feat(doc-scan): If built-in scanning not available, check for FairScan

Built-in scanning is not available for all build variants - e.g. not for
"generic", which is the flavor for the F-Droid release. It doesn't allow
the non-reproducible TinyOpenCV build.

If this is the case, we are checking whether the open source scanning app
FairScan is available (https://github.com/pynicolas/FairScan) and open
that one for scanning.

The declaration in the AndroidManifest is required since
Android 11 (API level 30), otherwise the Intent would always be null.
See https://developer.android.com/training/package-visibility

Signed-off-by: Philipp Hasper <vcs@hasper.info>

Author: PhilLab

app/src/androidTest/java/com/owncloud/android/ui/dialog/DialogFragmentIT.kt

@@ -434,6 +434,8 @@ class DialogFragmentIT : AbstractIT() {
             override fun newPresentation() = Unit
             override fun directCameraUpload() = Unit
             override fun scanDocUpload() = Unit
+            override fun scanDocUploadFromApp() = Unit
+            override fun isScanDocUploadFromAppAvailable(): Boolean = false
             override fun showTemplate(creator: Creator?, headline: String?) = Unit
             override fun createRichWorkspace() = Unit
         }

app/src/main/AndroidManifest.xml

@@ -107,6 +107,11 @@
         <intent>
             <action android:name="android.intent.action.GET_CONTENT" />
         </intent>
+        <intent>
+            <!-- Since Android 11 (API level 30), this is required to detect the availability of FairScan to use
+             for external document scanning. See https://developer.android.com/training/package-visibility -->
+            <action android:name="org.fairscan.app.action.SCAN_TO_PDF" />
+        </intent>
     </queries>
 
     <application

app/src/main/java/com/owncloud/android/ui/fragment/OCFileListBottomSheetActions.java

@@ -53,6 +53,16 @@ public interface OCFileListBottomSheetActions {
      */
     void scanDocUpload();
 
+    /**
+     * Offers scanning a document in a supported external app and then upload to the current folder.
+     */
+    void scanDocUploadFromApp();
+
+    /**
+     * @return true, if a supported external app is available for {@link #scanDocUploadFromApp()}
+     */
+    boolean isScanDocUploadFromAppAvailable();
+
     /**
      * open template selection for creator @link Creator
      */

app/src/main/java/com/owncloud/android/ui/fragment/OCFileListBottomSheetDialog.kt

@@ -204,6 +204,11 @@ class OCFileListBottomSheetDialog(
                     actions.scanDocUpload()
                     dismiss()
                 }
+            } else if (actions.isScanDocUploadFromAppAvailable) {
+                menuScanDocUpload.setOnClickListener {
+                    actions.scanDocUploadFromApp()
+                    dismiss()
+                }
             } else {
                 menuScanDocUpload.visibility = View.GONE
             }

app/src/main/java/com/owncloud/android/ui/fragment/OCFileListFragment.java

@@ -226,6 +226,8 @@ public class OCFileListFragment extends ExtendedListFragment implements
     private FloatingActionButton mFabMain;
     public static boolean isMultipleFileSelectedForCopyOrMove = false;
 
+    private static final Intent mFairScanIntent = new Intent("org.fairscan.app.action.SCAN_TO_PDF");
+
     @Inject DeviceInfo deviceInfo;
 
     protected enum MenuItemAddRemove {
@@ -587,6 +589,22 @@ public void scanDocUpload() {
         }
     }
 
+    @Override
+    public void scanDocUploadFromApp() {
+        requireActivity().startActivityForResult(
+            mFairScanIntent,
+            FileDisplayActivity.REQUEST_CODE__SELECT_CONTENT_FROM_APPS);
+    }
+
+    @Override
+    public boolean isScanDocUploadFromAppAvailable() {
+        var context = getActivity();
+        if (context == null) {
+            return false;
+        }
+        return mFairScanIntent.resolveActivity(context.getPackageManager()) != null;
+    }
+
     @Override
     public void uploadFiles() {
         if (!(getActivity() instanceof FileActivity fileActivity)) {