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.
/**
 * 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 ch.qos.logback.classic.ClassicConstants;
import ch.qos.logback.core.CoreConstants;

public class TargetLengthBasedClassNameAbbreviator implements Abbreviator {

    final int targetLength;

    public TargetLengthBasedClassNameAbbreviator(int targetLength) {
        this.targetLength = targetLength;
    }

    public String abbreviate(String fqClassName) {
        StringBuilder buf = new StringBuilder(targetLength);
        if (fqClassName == null) {
            throw new IllegalArgumentException("Class name may not be null");
        }

        int inLen = fqClassName.length();
        if (inLen < targetLength) {
            return fqClassName;
        }

        int[] dotIndexesArray = new int[ClassicConstants.MAX_DOTS];
        // a.b.c contains 2 dots but 2+1 parts.
        // see also http://jira.qos.ch/browse/LBCLASSIC-110
        int[] lengthArray = new int[ClassicConstants.MAX_DOTS + 1];

        int dotCount = computeDotIndexes(fqClassName, dotIndexesArray);

        // System.out.println();
        // System.out.println("Dot count for [" + className + "] is " + dotCount);
        // if there are not dots than abbreviation is not possible
        if (dotCount == 0) {
            return fqClassName;
        }
        // printArray("dotArray: ", dotArray);
        computeLengthArray(fqClassName, dotIndexesArray, lengthArray, dotCount);
        // printArray("lengthArray: ", lengthArray);
        for (int i = 0; i <= dotCount; i++) {
            if (i == 0) {
                buf.append(fqClassName.substring(0, lengthArray[i] - 1));
            } else {
                buf.append(fqClassName.substring(dotIndexesArray[i - 1], dotIndexesArray[i - 1] + lengthArray[i]));
            }
            // System.out.println("i=" + i + ", buf=" + buf);
        }

        return buf.toString();
    }

    static int computeDotIndexes(final String className, int[] dotArray) {
        int dotCount = 0;
        int k = 0;
        while (true) {
            // ignore the $ separator in our computations. This is both convenient
            // and sensible.
            k = className.indexOf(CoreConstants.DOT, k);
            if (k != -1 && dotCount < ClassicConstants.MAX_DOTS) {
                dotArray[dotCount] = k;
                dotCount++;
                k++;
            } else {
                break;
            }
        }
        return dotCount;
    }

    void computeLengthArray(final String className, int[] dotArray, int[] lengthArray, int dotCount) {
        int toTrim = className.length() - targetLength;
        // System.out.println("toTrim=" + toTrim);

        // int toTrimAvarage = 0;

        int len;
        for (int i = 0; i < dotCount; i++) {
            int previousDotPosition = -1;
            if (i > 0) {
                previousDotPosition = dotArray[i - 1];
            }
            int available = dotArray[i] - previousDotPosition - 1;
            // System.out.println("i=" + i + ", available = " + available);

            len = (available < 1) ? available : 1;
            // System.out.println("i=" + i + ", toTrim = " + toTrim);

            if (toTrim > 0) {
                len = (available < 1) ? available : 1;
            } else {
                len = available;
            }
            toTrim -= (available - len);
            lengthArray[i] = len + 1;
        }

        int lastDotIndex = dotCount - 1;
        lengthArray[dotCount] = className.length() - dotArray[lastDotIndex];
    }

    static void printArray(String msg, int[] ia) {
        System.out.print(msg);
        for (int i = 0; i < ia.length; i++) {
            if (i == 0) {
                System.out.print(ia[i]);
            } else {
                System.out.print(", " + ia[i]);
            }
        }
        System.out.println();
    }
}