1/* 2 * Copyright 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package androidx.room.writer 18 19import androidx.room.vo.Entity 20 21/** 22 * Sorts the entities by their foreign key dependencies. For example, when Entity A depends on 23 * Entity B, A is ordered before B. 24 */ 25class EntityDeleteComparator : Comparator<Entity> { 26 27 override fun compare(lhs: Entity, rhs: Entity): Int { 28 val ltr = lhs.shouldBeDeletedAfter(rhs) 29 val rtl = rhs.shouldBeDeletedAfter(lhs) 30 return when { 31 ltr == rtl -> 0 32 ltr -> -1 33 rtl -> 1 34 else -> 0 // Never happens 35 } 36 } 37} 38