EntityDeleteComparator.kt
/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.room.writer
import androidx.room.vo.Entity
/**
* Sorts the entities by their foreign key dependencies. For example, when Entity A depends on
* Entity B, A is ordered before B.
*/
class EntityDeleteComparator : Comparator<Entity> {
override fun compare(lhs: Entity, rhs: Entity): Int {
val ltr = lhs.shouldBeDeletedAfter(rhs)
val rtl = rhs.shouldBeDeletedAfter(lhs)
return when {
ltr == rtl -> 0
ltr -> -1
rtl -> 1
else -> 0 // Never happens
}
}
}