile())
                     .setDownloadCallback(getDownloadCallback(downloadId))
                     .setProgressListener(getProgressListener(downloadId))
+                    .setUseDuplicateLinks(true)
                     .build();
         } catch (IOException exception) {
             Log.e(TAG, "Could not build download client");
@@ -417,6 +418,7 @@ public class UpdaterController implements Controller {
                         .setDestination(update.getFile())
                         .setDownloadCallback(getDownloadCallback(downloadId))
                         .setProgressListener(getProgressListener(downloadId))
+                        .setUseDuplicateLinks(true)
                         .build();
             } catch (IOException exception) {
                 Log.e(TAG, "Could not build download client");

src/org/lineageos/updater/download/DownloadClient.java

@@ -63,6 +63,7 @@ public interface DownloadClient {
         private File mDestination;
         private DownloadClient.DownloadCallback mCallback;
         private DownloadClient.ProgressListener mProgressListener;
+        private boolean mUseDuplicateLinks;
 
         public DownloadClient build() throws IOException {
             if (mUrl == null) {
@@ -72,7 +73,8 @@ public interface DownloadClient {
             } else if (mCallback == null) {
                 throw new IllegalStateException("No download callback defined");
             }
-            return new HttpURLConnectionClient(mUrl, mDestination, mProgressListener, mCallback);
+            return new HttpURLConnectionClient(mUrl, mDestination, mProgressListener, mCallback,
+                    mUseDuplicateLinks);
         }
 
         public Builder setUrl(String url) {
@@ -94,5 +96,10 @@ public interface DownloadClient {
             mProgressListener = progressListener;
             return this;
         }
+
+        public Builder setUseDuplicateLinks(boolean useDuplicateLinks) {
+            mUseDuplicateLinks = useDuplicateLinks;
+            return this;
+        }
     }
 }

src/org/lineageos/updater/download/HttpURLConnectionClient.java

@@ -25,18 +25,23 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.HttpURLConnection;
 import java.net.URL;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
+import java.util.PriorityQueue;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 public class HttpURLConnectionClient implements DownloadClient {
 
     private final static String TAG = "HttpURLConnectionClient";
 
-    private final HttpURLConnection mClient;
+    private HttpURLConnection mClient;
 
     private final File mDestination;
     private final DownloadClient.ProgressListener mProgressListener;
     private final DownloadClient.DownloadCallback mCallback;
+    private final boolean mUseDuplicateLinks;
 
     private DownloadThread mDownloadThread;
 
@@ -54,11 +59,13 @@ public class HttpURLConnectionClient implements DownloadClient {
 
     HttpURLConnectionClient(String url, File destination,
             DownloadClient.ProgressListener progressListener,
-            DownloadClient.DownloadCallback callback) throws IOException {
+            DownloadClient.DownloadCallback callback,
+            boolean useDuplicateLinks) throws IOException {
         mClient = (HttpURLConnection) new URL(url).openConnection();
         mDestination = destination;
         mProgressListener = progressListener;
         mCallback = callback;
+        mUseDuplicateLinks = useDuplicateLinks;
     }
 
     @Override
@@ -113,6 +120,10 @@ public class HttpURLConnectionClient implements DownloadClient {
         return (statusCode / 100) == 2;
     }
 
+    private static boolean isRedirectCode(int statusCode) {
+        return (statusCode / 100) == 3;
+    }
+
     private static boolean isPartialContentCode(int statusCode) {
         return statusCode == 206;
     }
@@ -155,11 +166,100 @@ public class HttpURLConnectionClient implements DownloadClient {
             }
         }
 
+        private void changeClientUrl(URL newUrl) throws IOException {
+            String range = mClient.getRequestProperty("Range");
+            mClient.disconnect();
+            mClient = (HttpURLConnection) newUrl.openConnection();
+            if (range != null) {
+                mClient.setRequestProperty("Range", range);
+            }
+        }
+
+        private void handleDuplicateLinks() throws IOException {
+            String protocol = mClient.getURL().getProtocol();
+
+            class DuplicateLink {
+                private String mUrl;
+                private int mPriority;
+                private DuplicateLink(String url, int priority) {
+                    mUrl = url;
+                    mPriority = priority;
+                }
+            }
+
+            PriorityQueue<DuplicateLink> duplicates = null;
+
+            for (Map.Entry<String, List<String>> entry : mClient.getHeaderFields().entrySet()) {
+                if ("Link".equalsIgnoreCase((entry.getKey()))) {
+                    duplicates = new PriorityQueue<>(entry.getValue().size(),
+                            new Comparator<DuplicateLink>() {
+                                @Override
+                                public int compare(DuplicateLink d1, DuplicateLink d2) {
+                                    return Integer.compare(d1.mPriority, d2.mPriority);
+                                }
+                            });
+
+                    // https://tools.ietf.org/html/rfc6249
+                    // https://tools.ietf.org/html/rfc5988#section-5
+                    String regex = "(?i)<(.+)>\\s*;\\s*rel=duplicate(?:.*pri=([0-9]+).*|.*)?";
+                    Pattern pattern = Pattern.compile(regex);
+                    for (String field : entry.getValue()) {
+                        Matcher matcher = pattern.matcher(field);
+                        if (matcher.matches()) {
+                            String url = matcher.group(1);
+                            String pri = matcher.group(2);
+                            int priority = pri != null ? Integer.parseInt(pri) : 999999;
+                            duplicates.add(new DuplicateLink(url, priority));
+                            Log.d(TAG, "Adding duplicate link " + url);
+                        } else {
+                            Log.d(TAG, "Ignoring link " + field);
+                        }
+                    }
+                }
+            }
+
+            String newUrl = mClient.getHeaderField("Location");
+            for (;;) {
+                try {
+                    URL url = new URL(newUrl);
+                    if (!url.getProtocol().equals(protocol)) {
+                        // If we hadn't handled duplicate links, we wouldn't have
+                        // used this url.
+                        throw new IOException("Protocol changes are not allowed");
+                    }
+                    Log.d(TAG, "Downloading from " + newUrl);
+                    changeClientUrl(url);
+                    mClient.setConnectTimeout(5000);
+                    mClient.connect();
+                    if (!isSuccessCode(mClient.getResponseCode())) {
+                        throw new IOException("Server replied with " + mClient.getResponseCode());
+                    }
+                    return;
+                } catch (IOException e) {
+                    if (duplicates != null && !duplicates.isEmpty()) {
+                        DuplicateLink link = duplicates.poll();
+                        duplicates.remove(link);
+                        newUrl = link.mUrl;
+                        Log.e(TAG, "Using duplicate link " + link.mUrl, e);
+                    } else {
+                        throw e;
+                    }
+                }
+            }
+        }
+
         @Override
         public void run() {
             try {
+                mClient.setInstanceFollowRedirects(!mUseDuplicateLinks);
                 mClient.connect();
                 int responseCode = mClient.getResponseCode();
+
+                if (mUseDuplicateLinks && isRedirectCode(responseCode)) {
+                    handleDuplicateLinks();
+                    responseCode = mClient.getResponseCode();
+                }
+
                 mCallback.onResponse(responseCode, mClient.getURL().toString(), new Headers());
 
                 if (mResume && isPartialContentCode(responseCode)) {