LamiDecimalUnitFormat.java

/*******************************************************************************
 * Copyright (c) 2016 EfficiOS Inc., Jonathan Rajotte-Julien
 *
 * All rights reserved. This program and the accompanying materials are
 * made available under the terms of the Eclipse Public License v1.0 which
 * accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/

package org.eclipse.tracecompass.internal.provisional.analysis.lami.ui.format;

import java.math.BigDecimal;
import java.text.FieldPosition;

import org.eclipse.jdt.annotation.Nullable;
import org.eclipse.tracecompass.common.core.format.DecimalUnitFormat;
import org.eclipse.tracecompass.internal.provisional.analysis.lami.ui.viewers.LamiGraphRange;

/**
 * Decimal formatter for Lami graph
 *
 * Since the graph use normalized internal value the initial (external)
 * representation needs to be obtained. Subsequent formatting is done based on a
 * Double. Loss of precision could occurs based on the size. For now, loss of
 * precision for decimal values is not a big concern. If it ever become one the
 * use of Long while formatting might come in handy.
 *
 * @author Jonathan Rajotte-Julien
 */
public class LamiDecimalUnitFormat extends DecimalUnitFormat {

    /** Maximum amount of digits that can be represented into a double */
    private static final int BIG_DECIMAL_DIVISION_SCALE = 22;

    private static final long serialVersionUID = 977671266270661188L;

    private final @Nullable LamiGraphRange fInternalRange;
    private final @Nullable LamiGraphRange fExternalRange;

    /**
     * Default constructor
     */
    public LamiDecimalUnitFormat() {
        super();
        fInternalRange = null;
        fExternalRange = null;
    }

    /**
     * Constructor with internal and external LamiRange for scale transformation
     *
     * @param internalRange
     *            The internal range used for graph representation
     *
     * @param externalRange
     *            The external (real value) range shown to the user
     */
    public LamiDecimalUnitFormat(@Nullable LamiGraphRange internalRange, @Nullable LamiGraphRange externalRange) {
        super();
        fInternalRange = internalRange;
        fExternalRange = externalRange;
    }

    /**
     * Constructor with multiplication factor and internal and external
     * LamiRange for scale transformation.
     *
     * @param factor
     *            Multiplication factor to apply to the value
     * @param internalRange
     *            The internal range used for graph representation
     * @param externalRange
     *            The external (real value) range shown to the user
     */
    public LamiDecimalUnitFormat(double factor, @Nullable LamiGraphRange internalRange, @Nullable LamiGraphRange externalRange) {
        super(factor);
        fInternalRange = internalRange;
        fExternalRange = externalRange;
    }

    /**
     * @return the internal range definition
     */
    public @Nullable LamiGraphRange getInternalRange() {
        return fInternalRange;
    }

    /**
     * @return the external range definition
     */
    public @Nullable LamiGraphRange getExternalRange() {
        return fExternalRange;
    }

    @Override
    public StringBuffer format(@Nullable Object obj, @Nullable StringBuffer toAppendTo, @Nullable FieldPosition pos) {
        if (!(obj instanceof Number) || toAppendTo == null) {
            throw new IllegalArgumentException("Cannot format given Object as a Number: " + obj); //$NON-NLS-1$
        }

        @Nullable LamiGraphRange internalRange = fInternalRange;
        @Nullable LamiGraphRange externalRange = fExternalRange;
        if (internalRange == null || externalRange == null) {
            StringBuffer buffer = super.format(obj, toAppendTo, pos);
            return (buffer == null ? new StringBuffer() : buffer);
        }

        if (internalRange.getDelta().compareTo(BigDecimal.ZERO) == 0) {
            StringBuffer buffer = super.format(externalRange.getMinimum().doubleValue(), toAppendTo, pos);
            return (buffer == null ? new StringBuffer() : buffer);
        }

        if (externalRange.getDelta().compareTo(BigDecimal.ZERO) == 0) {
            StringBuffer buffer = super.format(externalRange.getMinimum().doubleValue(), toAppendTo, pos);
            return (buffer == null ? new StringBuffer() : buffer);
        }

        /* Find external value before formatting */
        BigDecimal externalValue = (new BigDecimal(obj.toString()))
                .subtract(internalRange.getMinimum())
                .multiply(externalRange.getDelta())
                .divide(internalRange.getDelta(), BIG_DECIMAL_DIVISION_SCALE, BigDecimal.ROUND_DOWN)
                .add(externalRange.getMinimum());

        Double value = externalValue.doubleValue();
        StringBuffer buffer = super.format(value, toAppendTo, pos);
        return (buffer == null ? new StringBuffer() : buffer);
    }
}