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A library for extracting object structure surface
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/*
* 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 wvlet.airframe.surface
import java.util.concurrent.ConcurrentHashMap
import wvlet.log.LogSupport
import scala.reflect.ClassTag
/**
* Create a default instance (zero) from Surface
*/
object Zero extends LogSupport {
import scala.jdk.CollectionConverters._
private val preregisteredZeroInstance = new ConcurrentHashMap[Surface, Any]().asScala
/**
* Register a zero instnce for the given type
*/
def register(surface: Surface, zero: Any): Unit = {
preregisteredZeroInstance += surface -> zero
}
type ZeroValueFactory = PartialFunction[Surface, Any]
type SurfaceFilter = PartialFunction[Surface, Surface]
private def isPrimitive: SurfaceFilter = {
case p if p.isPrimitive => p
}
private def isGenericWithTypeArgs: SurfaceFilter = {
case g: GenericSurface if g.typeArgs.length > 0 => g
}
private def zeroOfPrimitives: ZeroValueFactory = isPrimitive andThen {
case Primitive.String => ""
case Primitive.Boolean => false
case Primitive.Int => 0
case Primitive.Long => 0L
case Primitive.Float => 0f
case Primitive.Double => 0.0
case Primitive.Unit => null
case Primitive.Byte => 0.toByte
case Primitive.Short => 0.toShort
case Primitive.Char => 0.toChar
}
private def zeroOfRegisteredTypes: ZeroValueFactory = {
case t if preregisteredZeroInstance.contains(t) =>
preregisteredZeroInstance(t)
}
private def zeroOfArray: ZeroValueFactory = {
case ArraySurface(cl, elementSurface) =>
ClassTag(elementSurface.rawType).newArray(0)
}
private def zeroOfSpecialType: ZeroValueFactory = {
case s if s.isOption => None
case s
if s.rawType == classOf[Nothing] ||
s.rawType == classOf[AnyRef] ||
s.rawType == classOf[Any] =>
null
}
private def zeroOfScalaCollections: ZeroValueFactory = isGenericWithTypeArgs andThen {
case g if classOf[List[_]].isAssignableFrom(g.rawType) =>
List.empty
case g if classOf[Seq[_]].isAssignableFrom(g.rawType) =>
Seq.empty
case g if classOf[Map[_, _]].isAssignableFrom(g.rawType) =>
Map.empty
case g if classOf[Set[_]].isAssignableFrom(g.rawType) =>
Set.empty
}
private def zeroOfTuple: ZeroValueFactory = {
case t: TupleSurface =>
val args = t.typeArgs.map(s => zeroOf(s)).toIndexedSeq
t.typeArgs.size match {
case 1 => ()
case 2 => (args(0), args(1))
case 3 => (args(0), args(1), args(2))
case 4 => (args(0), args(1), args(2), args(3))
case 5 => (args(0), args(1), args(2), args(3), args(4))
case 6 => (args(0), args(1), args(2), args(3), args(4), args(5))
case 7 => (args(0), args(1), args(2), args(3), args(4), args(5), args(6))
case other =>
new UnsupportedOperationException(s"Zero.of[Tuple${other}] is not supported")
}
}
private def zeroOfInstantiatable: ZeroValueFactory = {
case t if t.objectFactory.isDefined =>
val factory = t.objectFactory.get
val args = t.params.map(x => x.getDefaultValue.getOrElse(zeroOf(x.surface)))
factory.newInstance(args)
}
private def fallBack: ZeroValueFactory = {
case _ => null
}
private val factory: ZeroValueFactory =
zeroOfPrimitives orElse
zeroOfRegisteredTypes orElse
zeroOfArray orElse
zeroOfTuple orElse
zeroOfSpecialType orElse
zeroOfScalaCollections orElse
zeroOfInstantiatable orElse
fallBack
def zeroOf(surface: Surface): Any = {
// Dealias function resolves the actual types of aliased surfaces, tagged surfaces etc.
val zero = factory.apply(surface.dealias)
zero
}
}