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   1 /**
   2  * Copyright (c) 2010-2023 Contributors to the openHAB project
   3  *
   4  * See the NOTICE file(s) distributed with this work for additional
   5  * information.
   6  *
   7  * This program and the accompanying materials are made available under the
   8  * terms of the Eclipse Public License 2.0 which is available at
   9  * http://www.eclipse.org/legal/epl-2.0
  10  *
  11  * SPDX-License-Identifier: EPL-2.0
  12  */
  13 package org.openhab.binding.surepetcare.internal.utils;
  14
  15 import java.io.IOException;
  16 import java.util.List;
  17
  18 import org.eclipse.jdt.annotation.NonNullByDefault;
  19 import org.eclipse.jdt.annotation.Nullable;
  20 import org.openhab.binding.surepetcare.internal.dto.SurePetcareDeviceCurfew;
  21 import org.openhab.binding.surepetcare.internal.dto.SurePetcareDeviceCurfewList;
  22
  23 import com.google.gson.Gson;
  24 import com.google.gson.TypeAdapter;
  25 import com.google.gson.TypeAdapterFactory;
  26 import com.google.gson.reflect.TypeToken;
  27 import com.google.gson.stream.JsonReader;
  28 import com.google.gson.stream.JsonToken;
  29 import com.google.gson.stream.JsonWriter;
  30 import com.google.gson.stream.MalformedJsonException;
  31
  32 /**
  33  * The {@link GsonColonDateTypeAdapter} class is a custom TypeAdapter factory to ensure deserialization always returns a
  34  * list even if the Json document contains only a single curfew object and not an array.
  35  *
  36  * See https://stackoverflow.com/questions/43412261/make-gson-accept-single-objects-where-it-expects-arrays
  37  *
  38  * @author Rene Scherer - Initial contribution
  39  */
  40 @NonNullByDefault
  41 public final class SurePetcareDeviceCurfewListTypeAdapterFactory<E> implements TypeAdapterFactory {
  42
  43     // Gson can instantiate it itself
  44     private SurePetcareDeviceCurfewListTypeAdapterFactory() {
  45     }
  46
  47     @Override
  48     public @Nullable <T> TypeAdapter<T> create(final @Nullable Gson gson, final @Nullable TypeToken<T> typeToken) {
  49         if (gson == null || typeToken == null) {
  50             return null;
  51         }
  52         final TypeAdapter<SurePetcareDeviceCurfew> elementTypeAdapter = gson
  53                 .getAdapter(TypeToken.get(SurePetcareDeviceCurfew.class));
  54         @SuppressWarnings("unchecked")
  55         final TypeAdapter<T> alwaysListTypeAdapter = (TypeAdapter<T>) new SurePetcareDeviceCurfewListTypeAdapter(
  56                 elementTypeAdapter).nullSafe();
  57         return alwaysListTypeAdapter;
  58     }
  59
  60     private static final class SurePetcareDeviceCurfewListTypeAdapter
  61             extends TypeAdapter<List<SurePetcareDeviceCurfew>> {
  62
  63         private final TypeAdapter<SurePetcareDeviceCurfew> elementTypeAdapter;
  64
  65         private SurePetcareDeviceCurfewListTypeAdapter(final TypeAdapter<SurePetcareDeviceCurfew> elementTypeAdapter) {
  66             this.elementTypeAdapter = elementTypeAdapter;
  67         }
  68
  69         @Override
  70         public void write(final @Nullable JsonWriter out, @Nullable final List<SurePetcareDeviceCurfew> list)
  71                 throws IOException {
  72             if (out != null && list != null) {
  73                 out.beginArray();
  74                 for (SurePetcareDeviceCurfew curfew : list) {
  75                     elementTypeAdapter.write(out, curfew);
  76                 }
  77                 out.endArray();
  78             }
  79         }
  80
  81         @Override
  82         public @Nullable List<SurePetcareDeviceCurfew> read(final @Nullable JsonReader in) throws IOException {
  83             // This is where we detect the list "type"
  84             final SurePetcareDeviceCurfewList list = new SurePetcareDeviceCurfewList();
  85             if (in != null) {
  86                 final JsonToken token = in.peek();
  87                 switch (token) {
  88                     case BEGIN_ARRAY:
  89                         // If it's a regular list, just consume [, <all elements>, and ]
  90                         in.beginArray();
  91                         while (in.hasNext()) {
  92                             SurePetcareDeviceCurfew cf = elementTypeAdapter.read(in);
  93                             if (cf != null) {
  94                                 list.add(cf);
  95                             }
  96                         }
  97                         in.endArray();
  98                         break;
  99                     case BEGIN_OBJECT:
 100                         SurePetcareDeviceCurfew cf = elementTypeAdapter.read(in);
 101                         if (cf != null) {
 102                             list.add(cf);
 103                         }
 104                         break;
 105                     case NULL:
 106                         throw new AssertionError(
 107                                 "Must never happen: check if the type adapter configured with .nullSafe()");
 108                     case STRING:
 109                     case NUMBER:
 110                     case BOOLEAN:
 111                     case NAME:
 112                     case END_ARRAY:
 113                     case END_OBJECT:
 114                     case END_DOCUMENT:
 115                         throw new MalformedJsonException("Unexpected token: " + token);
 116                     default:
 117                         throw new AssertionError("Must never happen: " + token);
 118                 }
 119             }
 120             return list;
 121         }
 122     }
 123 }