/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.apache.maven.model.building;
  
  import java.io.File;
  import java.nio.file.Path;
  import java.util.Map;
  import java.util.Objects;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.function.Supplier;
  
  import org.apache.maven.model.Model;
  import org.apache.maven.model.locator.ModelLocator;
  
  /**
   *
   * @since 4.0.0
   */
  class DefaultTransformerContext implements TransformerContext {
      final ModelLocator modelLocator;
  
      final Map<String, String> userProperties = new ConcurrentHashMap<>();
  
      final Map<Path, Holder> modelByPath = new ConcurrentHashMap<>();
  
      final Map<GAKey, Holder> modelByGA = new ConcurrentHashMap<>();
  
      public static class Holder {
          private volatile boolean set;
          private volatile Model model;
  
          Holder() {}
  
          Holder(Model model) {
              this.model = Objects.requireNonNull(model);
              this.set = true;
          }
  
          public static Model deref(Holder holder) {
              return holder != null ? holder.get() : null;
          }
  
          public Model get() {
              if (!set) {
                  synchronized (this) {
                      if (!set) {
                          try {
                              this.wait();
                          } catch (InterruptedException e) {
                              // Ignore
                          }
                      }
                  }
              }
              return model;
          }
  
          public Model computeIfAbsent(Supplier<Model> supplier) {
              if (!set) {
                  synchronized (this) {
                      if (!set) {
                          this.set = true;
                          this.model = supplier.get();
                          this.notifyAll();
                      }
                  }
              }
              return model;
          }
      }
  
      DefaultTransformerContext(ModelLocator modelLocator) {
          this.modelLocator = modelLocator;
      }
  
      @Override
      public String getUserProperty(String key) {
          return userProperties.get(key);
      }
  
      @Override
      public Model getRawModel(Path from, Path p) {
          return Holder.deref(modelByPath.get(p));
     }
 
     @Override
     public Model getRawModel(Path from, String groupId, String artifactId) {
         return Holder.deref(modelByGA.get(new GAKey(groupId, artifactId)));
     }
 
     @Override
     public Path locate(Path path) {
         File file = modelLocator.locateExistingPom(path.toFile());
         return file != null ? file.toPath() : null;
     }
 
     static class GAKey {
         private final String groupId;
         private final String artifactId;
         private final int hashCode;
 
         GAKey(String groupId, String artifactId) {
             this.groupId = groupId;
             this.artifactId = artifactId;
             this.hashCode = Objects.hash(groupId, artifactId);
         }
 
         @Override
         public int hashCode() {
             return hashCode;
         }
 
         @Override
         public boolean equals(Object obj) {
             if (this == obj) {
                 return true;
             }
             if (!(obj instanceof GAKey)) {
                 return false;
             }
 
             GAKey other = (GAKey) obj;
             return Objects.equals(artifactId, other.artifactId) && Objects.equals(groupId, other.groupId);
         }
     }
 }