Made YT proxyable

* allows usage of YouTubeLike services, e.g. invidious
* simplified some classes/code
* Added support for invidious
  * Some credits go to @B0pol's PR #555 for that ;)

Author: litetex

extractor/src/main/java/org/schabi/newpipe/extractor/InstanceBasedStreamingService.java

@@ -0,0 +1,9 @@
+package org.schabi.newpipe.extractor;
+
+import org.schabi.newpipe.extractor.instance.Instance;
+
+public interface InstanceBasedStreamingService<I extends Instance> {
+    I getInstance();
+
+    void setInstance(I instance);
+}

extractor/src/main/java/org/schabi/newpipe/extractor/ServiceList.java

@@ -31,7 +31,7 @@
 /**
  * A list of supported services.
  */
-@SuppressWarnings({"ConstantName", "InnerAssignment"}) // keep unusual names and inner assignments
+// keep unusual names and inner assignments
 public final class ServiceList {
     private ServiceList() {
         //no instance

extractor/src/main/java/org/schabi/newpipe/extractor/StreamingService.java

@@ -23,10 +23,11 @@
 import org.schabi.newpipe.extractor.suggestion.SuggestionExtractor;
 import org.schabi.newpipe.extractor.utils.Utils;
 
-import javax.annotation.Nullable;
 import java.util.Collections;
 import java.util.List;
 
+import javax.annotation.Nullable;
+
 /*
  * Copyright (C) Christian Schabesberger 2018 <[email protected]>
  * StreamingService.java is part of NewPipe.
@@ -97,13 +98,14 @@ public enum LinkType {
      * If you Implement one do not set id within your implementation of this extractor, instead
      * set the id when you put the extractor into {@link ServiceList}
      * All other parameters can be set directly from the overriding constructor.
-     * @param id the number of the service to identify him within the NewPipe frontend
-     * @param name the name of the service
+     *
+     * @param id           the number of the service to identify him within the NewPipe frontend
+     * @param name         the name of the service
      * @param capabilities the type of media this service can handle
      */
-    public StreamingService(final int id,
-                            final String name,
-                            final List<ServiceInfo.MediaCapability> capabilities) {
+    protected StreamingService(final int id,
+                               final String name,
+                               final List<ServiceInfo.MediaCapability> capabilities) {
         this.serviceId = id;
         this.serviceInfo = new ServiceInfo(name, capabilities);
     }
@@ -192,9 +194,10 @@ public FeedExtractor getFeedExtractor(final String url) throws ExtractionExcepti
 
     /**
      * Must create a new instance of a KioskList implementation.
+     *
      * @return a new KioskList instance
      */
-    public abstract KioskList getKioskList() throws ExtractionException;
+    public abstract KioskList getKioskList();
 
     /**
      * Must create a new instance of a ChannelExtractor implementation.

extractor/src/main/java/org/schabi/newpipe/extractor/channel/ChannelExtractor.java

@@ -35,13 +35,29 @@ public ChannelExtractor(final StreamingService service, final ListLinkHandler li
     }
 
     public abstract String getAvatarUrl() throws ParsingException;
+
     public abstract String getBannerUrl() throws ParsingException;
+
     public abstract String getFeedUrl() throws ParsingException;
+
     public abstract long getSubscriberCount() throws ParsingException;
+
     public abstract String getDescription() throws ParsingException;
-    public abstract String getParentChannelName() throws ParsingException;
-    public abstract String getParentChannelUrl() throws ParsingException;
-    public abstract String getParentChannelAvatarUrl() throws ParsingException;
-    public abstract boolean isVerified() throws ParsingException;
+
+    public String getParentChannelName() throws ParsingException {
+        return null;
+    }
+
+    public String getParentChannelUrl() throws ParsingException {
+        return null;
+    }
+
+    public String getParentChannelAvatarUrl() throws ParsingException {
+        return null;
+    }
+
+    public boolean isVerified() throws ParsingException {
+        return false;
+    }
 
 }

extractor/src/main/java/org/schabi/newpipe/extractor/channel/ChannelInfoItemExtractor.java

@@ -30,5 +30,7 @@ public interface ChannelInfoItemExtractor extends InfoItemExtractor {
 
     long getStreamCount() throws ParsingException;
 
-    boolean isVerified() throws ParsingException;
+    default boolean isVerified() throws ParsingException {
+        return false;
+    }
 }

extractor/src/main/java/org/schabi/newpipe/extractor/comments/CommentsInfoItemExtractor.java

@@ -4,7 +4,7 @@
 import org.schabi.newpipe.extractor.Page;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
 import org.schabi.newpipe.extractor.localization.DateWrapper;
-import org.schabi.newpipe.extractor.services.youtube.extractors.YoutubeCommentsInfoItemExtractor;
+import org.schabi.newpipe.extractor.services.youtube.youtube.extractors.YoutubeCommentsInfoItemExtractor;
 import org.schabi.newpipe.extractor.stream.StreamExtractor;
 import org.schabi.newpipe.extractor.utils.Utils;
 

extractor/src/main/java/org/schabi/newpipe/extractor/instance/AbstractInstance.java

@@ -0,0 +1,55 @@
+package org.schabi.newpipe.extractor.instance;
+
+import org.schabi.newpipe.extractor.utils.Utils;
+
+import java.net.URI;
+import java.util.Objects;
+
+import javax.annotation.Nonnull;
+
+public abstract class AbstractInstance implements Instance {
+
+    protected Boolean valid = null;
+
+    protected final String url;
+    protected String name;
+
+    protected AbstractInstance(final String url, final String name) {
+        this.url = removeTrailingSlashes(Objects.requireNonNull(url));
+        this.name = name;
+    }
+
+    @Nonnull
+    @Override
+    public String getName() {
+        return name;
+    }
+
+    @Nonnull
+    @Override
+    public String getUrl() {
+        return url;
+    }
+
+    public void setName(final String name) {
+        this.name = Objects.requireNonNull(name);
+    }
+
+    @Override
+    public void fetchMetadata() {
+        // Default: Do nothing
+    }
+
+    public static String removeTrailingSlashes(final String input) {
+        return input.replaceAll("/*$", "");
+    }
+
+    public static String tryExtractDomainFromUrl(final String url, final String fallback) {
+        Objects.requireNonNull(url);
+        try {
+            return Utils.removeMAndWWWFromHost(new URI(url).getHost());
+        } catch (final Exception ignored) {
+            return fallback;
+        }
+    }
+}

extractor/src/main/java/org/schabi/newpipe/extractor/instance/Instance.java

@@ -0,0 +1,46 @@
+package org.schabi.newpipe.extractor.instance;
+
+import javax.annotation.Nonnull;
+
+public interface Instance {
+
+    /**
+     * The name of the instance.
+     * <br/>
+     * Note: May only be available after {@link #fetchMetadata()} was called
+     *
+     * @return the instance-name
+     */
+    String getName();
+
+    /**
+     * The base url of this instance.
+     * <br/>
+     * Note that the url is returned without trailing slashes.
+     * Use {@link #getUrlWithTrailingSlash()} if you want a trailing slash.
+     *
+     * @return base url
+     */
+    @Nonnull
+    String getUrl();
+
+    default String getUrlWithTrailingSlash() {
+        return getUrl() + "/";
+    }
+
+
+    /**
+     * Fetch instance metadata.
+     *
+     * @throws InstanceMetaDataFetchException
+     */
+    void fetchMetadata();
+
+    /**
+     * Returns the service name, e.g. "Invidious" for an invidious instance.
+     * @return service name or <code>null</code> if the name of the streamingservice should be used
+     */
+    default String getServiceName() {
+        return null;
+    }
+}

extractor/src/main/java/org/schabi/newpipe/extractor/instance/InstanceMetaDataFetchException.java

@@ -0,0 +1,15 @@
+package org.schabi.newpipe.extractor.instance;
+
+public class InstanceMetaDataFetchException extends RuntimeException {
+    public InstanceMetaDataFetchException(final String message) {
+        super(message);
+    }
+
+    public InstanceMetaDataFetchException(final String message, final Throwable cause) {
+        super(message, cause);
+    }
+
+    public InstanceMetaDataFetchException(final Throwable cause) {
+        super(cause);
+    }
+}

extractor/src/main/java/org/schabi/newpipe/extractor/kiosk/KioskList.java

@@ -50,10 +50,9 @@ public KioskList(final StreamingService service) {
 
     public void addKioskEntry(final KioskExtractorFactory extractorFactory,
                               final ListLinkHandlerFactory handlerFactory,
-                              final String id)
-            throws Exception {
+                              final String id) {
         if (kioskList.get(id) != null) {
-            throw new Exception("Kiosk with type " + id + " already exists.");
+            throw new IllegalArgumentException("Kiosk with type " + id + " already exists.");
         }
         kioskList.put(id, new KioskEntry(extractorFactory, handlerFactory));
     }