Break out sling value properties

ValueFormat.java

// src: https://github.com/Adobe-Consulting-Services/acs-aem-commons/blob/10d9603878e4d534144aad8196af804652de67d3/bundle/src/main/java/com/adobe/acs/commons/mcp/model/ValueFormat.java
/*
 * #%L
 * ACS AEM Commons Bundle
 * %%
 * Copyright (C) 2017 Adobe
 * %%
 * 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.
 * #L%
 */

import java.lang.reflect.Field;
import java.util.function.Function;

/**
 * Describes the desired output format of a value within a report
 */
@SuppressWarnings({"checkstyle:constantname", "squid:S00115"})
public enum ValueFormat {
    plain, storageSize("_short", ValueFormat::getHumanSize);
    int columnCount = 1;
    String suffix = "";
    Function<Object, Object> altFunction;

    ValueFormat() {
    }

    ValueFormat(String alternate, Function<Object, Object> altFunc) {
        columnCount = 2;
        suffix = alternate;
        altFunction = altFunc;
    }

    public static ValueFormat forField(Enum anEnum) {
        try {
            Field field = anEnum.getDeclaringClass().getField(anEnum.name());
            if (!field.isAnnotationPresent(FieldFormat.class)) {
                return ValueFormat.plain;
            } else {
                FieldFormat rf = field.getAnnotation(FieldFormat.class);
                return rf.value();
            }
        } catch (IllegalArgumentException | NoSuchFieldException | SecurityException ex) {
            // Ignore errors, assume plain
        }
        return ValueFormat.plain;
    }

    public Object getAlternateValue(Object val) {
        return altFunction.apply(val);
    }

    public static String getHumanSize(Object val) {
        if (val == null) {
            return null;
        }
        Long bytes = (val instanceof Long) ? (Long) val : Long.parseLong(String.valueOf(val));
        return humanReadableByteCount(bytes, false);
    }
    
 // From: https://programming.guide/worlds-most-copied-so-snippet.html
    public static strictfp String humanReadableByteCount(long bytes, boolean si) {
        int unit = si ? 1000 : 1024;
        long absBytes = bytes == Long.MIN_VALUE ? Long.MAX_VALUE : Math.abs(bytes);
        if (absBytes < unit) {
          return bytes + " B";
        }
        int exp = (int) (Math.log(absBytes) / Math.log(unit));
        long th = (long) (Math.pow(unit, exp) * (unit - 0.05));
        if (exp < 6 && absBytes >= th - ((th & 0xfff) == 0xd00 ? 52 : 0))  {
          exp++; 
        }
        String pre = (si ? "kMGTPE" : "KMGTPE").charAt(exp - 1) + (si ? "" : "i");
        if (exp > 4) {
            bytes /= unit;
            exp -= 1;
        }
        return String.format("%.1f %sB", bytes / Math.pow(unit, exp), pre);
    }
}

// test
// src: https://github.com/Adobe-Consulting-Services/acs-aem-commons/blob/10d9603878e4d534144aad8196af804652de67d3/bundle/src/test/java/com/adobe/acs/commons/mcp/model/ValueFormatTest.java
import org.junit.Test;

import static org.junit.Assert.*;

/**
 * Basic sanity check of value formats in MCP
 */
public class ValueFormatTest {

    private static String ONE = String.format("%.1f", 1f);

    enum FieldEnum {
        @FieldFormat(ValueFormat.plain)
        somePlainField,
        @FieldFormat(ValueFormat.storageSize)
        someStorageSizeField,
        someUnannotatedField
    }
    
    @Test
    public void testDefinedAnnotations() {
        assertEquals(ValueFormat.plain, ValueFormat.forField(FieldEnum.somePlainField));
        assertEquals(ValueFormat.storageSize, ValueFormat.forField(FieldEnum.someStorageSizeField));
    }
    
    @Test
    public void testUndefinedAnnotations() {
        assertEquals(ValueFormat.plain, ValueFormat.forField(FieldEnum.someUnannotatedField));
    }
    
    @Test
    public void oneKb() {
        assertEquals(ONE + " KiB", ValueFormat.getHumanSize(1 << 10));
    }
    
    @Test
    public void oneMb() {
        assertEquals(ONE + " MiB", ValueFormat.getHumanSize(1 << 20));
    }    
    
    @Test
    public void oneGb() {
        assertEquals(ONE + " GiB", ValueFormat.getHumanSize(1 << 30));
    }
    
    @Test
    public void onetb() {
        assertEquals(ONE + " TiB", ValueFormat.getHumanSize(((long) (1 << 30)) * 1024L));
    }
}