add kiosk description

docs/03_Implement_a_service.md

@@ -1,17 +1,17 @@
 # Implement a service
 
-Services or better service connectors are the parts of NewPipe which communicative with an actual service like YouTube.
+Services or better service connectors are the parts of NewPipe which communicate with an actual service like YouTube.
 This Page will describe how you can implement and add your own to the extractor. Please make sure you read and understand the
 [Concept of Extractors](https://teamnewpipe.github.io/documentation/01_Concept_of_the_extractor/)
 and the [Concept of LinkHandler](https://teamnewpipe.github.io/documentation/02_Concept_of_LinkHandler/)
 before doing this.
 
 ### Required and optional parts
-Please be aware that your extractor has to implement certain parts, but does not have to implement all.
+Your service does not have to implement everything. Some parts are optional.
 This is because not all services support every feature other services support. For example, it might be that a certain
-service does not support channels. If so, you can leve out the implementation of channels, and make the corresponding
+service does not support channels. If so, you can leave out the implementation of channels, and make the corresponding
-factory methode of the your __StreamingService__ implementation return __null__. The forntend will then automatically
+factory methode of the your __StreamingService__ implementation return __null__. The forntend will handle the lack of
-leave out these parts.
+having channels then.
 
 However if you start to implement one of the optional parts of the list below, you have to implement all parts/classes
 of it. NewPipe will crash if you only implement the extractor for the list item of a channel, but not the channel extractor itself.
@@ -43,7 +43,9 @@ If you need to introduce new libraries please tell us before you do it.
 ### Head of Service
 
 First of all if you want to create a new service you should create a new package below `org.schabi.newpipe.services`
-, with the name of your service as package name. Here you must put an implementation of these two classes:
+, with the name of your service as package name.
+
+__Parts required to be implemented:__
 
 - [StreamingService](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/StreamingService.html)
 - [ServiceInfo](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/StreamingService.ServiceInfo.html)
@@ -67,13 +69,15 @@ So when adding your service just give it the ID of the previously last service i
 
 ### Stream
 
-Streams are considered single entities of video or audio, the come along with metainformation like a title, a description,
+Streams are considered single entities of video or audio, they come along with metainformation like a title, a description,
 next/related videos, thumbnail and commends. For getting the url to the actual stream data as well as this metainformation
 StreamExtractor is used. The LinkHandlerFactory will represent a link to such a stream. StreamInfoItemExtractor will
 extract one item in a list of items representing such Streams, like a search result or a playlist.
 Since every Streaming service (obviously) provides streams this is required to implement. Otherwise your service was
 pretty useless :)
 
+__Parts required to be implemented:__
+
 - [StreamExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/stream/StreamExtractor.html)
 - [StreamInfoItemExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/stream/StreamInfoItemExtractor.html)
 - [LinkHandlerFactory](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/linkhandler/LinkHandlerFactory.html)
@@ -83,13 +87,17 @@ The SearchExtractor is also required to be implemented. It will take a search qu
 and return a list of search results. Since many services support a suggestion popup while you type you will also want to implement
 a __SuggestionExtractor__. This will make it possible for the frontend to as well display a suggestion while typing.
 
+__Parts required to be implemented:__
+
 - [SearchExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/search/SearchExtractor.html)
 - [SearchQueryHandlerFactory](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/linkhandler/SearchQueryHandlerFactory.html)
 - [SuggestionExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/SuggestionExtractor.html) _(optional)_
 
 ### Playlist
 Playlists are lists of streams provided by the service (you may not have to take care about locally saved playlists. This will be handled by the frontend).
-A playlist may only contains __StreamItems__, but no other __InfoItem__ types.
+A playlist may only contains __StreamInfoItems__, but no other __InfoItem__ types.
+
+__Parts required to be implemented:__
 
 - [PlaylistExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/playlist/PlaylistExtractor.html)
 - [PlayListInfoItemExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/playlist/PlaylistExtractor.html)
@@ -100,11 +108,59 @@ A Channel is mostly a [Playlist](#playlist), the only diferens is that it does n
 user, a channel, or any entity that could be represented as a user. This is why the metadata supported by the channel extractor
 differs form the one of a playlist.
 
+__Parts required to be implemented:__
+
 - [ChannelExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/channel/ChannelExtractor.html)
 - [ChannelInfoItemExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/channel/ChannelExtractor.html)
 - [ListLinkHandlerFactory](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/linkhandler/ListLinkHandlerFactory.html)
 
 ### Kiosk
-- [KioskExtractorFactory](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/kiosk/KioskList.KioskExtractorFactory.html)
+A kiosk is a list of __InfoItems__ which will be displayed on the main page of NewPipe. A kiosk is mostly similar to the content
+displayed on the main page of a video platform. A kiosk could be something like "Top 20", "Charts", "News", "Creators selection" etc.
+Kiosk are controversial, many people may not like them. If you don't like them as well please don't refuse to add them thought.
+Your service would look pretty empty if you select it and no video is being displayed. Also you should not override the preference of the user,
+since users of NewPipe can decide by the settings weather they want to see the kiosk page or not.
+
+#### Multiple Kiosks
+Most services will implement more than one Kiosk, so a service might have a "Top 20" for different categories like "Country Music", "Techno" ets.
+This is why the extractor will let you implement multiple __KioskExtractors__. Since different kiosk pages might also differ 
+with their HTML structure every page you want to support has to be implemented as its own __KioskExtractor__.
+However if the pages are similar you can use the same Implementation, but set the page type when you instantiate your __KioskExtractor__
+through the __KioskList.KioskExtractorFactory__.
+
+Every Kiosk you implement needs to be added to your __KioskList__ which you return with your
+__StreamingService__ implementation.
+
+It is also important to set the default kiosk. This will be the kiosk that will be shown by the first start of your service.
+
+An example implementation of the
+[getKioskList()](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/StreamingService.html)
+could look like this:
+```java
+@Override
+public KioskList getKioskList() throws ExtractionException {
+    KioskList list = new KioskList(getServiceId());
+
+    list.addKioskEntry(new KioskList.KioskExtractorFactory() {
+        @Override
+        public KioskExtractor createNewKiosk(StreamingService streamingService,
+                                             String url,
+                                             String id,
+                                             Localization local)
+        throws ExtractionException {
+            return new YoutubeTrendingExtractor(YoutubeService.this,
+                    new YoutubeTrendingLinkHandlerFactory().fromUrl(url), id, local);
+        }
+    }, new YoutubeTrendingLinkHandlerFactory(), "Trending");
+
+    list.setDefaultKiosk("Trending");
+    return list;
+}
+
+```
+
+__Parts required to be implemented:__
+
+- [KioskList.KioskExtractorFactory](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/kiosk/KioskList.KioskExtractorFactory.html)
 - [KioskExtractor](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/kiosk/KioskExtractor.html)
 - [ListLinkHandlerFactory](https://teamnewpipe.github.io/NewPipeExtractor/javadoc/org/schabi/newpipe/extractor/linkhandler/ListLinkHandlerFactory.html)