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Henplus » henplus » property » EnumeratedPropertyHolder.java
/*
 * This is free software, licensed under the Gnu Public License (GPL)
 * get a copy from <http://www.gnu.org/licenses/gpl.html>
 * $Id: EnumeratedPropertyHolder.java,v 1.6 2004/03/07 14:22:02 hzeller Exp $ 
 * author: Henner Zeller <H.Zeller@acm.org>
 */
package henplus.property;

import java.util.Iterator;
import java.util.Collection;

import henplus.view.util.NameCompleter;

/**
 * A PropertyHolder, that can change its values to a fixed set of
 * values.
 */
public abstract class EnumeratedPropertyHolder extends PropertyHolder {
    private final String _values[];
    private final NameCompleter _completer;

    /**
     * create a new EnumeratedPropertyHolder that gets an array of
     * Strings with possible values of this property.
     *
     * @param enumeratedValues the Values this property can take.
     */
    public EnumeratedPropertyHolder(String[] enumeratedValues) {
        _values = enumeratedValues;
        _completer = new NameCompleter(enumeratedValues);
    }

    /**
     * same with collection as Input.
     */
    public EnumeratedPropertyHolder(Collection values) {
        this((String[])values.toArray(new String[ values.size() ]));
    }

    /**
     * do not override this method but the 
     * {@link #enumeratedPropertyChanged(int, String)} method instead.
     */
    protected final String propertyChanged(String newValue) throws Exception {
        if (newValue == null) {
            throw new Exception("'null' not a valid value");
        }
        newValue = newValue.trim();

        Iterator possibleValues = _completer.getAlternatives(newValue);
        if (possibleValues == null || !possibleValues.hasNext()) {
            StringBuffer expected = new StringBuffer();
            for (int i=0; i < _values.length; ++i) {
                if (i != 0) expected.append(", ");
                expected.append(_values[i]);
            }
            throw new Exception("'" + newValue + "' does not match any of ["
                                + expected.toString() + "]");
        }

        String value = (String) possibleValues.next();
        if (possibleValues.hasNext()) {
            StringBuffer matching = new StringBuffer(value);
            do {
                matching.append(", ");
                matching.append((String) possibleValues.next());
            } 
            while (possibleValues.hasNext());
            
            throw new Exception("'" + newValue + "' ambiguous. Matches ["
                                + matching.toString() + "]");
        }

        int index = -1;
        // small size of array -- linear search acceptable
        for (int i=0; i < _values.length; ++i) {
            if (value.equals(_values[i])) {
                index = i;
                break;
            }
        }
        
        enumeratedPropertyChanged(index, value);
        return value;
    }

    /**
     * to be overridden to get informed of the change and veto
     * it.
     * @param index the index of the property that changed
     * @param value the new value of that property
     * @throws Exception to veto that change.
     */
    protected abstract void enumeratedPropertyChanged(int index, String value)
        throws Exception;

    public Iterator completeValue(String partialValue) {
        return _completer.getAlternatives(partialValue);
    }
}

/*
 * Local variables:
 * c-basic-offset: 4
 * compile-command: "ant -emacs -find build.xml"
 * End:
 */
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