Lift Framework example source code file (Diff.scala)

This example Lift Framework source code file (Diff.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lift Framework tags/keywords

diff, diff, jarray, jdouble, jfield, jint, jnothing, jnothing, jobject, jvalue, jvalue, list, list, nil

The Lift Framework Diff.scala source code

/*
 * 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 net.liftweb 
package json 

/** A difference between two JSONs (j1 diff j2).
 * @param changed what has changed from j1 to j2
 * @param added what has been added to j2
 * @param deleted what has been deleted from j1
 */
case class Diff(changed: JValue, added: JValue, deleted: JValue) {
  def map(f: JValue => JValue): Diff = {
    def applyTo(x: JValue) = x match {
      case JNothing => JNothing
      case _ => f(x)
    }
    Diff(applyTo(changed), applyTo(added), applyTo(deleted))
  }
}

/** Computes a diff between two JSONs.
 */
object Diff {
  /** Return a diff.
   * <p>
   * Example:<pre>
   * val Diff(c, a, d) = ("name", "joe") ~ ("age", 10) diff ("fname", "joe") ~ ("age", 11)
   * c = JObject(JField("age",JInt(11)) :: Nil)
   * a = JObject(JField("fname",JString("joe")) :: Nil)
   * d = JObject(JField("name",JString("joe")) :: Nil)
   * </pre>
   */
  def diff(val1: JValue, val2: JValue): Diff = (val1, val2) match {
    case (x, y) if x == y => Diff(JNothing, JNothing, JNothing)
    case (JObject(xs), JObject(ys)) => diffFields(xs, ys)
    case (JArray(xs), JArray(ys)) => diffVals(xs, ys)
    case (JField(xn, xv), JField(yn, yv)) if (xn == yn) => diff(xv, yv) map (JField(xn, _))
    case (x @ JField(xn, xv), y @ JField(yn, yv)) if (xn != yn) => Diff(JNothing, y, x)
    case (JInt(x), JInt(y)) if (x != y) => Diff(JInt(y), JNothing, JNothing)
    case (JDouble(x), JDouble(y)) if (x != y) => Diff(JDouble(y), JNothing, JNothing)
    case (JString(x), JString(y)) if (x != y) => Diff(JString(y), JNothing, JNothing)
    case (JBool(x), JBool(y)) if (x != y) => Diff(JBool(y), JNothing, JNothing)
    case (x, y) => Diff(JNothing, y, x)
  }

  private def diffFields(vs1: List[JField], vs2: List[JField]) = {
    def diffRec(xleft: List[JField], yleft: List[JField]): Diff = xleft match {
      case Nil => Diff(JNothing, if (yleft.isEmpty) JNothing else JObject(yleft), JNothing)
      case x :: xs => yleft find (_.name == x.name) match {
        case Some(y) =>
          val Diff(c1, a1, d1) = diff(x, y)
          val Diff(c2, a2, d2) = diffRec(xs, yleft filterNot (_ == y))
          Diff(c1 ++ c2, a1 ++ a2, d1 ++ d2) map {
            case f: JField => JObject(f :: Nil)
            case x => x
          }
        case None =>
          val Diff(c, a, d) = diffRec(xs, yleft)
          Diff(c, a, JObject(x :: Nil) merge d)
      }
    }

    diffRec(vs1, vs2)
  }

  private def diffVals(vs1: List[JValue], vs2: List[JValue]) = {
    def diffRec(xleft: List[JValue], yleft: List[JValue]): Diff = (xleft, yleft) match {
      case (xs, Nil) => Diff(JNothing, JNothing, if (xs.isEmpty) JNothing else JArray(xs))
      case (Nil, ys) => Diff(JNothing, if (ys.isEmpty) JNothing else JArray(ys), JNothing)
      case (x :: xs, y :: ys) =>
        val Diff(c1, a1, d1) = diff(x, y)
        val Diff(c2, a2, d2) = diffRec(xs, ys)
        Diff(c1 ++ c2, a1 ++ a2, d1 ++ d2)
    }

    diffRec(vs1, vs2)
  }

  private[json] trait Diffable { this: JValue =>
    /** Return a diff.
     * @see net.liftweb.json.Diff#diff
     */
    def diff(other: JValue) = Diff.diff(this, other)
  }
}