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import jdk.nashorn.api.scripting.AbstractJSObject;

import java.nio.DoubleBuffer;

/**

 * Simple class demonstrating pluggable script object

 * implementation. By implementing jdk.nashorn.api.scripting.JSObject

 * (or extending AbstractJSObject which implements it), you

 * can supply a friendly script object. Nashorn will call

 * 'magic' methods on such a class on 'obj.foo, obj.foo = 33,

 * obj.bar()' etc. from script.

 *

 * In this example, Java nio DoubleBuffer object is wrapped

 * as a friendly script object that provides indexed acces

 * to buffer content and also support array-like "length"

 * readonly property to retrieve buffer's capacity. This class

 * also demonstrates a function valued property called "buf".

 * On 'buf' method, we return the underlying nio buffer object

 * that is being wrapped.

 */

public class BufferArray extends AbstractJSObject {

    // underlying nio buffer

    private final DoubleBuffer buf;

    public BufferArray(int size) {

        buf = DoubleBuffer.allocate(size);

    }

    public BufferArray(DoubleBuffer buf) {

        this.buf = buf;

    }

    // called to check if indexed property exists

    @Override

    public boolean hasSlot(int index) {

        return index > 0 && index < buf.capacity();

    }

    // get the value from that index

    @Override

    public Object getSlot(int index) {

       return buf.get(index);

    }

    // set the value at that index

    @Override

    public void setSlot(int index, Object value) {

       buf.put(index, ((Number)value).doubleValue());

    }

    // do you have a property of that given name?

    @Override

    public boolean hasMember(String name) {

       return "length".equals(name) || "buf".equals(name);

    }

    // get the value of that named property

    @Override

    public Object getMember(String name) {

       switch (name) {

          case "length":

              return buf.capacity();

          case "buf":

              // return a 'function' value for this property

              return new AbstractJSObject() {

                  @Override

                  public Object call(Object thiz, Object... args) {

                      return BufferArray.this.buf;

                  }

                  // yes, I'm a function !

                  @Override

                  public boolean isFunction() {

                      return true;

                  }

              };

       }

       return null;

    }

}