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package atom.widget;

import atom.view.AbstractView;
import atom.view.View;
import atom.view.ViewGroup;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlTransient;
import javax.xml.bind.annotation.XmlType;

/**
 * An abstract view containing data set adapter.
 *
 * @param  an corresponded adapter type
 * @author Alex Voloshyn
 * @author Serge Voloshyn
 * @version 1.1 4/20/14
 */
@XmlType(namespace = AbstractView.LAYOUT_NAMESPACE)
public abstract class AdapterView extends ViewGroup {
    /**
     * Use serialVersionUID from JDK 1.0.2 for interoperability.
     */
    private static final long serialVersionUID = 1987332379271969375L;
    /**
     * Name of the field containing selected item position value.
     */
    public static final String SELECTED_NAME = "selectedItemPosition";
    /**
     * Represents an invalid position. All valid positions are in the range 0 to
     * 1 less than the number of items in the current adapter.
     */
    public static final int INVALID_POSITION = -1;

    /**
     * Provide adaptation of the corresponded adapter to the current view.
     */
    protected abstract void adapt();

    /**
     * An instance of the data adapter for current view.
     */
    private A adapter;

    /**
     * The position of the currently selected item within the adapter's data
     * set.
     */
    private int selectedItemPosition = INVALID_POSITION;

    /**
     * Simple constructor to use when creating a view group from code.
     */
    public AdapterView() {
        super();
    }

    /**
     * Simple constructor that creates AdapterView with defined
     * identifier.
     *
     * @param viewId a string used to identify the view
     * @see #setViewId(String)
     */
    protected AdapterView(final String viewId) {
        super(viewId);
    }


    /**
     * Sets the adapter that provides the data and the views to represent the
     * data in this widget.
     *
     * @param anAdapter the adapter to use to create this view's content
     */
    public final void setAdapter(final A anAdapter) {
        adapter = anAdapter;
    }

    /**
     * Retrieve the adapter that provides the data and the views to represent
     * the data in this widget.
     *
     * @return the adapter to use to create this view's content
     */
    @XmlTransient
    public final A getAdapter() {
        return adapter;
    }

    /**
     * Return the position of the currently selected item within the adapter's
     * data set.
     *
     * @return int position (starting at 0), or {@link #INVALID_POSITION} if
     *         there is nothing selected
     */
    @XmlAttribute(name = "selected")
    public final int getSelectedItemPosition() {
        return selectedItemPosition;
    }

    /**
     * Sets the position of the currently selected item within the adapter's
     * data set.
     *
     * @param selected int position (starting at 0), or
     *                 {@link #INVALID_POSITION} if there is nothing selected
     */
    public final void setSelectedItemPosition(final int selected) {
        selectedItemPosition = selected;
        fireChange(SELECTED_NAME, selected);
    }

    /**
     * Retrieve the view corresponding to the currently selected item.
     *
     * @return the view corresponding to the currently selected item, or null
     *         if nothing is selected
     */
    public final View getSelectedView() {
        final int childrenListIndex = getChildrenListIndex();
        if (childrenListIndex < 0
                || childrenListIndex >= getChildren().size()) {
            return null;
        }
        return getChildren().get(childrenListIndex);
    }

    /**
     * Get index of selected item within children list.
     *
     * @return index of selected item within children list
     */
    protected int getChildrenListIndex() {
        return selectedItemPosition;
    }

    /**
     * Get item associated with selected item position.
     *
     * @param  expected item type
     * @return the last selected item, if selected item position within
     *         the allowed range.
     */
    @SuppressWarnings("unchecked")
    public final  T getSelectedItem() {
        if (adapter == null || selectedItemPosition < 0
                || selectedItemPosition > adapter.getCount()) {
            return null;
        }
        return (T) adapter.getItem(selectedItemPosition);
    }
}