/*
    * 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.basepom.mojo.propertyhelper;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import java.util.Map;
  import java.util.Optional;
  import java.util.Properties;
  
  public interface ValueProvider {
  
      ValueProvider NULL_PROVIDER = new NullProvider();
  
      Optional<String> getValue();
  
      void setValue(String value);
  
      class NullProvider
              implements ValueProvider {
  
          private NullProvider() {
          }
  
          @Override
          public Optional<String> getValue() {
              return Optional.empty();
          }
  
          @Override
          public void setValue(final String value) {
          }
      }
  
      class StaticValueProvider
              implements ValueProvider {
  
          private String value;
  
          StaticValueProvider() {
          }
  
          @Override
          public Optional<String> getValue() {
              return Optional.ofNullable(value);
          }
  
          @Override
          public void setValue(final String value) {
              this.value = value;
          }
      }
  
      class MapValueProvider
              implements ValueProvider {
  
          private final Map<String, String> values;
          private final String valueName;
  
          MapValueProvider(final Map<String, String> values, final String valueName) {
              this.valueName = checkNotNull(valueName, "valueName is null");
              this.values = values;
          }
  
          @Override
          public Optional<String> getValue() {
              return Optional.ofNullable(values.get(valueName));
          }
  
          @Override
          public void setValue(final String value) {
              checkNotNull(value, "value is null");
              values.put(valueName, value);
          }
      }
  
      class PropertyProvider
              implements ValueProvider {
  
          private final Properties props;
          private final String propertyName;
  
          PropertyProvider(final Properties props, final String propertyName) {
              this.props = props;
              this.propertyName = checkNotNull(propertyName, "propertyName is null");
          }
  
         @Override
         public Optional<String> getValue() {
             return Optional.ofNullable(props.getProperty(propertyName));
         }
 
         @Override
         public void setValue(final String value) {
             checkNotNull(value, "value is null");
             props.setProperty(propertyName, value);
         }
     }
 }