/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
    *
    * This program and the accompanying materials are dual-licensed under
    * either the terms of the Eclipse Public License v1.0 as published by
    * the Eclipse Foundation
    *
    *   or (per the licensee's choosing)
   *
   * under the terms of the GNU Lesser General Public License version 2.1
   * as published by the Free Software Foundation.
   */
  package ch.qos.logback.classic.pattern;
  
  import static ch.qos.logback.core.CoreConstants.DOT;
  
  public class TargetLengthBasedClassNameAbbreviator implements Abbreviator {
  
      final int targetLength;
  
      public TargetLengthBasedClassNameAbbreviator(int targetLength) {
          this.targetLength = targetLength;
      }
  
      public String abbreviate(String fqClassName) {
          if (fqClassName == null) {
              throw new IllegalArgumentException("Class name may not be null");
          }
  
          int inLen = fqClassName.length();
          if (inLen < targetLength) {
              return fqClassName;
          }
  
          StringBuilder buf = new StringBuilder(inLen);
  
          int rightMostDotIndex = fqClassName.lastIndexOf(DOT);
  
          if (rightMostDotIndex == -1)
              return fqClassName;
  
          // length of last segment including the dot
          int lastSegmentLength = inLen - rightMostDotIndex;
  
          int leftSegments_TargetLen = targetLength - lastSegmentLength;
          if (leftSegments_TargetLen < 0)
              leftSegments_TargetLen = 0;
  
          int leftSegmentsLen = inLen - lastSegmentLength;
  
          // maxPossibleTrim denotes the maximum number of characters we aim to trim
          // the actual number of character trimmed may be higher since segments, when
          // reduced, are reduced to just one character
          int maxPossibleTrim = leftSegmentsLen - leftSegments_TargetLen;
  
          int trimmed = 0;
          boolean inDotState = true;
  
          int i = 0;
          for (; i < rightMostDotIndex; i++) {
              char c = fqClassName.charAt(i);
              if (c == DOT) {
                  // if trimmed too many characters, let us stop
                  if (trimmed >= maxPossibleTrim)
                      break;
                  buf.append(c);
                  inDotState = true;
              } else {
                  if (inDotState) {
                      buf.append(c);
                      inDotState = false;
                  } else {
                      trimmed++;
                  }
              }
          }
          // append from the position of i which may include the last seen DOT
          buf.append(fqClassName.substring(i));
          return buf.toString();
      }
  }