Added option te delete chapter after reading.

Go to Setting > Downloads to toggle: default = false.

app/src/main/java/eu/kanade/tachiyomi/data/preference/PreferencesHelper.java

@@ -185,6 +185,14 @@ public class PreferencesHelper {
         return prefs.getBoolean(getKey(R.string.pref_download_only_over_wifi_key), true);
     }
 
+    /**
+     * Returns preference of deletion after reading chapter
+     * @return preference of deletion
+     */
+    public boolean deleteChapterAfterReading() {
+        return prefs.getBoolean(getKey(R.string.pref_delete_after_reading_key), false);
+    }
+
     public static int getLibraryUpdateInterval(Context context) {
         return PreferenceManager.getDefaultSharedPreferences(context).getInt(
                 context.getString(R.string.pref_library_update_interval_key), 0);

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderPresenter.java

@@ -80,7 +80,8 @@ public class ReaderPresenter extends BasePresenter<ReaderActivity> {
                 (view, pair) -> view.onAdjacentChapters(pair.first, pair.second));
 
         startable(PRELOAD_NEXT_CHAPTER, this::getPreloadNextChapterObservable,
-            next -> {},
+                next -> {
+                },
                 error -> Timber.e("Error preloading chapter"));
 
 
@@ -316,6 +317,16 @@ public class ReaderPresenter extends BasePresenter<ReaderActivity> {
         // Save current progress of the chapter. Mark as read if the chapter is finished
         if (activePage.isLastPage()) {
             activeChapter.read = true;
+
+            // Check if user want to delete manga after reading it.
+            if (prefs.deleteChapterAfterReading()) {
+                // Check if the chapter is downloaded.
+                if (activeChapter.isDownloaded()) {
+                    // Delete chapter.
+                    Observable<Chapter> chapterObservable = Observable.just(activeChapter);
+                    onDelete(chapterObservable, manga);
+                }
+            }
         }
         db.insertChapter(activeChapter).asRxObservable().subscribe();
     }
@@ -399,6 +410,55 @@ public class ReaderPresenter extends BasePresenter<ReaderActivity> {
         }
     }
 
+    /**
+     * Start deleting chapter
+     *
+     * @param chapters selected chapters
+     * @param manga    manga that belongs to chapter
+     * @return success of deletion.
+     */
+    protected boolean onDelete(Observable<Chapter> chapters, Manga manga) {
+        Observable<Chapter> observable = chapters
+                .concatMap(chapter -> {
+                    deleteChapter(chapter, manga);
+                    return Observable.just(chapter);
+                })
+                .subscribeOn(Schedulers.io())
+                .observeOn(AndroidSchedulers.mainThread())
+                .doOnNext(chapter -> {
+                    chapter.status = Download.NOT_DOWNLOADED;
+                });
+
+        deleteChapters(observable);
+
+        return true;
+    }
+
+    /**
+     * Delete selected chapter
+     *
+     * @param chapter chapter that is selected
+     * @param manga   manga that belongs to chapter
+     */
+    public void deleteChapter(Chapter chapter, Manga manga) {
+        Source source = sourceManager.get(manga.source);
+        downloadManager.deleteChapter(source, manga, chapter);
+    }
+
+    /**
+     * Delete selected chapter observable
+     *
+     * @param selectedChapters chapter that are selected
+     */
+    public void deleteChapters(Observable<Chapter> selectedChapters) {
+        add(selectedChapters
+                .subscribe(chapter -> {
+                    downloadManager.getQueue().remove(chapter);
+                }, error -> {
+                    Timber.e(error.getMessage());
+                }));
+    }
+
     public void updateMangaViewer(int viewer) {
         manga.viewer = viewer;
         db.insertManga(manga).executeAsBlocking();

app/src/main/res/values/keys.xml

@@ -32,6 +32,7 @@
     <string name="pref_download_directory_key">pref_download_directory_key</string>
     <string name="pref_download_slots_key">pref_download_slots_key</string>
     <string name="pref_download_only_over_wifi_key">pref_download_only_over_wifi_key</string>
+    <string name="pref_delete_after_reading_key">pref_delete_after_reading_key</string>
 
     <string name="pref_clear_chapter_cache_key">pref_clear_chapter_cache_key</string>
     <string name="pref_clear_database_key">pref_clear_database_key</string>

app/src/main/res/values/strings.xml

@@ -123,6 +123,7 @@
     <string name="pref_download_directory">Downloads directory</string>
     <string name="pref_download_slots">Simultaneous downloads</string>
     <string name="pref_download_only_over_wifi">Only download over Wi-Fi</string>
+    <string name="pref_delete_after_reading">Delete chapter after reading</string>
 
       <!-- Advanced section -->
     <string name="pref_clear_chapter_cache">Clear chapter cache</string>

app/src/main/res/xml/pref_downloads.xml

@@ -10,6 +10,10 @@
         android:key="@string/pref_download_only_over_wifi_key"
         android:defaultValue="true"/>
 
+    <SwitchPreference android:title="@string/pref_delete_after_reading"
+                      android:key="@string/pref_delete_after_reading_key"
+                      android:defaultValue="false" />
+
     <eu.kanade.tachiyomi.widget.preference.IntListPreference
         android:title="@string/pref_download_slots"
         android:key="@string/pref_download_slots_key"