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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.swing;

import java.awt.Component;

/**
 * An instance of the <code>Spring</code> class holds three properties that
 * characterize its behavior: the <em>minimum</em>, <em>preferred</em>, and
 * <em>maximum</em> values. Each of these properties may be involved in
 * defining its fourth, <em>value</em>, property based on a series of rules.
 * <p>
 * An instance of the <code>Spring</code> class can be visualized as a
 * mechanical spring that provides a corrective force as the spring is compressed
 * or stretched away from its preferred value. This force is modelled
 * as linear function of the distance from the preferred value, but with
 * two different constants -- one for the compressional force and one for the
 * tensional one. Those constants are specified by the minimum and maximum
 * values of the spring such that a spring at its minimum value produces an
 * equal and opposite force to that which is created when it is at its
 * maximum value. The difference between the <em>preferred</em> and
 * <em>minimum</em> values, therefore, represents the ease with which the
 * spring can be compressed and the difference between its <em>maximum</em>
 * and <em>preferred</em> values, indicates the ease with which the
 * <code>Spring</code> can be extended.
 * See the {@link #sum} method for details.
 *
 * <p>
 * By defining simple arithmetic operations on <code>Spring</code>s,
 * the behavior of a collection of <code>Spring</code>s
 * can be reduced to that of an ordinary (non-compound) <code>Spring</code>. We define
 * the "+", "-", <em>max</em>, and <em>min</em> operators on
 * <code>Spring</code>s so that, in each case, the result is a <code>Spring</code>
 * whose characteristics bear a useful mathematical relationship to its constituent
 * springs.
 *
 * <p>
 * A <code>Spring</code> can be treated as a pair of intervals
 * with a single common point: the preferred value.
 * The following rules define some of the
 * arithmetic operators that can be applied to intervals
 * (<code>[a, b]</code> refers to the interval
 * from <code>a</code>
 * to <code>b</code>,
 * where <code>a &lt;= b</code>).
 *
 * <pre>
 * [a1, b1] + [a2, b2] = [a1 + a2, b1 + b2]
 *
 * -[a, b] = [-b, -a]
 *
 * max([a1, b1], [a2, b2]) = [max(a1, a2), max(b1, b2)]
 * </pre>
 * <p>
 *
 * If we denote <code>Spring</code>s as <code>[a, b, c]</code>,
 * where <code>a &lt;= b &lt;= c</code>, we can define the same
 * arithmetic operators on <code>Spring</code>s:
 *
 * <pre>
 * [a1, b1, c1] + [a2, b2, c2] = [a1 + a2, b1 + b2, c1 + c2]
 *
 * -[a, b, c] = [-c, -b, -a]
 *
 * max([a1, b1, c1], [a2, b2, c2]) = [max(a1, a2), max(b1, b2), max(c1, c2)]
 * </pre>
 * <p>
 * With both intervals and <code>Spring</code>s we can define "-" and <em>min</em>
 * in terms of negation:
 *
 * <pre>
 * X - Y = X + (-Y)
 *
 * min(X, Y) = -max(-X, -Y)
 * </pre>
 * <p>
 * For the static methods in this class that embody the arithmetic
 * operators, we do not actually perform the operation in question as
 * that would snapshot the values of the properties of the method's arguments
 * at the time the static method is called. Instead, the static methods
 * create a new <code>Spring</code> instance containing references to
 * the method's arguments so that the characteristics of the new spring track the
 * potentially changing characteristics of the springs from which it
 * was made. This is a little like the idea of a <em>lazy value</em>
 * in a functional language.
 * <p>
 * If you are implementing a <code>SpringLayout</code> you
 * can find further information and examples in
 * <a
 href="https://docs.oracle.com/javase/tutorial/uiswing/layout/spring.html">How to Use SpringLayout</a>,
 * a section in <em>The Java Tutorial.</em>
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with
 * future Swing releases. The current serialization support is
 * appropriate for short term storage or RMI between applications running
 * the same version of Swing. As of 1.4, support for long term storage
 * of all JavaBeans&trade;
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @see SpringLayout
 * @see SpringLayout.Constraints
 *
 * @author Philip Milne
 * @since 1.4
 */
public abstract class Spring {

 /**
 * An integer value signifying that a property value has not yet been calculated.
 */
 public static final int UNSET = Integer.MIN_VALUE;

 /**
 * Used by factory methods to create a <code>Spring</code>.
 *
 * @see #constant(int)
 * @see #constant(int, int, int)
 * @see #max
 * @see #minus
 * @see #sum
 * @see SpringLayout.Constraints
 */
 protected Spring() {}

 /**
 * Returns the <em>minimum</em> value of this <code>Spring</code>.
 *
 * @return the <code>minimumValue</code> property of this <code>Spring</code>
 */
 public abstract int getMinimumValue();

 /**
 * Returns the <em>preferred</em> value of this <code>Spring</code>.
 *
 * @return the <code>preferredValue</code> of this <code>Spring</code>
 */
 public abstract int getPreferredValue();

 /**
 * Returns the <em>maximum</em> value of this <code>Spring</code>.
 *
 * @return the <code>maximumValue</code> property of this <code>Spring</code>
 */
 public abstract int getMaximumValue();

 /**
 * Returns the current <em>value</em> of this <code>Spring</code>.
 *
 * @return the <code>value</code> property of this <code>Spring</code>
 *
 * @see #setValue
 */
 public abstract int getValue();

 /**
 * Sets the current <em>value</em> of this <code>Spring</code> to <code>value</code>.
 *
 * @param value the new setting of the <code>value</code> property
 *
 * @see #getValue
 */
 public abstract void setValue(int value);

 private double range(boolean contract) {
 return contract ? (getPreferredValue() - getMinimumValue()) :
 (getMaximumValue() - getPreferredValue());
 }

 /*pp*/ double getStrain() {
 double delta = (getValue() - getPreferredValue());
 return delta/range(getValue() < getPreferredValue());
 }

 /*pp*/ void setStrain(double strain) {
 setValue(getPreferredValue() + (int)(strain * range(strain < 0)));
 }

 /*pp*/ boolean isCyclic(SpringLayout l) {
 return false;
 }

 /*pp*/ static abstract class AbstractSpring extends Spring {
 protected int size = UNSET;

 public int getValue() {
 return size != UNSET ? size : getPreferredValue();
 }

 public final void setValue(int size) {
 if (this.size == size) {
 return;
 }
 if (size == UNSET) {
 clear();
 } else {
 setNonClearValue(size);
 }
 }

 protected void clear() {
 size = UNSET;
 }

 protected void setNonClearValue(int size) {
 this.size = size;
 }
 }

 private static class StaticSpring extends AbstractSpring {
 protected int min;
 protected int pref;
 protected int max;

 public StaticSpring(int pref) {
 this(pref, pref, pref);
 }

 public StaticSpring(int min, int pref, int max) {
 this.min = min;
 this.pref = pref;
 this.max = max;
 }

 public String toString() {
 return "StaticSpring [" + min + ", " + pref + ", " + max + "]";
 }

 public int getMinimumValue() {
 return min;
 }

 public int getPreferredValue() {
 return pref;
 }

 public int getMaximumValue() {
 return max;
 }
 }

 private static class NegativeSpring extends Spring {
 private Spring s;

 public NegativeSpring(Spring s) {
 this.s = s;
 }

// Note the use of max value rather than minimum value here.
// See the opening preamble on arithmetic with springs.

 public int getMinimumValue() {
 return -s.getMaximumValue();
 }

 public int getPreferredValue() {
 return -s.getPreferredValue();
 }

 public int getMaximumValue() {
 return -s.getMinimumValue();
 }

 public int getValue() {
 return -s.getValue();
 }

 public void setValue(int size) {
 // No need to check for UNSET as
 // Integer.MIN_VALUE == -Integer.MIN_VALUE.
 s.setValue(-size);
 }

 /*pp*/ boolean isCyclic(SpringLayout l) {
 return s.isCyclic(l);
 }
 }

 private static class ScaleSpring extends Spring {
 private Spring s;
 private float factor;

 private ScaleSpring(Spring s, float factor) {
 this.s = s;
 this.factor = factor;
 }

 public int getMinimumValue() {
 return Math.round((factor < 0 ? s.getMaximumValue() : s.getMinimumValue()) * factor);
 }

 public int getPreferredValue() {
 return Math.round(s.getPreferredValue() * factor);
 }

 public int getMaximumValue() {
 return Math.round((factor < 0 ? s.getMinimumValue() : s.getMaximumValue()) * factor);
 }

 public int getValue() {
 return Math.round(s.getValue() * factor);
 }

 public void setValue(int value) {
 if (value == UNSET) {
 s.setValue(UNSET);
 } else {
 s.setValue(Math.round(value / factor));
 }
 }

 /*pp*/ boolean isCyclic(SpringLayout l) {
 return s.isCyclic(l);
 }
 }

 /*pp*/ static class WidthSpring extends AbstractSpring {
 /*pp*/ Component c;

 public WidthSpring(Component c) {
 this.c = c;
 }

 public int getMinimumValue() {
 return c.getMinimumSize().width;
 }

 public int getPreferredValue() {
 return c.getPreferredSize().width;
 }

 public int getMaximumValue() {
 // We will be doing arithmetic with the results of this call,
 // so if a returned value is Integer.MAX_VALUE we will get
 // arithmetic overflow. Truncate such values.
 return Math.min(Short.MAX_VALUE, c.getMaximumSize().width);
 }
 }

 /*pp*/ static class HeightSpring extends AbstractSpring {
 /*pp*/ Component c;

 public HeightSpring(Component c) {
 this.c = c;
 }

 public int getMinimumValue() {
 return c.getMinimumSize().height;
 }

 public int getPreferredValue() {
 return c.getPreferredSize().height;
 }

 public int getMaximumValue() {
 return Math.min(Short.MAX_VALUE, c.getMaximumSize().height);
 }
 }

 /*pp*/ static abstract class SpringMap extends Spring {
 private Spring s;

 public SpringMap(Spring s) {
 this.s = s;
 }

 protected abstract int map(int i);

 protected abstract int inv(int i);

 public int getMinimumValue() {
 return map(s.getMinimumValue());
 }

 public int getPreferredValue() {
 return map(s.getPreferredValue());
 }

 public int getMaximumValue() {
 return Math.min(Short.MAX_VALUE, map(s.getMaximumValue()));
 }

 public int getValue() {
 return map(s.getValue());
 }

 public void setValue(int value) {
 if (value == UNSET) {
 s.setValue(UNSET);
 } else {
 s.setValue(inv(value));
 }
 }

 /*pp*/ boolean isCyclic(SpringLayout l) {
 return s.isCyclic(l);
 }
 }

// Use the instance variables of the StaticSpring superclass to
// cache values that have already been calculated.
 /*pp*/ static abstract class CompoundSpring extends StaticSpring {
 protected Spring s1;
 protected Spring s2;

 public CompoundSpring(Spring s1, Spring s2) {
 super(UNSET);
 this.s1 = s1;
 this.s2 = s2;
 }

 public String toString() {
 return "CompoundSpring of " + s1 + " and " + s2;
 }

 protected void clear() {
 super.clear();
 min = pref = max = UNSET;
 s1.setValue(UNSET);
 s2.setValue(UNSET);
 }

 protected abstract int op(int x, int y);

 public int getMinimumValue() {
 if (min == UNSET) {
 min = op(s1.getMinimumValue(), s2.getMinimumValue());
 }
 return min;
 }

 public int getPreferredValue() {
 if (pref == UNSET) {
 pref = op(s1.getPreferredValue(), s2.getPreferredValue());
 }
 return pref;
 }

 public int getMaximumValue() {
 if (max == UNSET) {
 max = op(s1.getMaximumValue(), s2.getMaximumValue());
 }
 return max;
 }

 public int getValue() {
 if (size == UNSET) {
 size = op(s1.getValue(), s2.getValue());
 }
 return size;
 }

 /*pp*/ boolean isCyclic(SpringLayout l) {
 return l.isCyclic(s1) || l.isCyclic(s2);
 }
 };

 private static class SumSpring extends CompoundSpring {
 public SumSpring(Spring s1, Spring s2) {
 super(s1, s2);
 }

 protected int op(int x, int y) {
 return x + y;
 }

 protected void setNonClearValue(int size) {
 super.setNonClearValue(size);
 s1.setStrain(this.getStrain());
 s2.setValue(size - s1.getValue());
 }
 }

 private static class MaxSpring extends CompoundSpring {

 public MaxSpring(Spring s1, Spring s2) {
 super(s1, s2);
 }

 protected int op(int x, int y) {
 return Math.max(x, y);
 }

 protected void setNonClearValue(int size) {
 super.setNonClearValue(size);
 s1.setValue(size);
 s2.setValue(size);
 }
 }

 /**
 * Returns a strut -- a spring whose <em>minimum</em>, <em>preferred</em>, and
 * <em>maximum</em> values each have the value <code>pref</code>.
 *
 * @param pref the <em>minimum</em>, <em>preferred</em>, and
 * <em>maximum</em> values of the new spring
 * @return a spring whose <em>minimum</em>, <em>preferred</em>, and
 * <em>maximum</em> values each have the value <code>pref</code>
 *
 * @see Spring
 */
 public static Spring constant(int pref) {
 return constant(pref, pref, pref);
 }

 /**
 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, and
 * <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>,
 * and <code>max</code> respectively.
 *
 * @param min the <em>minimum</em> value of the new spring
 * @param pref the <em>preferred</em> value of the new spring
 * @param max the <em>maximum</em> value of the new spring
 * @return a spring whose <em>minimum</em>, <em>preferred</em>, and
 * <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>,
 * and <code>max</code> respectively
 *
 * @see Spring
 */
 public static Spring constant(int min, int pref, int max) {
 return new StaticSpring(min, pref, max);
 }


 /**
 * Returns <code>-s</code>: a spring running in the opposite direction to <code>s</code>.
 *
 * @return <code>-s</code>: a spring running in the opposite direction to <code>s</code>
 *
 * @see Spring
 */
 public static Spring minus(Spring s) {
 return new NegativeSpring(s);
 }

 /**
 * Returns <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code>
 * in series. In a sum, <code>s3</code>, of two springs, <code>s1</code> and <code>s2</code>,
 * the <em>strains</em> of <code>s1</code>, <code>s2</code>, and <code>s3</code> are maintained
 * at the same level (to within the precision implied by their integer <em>value</em>s).
 * The strain of a spring in compression is:
 * <pre>
 * value - pref
 * ------------
 * pref - min
 * </pre>
 * and the strain of a spring in tension is:
 * <pre>
 * value - pref
 * ------------
 * max - pref
 * </pre>
 * When <code>setValue</code> is called on the sum spring, <code>s3</code>, the strain
 * in <code>s3</code> is calculated using one of the formulas above. Once the strain of
 * the sum is known, the <em>value</em>s of <code>s1</code> and <code>s2</code> are
 * then set so that they are have a strain equal to that of the sum. The formulas are
 * evaluated so as to take rounding errors into account and ensure that the sum of
 * the <em>value</em>s of <code>s1</code> and <code>s2</code> is exactly equal to
 * the <em>value</em> of <code>s3</code>.
 *
 * @return <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code> in series
 *
 * @see Spring
 */
 public static Spring sum(Spring s1, Spring s2) {
 return new SumSpring(s1, s2);
 }

 /**
 * Returns <code>max(s1, s2)</code>: a spring whose value is always greater than (or equal to)
 * the values of both <code>s1</code> and <code>s2</code>.
 *
 * @return <code>max(s1, s2)</code>: a spring whose value is always greater than (or equal to)
 * the values of both <code>s1</code> and <code>s2</code>
 * @see Spring
 */
 public static Spring max(Spring s1, Spring s2) {
 return new MaxSpring(s1, s2);
 }

 // Remove these, they're not used often and can be created using minus -
 // as per these implementations.

 /*pp*/ static Spring difference(Spring s1, Spring s2) {
 return sum(s1, minus(s2));
 }

 /*
 public static Spring min(Spring s1, Spring s2) {
 return minus(max(minus(s1), minus(s2)));
 }
 */

 /**
 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
 * and <em>value</em> properties are each multiples of the properties of the
 * argument spring, <code>s</code>. Minimum and maximum properties are
 * swapped when <code>factor</code> is negative (in accordance with the
 * rules of interval arithmetic).
 * <p>
 * When factor is, for example, 0.5f the result represents 'the mid-point'
 * of its input - an operation that is useful for centering components in
 * a container.
 *
 * @param s the spring to scale
 * @param factor amount to scale by.
 * @return a spring whose properties are those of the input spring <code>s</code>
 * multiplied by <code>factor</code>
 * @throws NullPointerException if <code>s</code> is null
 * @since 1.5
 */
 public static Spring scale(Spring s, float factor) {
 checkArg(s);
 return new ScaleSpring(s, factor);
 }

 /**
 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
 * and <em>value</em> properties are defined by the widths of the <em>minimumSize</em>,
 * <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> properties
 * of the supplied component. The returned spring is a 'wrapper' implementation
 * whose methods call the appropriate size methods of the supplied component.
 * The minimum, preferred, maximum and value properties of the returned spring
 * therefore report the current state of the appropriate properties in the
 * component and track them as they change.
 *
 * @param c Component used for calculating size
 * @return a spring whose properties are defined by the horizontal component
 * of the component's size methods.
 * @throws NullPointerException if <code>c</code> is null
 * @since 1.5
 */
 public static Spring width(Component c) {
 checkArg(c);
 return new WidthSpring(c);
 }

 /**
 * Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
 * and <em>value</em> properties are defined by the heights of the <em>minimumSize</em>,
 * <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> properties
 * of the supplied component. The returned spring is a 'wrapper' implementation
 * whose methods call the appropriate size methods of the supplied component.
 * The minimum, preferred, maximum and value properties of the returned spring
 * therefore report the current state of the appropriate properties in the
 * component and track them as they change.
 *
 * @param c Component used for calculating size
 * @return a spring whose properties are defined by the vertical component
 * of the component's size methods.
 * @throws NullPointerException if <code>c</code> is null
 * @since 1.5
 */
 public static Spring height(Component c) {
 checkArg(c);
 return new HeightSpring(c);
 }


 /**
 * If <code>s</code> is null, this throws an NullPointerException.
 */
 private static void checkArg(Object s) {
 if (s == null) {
 throw new NullPointerException("Argument must not be null");
 }
 }
}