/*
 * 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.juneau.config.store;

import static org.apache.juneau.commons.utils.AssertionUtils.*;
import static org.apache.juneau.commons.utils.Utils.*;

import java.io.*;
import java.lang.annotation.*;
import java.util.concurrent.*;

import org.apache.juneau.*;
import org.apache.juneau.commons.collections.*;

/**
 * Filesystem-based storage location for configuration files.
 *
 * <p>
 * Points to a file system directory containing configuration files.
 *
 * <h5 class='section'>Notes:</h5><ul>
 *    <li class='note'>This class is thread safe and reusable.
 * </ul>
 */
@SuppressWarnings("resource")
public class MemoryStore extends ConfigStore {
   /**
    * Builder class.
    */
   public static class Builder extends ConfigStore.Builder {

      /**
       * Constructor, default settings.
       */
      protected Builder() {}

      /**
       * Copy constructor.
       *
       * @param copyFrom The builder to copy from.
       *    <br>Cannot be <jk>null</jk>.
       */
      protected Builder(Builder copyFrom) {
         super(assertArgNotNull("copyFrom", copyFrom));
      }

      /**
       * Copy constructor.
       *
       * @param copyFrom The bean to copy from.
       *    <br>Cannot be <jk>null</jk>.
       */
      protected Builder(MemoryStore copyFrom) {
         super(assertArgNotNull("copyFrom", copyFrom));
         type(copyFrom.getClass());
      }

      @Override /* Overridden from Builder */
      public Builder annotations(Annotation...values) {
         super.annotations(values);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder apply(AnnotationWorkList work) {
         super.apply(work);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder applyAnnotations(Class<?>...from) {
         super.applyAnnotations(from);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder applyAnnotations(Object...from) {
         super.applyAnnotations(from);
         return this;
      }

      @Override /* Overridden from Context.Builder */
      public MemoryStore build() {
         return build(MemoryStore.class);
      }

      @Override /* Overridden from Builder */
      public Builder cache(Cache<HashKey,? extends org.apache.juneau.Context> value) {
         super.cache(value);
         return this;
      }

      @Override /* Overridden from Context.Builder */
      public Builder copy() {
         return new Builder(this);
      }

      @Override /* Overridden from Builder */
      public Builder debug() {
         super.debug();
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder debug(boolean value) {
         super.debug(value);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder impl(Context value) {
         super.impl(value);
         return this;
      }

      @Override /* Overridden from Builder */
      public Builder type(Class<? extends org.apache.juneau.Context> value) {
         super.type(value);
         return this;
      }
   }

   /** Default memory store, all default values.*/
   public static final MemoryStore DEFAULT = MemoryStore.create().build();

   /**
    * Creates a new builder for this object.
    *
    * @return A new builder.
    */
   public static Builder create() {
      return new Builder();
   }

   private final ConcurrentHashMap<String,String> cache = new ConcurrentHashMap<>();

   /**
    * Constructor.
    *
    * @param builder The builder for this object.
    */
   public MemoryStore(Builder builder) {
      super(builder);
   }

   /**
    * No-op.
    */
   @Override /* Overridden from Closeable */
   public void close() throws IOException {
      // No-op
   }

   @Override /* Overridden from Context */
   public Builder copy() {
      return new Builder(this);
   }

   @Override /* Overridden from ConfigStore */
   public synchronized boolean exists(String name) {
      return cache.containsKey(name);
   }

   @Override /* Overridden from ConfigStore */
   public synchronized String read(String name) {
      return emptyIfNull(cache.get(name));
   }

   @Override /* Overridden from ConfigStore */
   public synchronized MemoryStore update(String name, String newContents) {
      if (newContents == null)
         cache.remove(name);
      else
         cache.put(name, newContents);
      super.update(name, newContents);  // Trigger any listeners.
      return this;
   }

   @Override /* Overridden from ConfigStore */
   public synchronized String write(String name, String expectedContents, String newContents) {

      // This is a no-op.
      if (eq(expectedContents, newContents))
         return null;

      var currentContents = read(name);

      if (nn(expectedContents) && neq(currentContents, expectedContents))
         return currentContents;

      update(name, newContents);

      return null;
   }
}