/*
    * 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.internal.impl.model;
  
  import java.util.Objects;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.function.Supplier;
  
  import org.apache.maven.api.services.Source;
  import org.apache.maven.api.services.model.ModelCache;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A model builder cache backed by the repository system cache.
   *
   */
  public class DefaultModelCache implements ModelCache {
  
      private final ConcurrentMap<Object, Supplier<?>> cache;
  
      public DefaultModelCache() {
          this(new ConcurrentHashMap<>());
      }
  
      private DefaultModelCache(ConcurrentMap<Object, Supplier<?>> cache) {
          this.cache = requireNonNull(cache);
      }
  
      @Override
      @SuppressWarnings({"unchecked"})
      public <T> T computeIfAbsent(String groupId, String artifactId, String version, String tag, Supplier<T> data) {
          return (T) computeIfAbsent(new GavCacheKey(groupId, artifactId, version, tag), data);
      }
  
      @Override
      @SuppressWarnings({"unchecked"})
      public <T> T computeIfAbsent(Source path, String tag, Supplier<T> data) {
          return (T) computeIfAbsent(new SourceCacheKey(path, tag), data);
      }
  
      @Override
      public void clear() {
          cache.clear();
      }
  
      protected Object computeIfAbsent(Object key, Supplier<?> data) {
          return cache.computeIfAbsent(key, k -> new CachingSupplier<>(data)).get();
      }
  
      static class GavCacheKey {
  
          private final String gav;
  
          private final String tag;
  
          private final int hash;
  
          GavCacheKey(String groupId, String artifactId, String version, String tag) {
              this(gav(groupId, artifactId, version), tag);
          }
  
          GavCacheKey(String gav, String tag) {
              this.gav = gav;
              this.tag = tag;
              this.hash = Objects.hash(gav, tag);
          }
  
          private static String gav(String groupId, String artifactId, String version) {
              StringBuilder sb = new StringBuilder();
              if (groupId != null) {
                  sb.append(groupId);
              }
              sb.append(":");
              if (artifactId != null) {
                  sb.append(artifactId);
              }
              sb.append(":");
              if (version != null) {
                  sb.append(version);
              }
              return sb.toString();
         }
 
         @Override
         public boolean equals(Object obj) {
             if (this == obj) {
                 return true;
             }
             if (null == obj || !getClass().equals(obj.getClass())) {
                 return false;
             }
             GavCacheKey that = (GavCacheKey) obj;
             return Objects.equals(this.gav, that.gav) && Objects.equals(this.tag, that.tag);
         }
 
         @Override
         public int hashCode() {
             return hash;
         }
 
         @Override
         public String toString() {
             return "GavCacheKey[" + "gav='" + gav + '\'' + ", tag='" + tag + '\'' + ']';
         }
     }
 
     private static final class SourceCacheKey {
         private final Source source;
 
         private final String tag;
 
         private final int hash;
 
         SourceCacheKey(Source source, String tag) {
             this.source = source;
             this.tag = tag;
             this.hash = Objects.hash(source, tag);
         }
 
         @Override
         public String toString() {
             return "SourceCacheKey[" + "location=" + source.getLocation() + ", tag=" + tag + ", path="
                     + source.getPath() + ']';
         }
 
         @Override
         public boolean equals(Object obj) {
             if (this == obj) {
                 return true;
             }
             if (null == obj || !getClass().equals(obj.getClass())) {
                 return false;
             }
             SourceCacheKey that = (SourceCacheKey) obj;
             return Objects.equals(this.source, that.source) && Objects.equals(this.tag, that.tag);
         }
 
         @Override
         public int hashCode() {
             return hash;
         }
     }
 
     static class CachingSupplier<T> implements Supplier<T> {
         final Supplier<T> supplier;
         volatile Object value;
 
         CachingSupplier(Supplier<T> supplier) {
             this.supplier = supplier;
         }
 
         @Override
         @SuppressWarnings({"unchecked", "checkstyle:InnerAssignment"})
         public T get() {
             Object v;
             if ((v = value) == null) {
                 synchronized (this) {
                     if ((v = value) == null) {
                         try {
                             v = value = supplier.get();
                         } catch (Exception e) {
                             v = value = new AltRes(e);
                         }
                     }
                 }
             }
             if (v instanceof AltRes) {
                 uncheckedThrow(((AltRes) v).t);
             }
             return (T) v;
         }
 
         static class AltRes {
             final Throwable t;
 
             AltRes(Throwable t) {
                 this.t = t;
             }
         }
     }
 
     @SuppressWarnings("unchecked")
     static <T extends Throwable> void uncheckedThrow(Throwable t) throws T {
         throw (T) t; // rely on vacuous cast
     }
 }