org.json4s.Merge.scala Maven / Gradle / Ivy
/*
* Copyright 2009-2010 WorldWide Conferencing, LLC
*
* 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 org.json4s
import JsonAST._
import scala.annotation.tailrec
/** Use fundep encoding to improve return type of merge function
* (see: http://www.chuusai.com/2011/07/16/fundeps-in-scala/)
*
* JObject merge JObject = JObject
* JArray merge JArray = JArray
* _ merge _ = JValue
*/
private[json4s] trait MergeDep[A <: JValue, B <: JValue, R <: JValue] {
def apply(val1: A, val2: B): R
}
private[json4s] trait LowPriorityMergeDep {
implicit def jjj[A <: JValue, B <: JValue] = new MergeDep[A, B, JValue] {
def apply(val1: A, val2: B): JValue = merge(val1, val2)
private def merge(val1: JValue, val2: JValue): JValue = (val1, val2) match {
case (JObject(xs), JObject(ys)) => JObject(Merge.mergeFields(xs, ys))
case (JArray(xs), JArray(ys)) => JArray(Merge.mergeVals(xs, ys))
case (JNothing, x) => x
case (x, JNothing) => x
case (_, y) => y
}
}
}
private[json4s] trait MergeDeps extends LowPriorityMergeDep {
implicit object ooo extends MergeDep[JObject, JObject, JObject] {
def apply(val1: JObject, val2: JObject): JObject = JObject(Merge.mergeFields(val1.obj, val2.obj))
}
implicit object aaa extends MergeDep[JArray, JArray, JArray] {
def apply(val1: JArray, val2: JArray): JArray = JArray(Merge.mergeVals(val1.arr, val2.arr))
}
}
/** Function to merge two JSONs.
*/
object Merge {
/** Return merged JSON.
*
* Example:
* val m = ("name", "joe") ~ ("age", 10) merge ("name", "joe") ~ ("iq", 105)
* m: JObject(List((name,JString(joe)), (age,JInt(10)), (iq,JInt(105))))
*
*/
def merge[A <: JValue, B <: JValue, R <: JValue]
(val1: A, val2: B)(implicit instance: MergeDep[A, B, R]): R = instance(val1, val2)
private[json4s] def mergeFields(vs1: List[JField], vs2: List[JField]): List[JField] = {
@tailrec
def mergeRec(acc: List[JField], xleft: List[JField], yleft: List[JField]): List[JField] = xleft match {
case Nil => acc ++ yleft
case (xn, xv) :: xs => yleft find (_._1 == xn) match {
case Some(y @ (yn@_, yv)) =>
mergeRec(acc ++ List(JField(xn, merge(xv, yv))), xs, yleft filterNot (_ == y))
case None => mergeRec(acc ++ List(JField(xn, xv)), xs, yleft)
}
}
mergeRec(List(), vs1, vs2)
}
private[json4s] def mergeVals(vs1: List[JValue], vs2: List[JValue]): List[JValue] = {
@tailrec
def mergeRec(acc: List[JValue], xleft: List[JValue], yleft: List[JValue]): List[JValue] = xleft match {
case Nil => acc ++ yleft
case x :: xs => yleft find (_ == x) match {
case Some(y) => mergeRec(acc ++ List(merge(x,y)), xs, yleft filterNot (_ == y))
case None => mergeRec(acc ++ List(x), xs, yleft)
}
}
mergeRec(List(), vs1, vs2)
}
private[json4s] trait Mergeable extends MergeDeps {
implicit def j2m[A <: JValue](json: A): MergeSyntax[A] = new MergeSyntax(json)
class MergeSyntax[A <: JValue](json: A) {
/** Return merged JSON.
* @see org.json4s.Merge#merge
*/
def merge[B <: JValue, R <: JValue](other: B)(implicit instance: MergeDep[A, B, R]): R =
Merge.merge(json, other)(instance)
}
}
}