com.tananaev.jsonpatch.JsonPatchFactory Maven / Gradle / Ivy

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/*
 Copyright 2014 C. A. Fitzgerald

 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 com.tananaev.jsonpatch;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.tananaev.jsonpatch.operation.MoveOperation;
import com.tananaev.jsonpatch.operation.RemoveOperation;
import com.tananaev.jsonpatch.operation.ReplaceOperation;
import com.tananaev.jsonpatch.operation.AddOperation;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.SortedSet;
import java.util.TreeSet;

public class JsonPatchFactory {

    private LongestCommonSubsequenceFactory lcsf = new LongestCommonSubsequenceFactory();

    public JsonPatch create( JsonElement elementA, JsonElement elementB ){
        JsonPatch patch = new JsonPatch();
        PostProcessor pp = new PostProcessor();

        boolean loop = true;

        while ( loop ) {
            JsonElement temp = patch.apply( elementA );
            loop = processPatch(patch, new JsonPath("/"), temp, elementB);
        }

        return patch;
    }

    private boolean processPatch( JsonPatch patch, JsonPath path, JsonElement elementA, JsonElement elementB ){
        if ( elementA == null ){
            patch.add( new ReplaceOperation(path, elementB));
            return true;
        }

        if ( elementA.equals(elementB) ){
            return false;
        }

        if ( elementA.isJsonArray() && elementB.isJsonArray() ){
            return processArrayPatch( patch, path, elementA.getAsJsonArray(), elementB.getAsJsonArray() );
        } else if ( elementA.isJsonObject() && elementB.isJsonObject() ){
            return processObjectPatch(patch, path, elementA.getAsJsonObject(), elementB.getAsJsonObject());
        } else {
            patch.add( new ReplaceOperation(path, elementB));
            return true;
        }
    }

    private boolean processObjectPatch( JsonPatch patch, JsonPath path, JsonObject elementA, JsonObject elementB ) {

        SortedSet elementAProps = extractProps(elementA);
        SortedSet elementBProps = extractProps(elementB);

        for ( String prop : elementAProps ){
                JsonElement aValue = elementA.get(prop);
            if ( elementB.has( prop ) ){
                elementBProps.remove(prop);
                JsonElement bValue = elementB.get(prop);
                if (!aValue.equals(bValue)) {
                    // item exist in both but do not match
                    return processPatch( patch, path.append(prop), aValue, bValue );
                }
            } else {
                //item in original but not in target

                //look for move
                for ( String bProp: elementBProps ){
                    if ( elementB.get(bProp).equals(aValue) ){
                        patch.addLast(new MoveOperation(path.append(prop), path.append(bProp)));
                        return true;
                    }
                }

                patch.addLast(new RemoveOperation(path.append(prop)));
                return true;
            }
        }

        if ( elementBProps.size() != 0 ){
            String prop = elementBProps.first();
            //look for copy
            patch.addLast(new AddOperation(path.append(prop), elementB.get(prop)));
            return true;
        }
        throw new JsonPatchException("theoretically Unreachable");
    }

    private boolean processArrayPatch( JsonPatch patch, JsonPath path, JsonArray elementA, JsonArray elementB ) {
        List listA = convertToList(elementA);
        List listB = convertToList(elementB);

        if ( listA.isEmpty() ){
            patch.add( new AddOperation(path.append("-"),listB.get(0) ));
            return true;
        }

        List common = lcsf.search(listA, listB);

        int startOfCommonInA = lcsf.findStartIndex(common, listA);
        int startOfCommonInB = lcsf.findStartIndex(common, listB);

        if ( listB.size() == common.size() ){
            if ( startOfCommonInA != 0 ){
                patch.addLast(new RemoveOperation(path.append(0)));
                return true;
            } else {
                patch.addLast(new RemoveOperation(path.append(startOfCommonInA+common.size())));
                return true;
            }
        }

        if ( startOfCommonInB != 0 ){
            int targetPos = startOfCommonInB - 1;
            int targetPosA = startOfCommonInA;
            return expandCommon(patch, path, listA, listB, common, startOfCommonInA, targetPos, targetPosA);
        } else {
            int targetPos = startOfCommonInB + common.size();
            int targetPosA = startOfCommonInA + common.size();
            return expandCommon(patch, path, listA, listB, common, startOfCommonInA, targetPos, targetPosA);
        }

    }

    private SortedSet extractProps(JsonObject elementA) {
        SortedSet result = new TreeSet();
        for ( Map.Entry entry : elementA.entrySet() ){
            result.add(entry.getKey());
        }
        return result;
    }

    private boolean expandCommon(JsonPatch patch, JsonPath path, List listA, List listB, List common, int startOfCommonInA, int targetPos, int targetPosA) {
        JsonElement target = listB.get(targetPos);

        if ( listA.size() > targetPosA ) {
            if (!listB.contains(listA.get(targetPosA))) {
                patch.addLast(new RemoveOperation(path.append(targetPosA)));
                return true;
            }
        }

        for ( int occurance : findOccurnacesIn(target, listA )){
            if ( occurance >= startOfCommonInA+common.size() ) {
                patch.addLast(new MoveOperation(path.append(occurance), path.append(targetPosA)));
                return true;
            }
            if ( occurance < startOfCommonInA ) {

                int to = (targetPosA < occurance ) ? targetPosA -1 : targetPosA ;

                patch.addLast(new MoveOperation(
                        path.append(  occurance ),
                        path.append( (to >= listA.size())? "-": Integer.toString(to))));
                return true;
            }
        }
        patch.addLast(new AddOperation(path.append(targetPosA), target));
        return true;
    }


    private  List findOccurnacesIn(T item, List list){
        List result = new ArrayList<>();
        for ( int c = 0; c < list.size(); c++){

            if ( list.get(c).equals(item) ){
                result.add(c);
            }
        }
        return result;
    }

    private List convertToList(JsonArray array){
        List result = new ArrayList<>();

        for ( JsonElement element: array){
            result.add(element);
        }

        return result;
    }

}