/*
 * 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.commons.lang;

import static org.apache.juneau.commons.utils.Shorts.*;
import static org.apache.juneau.commons.utils.StringUtils.*;

import java.util.*;

/**
 * Represents a version string such as <js>"1.2"</js> or <js>"1.2.3"</js>
 *
 * <p>
 * Used to compare version numbers.
 *
 * <h5 class='section'>Equality vs. matching:</h5>
 * <p>
 * {@link #equals(Object)}, {@link #hashCode()} and {@link #compareTo(Version)} are <b>strict</b> and
 * mutually consistent &mdash; two versions are only equal when their full part sequences are identical
 * (e.g. <js>"1.2"</js> is <b>not</b> equal to <js>"1.2.3"</js> or <js>"1.2.0"</js>).  For the looser
 * prefix/compatibility comparison (where trailing parts are ignored), use {@link #matches(Version)}.
 */
public class Version implements Comparable<Version> {

   /**
    * Static creator.
    *
    * @param value
    *    A string of the form <js>"#.#..."</js> where there can be any number of parts.
    *    <br>Valid values:
    *    <ul>
    *       <li><js>"1.2"</js>
    *       <li><js>"1.2.3"</js>
    *       <li><js>"0.1"</js>
    *       <li><js>".1"</js>
    *    </ul>
    *    <br>Can be <jk>null</jk>.
    * @return A new header bean, or <jk>null</jk> if the value is <jk>null</jk>.
    */
   public static Version of(String value) {
      if (value == null)
         return null;
      return new Version(value);
   }

   private final int[] parts;

   /**
    * Constructor
    *
    * @param value
    *    A string of the form <js>"#.#..."</js> where there can be any number of parts.
    *    <br>Valid values:
    *    <ul>
    *       <li><js>"1.2"</js>
    *       <li><js>"1.2.3"</js>
    *       <li><js>"0.1"</js>
    *       <li><js>".1"</js>
    *    </ul>
    *    Any parts that are not numeric are interpreted as {@link Integer#MAX_VALUE}
    *    <br>Can be <jk>null</jk> or empty (treated as version <js>"0"</js>).
    */
   public Version(String value) {
      if (isEmpty(value))
         value = "0";
      String[] sParts = splita(value, '.');
      parts = new int[sParts.length];
      for (var i = 0; i < sParts.length; i++) {
         try {
            parts[i] = sParts[i].isEmpty() ? 0 : Integer.parseInt(sParts[i]);
         } catch (@SuppressWarnings("unused") NumberFormatException e) {
            parts[i] = Integer.MAX_VALUE;
         }
      }
   }

   @Override
   public int compareTo(Version v) {
      for (int i = 0; i < Math.min(parts.length, v.parts.length); i++) {
         var c = parts[i] - v.parts[i];
         if (c != 0)
            return c;
      }
      return parts.length - v.parts.length;
   }

   @Override /* Overridden from Object */
   public boolean equals(Object o) {
      return o instanceof Version o2 && Arrays.equals(parts, o2.parts);
   }

   /**
    * Returns the maintenance version part (i.e. part at index 2).
    *
    * @return The version part, never <jk>null</jk>.
    */
   public Optional<Integer> getMaintenance() { return getPart(2); }

   /**
    * Returns the major version part (i.e. part at index 0).
    *
    * @return The version part, never <jk>null</jk>.
    */
   public Optional<Integer> getMajor() { return getPart(0); }

   /**
    * Returns the minor version part (i.e. part at index 1).
    *
    * @return The version part, never <jk>null</jk>.
    */
   public Optional<Integer> getMinor() { return getPart(1); }

   /**
    * Returns the version part at the specified zero-indexed value.
    *
    * @param index The index of the version part.
    * @return The version part, never <jk>null</jk>.
    */
   public Optional<Integer> getPart(int index) {
      if (index < 0 || parts.length <= index)
         return oe();
      return o(parts[index]);
   }

   @Override /* Overridden from Object */
   public int hashCode() {
      return Arrays.hashCode(parts);
   }

   /**
    * Returns <jk>true</jk> if the specified version is at least this version.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bjava'>
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2"</js>).isAtLeast(Version.<jsm>of</jsm>(<js>"1"</js>)));
    *    <jsm>assertFalse</jsm>(Version.<jsm>of</jsm>(<js>"1.2"</js>).isAtLeast(Version.<jsm>of</jsm>(<js>"2"</js>)));
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2"</js>).isAtLeast(Version.<jsm>of</jsm>(<js>"1.2.3"</js>)));
    *    <jsm>assertFalse</jsm>(Version.<jsm>of</jsm>(<js>"1.2.0"</js>).isAtLeast(Version.<jsm>of</jsm>(<js>"1.2.3"</js>)));
    * </p>
    *
    * @param v The version to compare to.  Must not be <jk>null</jk>.
    * @return <jk>true</jk> if the specified version is at least this version.
    */
   public boolean isAtLeast(Version v) {
      return isAtLeast(v, false);
   }

   /**
    * Returns <jk>true</jk> if the specified version is at least this version.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bjava'>
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).isAtLeast(Version.<jsm>of</jsm>(<js>"1.2.3"</js>, <jk>false</jk>)));
    *    <jsm>assertFalse</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).isAtLeast(Version.<jsm>of</jsm>(<js>"1.2.3"</js>, <jk>true</jk>)));
    * </p>
    *
    * @param v The version to compare to.  Must not be <jk>null</jk>.
    * @param exclusive Match down-to-version but not including.
    * @return <jk>true</jk> if the specified version is at least this version.
    */
   public boolean isAtLeast(Version v, boolean exclusive) {
      for (int i = 0; i < Math.min(parts.length, v.parts.length); i++) {
         var c = v.parts[i] - parts[i];
         if (c > 0)
            return false;
         else if (c < 0)
            return true;
      }
      for (var i = parts.length; i < v.parts.length; i++)
         if (v.parts[i] != 0)
            return false;
      // If this version has more parts than v, check if any extra parts are non-zero
      // If they are, then this > v, so return true (this is greater than v)
      for (var i = v.parts.length; i < parts.length; i++)
         if (parts[i] > 0)
            return true;  // this > v, so always return true
      return ! exclusive;
   }

   /**
    * Returns <jk>true</jk> if the specified version is at most this version.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bjava'>
    *    <jsm>assertFalse</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).isAtMost(Version.<jsm>of</jsm>(<js>"1"</js>)));
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).isAtMost(Version.<jsm>of</jsm>(<js>"2"</js>)));
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).isAtMost(Version.<jsm>of</jsm>(<js>"1.2"</js>)));
    *    <jsm>assertFalse</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).isAtMost(Version.<jsm>of</jsm>(<js>"1.2.0"</js>)));
    * </p>
    *
    * @param v The version to compare to.  Must not be <jk>null</jk>.
    * @return <jk>true</jk> if the specified version is at most this version.
    */
   public boolean isAtMost(Version v) {
      return isAtMost(v, false);
   }

   /**
    * Returns <jk>true</jk> if the specified version is at most this version.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bjava'>
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).isAtMost(Version.<jsm>of</jsm>(<js>"1.2.3"</js>, <jk>false</jk>)));
    *    <jsm>assertFalse</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).isAtMost(Version.<jsm>of</jsm>(<js>"1.2.3"</js>, <jk>true</jk>)));
    * </p>
    *
    * @param v The version to compare to.  Must not be <jk>null</jk>.
    * @param exclusive Match up-to-version but not including.
    * @return <jk>true</jk> if the specified version is at most this version.
    */
   public boolean isAtMost(Version v, boolean exclusive) {
      for (int i = 0; i < Math.min(parts.length, v.parts.length); i++) {
         var c = parts[i] - v.parts[i];
         if (c > 0)
            return false;
         else if (c < 0)
            return true;
      }
      for (var i = parts.length; i < v.parts.length; i++)
         if (v.parts[i] > 0)
            return true;
      return ! exclusive;
   }

   /**
    * Returns <jk>true</jk> if this version matches the specified version, comparing only the parts they have in
    * common (i.e. one version is a prefix of the other).
    *
    * <p>
    * This is a looser comparison than {@link #equals(Object)}, which requires the full version part sequences to be
    * identical.  Two versions <i>match</i> when every part up to the length of the shorter version is identical; any
    * trailing parts on the longer version are ignored.  Unlike {@link #equals(Object)}, this relation is <b>not</b>
    * consistent with {@link #hashCode()} and must never be used as the basis for hash- or tree-based collection
    * membership.
    *
    * <h5 class='section'>Example:</h5>
    * <p class='bjava'>
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).matches(Version.<jsm>of</jsm>(<js>"1.2.3"</js>)));
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).matches(Version.<jsm>of</jsm>(<js>"1.2"</js>)));
    *    <jsm>assertTrue</jsm>(Version.<jsm>of</jsm>(<js>"1.2"</js>).matches(Version.<jsm>of</jsm>(<js>"1.2.3"</js>)));
    *    <jsm>assertFalse</jsm>(Version.<jsm>of</jsm>(<js>"1.2.3"</js>).matches(Version.<jsm>of</jsm>(<js>"1.2.4"</js>)));
    * </p>
    *
    * @param v The version to compare to.  Must not be <jk>null</jk>.
    * @return <jk>true</jk> if this version matches the specified version on their common parts.
    */
   public boolean matches(Version v) {
      for (int i = 0; i < Math.min(parts.length, v.parts.length); i++)
         if (v.parts[i] - parts[i] != 0)
            return false;
      return true;
   }

   @Override /* Overridden from Object */
   public String toString() {
      return join(parts, '.');
   }
}