Add 'is subtask' filter

app/src/main/java/org/tasks/filters/FilterCriteriaProvider.kt

@@ -5,6 +5,7 @@ import com.todoroo.andlib.sql.Criterion.Companion.and
 import com.todoroo.andlib.sql.Criterion.Companion.or
 import com.todoroo.andlib.sql.Field.Companion.field
 import com.todoroo.andlib.sql.Join.Companion.inner
+import com.todoroo.andlib.sql.Join.Companion.left
 import com.todoroo.andlib.sql.Query.Companion.select
 import com.todoroo.astrid.api.*
 import com.todoroo.astrid.data.Task
@@ -35,6 +36,7 @@ class FilterCriteriaProvider @Inject constructor(
             IDENTIFIER_RECUR -> recurringFilter
             IDENTIFIER_COMPLETED -> completedFilter
             IDENTIFIER_HIDDEN -> hiddenFilter
+            IDENTIFIER_SUBTASK -> subtaskFilter
             else -> throw RuntimeException("Unknown identifier: $identifier")
         }
     }
@@ -63,6 +65,7 @@ class FilterCriteriaProvider @Inject constructor(
         result.add(recurringFilter)
         result.add(completedFilter)
         result.add(hiddenFilter)
+        result.add(subtaskFilter)
         return result
     }
 
@@ -120,6 +123,20 @@ class FilterCriteriaProvider @Inject constructor(
                         .toString()
         )
 
+    private val subtaskFilter: CustomFilterCriterion
+        get() = BooleanCriterion(
+                IDENTIFIER_SUBTASK,
+                context.getString(R.string.custom_filter_is_subtask),
+                select(Task.ID)
+                        .from(Task.TABLE)
+                        .join(left(GoogleTask.TABLE, GoogleTask.TASK.eq(Task.ID)))
+                        .where(or(
+                                field("${Task.PARENT}>0").eq(1),
+                                field("${GoogleTask.PARENT}>0").eq(1)
+                        ))
+                        .toString()
+        )
+
     val tagNameContainsFilter: CustomFilterCriterion
         get() = TextInputCriterion(
                 IDENTIFIER_TAG_CONTAINS,
@@ -265,5 +282,6 @@ class FilterCriteriaProvider @Inject constructor(
         private const val IDENTIFIER_RECUR = "recur"
         private const val IDENTIFIER_COMPLETED = "completed"
         private const val IDENTIFIER_HIDDEN = "hidden"
+        private const val IDENTIFIER_SUBTASK = "subtask"
     }
 }

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

@@ -656,4 +656,5 @@ File %1$s contained %2$s.\n\n
   <string name="multi_select_reschedule">Reschedule</string>
   <string name="date_picker_multiple">Multiple</string>
   <string name="delete_comment">Delete this comment?</string>
+  <string name="custom_filter_is_subtask">Is subtask</string>
 </resources>