bug fix + more logging

[debian/openrocket] / src / net / sf / openrocket / rocketcomponent / RocketComponent.java

package net.sf.openrocket.rocketcomponent;

import java.awt.Color;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.EmptyStackException;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Stack;

import javax.swing.event.ChangeListener;

import net.sf.openrocket.logging.TraceException;
import net.sf.openrocket.util.BugException;
import net.sf.openrocket.util.ChangeSource;
import net.sf.openrocket.util.Coordinate;
import net.sf.openrocket.util.LineStyle;
import net.sf.openrocket.util.MathUtil;
import net.sf.openrocket.util.UniqueID;


public abstract class RocketComponent implements ChangeSource, Cloneable,
                Iterable<RocketComponent> {
        
        /*
         * Text is suitable to the form
         *    Position relative to:  <title>
         */
        public enum Position {
                /** Position relative to the top of the parent component. */
                TOP("Top of the parent component"),
                /** Position relative to the middle of the parent component. */
                MIDDLE("Middle of the parent component"),
                /** Position relative to the bottom of the parent component. */
                BOTTOM("Bottom of the parent component"),
                /** Position after the parent component (for body components). */
                AFTER("After the parent component"),
                /** Specify an absolute X-coordinate position. */
                ABSOLUTE("Tip of the nose cone");
                
                private String title;
                
                Position(String title) {
                        this.title = title;
                }
                
                @Override
                public String toString() {
                        return title;
                }
        }
        
        ////////  Parent/child trees
        /**
         * Parent component of the current component, or null if none exists.
         */
        private RocketComponent parent = null;
        
        /**
         * List of child components of this component.
         */
        private List<RocketComponent> children = new ArrayList<RocketComponent>();
        

        ////////  Parameters common to all components:
        
        /**
         * Characteristic length of the component.  This is used in calculating the coordinate
         * transformations and positions of other components in reference to this component.
         * This may and should be used as the "true" length of the component, where applicable.
         * By default it is zero, i.e. no translation.
         */
        protected double length = 0;
        
        /**
         * Positioning of this component relative to the parent component.
         */
        protected Position relativePosition;
        
        /**
         * Offset of the position of this component relative to the normal position given by
         * relativePosition.  By default zero, i.e. no position change.
         */
        protected double position = 0;
        

        // Color of the component, null means to use the default color
        private Color color = null;
        private LineStyle lineStyle = null;
        

        // Override mass/CG
        private double overrideMass = 0;
        private boolean massOverriden = false;
        private double overrideCGX = 0;
        private boolean cgOverriden = false;
        
        private boolean overrideSubcomponents = false;
        

        // User-given name of the component
        private String name = null;
        
        // User-specified comment
        private String comment = "";
        
        // Unique ID of the component
        private String id = null;
        
        /**
         * When invalidated is non-null this component cannot be used anymore.
         * This is a safety mechanism to prevent accidental use after calling {@link #copyFrom(RocketComponent)}.
         */
        private TraceException invalidated = null;
        
        ////  NOTE !!!  All fields must be copied in the method copyFrom()!  ////
        


        /**
         * Default constructor.  Sets the name of the component to the component's static name
         * and the relative position of the component.
         */
        public RocketComponent(Position relativePosition) {
                // These must not fire any events, due to Rocket undo system initialization
                this.name = getComponentName();
                this.relativePosition = relativePosition;
                newID();
        }
        
        



        ////////////  Methods that must be implemented  ////////////
        

        /**
         * Static component name.  The name may not vary of the parameters, it must be static.
         */
        public abstract String getComponentName(); // Static component type name
        
        /**
         * Return the component mass (regardless of mass overriding).
         */
        public abstract double getComponentMass(); // Mass of non-overridden component
        
        /**
         * Return the component CG and mass (regardless of CG or mass overriding).
         */
        public abstract Coordinate getComponentCG(); // CG of non-overridden component
        

        /**
         * Return the longitudal (around the y- or z-axis) unitary moment of inertia.  
         * The unitary moment of inertia is the moment of inertia with the assumption that
         * the mass of the component is one kilogram.  The inertia is measured in
         * respect to the non-overridden CG.
         * 
         * @return   the longitudal unitary moment of inertia of this component.
         */
        public abstract double getLongitudalUnitInertia();
        
        
        /**
         * Return the rotational (around the x-axis) unitary moment of inertia.  
         * The unitary moment of inertia is the moment of inertia with the assumption that
         * the mass of the component is one kilogram.  The inertia is measured in
         * respect to the non-overridden CG.
         * 
         * @return   the rotational unitary moment of inertia of this component.
         */
        public abstract double getRotationalUnitInertia();
        
        
        /**
         * Test whether this component allows any children components.  This method must
         * return true if and only if {@link #isCompatible(Class)} returns true for any
         * rocket component class.
         * 
         * @return      <code>true</code> if children can be attached to this component, <code>false</code> otherwise.
         */
        public abstract boolean allowsChildren();
        
        /**
         * Test whether the given component type can be added to this component.  This type safety
         * is enforced by the <code>addChild()</code> methods.  The return value of this method
         * may change to reflect the current state of this component (e.g. two components of some
         * type cannot be placed as children).
         * 
         * @param type  The RocketComponent class type to add.
         * @return      Whether such a component can be added.
         */
        public abstract boolean isCompatible(Class<? extends RocketComponent> type);
        
        
        /* Non-abstract helper method */
        /**
         * Test whether the given component can be added to this component.  This is equivalent
         * to calling <code>isCompatible(c.getClass())</code>.
         * 
         * @param c  Component to test.
         * @return   Whether the component can be added.
         * @see #isCompatible(Class)
         */
        public final boolean isCompatible(RocketComponent c) {
                return isCompatible(c.getClass());
        }
        
        

        /**
         * Return a collection of bounding coordinates.  The coordinates must be such that
         * the component is fully enclosed in their convex hull.
         * 
         * @return      a collection of coordinates that bound the component.
         */
        public abstract Collection<Coordinate> getComponentBounds();
        
        /**
         * Return true if the component may have an aerodynamic effect on the rocket.
         */
        public abstract boolean isAerodynamic();
        
        /**
         * Return true if the component may have an effect on the rocket's mass.
         */
        public abstract boolean isMassive();
        
        



        ////////////  Methods that may be overridden  ////////////
        

        /**
         * Shift the coordinates in the array corresponding to radial movement.  A component
         * that has a radial position must shift the coordinates in this array suitably.
         * If the component is clustered, then a new array must be returned with a
         * coordinate for each cluster.
         * <p>
         * The default implementation simply returns the array, and thus produces no shift.
         * 
         * @param c   an array of coordinates to shift.
         * @return    an array of shifted coordinates.  The method may modify the contents
         *                        of the passed array and return the array itself.
         */
        public Coordinate[] shiftCoordinates(Coordinate[] c) {
                checkState();
                return c;
        }
        
        
        /**
         * Called when any component in the tree fires a ComponentChangeEvent.  This is by 
         * default a no-op, but subclasses may override this method to e.g. invalidate 
         * cached data.  The overriding method *must* call 
         * <code>super.componentChanged(e)</code> at some point.
         * 
         * @param e  The event fired
         */
        protected void componentChanged(ComponentChangeEvent e) {
                // No-op
                checkState();
        }
        
        


        /**
         * Return a descriptive name of the component.
         * 
         * The description may include extra information about the type of component,
         * e.g. "Conical nose cone".
         * 
         * @return A string describing the component.
         */
        @Override
        public final String toString() {
                if (name.equals(""))
                        return getComponentName();
                else
                        return name;
        }
        
        
        public final void printStructure() {
                System.out.println("Rocket structure from '" + this.toString() + "':");
                printStructure(0);
        }
        
        private void printStructure(int level) {
                String s = "";
                
                for (int i = 0; i < level; i++) {
                        s += "  ";
                }
                s += this.toString() + " (" + this.getComponentName() + ")";
                System.out.println(s);
                
                for (RocketComponent c : children) {
                        c.printStructure(level + 1);
                }
        }
        
        
        /**
         * Make a deep copy of the rocket component tree structure from this component
         * downwards for copying purposes.  Each component in the copy will be assigned
         * a new component ID, making it a safe copy.  This method does not fire any events.
         * 
         * @return A deep copy of the structure.
         */
        public final RocketComponent copy() {
                RocketComponent clone = copyWithOriginalID();
                
                Iterator<RocketComponent> iterator = clone.deepIterator(true);
                while (iterator.hasNext()) {
                        iterator.next().newID();
                }
                return clone;
        }
        
        

        /**
         * Make a deep copy of the rocket component tree structure from this component
         * downwards while maintaining the component ID's.  The purpose of this method is
         * to allow copies to be created with the original ID's for the purpose of the
         * undo/redo mechanism.  This method should not be used for other purposes,
         * such as copy/paste.  This method does not fire any events.
         * <p>
         * This method must be overridden by any component that refers to mutable objects, 
         * or if some fields should not be copied.  This should be performed by
         * <code>RocketComponent c = super.copyWithOriginalID();</code> and then cloning/modifying
         * the appropriate fields.
         * <p>
         * This is not performed as serializing/deserializing for performance reasons.
         * 
         * @return A deep copy of the structure.
         */
        protected RocketComponent copyWithOriginalID() {
                checkState();
                RocketComponent clone;
                try {
                        clone = (RocketComponent) this.clone();
                } catch (CloneNotSupportedException e) {
                        throw new BugException("CloneNotSupportedException encountered, " +
                                        "report a bug!", e);
                }
                
                // Reset all parent/child information
                clone.parent = null;
                clone.children = new ArrayList<RocketComponent>();
                
                // Add copied children to the structure without firing events.
                for (RocketComponent child : this.children) {
                        RocketComponent childCopy = child.copyWithOriginalID();
                        // Don't use add method since it fires events
                        clone.children.add(childCopy);
                        childCopy.parent = clone;
                }
                
                return clone;
        }
        
        
        //////////////  Methods that may not be overridden  ////////////
        


        ////////// Common parameter setting/getting //////////
        
        /**
         * Return the color of the object to use in 2D figures, or <code>null</code>
         * to use the default color.
         */
        public final Color getColor() {
                return color;
        }
        
        /**
         * Set the color of the object to use in 2D figures.  
         */
        public final void setColor(Color c) {
                if ((color == null && c == null) ||
                                (color != null && color.equals(c)))
                        return;
                
                checkState();
                this.color = c;
                fireComponentChangeEvent(ComponentChangeEvent.NONFUNCTIONAL_CHANGE);
        }
        
        
        public final LineStyle getLineStyle() {
                return lineStyle;
        }
        
        public final void setLineStyle(LineStyle style) {
                if (this.lineStyle == style)
                        return;
                checkState();
                this.lineStyle = style;
                fireComponentChangeEvent(ComponentChangeEvent.NONFUNCTIONAL_CHANGE);
        }
        
        


        /**
         * Get the current override mass.  The mass is not necessarily in use
         * at the moment.
         * 
         * @return  the override mass
         */
        public final double getOverrideMass() {
                return overrideMass;
        }
        
        /**
         * Set the current override mass.  The mass is not set to use by this
         * method.
         * 
         * @param m  the override mass
         */
        public final void setOverrideMass(double m) {
                if (MathUtil.equals(m, overrideMass))
                        return;
                checkState();
                overrideMass = Math.max(m, 0);
                if (massOverriden)
                        fireComponentChangeEvent(ComponentChangeEvent.MASS_CHANGE);
        }
        
        /**
         * Return whether mass override is active for this component.  This does NOT
         * take into account whether a parent component is overriding the mass.
         * 
         * @return  whether the mass is overridden
         */
        public final boolean isMassOverridden() {
                return massOverriden;
        }
        
        /**
         * Set whether the mass is currently overridden.
         * 
         * @param o  whether the mass is overridden
         */
        public final void setMassOverridden(boolean o) {
                if (massOverriden == o) {
                        return;
                }
                checkState();
                massOverriden = o;
                fireComponentChangeEvent(ComponentChangeEvent.MASS_CHANGE);
        }
        
        



        /**
         * Return the current override CG.  The CG is not necessarily overridden.
         * 
         * @return  the override CG
         */
        public final Coordinate getOverrideCG() {
                return getComponentCG().setX(overrideCGX);
        }
        
        /**
         * Return the x-coordinate of the current override CG.
         * 
         * @return      the x-coordinate of the override CG.
         */
        public final double getOverrideCGX() {
                return overrideCGX;
        }
        
        /**
         * Set the current override CG to (x,0,0).
         * 
         * @param x  the x-coordinate of the override CG to set.
         */
        public final void setOverrideCGX(double x) {
                if (MathUtil.equals(overrideCGX, x))
                        return;
                checkState();
                this.overrideCGX = x;
                if (isCGOverridden())
                        fireComponentChangeEvent(ComponentChangeEvent.MASS_CHANGE);
                else
                        fireComponentChangeEvent(ComponentChangeEvent.NONFUNCTIONAL_CHANGE);
        }
        
        /**
         * Return whether the CG is currently overridden.
         * 
         * @return  whether the CG is overridden
         */
        public final boolean isCGOverridden() {
                return cgOverriden;
        }
        
        /**
         * Set whether the CG is currently overridden.
         * 
         * @param o  whether the CG is overridden
         */
        public final void setCGOverridden(boolean o) {
                if (cgOverriden == o) {
                        return;
                }
                checkState();
                cgOverriden = o;
                fireComponentChangeEvent(ComponentChangeEvent.MASS_CHANGE);
        }
        
        

        /**
         * Return whether the mass and/or CG override overrides all subcomponent values
         * as well.  The default implementation is a normal getter/setter implementation,
         * however, subclasses are allowed to override this behavior if some subclass
         * always or never overrides subcomponents.  In this case the subclass should
         * also override {@link #isOverrideSubcomponentsEnabled()} to return
         * <code>false</code>.
         * 
         * @return      whether the current mass and/or CG override overrides subcomponents as well.
         */
        public boolean getOverrideSubcomponents() {
                return overrideSubcomponents;
        }
        
        
        /**
         * Set whether the mass and/or CG override overrides all subcomponent values
         * as well.  See {@link #getOverrideSubcomponents()} for details.
         * 
         * @param override      whether the mass and/or CG override overrides all subcomponent.
         */
        public void setOverrideSubcomponents(boolean override) {
                if (overrideSubcomponents == override) {
                        return;
                }
                checkState();
                overrideSubcomponents = override;
                fireComponentChangeEvent(ComponentChangeEvent.MASS_CHANGE);
        }
        
        /**
         * Return whether the option to override all subcomponents is enabled or not.
         * The default implementation returns <code>false</code> if neither mass nor
         * CG is overridden, <code>true</code> otherwise.
         * <p>
         * This method may be overridden if the setting of overriding subcomponents
         * cannot be set.
         * 
         * @return      whether the option to override subcomponents is currently enabled.
         */
        public boolean isOverrideSubcomponentsEnabled() {
                return isCGOverridden() || isMassOverridden();
        }
        
        


        /**
         * Get the user-defined name of the component.
         */
        public final String getName() {
                return name;
        }
        
        /**
         * Set the user-defined name of the component.  If name==null, sets the name to
         * the default name, currently the component name.
         */
        public final void setName(String name) {
                if (this.name.equals(name)) {
                        return;
                }
                checkState();
                if (name == null || name.matches("^\\s*$"))
                        this.name = getComponentName();
                else
                        this.name = name;
                fireComponentChangeEvent(ComponentChangeEvent.NONFUNCTIONAL_CHANGE);
        }
        
        
        /**
         * Return the comment of the component.  The component may contain multiple lines
         * using \n as a newline separator.
         * 
         * @return  the comment of the component.
         */
        public final String getComment() {
                return comment;
        }
        
        /**
         * Set the comment of the component.
         * 
         * @param comment  the comment of the component.
         */
        public final void setComment(String comment) {
                if (this.comment.equals(comment))
                        return;
                checkState();
                if (comment == null)
                        this.comment = "";
                else
                        this.comment = comment;
                fireComponentChangeEvent(ComponentChangeEvent.NONFUNCTIONAL_CHANGE);
        }
        
        

        /**
         * Returns the unique ID of the component.
         * 
         * @return      the ID of the component.
         */
        public final String getID() {
                return id;
        }
        
        /**
         * Generate a new ID for this component.
         */
        private final void newID() {
                this.id = UniqueID.uuid();
        }
        
        


        /**
         * Get the characteristic length of the component, for example the length of a body tube
         * of the length of the root chord of a fin.  This is used in positioning the component
         * relative to its parent.
         * 
         * If the length of a component is settable, the class must define the setter method
         * itself.
         */
        public final double getLength() {
                return length;
        }
        
        /**
         * Get the positioning of the component relative to its parent component.
         * This is one of the enums of {@link Position}.  A setter method is not provided,
         * but can be provided by a subclass.
         */
        public final Position getRelativePosition() {
                return relativePosition;
        }
        
        
        /**
         * Set the positioning of the component relative to its parent component.
         * The actual position of the component is maintained to the best ability.
         * <p>
         * The default implementation is of protected visibility, since many components
         * do not support setting the relative position.  A component that does support
         * it should override this with a public method that simply calls this
         * supermethod AND fire a suitable ComponentChangeEvent.
         * 
         * @param position      the relative positioning.
         */
        protected void setRelativePosition(RocketComponent.Position position) {
                if (this.relativePosition == position)
                        return;
                checkState();
                
                // Update position so as not to move the component
                if (this.parent != null) {
                        double thisPos = this.toRelative(Coordinate.NUL, this.parent)[0].x;
                        
                        switch (position) {
                        case ABSOLUTE:
                                this.position = this.toAbsolute(Coordinate.NUL)[0].x;
                                break;
                        
                        case TOP:
                                this.position = thisPos;
                                break;
                        
                        case MIDDLE:
                                this.position = thisPos - (this.parent.length - this.length) / 2;
                                break;
                        
                        case BOTTOM:
                                this.position = thisPos - (this.parent.length - this.length);
                                break;
                        
                        default:
                                throw new BugException("Unknown position type: " + position);
                        }
                }
                
                this.relativePosition = position;
                fireComponentChangeEvent(ComponentChangeEvent.BOTH_CHANGE);
        }
        
        


        /**
         * Get the position value of the component.  The exact meaning of the value is
         * dependent on the current relative positioning.
         * 
         * @return  the positional value.
         */
        public final double getPositionValue() {
                return position;
        }
        
        
        /**
         * Set the position value of the component.  The exact meaning of the value
         * depends on the current relative positioning.
         * <p>
         * The default implementation is of protected visibility, since many components
         * do not support setting the relative position.  A component that does support
         * it should override this with a public method that simply calls this
         * supermethod AND fire a suitable ComponentChangeEvent.
         * 
         * @param value         the position value of the component.
         */
        public void setPositionValue(double value) {
                if (MathUtil.equals(this.position, value))
                        return;
                checkState();
                this.position = value;
        }
        
        

        ///////////  Coordinate changes  ///////////
        
        /**
         * Returns coordinate c in absolute coordinates.  Equivalent to toComponent(c,null).
         */
        public Coordinate[] toAbsolute(Coordinate c) {
                checkState();
                return toRelative(c, null);
        }
        
        
        /**
         * Return coordinate <code>c</code> described in the coordinate system of 
         * <code>dest</code>.  If <code>dest</code> is <code>null</code> returns
         * absolute coordinates.
         * <p>
         * This method returns an array of coordinates, each of which represents a
         * position of the coordinate in clustered cases.  The array is guaranteed
         * to contain at least one element.  
         * <p>
         * The current implementation does not support rotating components.
         * 
         * @param c    Coordinate in the component's coordinate system.
         * @param dest Destination component coordinate system.
         * @return     an array of coordinates describing <code>c</code> in coordinates
         *                         relative to <code>dest</code>.
         */
        public final Coordinate[] toRelative(Coordinate c, RocketComponent dest) {
                checkState();
                double absoluteX = Double.NaN;
                RocketComponent search = dest;
                Coordinate[] array = new Coordinate[1];
                array[0] = c;
                
                RocketComponent component = this;
                while ((component != search) && (component.parent != null)) {
                        
                        array = component.shiftCoordinates(array);
                        
                        switch (component.relativePosition) {
                        case TOP:
                                for (int i = 0; i < array.length; i++) {
                                        array[i] = array[i].add(component.position, 0, 0);
                                }
                                break;
                        
                        case MIDDLE:
                                for (int i = 0; i < array.length; i++) {
                                        array[i] = array[i].add(component.position +
                                                        (component.parent.length - component.length) / 2, 0, 0);
                                }
                                break;
                        
                        case BOTTOM:
                                for (int i = 0; i < array.length; i++) {
                                        array[i] = array[i].add(component.position +
                                                        (component.parent.length - component.length), 0, 0);
                                }
                                break;
                        
                        case AFTER:
                                // Add length of all previous brother-components with POSITION_RELATIVE_AFTER
                                int index = component.parent.children.indexOf(component);
                                assert (index >= 0);
                                for (index--; index >= 0; index--) {
                                        RocketComponent comp = component.parent.children.get(index);
                                        double length = comp.getTotalLength();
                                        for (int i = 0; i < array.length; i++) {
                                                array[i] = array[i].add(length, 0, 0);
                                        }
                                }
                                for (int i = 0; i < array.length; i++) {
                                        array[i] = array[i].add(component.position + component.parent.length, 0, 0);
                                }
                                break;
                        
                        case ABSOLUTE:
                                search = null; // Requires back-search if dest!=null
                                if (Double.isNaN(absoluteX)) {
                                        absoluteX = component.position;
                                }
                                break;
                        
                        default:
                                throw new BugException("Unknown relative positioning type of component" +
                                                component + ": " + component.relativePosition);
                        }
                        
                        component = component.parent; // parent != null
                }
                
                if (!Double.isNaN(absoluteX)) {
                        for (int i = 0; i < array.length; i++) {
                                array[i] = array[i].setX(absoluteX + c.x);
                        }
                }
                
                // Check whether destination has been found or whether to backtrack
                // TODO: LOW: Backtracking into clustered components uses only one component 
                if ((dest != null) && (component != dest)) {
                        Coordinate[] origin = dest.toAbsolute(Coordinate.NUL);
                        for (int i = 0; i < array.length; i++) {
                                array[i] = array[i].sub(origin[0]);
                        }
                }
                
                return array;
        }
        
        
        /**
         * Recursively sum the lengths of all subcomponents that have position 
         * Position.AFTER.
         * 
         * @return  Sum of the lengths.
         */
        private final double getTotalLength() {
                checkState();
                double l = 0;
                if (relativePosition == Position.AFTER)
                        l = length;
                for (int i = 0; i < children.size(); i++)
                        l += children.get(i).getTotalLength();
                return l;
        }
        
        

        /////////// Total mass and CG calculation ////////////
        
        /**
         * Return the (possibly overridden) mass of component.
         * 
         * @return The mass of the component or the given override mass.
         */
        public final double getMass() {
                if (massOverriden)
                        return overrideMass;
                return getComponentMass();
        }
        
        /**
         * Return the (possibly overridden) center of gravity and mass.
         * 
         * Returns the CG with the weight of the coordinate set to the weight of the component.
         * Both CG and mass may be separately overridden.
         * 
         * @return The CG of the component or the given override CG.
         */
        public final Coordinate getCG() {
                checkState();
                if (cgOverriden)
                        return getOverrideCG().setWeight(getMass());
                
                if (massOverriden)
                        return getComponentCG().setWeight(getMass());
                
                return getComponentCG();
        }
        
        
        /**
         * Return the longitudal (around the y- or z-axis) moment of inertia of this component.
         * The moment of inertia is scaled in reference to the (possibly overridden) mass
         * and is relative to the non-overridden CG.
         * 
         * @return    the longitudal moment of inertia of this component.
         */
        public final double getLongitudalInertia() {
                checkState();
                return getLongitudalUnitInertia() * getMass();
        }
        
        /**
         * Return the rotational (around the y- or z-axis) moment of inertia of this component.
         * The moment of inertia is scaled in reference to the (possibly overridden) mass
         * and is relative to the non-overridden CG.
         * 
         * @return    the rotational moment of inertia of this component.
         */
        public final double getRotationalInertia() {
                checkState();
                return getRotationalUnitInertia() * getMass();
        }
        
        

        ///////////  Children handling  ///////////
        

        /**
         * Adds a child to the rocket component tree.  The component is added to the end
         * of the component's child list.  This is a helper method that calls 
         * {@link #addChild(RocketComponent,int)}.
         * 
         * @param component  The component to add.
         * @throws IllegalArgumentException  if the component is already part of some 
         *                                                                       component tree.
         * @see #addChild(RocketComponent,int)
         */
        public final void addChild(RocketComponent component) {
                checkState();
                addChild(component, children.size());
        }
        
        
        /**
         * Adds a child to the rocket component tree.  The component is added to 
         * the given position of the component's child list.
         * <p>
         * This method may be overridden to enforce more strict component addition rules.  
         * The tests should be performed first and then this method called.
         * 
         * @param component  The component to add.
         * @param position   Position to add component to.
         * @throws IllegalArgumentException  If the component is already part of 
         *                                                                       some component tree.
         */
        public void addChild(RocketComponent component, int position) {
                checkState();
                if (component.parent != null) {
                        throw new IllegalArgumentException("component " + component.getComponentName() +
                                        " is already in a tree");
                }
                if (!isCompatible(component)) {
                        throw new IllegalStateException("Component " + component.getComponentName() +
                                        " not currently compatible with component " + getComponentName());
                }
                
                children.add(position, component);
                component.parent = this;
                
                fireAddRemoveEvent(component);
        }
        
        
        /**
         * Removes a child from the rocket component tree.
         * 
         * @param n  remove the n'th child.
         * @throws IndexOutOfBoundsException  if n is out of bounds
         */
        public final void removeChild(int n) {
                checkState();
                RocketComponent component = children.remove(n);
                component.parent = null;
                fireAddRemoveEvent(component);
        }
        
        /**
         * Removes a child from the rocket component tree.  Does nothing if the component
         * is not present as a child.
         * 
         * @param component             the component to remove
         * @return                              whether the component was a child
         */
        public final boolean removeChild(RocketComponent component) {
                checkState();
                if (children.remove(component)) {
                        component.parent = null;
                        fireAddRemoveEvent(component);
                        return true;
                }
                return false;
        }
        
        


        /**
         * Move a child to another position.
         * 
         * @param component     the component to move
         * @param position      the component's new position
         * @throws IllegalArgumentException If an illegal placement was attempted.
         */
        public final void moveChild(RocketComponent component, int position) {
                checkState();
                if (children.remove(component)) {
                        children.add(position, component);
                        fireAddRemoveEvent(component);
                }
        }
        
        
        /**
         * Fires an AERODYNAMIC_CHANGE, MASS_CHANGE or OTHER_CHANGE event depending on the
         * type of component removed.
         */
        private void fireAddRemoveEvent(RocketComponent component) {
                Iterator<RocketComponent> iter = component.deepIterator(true);
                int type = ComponentChangeEvent.TREE_CHANGE;
                while (iter.hasNext()) {
                        RocketComponent c = iter.next();
                        if (c.isAerodynamic())
                                type |= ComponentChangeEvent.AERODYNAMIC_CHANGE;
                        if (c.isMassive())
                                type |= ComponentChangeEvent.MASS_CHANGE;
                }
                
                fireComponentChangeEvent(type);
        }
        
        
        public final int getChildCount() {
                checkState();
                return children.size();
        }
        
        public final RocketComponent getChild(int n) {
                checkState();
                return children.get(n);
        }
        
        public final RocketComponent[] getChildren() {
                checkState();
                return children.toArray(new RocketComponent[0]);
        }
        
        
        /**
         * Returns the position of the child in this components child list, or -1 if the
         * component is not a child of this component.
         * 
         * @param child  The child to search for.
         * @return  Position in the list or -1 if not found.
         */
        public final int getChildPosition(RocketComponent child) {
                checkState();
                return children.indexOf(child);
        }
        
        /**
         * Get the parent component of this component.  Returns <code>null</code> if the component
         * has no parent.
         * 
         * @return  The parent of this component or <code>null</code>.
         */
        public final RocketComponent getParent() {
                checkState();
                return parent;
        }
        
        /**
         * Get the root component of the component tree.
         * 
         * @return  The root component of the component tree.
         */
        public final RocketComponent getRoot() {
                checkState();
                RocketComponent gp = this;
                while (gp.parent != null)
                        gp = gp.parent;
                return gp;
        }
        
        /**
         * Returns the root Rocket component of this component tree.  Throws an 
         * IllegalStateException if the root component is not a Rocket.
         * 
         * @return  The root Rocket component of the component tree.
         * @throws  IllegalStateException  If the root component is not a Rocket.
         */
        public final Rocket getRocket() {
                checkState();
                RocketComponent r = getRoot();
                if (r instanceof Rocket)
                        return (Rocket) r;
                throw new IllegalStateException("getRocket() called with root component "
                                + r.getComponentName());
        }
        
        
        /**
         * Return the Stage component that this component belongs to.  Throws an
         * IllegalStateException if a Stage is not in the parentage of this component.
         * 
         * @return      The Stage component this component belongs to.
         * @throws      IllegalStateException   if a Stage component is not in the parentage.
         */
        public final Stage getStage() {
                checkState();
                RocketComponent c = this;
                while (c != null) {
                        if (c instanceof Stage)
                                return (Stage) c;
                        c = c.getParent();
                }
                throw new IllegalStateException("getStage() called without Stage as a parent.");
        }
        
        /**
         * Return the stage number of the stage this component belongs to.  The stages
         * are numbered from zero upwards.
         * 
         * @return   the stage number this component belongs to.
         */
        public final int getStageNumber() {
                checkState();
                if (parent == null) {
                        throw new IllegalArgumentException("getStageNumber() called for root component");
                }
                
                RocketComponent stage = this;
                while (!(stage instanceof Stage)) {
                        stage = stage.parent;
                        if (stage == null || stage.parent == null) {
                                throw new IllegalStateException("getStageNumber() could not find parent " +
                                                "stage.");
                        }
                }
                return stage.parent.getChildPosition(stage);
        }
        
        
        /**
         * Find a component with the given ID.  The component tree is searched from this component
         * down (including this component) for the ID and the corresponding component is returned,
         * or null if not found.
         * 
         * @param idToFind  ID to search for.
         * @return    The component with the ID, or null if not found.
         */
        public final RocketComponent findComponent(String idToFind) {
                checkState();
                Iterator<RocketComponent> iter = this.deepIterator(true);
                while (iter.hasNext()) {
                        RocketComponent c = iter.next();
                        if (c.getID().equals(idToFind))
                                return c;
                }
                return null;
        }
        
        
        public final RocketComponent getPreviousComponent() {
                checkState();
                if (parent == null)
                        return null;
                int pos = parent.getChildPosition(this);
                if (pos < 0) {
                        StringBuffer sb = new StringBuffer();
                        sb.append("Inconsistent internal state: ");
                        sb.append("this=").append(this).append('[')
                                        .append(System.identityHashCode(this)).append(']');
                        sb.append(" parent.children=[");
                        for (int i = 0; i < parent.children.size(); i++) {
                                RocketComponent c = parent.children.get(i);
                                sb.append(c).append('[').append(System.identityHashCode(c)).append(']');
                                if (i < parent.children.size() - 1)
                                        sb.append(", ");
                        }
                        sb.append(']');
                        throw new IllegalStateException(sb.toString());
                }
                assert (pos >= 0);
                if (pos == 0)
                        return parent;
                RocketComponent c = parent.getChild(pos - 1);
                while (c.getChildCount() > 0)
                        c = c.getChild(c.getChildCount() - 1);
                return c;
        }
        
        public final RocketComponent getNextComponent() {
                checkState();
                if (getChildCount() > 0)
                        return getChild(0);
                
                RocketComponent current = this;
                RocketComponent parent = this.parent;
                
                while (parent != null) {
                        int pos = parent.getChildPosition(current);
                        if (pos < parent.getChildCount() - 1)
                                return parent.getChild(pos + 1);
                        
                        current = parent;
                        parent = current.parent;
                }
                return null;
        }
        
        
        ///////////  Event handling  //////////
        //
        // Listener lists are provided by the root Rocket component,
        // a single listener list for the whole rocket.
        //
        
        /**
         * Adds a ComponentChangeListener to the rocket tree.  The listener is added to the root
         * component, which must be of type Rocket (which overrides this method).  Events of all
         * subcomponents are sent to all listeners.
         * 
         * @throws IllegalStateException - if the root component is not a Rocket
         */
        public void addComponentChangeListener(ComponentChangeListener l) {
                checkState();
                getRocket().addComponentChangeListener(l);
        }
        
        /**
         * Removes a ComponentChangeListener from the rocket tree.  The listener is removed from
         * the root component, which must be of type Rocket (which overrides this method).
         * Does nothing if the root component is not a Rocket.  (The asymmetry is so
         * that listeners can always be removed just in case.)
         * 
         * @param l  Listener to remove
         */
        public void removeComponentChangeListener(ComponentChangeListener l) {
                if (parent != null) {
                        getRoot().removeComponentChangeListener(l);
                }
        }
        
        
        /**
         * Adds a <code>ChangeListener</code> to the rocket tree.  This is identical to 
         * <code>addComponentChangeListener()</code> except that it uses a 
         * <code>ChangeListener</code>.  The same events are dispatched to the
         * <code>ChangeListener</code>, as <code>ComponentChangeEvent</code> is a subclass 
         * of <code>ChangeEvent</code>.
         * 
         * @throws IllegalStateException - if the root component is not a <code>Rocket</code>
         */
        public void addChangeListener(ChangeListener l) {
                checkState();
                getRocket().addChangeListener(l);
        }
        
        /**
         * Removes a ChangeListener from the rocket tree.  This is identical to
         * removeComponentChangeListener() except it uses a ChangeListener.
         * Does nothing if the root component is not a Rocket.  (The asymmetry is so
         * that listeners can always be removed just in case.)
         * 
         * @param l  Listener to remove
         */
        public void removeChangeListener(ChangeListener l) {
                if (this.parent != null) {
                        getRoot().removeChangeListener(l);
                }
        }
        
        
        /**
         * Fires a ComponentChangeEvent on the rocket structure.  The call is passed to the 
         * root component, which must be of type Rocket (which overrides this method).
         * Events of all subcomponents are sent to all listeners.
         * 
         * If the component tree root is not a Rocket, the event is ignored.  This is the 
         * case when constructing components not in any Rocket tree.  In this case it 
         * would be impossible for the component to have listeners in any case.
         *  
         * @param e  Event to send
         */
        protected void fireComponentChangeEvent(ComponentChangeEvent e) {
                checkState();
                if (parent == null) {
                        /* Ignore if root invalid. */
                        return;
                }
                getRoot().fireComponentChangeEvent(e);
        }
        
        
        /**
         * Fires a ComponentChangeEvent of the given type.  The source of the event is set to
         * this component.
         * 
         * @param type  Type of event
         * @see #fireComponentChangeEvent(ComponentChangeEvent)
         */
        protected void fireComponentChangeEvent(int type) {
                fireComponentChangeEvent(new ComponentChangeEvent(this, type));
        }
        
        
        /**
         * Checks whether this component has been invalidated and should no longer be used.
         * This is a safety check that in-place replaced components are no longer used.
         * All non-trivial methods (with the exception of methods simply getting a property)
         * should call this method before changing or computing anything.
         * 
         * @throws      BugException    if this component has been invalidated by {@link #copyFrom(RocketComponent)}.
         */
        protected void checkState() {
                if (invalidated != null) {
                        throw new BugException("This component has been invalidated.  Cause is the point of invalidation.",
                                        invalidated);
                }
        }
        
        
        ///////////  Iterator implementation  //////////
        
        /**
         * Private inner class to implement the Iterator.
         * 
         * This iterator is fail-fast if the root of the structure is a Rocket.
         */
        private class RocketComponentIterator implements Iterator<RocketComponent> {
                // Stack holds iterators which still have some components left.
                private final Stack<Iterator<RocketComponent>> iteratorstack =
                                        new Stack<Iterator<RocketComponent>>();
                
                private final Rocket root;
                private final int treeModID;
                
                private final RocketComponent original;
                private boolean returnSelf = false;
                
                // Construct iterator with component's child's iterator, if it has elements
                public RocketComponentIterator(RocketComponent c, boolean returnSelf) {
                        
                        RocketComponent gp = c.getRoot();
                        if (gp instanceof Rocket) {
                                root = (Rocket) gp;
                                treeModID = root.getTreeModID();
                        } else {
                                root = null;
                                treeModID = -1;
                        }
                        
                        Iterator<RocketComponent> i = c.children.iterator();
                        if (i.hasNext())
                                iteratorstack.push(i);
                        
                        this.original = c;
                        this.returnSelf = returnSelf;
                }
                
                public boolean hasNext() {
                        checkState();
                        checkID();
                        if (returnSelf)
                                return true;
                        return !iteratorstack.empty(); // Elements remain if stack is not empty
                }
                
                public RocketComponent next() {
                        Iterator<RocketComponent> i;
                        
                        checkState();
                        checkID();
                        
                        // Return original component first
                        if (returnSelf) {
                                returnSelf = false;
                                return original;
                        }
                        
                        // Peek first iterator from stack, throw exception if empty
                        try {
                                i = iteratorstack.peek();
                        } catch (EmptyStackException e) {
                                throw new NoSuchElementException("No further elements in " +
                                                "RocketComponent iterator");
                        }
                        
                        // Retrieve next component of the iterator, remove iterator from stack if empty
                        RocketComponent c = i.next();
                        if (!i.hasNext())
                                iteratorstack.pop();
                        
                        // Add iterator of component children to stack if it has children
                        i = c.children.iterator();
                        if (i.hasNext())
                                iteratorstack.push(i);
                        
                        return c;
                }
                
                private void checkID() {
                        if (root != null) {
                                if (root.getTreeModID() != treeModID) {
                                        throw new IllegalStateException("Rocket modified while being iterated");
                                }
                        }
                }
                
                public void remove() {
                        throw new UnsupportedOperationException("remove() not supported by " +
                                        "RocketComponent iterator");
                }
        }
        
        /**
         * Returns an iterator that iterates over all children and sub-children.
         * 
         * The iterator iterates through all children below this object, including itself if
         * returnSelf is true.  The order of the iteration is not specified
         * (it may be specified in the future).
         * 
         * If an iterator iterating over only the direct children of the component is required,
         * use  component.getChildren().iterator()
         * 
         * @param returnSelf boolean value specifying whether the component itself should be 
         *                                       returned
         * @return An iterator for the children and sub-children.
         */
        public final Iterator<RocketComponent> deepIterator(boolean returnSelf) {
                checkState();
                return new RocketComponentIterator(this, returnSelf);
        }
        
        /**
         * Returns an iterator that iterates over all children and sub-children.
         * 
         * The iterator does NOT return the component itself.  It is thus equivalent to
         * deepIterator(false).
         * 
         * @see #iterator()
         * @return An iterator for the children and sub-children.
         */
        public final Iterator<RocketComponent> deepIterator() {
                checkState();
                return new RocketComponentIterator(this, false);
        }
        
        
        /**
         * Return an iterator that iterates of the children of the component.  The iterator
         * does NOT recurse to sub-children nor return itself.
         * 
         * @return An iterator for the children.
         */
        public final Iterator<RocketComponent> iterator() {
                checkState();
                return Collections.unmodifiableList(children).iterator();
        }
        
        


        /**
         * Compare component equality based on the ID of this component.  Only the
         * ID and class type is used for a basis of comparison.
         */
        @Override
        public boolean equals(Object obj) {
                if (this == obj)
                        return true;
                if (obj == null)
                        return false;
                if (this.getClass() != obj.getClass())
                        return false;
                RocketComponent other = (RocketComponent) obj;
                return this.id.equals(other.id);
        }
        
        

        @Override
        public int hashCode() {
                return id.hashCode();
        }
        
        

        ////////////  Helper methods for subclasses
        



        /**
         * Helper method to add rotationally symmetric bounds at the specified coordinates.
         * The X-axis value is <code>x</code> and the radius at the specified position is
         * <code>r</code>. 
         */
        protected static final void addBound(Collection<Coordinate> bounds, double x, double r) {
                bounds.add(new Coordinate(x, -r, -r));
                bounds.add(new Coordinate(x, r, -r));
                bounds.add(new Coordinate(x, r, r));
                bounds.add(new Coordinate(x, -r, r));
        }
        
        
        protected static final Coordinate ringCG(double outerRadius, double innerRadius,
                        double x1, double x2, double density) {
                return new Coordinate((x1 + x2) / 2, 0, 0,
                                ringMass(outerRadius, innerRadius, x2 - x1, density));
        }
        
        protected static final double ringMass(double outerRadius, double innerRadius,
                        double length, double density) {
                return Math.PI * (MathUtil.pow2(outerRadius) - MathUtil.pow2(innerRadius)) *
                                        length * density;
        }
        
        protected static final double ringLongitudalUnitInertia(double outerRadius,
                        double innerRadius, double length) {
                // 1/12 * (3 * (r1^2 + r2^2) + h^2)
                return (3 * (MathUtil.pow2(innerRadius) + MathUtil.pow2(outerRadius)) + MathUtil.pow2(length)) / 12;
        }
        
        protected static final double ringRotationalUnitInertia(double outerRadius,
                        double innerRadius) {
                // 1/2 * (r1^2 + r2^2)
                return (MathUtil.pow2(innerRadius) + MathUtil.pow2(outerRadius)) / 2;
        }
        
        

        ////////////  OTHER
        

        /**
         * Loads the RocketComponent fields from the given component.  This method is meant
         * for in-place replacement of a component.  It is used with the undo/redo
         * mechanism and when converting a finset into a freeform fin set.
         * This component must not have a parent, otherwise this method will fail.
         * <p>
         * The fields are copied by reference, and the supplied component must not be used
         * after the call, as it is in an undefined state.  This is enforced by invalidating
         * the source component.
         * 
         * TODO: MEDIUM: Make general to copy all private/protected fields...
         */
        protected void copyFrom(RocketComponent src) {
                checkState();
                
                if (this.parent != null) {
                        throw new UnsupportedOperationException("copyFrom called for non-root component "
                                        + this);
                }
                
                // Set parents and children
                this.children = src.children;
                src.children = new ArrayList<RocketComponent>();
                
                for (RocketComponent c : this.children) {
                        c.parent = this;
                }
                
                // Set all parameters
                this.length = src.length;
                this.relativePosition = src.relativePosition;
                this.position = src.position;
                this.color = src.color;
                this.lineStyle = src.lineStyle;
                this.overrideMass = src.overrideMass;
                this.massOverriden = src.massOverriden;
                this.overrideCGX = src.overrideCGX;
                this.cgOverriden = src.cgOverriden;
                this.overrideSubcomponents = src.overrideSubcomponents;
                this.name = src.name;
                this.comment = src.comment;
                this.id = src.id;
                
                src.invalidated = new TraceException();
        }
        
}