/*
 * Copyright (c) 2015 Spotify AB.
 * Copyright (c) 2015 Jeppe Schou.
 *
 * Licensed 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 com.spotify.docker.client;

public final class VersionCompare {

  private VersionCompare() {
  }

  /**
   * Compares two version strings. <p>
   *   https://stackoverflow.com/questions/6701948/efficient-way-to-compare-version-strings-in-java
   * </p> Use this instead of String.compareTo() for a non-lexicographical comparison that works for
   * version strings. e.g. "1.10".compareTo("1.6").
   *
   * @param str1 a string of ordinal numbers separated by decimal points.
   * @param str2 a string of ordinal numbers separated by decimal points.
   * @return The result is a negative integer if str1 is _numerically_ less than str2. The result is
   * a positive integer if str1 is _numerically_ greater than str2. The result is zero if the
   * strings are _numerically_ equal. N.B. It does not work if "1.10" is supposed to be equal to
   * "1.10.0".
   */
  public static int compareVersion(String str1, String str2) {
    final String[] vals1 = str1.split("\\.");
    final String[] vals2 = str2.split("\\.");
    int i = 0;
    // set index to first non-equal ordinal or length of shortest version string
    while (i < vals1.length && i < vals2.length && vals1[i].equals(vals2[i])) {
      i++;
    }
    // compare first non-equal ordinal number
    if (i < vals1.length && i < vals2.length) {
      final int diff = Integer.valueOf(vals1[i]).compareTo(Integer.valueOf(vals2[i]));
      return Integer.signum(diff);
    } else {
      // the strings are equal or one string is a substring of the other
      // e.g. "1.2.3" = "1.2.3" or "1.2.3" < "1.2.3.4"
      return Integer.signum(vals1.length - vals2.length);
    }
  }
}
