DatabaseProcessingStep.kt

/*
 * Copyright (C) 2020 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

import androidx.room.ext.asTypeElement
import androidx.room.processor.Context
import androidx.room.processor.DatabaseProcessor
import androidx.room.processor.MissingTypeException
import androidx.room.processor.ProcessorErrors
import androidx.room.vo.DaoMethod
import androidx.room.vo.Warning
import androidx.room.writer.DaoWriter
import androidx.room.writer.DatabaseWriter
import com.google.auto.common.BasicAnnotationProcessor
import com.google.common.collect.SetMultimap
import java.io.File
import javax.annotation.processing.ProcessingEnvironment
import javax.lang.model.element.Element

class DatabaseProcessingStep(val processingEnv: ProcessingEnvironment) :
    BasicAnnotationProcessor.ProcessingStep {
    override fun process(
        elementsByAnnotation: SetMultimap<Class<out Annotation>, Element>
    ): MutableSet<Element> {
        val context = Context(processingEnv)
        val rejectedElements = mutableSetOf<Element>()
        val databases = elementsByAnnotation[Database::class.java]
            ?.mapNotNull {
                try {
                    DatabaseProcessor(
                        context,
                        it.asTypeElement()
                    ).process()
                } catch (ex: MissingTypeException) {
                    // Abandon processing this database class since it needed a type element
                    // that is missing. It is possible that the type will be generated by a
                    // further annotation processing round, so we will try again by adding
                    // this class element to a deferred set.
                    rejectedElements.add(it)
                    null
                }
            }
        val daoMethodsMap = databases?.flatMap { db -> db.daoMethods.map { it to db } }?.toMap()
        daoMethodsMap?.let {
            prepareDaosForWriting(databases, it.keys.toList())
            it.forEach { (daoMethod, db) ->
                DaoWriter(
                    daoMethod.dao,
                    db.element,
                    context.processingEnv
                )
                    .write(context.processingEnv)
            }
        }

        databases?.forEach { db ->
            DatabaseWriter(db).write(context.processingEnv)
            if (db.exportSchema) {
                val schemaOutFolder = context.schemaOutFolder
                if (schemaOutFolder == null) {
                    context.logger.w(
                        Warning.MISSING_SCHEMA_LOCATION, db.element,
                        ProcessorErrors.MISSING_SCHEMA_EXPORT_DIRECTORY
                    )
                } else {
                    if (!schemaOutFolder.exists()) {
                        schemaOutFolder.mkdirs()
                    }
                    val qName = db.element.qualifiedName.toString()
                    val dbSchemaFolder = File(schemaOutFolder, qName)
                    if (!dbSchemaFolder.exists()) {
                        dbSchemaFolder.mkdirs()
                    }
                    db.exportSchema(
                        File(
                            dbSchemaFolder,
                            "${db.version}.json"
                        )
                    )
                }
            }
        }
        return rejectedElements
    }

    override fun annotations(): MutableSet<out Class<out Annotation>> {
        return mutableSetOf(Database::class.java)
    }

    /**
     * Traverses all dao methods and assigns them suffix if they are used in multiple databases.
     */
    private fun prepareDaosForWriting(
        databases: List<androidx.room.vo.Database>,
        daoMethods: List<DaoMethod>
    ) {
        daoMethods.groupBy { it.dao.typeName }
            // if used only in 1 database, nothing to do.
            .filter { entry -> entry.value.size > 1 }
            .forEach { entry ->
                entry.value.groupBy { daoMethod ->
                    // first suffix guess: Database's simple name
                    val db = databases.first { db -> db.daoMethods.contains(daoMethod) }
                    db.typeName.simpleName()
                }.forEach { (dbName, methods) ->
                    if (methods.size == 1) {
                        // good, db names do not clash, use db name as suffix
                        methods.first().dao.setSuffix(dbName)
                    } else {
                        // ok looks like a dao is used in 2 different databases both of
                        // which have the same name. enumerate.
                        methods.forEachIndexed { index, method ->
                            method.dao.setSuffix("${dbName}_$index")
                        }
                    }
                }
            }
    }
}