package appeng.util;

import java.util.EnumSet;

/**
 * Simple utility class to help with select the "next" or "previous" value in a list of options represented
 * by an enumeration.
 */
public final class EnumCycler {

    private EnumCycler() {
    }

    public static <T extends Enum<T>> T rotateEnum( T ce, final boolean backwards, final EnumSet<T> validOptions )
    {
        do
        {
            if( backwards )
            {
                ce = prevEnum( ce );
            }
            else
            {
                ce = next( ce );
            }
        }
        while( !validOptions.contains( ce ) );

        return ce;
    }

    /*
     * Simple way to cycle an enum...
     */
    public static <T extends Enum<T>> T prevEnum( final T ce )
    {
        T[] values = ce.getDeclaringClass().getEnumConstants();

        int pLoc = ce.ordinal() - 1;
        if( pLoc < 0 )
        {
            pLoc = values.length - 1;
        }

        if( pLoc < 0 || pLoc >= values.length )
        {
            pLoc = 0;
        }

        return values[pLoc];
    }

    /*
     * Simple way to cycle an enum...
     */
    public static <T extends Enum<T>> T next(final T ce )
    {
        T[] values = ce.getDeclaringClass().getEnumConstants();

        int pLoc = ce.ordinal() + 1;
        if( pLoc >= values.length )
        {
            pLoc = 0;
        }

        if( pLoc < 0 || pLoc >= values.length )
        {
            pLoc = 0;
        }

        return values[pLoc];
    }

}