/*
 * 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.geode;

import java.io.IOException;
import java.io.Reader;

import org.apache.geode.internal.statistics.StatArchiveFormat;

/**
 * Instances of this interface provide methods that create instances of {@link StatisticDescriptor}
 * and {@link StatisticsType}. Every {@link StatisticsFactory} is also a type factory.
 *
 * <P>
 *
 * A <code>StatisticsTypeFactory</code> can create a {@link StatisticDescriptor statistic} of three
 * numeric types: <code>int</code>, <code>long</code>, and <code>double</code>. A statistic
 * (<code>StatisticDescriptor</code>) can either be a <I>gauge</I> meaning that its value can
 * increase and decrease or a <I>counter</I> meaning that its value is strictly increasing. Marking
 * a statistic as a counter allows statistic display tools to properly display a statistics whose
 * value "wraps around" (that is, exceeds its maximum value).
 *
 * <P>
 * The following code is an example of how to create a type using XML. In this example the type has
 * two stats whose values always increase:
 *
 * <pre>
    StatisticsTypeFactory f = ...;
    StatisticsType t = f.createType(
        "StatSampler",
        "Stats on the statistic sampler.",
        new StatisticDescriptor[] {
            f.createIntCounter("sampleCount",
                               "Total number of samples taken by this sampler.",
                               "samples"),
            f.createLongCounter("sampleTime",
                                "Total amount of time spent taking samples.",
                                "milliseconds"),
        }
    );
 * </pre>
 * <P>
 * The following is an example of how to create the same type using XML. The XML data:
 *
 * <pre>
    &lt;?xml version="1.0" encoding="UTF-8"?&gt;
    &lt;!DOCTYPE statistics PUBLIC
      "-//GemStone Systems, Inc.//GemFire Statistics Type//EN"
      "http://www.gemstone.com/dtd/statisticsType.dtd"&gt;
    &lt;statistics&gt;
      &lt;type name="StatSampler"&gt;
        &lt;description&gt;Stats on the statistic sampler.&lt;/description&gt;
        &lt;stat name="sampleCount" storage="int" counter="true"&gt;
          &lt;description&gt;Total number of samples taken by this sampler.&lt;/description&gt;
          &lt;unit&gt;samples&lt;/unit&gt;
        &lt;/stat&gt;
        &lt;stat name="sampleTime" storage="long" counter="true"&gt;
          &lt;description&gt;Total amount of time spent taking samples.&lt;/description&gt;
          &lt;unit&gt;milliseconds&lt;/unit&gt;
        &lt;/stat&gt;
      &lt;/type&gt;
    &lt;/statistics&gt;
 * </pre>
 *
 * The code to create the type:
 *
 * <pre>
      StatisticsTypeFactory f = ...;
      Reader r = new InputStreamReader("fileContainingXmlData"));
      StatisticsType type = f.createTypesFromXml(r)[0];
 * </pre>
 * <P>
 *
 * @see <A href="package-summary.html#statistics">Package introduction</A>
 *
 *
 * @since GemFire 3.0
 */
public interface StatisticsTypeFactory {

  /**
   * Creates and returns an int counter {@link StatisticDescriptor} with the given
   * <code>name</code>, <code>description</code>, <code>units</code>, and with larger values
   * indicating better performance.
   */
  public StatisticDescriptor createIntCounter(String name, String description, String units);

  /**
   * Creates and returns a long counter {@link StatisticDescriptor} with the given
   * <code>name</code>, <code>description</code>, <code>units</code>, and with larger values
   * indicating better performance.
   */
  public StatisticDescriptor createLongCounter(String name, String description, String units);

  /**
   * Creates and returns a double counter {@link StatisticDescriptor} with the given
   * <code>name</code>, <code>description</code>, <code>units</code>, and with larger values
   * indicating better performance.
   */
  public StatisticDescriptor createDoubleCounter(String name, String description, String units);

  /**
   * Creates and returns an int gauge {@link StatisticDescriptor} with the given <code>name</code>,
   * <code>description</code>, <code>units</code>, and with smaller values indicating better
   * performance.
   */
  public StatisticDescriptor createIntGauge(String name, String description, String units);

  /**
   * Creates and returns a long gauge {@link StatisticDescriptor} with the given <code>name</code>,
   * <code>description</code>, <code>units</code>, and with smaller values indicating better
   * performance.
   */
  public StatisticDescriptor createLongGauge(String name, String description, String units);

  /**
   * Creates and returns a double gauge {@link StatisticDescriptor} with the given
   * <code>name</code>, <code>description</code>, <code>units</code>, and with smaller values
   * indicating better performance.
   */
  public StatisticDescriptor createDoubleGauge(String name, String description, String units);

  /**
   * Creates and returns an int counter {@link StatisticDescriptor} with the given
   * <code>name</code>, <code>description</code>, <code>largerBetter</code>, and <code>units</code>.
   */
  public StatisticDescriptor createIntCounter(String name, String description, String units,
      boolean largerBetter);

  /**
   * Creates and returns a long counter {@link StatisticDescriptor} with the given
   * <code>name</code>, <code>description</code>, <code>largerBetter</code>, and <code>units</code>.
   */
  public StatisticDescriptor createLongCounter(String name, String description, String units,
      boolean largerBetter);

  /**
   * Creates and returns a double counter {@link StatisticDescriptor} with the given
   * <code>name</code>, <code>description</code>, <code>largerBetter</code>, and <code>units</code>.
   */
  public StatisticDescriptor createDoubleCounter(String name, String description, String units,
      boolean largerBetter);

  /**
   * Creates and returns an int gauge {@link StatisticDescriptor} with the given <code>name</code>,
   * <code>description</code>, <code>largerBetter</code>, and <code>units</code>.
   */
  public StatisticDescriptor createIntGauge(String name, String description, String units,
      boolean largerBetter);

  /**
   * Creates and returns a long gauge {@link StatisticDescriptor} with the given <code>name</code>,
   * <code>description</code>, <code>largerBetter</code>, and <code>units</code>.
   */
  public StatisticDescriptor createLongGauge(String name, String description, String units,
      boolean largerBetter);

  /**
   * Creates and returns a double gauge {@link StatisticDescriptor} with the given
   * <code>name</code>, <code>description</code>, <code>largerBetter</code>, and <code>units</code>.
   */
  public StatisticDescriptor createDoubleGauge(String name, String description, String units,
      boolean largerBetter);


  /**
   * The maximum number of descriptors a single statistics type can have.
   * <P>
   * Current value is: <code>254</code>
   */
  public final int MAX_DESCRIPTORS_PER_TYPE = StatArchiveFormat.ILLEGAL_STAT_OFFSET - 1;

  /**
   * Creates or finds and returns a {@link StatisticsType} with the given <code>name</code>,
   * <code>description</code>, and {@link StatisticDescriptor statistic descriptions}.
   *
   * @throws IllegalArgumentException if a type with the given <code>name</code> already exists and
   *         it differs from the given parameters.
   */
  public StatisticsType createType(String name, String description, StatisticDescriptor[] stats);

  /**
   * Finds and returns an already created {@link StatisticsType} with the given <code>name</code>.
   * Returns <code>null</code> if the type does not exist.
   */
  public StatisticsType findType(String name);

  /**
   * Creates one or more {@link StatisticsType} from the contents of the given <code>reader</code>.
   * The created types can be found by calling {@link #findType}.
   *
   * @param reader The source of the XML data which must comply with the
   *        <code>statisticsType.dtd</code>.
   *
   * @throws IllegalArgumentException if a type defined in the reader already exists
   * @throws IOException Something went wrong while reading from <code>reader</code>
   */
  public StatisticsType[] createTypesFromXml(Reader reader) throws IOException;
}
