/*
 * 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.rest.stats;

import static org.apache.juneau.internal.CollectionUtils.*;

import java.util.*;
import java.util.concurrent.atomic.*;

import org.apache.juneau.common.utils.*;
import org.apache.juneau.cp.*;
import org.apache.juneau.internal.*;
import org.apache.juneau.marshaller.*;

/**
 * Represents an entry in {@link ThrownStore}.
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/ExecutionStatistics">REST method execution statistics</a>
 * </ul>
 */
public class ThrownStats implements Cloneable {

   //-----------------------------------------------------------------------------------------------------------------
   // Static
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * Static creator.
    *
    * @param beanStore The bean store to use for creating beans.
    * @return A new builder for this object.
    */
   public static Builder create(BeanStore beanStore) {
      return new Builder(beanStore);
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Builder
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * Builder class.
    */
   public static class Builder {

      final BeanStore beanStore;
      Throwable throwable;
      long hash;
      List<String> stackTrace;
      ThrownStats causedBy;

      BeanCreator<ThrownStats> creator;

      /**
       * Constructor.
       *
       * @param beanStore The bean store to use for creating beans.
       */
      protected Builder(BeanStore beanStore) {
         this.beanStore = beanStore;
         this.creator = beanStore.createBean(ThrownStats.class).builder(Builder.class, this);
      }

      /**
       * Create a new {@link ThrownStats} using this builder.
       *
       * @return A new {@link ThrownStats}
       */
      public ThrownStats build() {
         return creator.run();
      }

      /**
       * Specifies a subclass of {@link ThrownStats} to create when the {@link #build()} method is called.
       *
       * @param value The new value for this setting.
       * @return This object.
       */
      public Builder type(Class<? extends ThrownStats> value) {
         creator.type(value == null ? ThrownStats.class : value);
         return this;
      }

      /**
       * Specifies the thrown exception.
       *
       * @param value The new value for this setting.
       * @return This object.
       */
      public Builder throwable(Throwable value) {
         this.throwable = value;
         return this;
      }

      /**
       * Specifies the calculated hash.
       *
       * @param value The new value for this setting.
       * @return This object.
       */
      public Builder hash(long value) {
         this.hash = value;
         return this;
      }

      /**
       * Specifies the normalized stacktrace.
       *
       * @param value The new value for this setting.
       * @return This object.
       */
      public Builder stackTrace(List<String> value) {
         this.stackTrace = value;
         return this;
      }

      /**
       * Specifies the caused-by exception.
       *
       * @param value The new value for this setting.
       * @return This object.
       */
      public Builder causedBy(ThrownStats value) {
         this.causedBy = value;
         return this;
      }
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Instance
   //-----------------------------------------------------------------------------------------------------------------

   private final long guid;
   private final long hash;
   private final Class<?> thrownClass;
   private final String firstMessage;
   private final List<String> stackTrace;
   private final Optional<ThrownStats> causedBy;

   private final AtomicInteger count;
   private final AtomicLong firstOccurrence, lastOccurrence;

   /**
    * Constructor.
    *
    * @param builder The builder for this object.
    */
   protected ThrownStats(Builder builder) {
      this.guid = new Random().nextLong();
      this.thrownClass = builder.throwable.getClass();
      this.firstMessage = builder.throwable.getMessage();
      this.stackTrace = listBuilder(builder.stackTrace).copy().unmodifiable().build();
      this.causedBy = Utils.opt(builder.causedBy);
      this.hash = builder.hash;
      this.count = new AtomicInteger(0);
      long ct = System.currentTimeMillis();
      this.firstOccurrence = new AtomicLong(ct);
      this.lastOccurrence = new AtomicLong(ct);
   }

   /**
    * Copy constructor.
    */
   private ThrownStats(ThrownStats x) {
      this.guid = x.guid;
      this.thrownClass = x.thrownClass;
      this.firstMessage = x.firstMessage;
      this.stackTrace = listBuilder(x.stackTrace).copy().unmodifiable().build();
      this.causedBy = Utils.opt(x.causedBy.isPresent() ? x.causedBy.get().clone() : null);
      this.hash = x.hash;
      this.count = new AtomicInteger(x.count.get());
      this.firstOccurrence = new AtomicLong(x.firstOccurrence.get());
      this.lastOccurrence = new AtomicLong(x.lastOccurrence.get());
   }

   /**
    * Returns a globally unique ID for this object.
    *
    * <p>
    * A random long generated during the creation of this object.
    * Allows this object to be differentiated from other similar objects in multi-node environments so that
    * statistics can be reliably stored in a centralized location.
    *
    * @return The globally unique ID for this object.
    */
   public long getGuid() {
      return guid;
   }

   /**
    * Returns a hash of this exception that can typically be used to uniquely identify it.
    *
    * @return A hash of this exception.
    */
   public long getHash() {
      return hash;
   }

   /**
    * Returns the exception class.
    *
    * @return The exception class.
    */
   public Class<?> getThrownClass() {
      return thrownClass;
   }

   /**
    * Returns the number of times this exception occurred at a specific location in code.
    *
    * @return The number of times this exception occurred at a specific location in code.
    */
   public int getCount() {
      return count.intValue();
   }

   /**
    * Returns the UTC time of the first occurrence of this exception at a specific location in code.
    *
    * @return The UTC time of the first occurrence of this exception at a specific location in code.
    */
   public long getFirstOccurrence() {
      return firstOccurrence.longValue();
   }

   /**
    * Returns the UTC time of the last occurrence of this exception at a specific location in code.
    *
    * @return The UTC time of the last occurrence of this exception at a specific location in code.
    */
   public long getLastOccurrence() {
      return lastOccurrence.longValue();
   }

   /**
    * Returns the message of the first exception at a specific location in code.
    *
    * @return The message of the first exception at a specific location in code.
    */
   public String getFirstMessage() {
      return firstMessage;
   }

   /**
    * Returns the stack trace of the first exception at a specific location in code.
    *
    * @return The stack trace of the first exception at a specific location in code.
    */
   public List<String> getStackTrace() {
      return stackTrace;
   }

   /**
    * Returns the stats on the caused-by exception.
    *
    * @return The stats on the caused-by exception, never <jk>null</jk>.
    */
   public Optional<ThrownStats> getCausedBy() {
      return causedBy;
   }

   /**
    * Increments the occurrence count of this exception.
    *
    * @return This object.
    */
   public ThrownStats increment() {
      count.incrementAndGet();
      lastOccurrence.set(System.currentTimeMillis());
      causedBy.ifPresent(ThrownStats::increment);
      return this;
   }

   @Override /* Object */
   public String toString() {
      return Json5.of(this);
   }

   @Override /* Object */
   public ThrownStats clone() {
      return new ThrownStats(this);
   }
}