vaadin-framework/client/src/main/java/com/vaadin/client/connectors/grid/GridDropTargetExtensionConnector.java

/*
 * Copyright 2000-2016 Vaadin Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.vaadin.client.connectors.grid;

import java.util.Objects;
import java.util.Optional;

import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.dom.client.TableRowElement;
import com.google.gwt.user.client.Window;
import com.vaadin.client.ServerConnector;
import com.vaadin.client.WidgetUtil;
import com.vaadin.client.extensions.DropTargetExtensionConnector;
import com.vaadin.client.widget.escalator.RowContainer;
import com.vaadin.client.widgets.Escalator;
import com.vaadin.shared.ui.Connect;
import com.vaadin.shared.ui.grid.DropLocation;
import com.vaadin.shared.ui.grid.DropMode;
import com.vaadin.shared.ui.grid.GridDropTargetExtensionRpc;
import com.vaadin.shared.ui.grid.GridDropTargetExtensionState;
import com.vaadin.shared.ui.grid.GridState;
import com.vaadin.ui.GridDropTargetExtension;

import elemental.events.Event;
import elemental.json.JsonObject;

/**
 * Makes Grid an HTML5 drop target. This is the client side counterpart of
 * {@link GridDropTargetExtension}.
 *
 * @author Vaadin Ltd
 * @since
 */
@Connect(GridDropTargetExtension.class)
public class GridDropTargetExtensionConnector extends
        DropTargetExtensionConnector {

    // Drag over class name suffixes
    private final static String CLASS_SUFFIX_BEFORE = "-before";
    private final static String CLASS_SUFFIX_AFTER = "-after";

    // Drag over class names
    private final static String CLASS_DRAG_OVER_BEFORE =
            CLASS_DRAG_OVER + CLASS_SUFFIX_BEFORE;
    private final static String CLASS_DRAG_OVER_AFTER =
            CLASS_DRAG_OVER + CLASS_SUFFIX_AFTER;

    /**
     * Current drag over class name
     */
    private String dragOverClassName;

    private GridConnector gridConnector;

    @Override
    protected void extend(ServerConnector target) {
        gridConnector = (GridConnector) target;

        super.extend(target);
    }

    @Override
    protected void sendDropEventToServer(String dataTransferText,
            Event dropEvent) {

        String rowKey = null;
        DropLocation dropLocation = null;

        Optional<TableRowElement> targetRow = getTargetRow(
                (Element) dropEvent.getTarget());
        if (targetRow.isPresent()) {
            rowKey = getRowData(targetRow.get())
                    .getString(GridState.JSONKEY_ROWKEY);
            dropLocation = getDropLocation(targetRow.get(),
                    (NativeEvent) dropEvent);
        }

        getRpcProxy(GridDropTargetExtensionRpc.class)
                .drop(dataTransferText, rowKey, dropLocation);
    }

    private JsonObject getRowData(TableRowElement row) {
        int rowIndex = ((Escalator.AbstractRowContainer) getGridBody())
                .getLogicalRowIndex(row);
        return gridConnector.getDataSource().getRow(rowIndex);
    }

    /**
     * Returns the location of the event within the row.
     */
    private DropLocation getDropLocation(Element target, NativeEvent event) {
        if (getState().dropMode == DropMode.BETWEEN) {
            if (getRelativeY(target, event) < (target.getOffsetHeight() / 2)) {
                return DropLocation.ABOVE;
            } else {
                return DropLocation.BELOW;
            }
        }
        return DropLocation.ON_TOP;
    }

    private int getRelativeY(Element element, NativeEvent event) {
        int relativeTop = element.getAbsoluteTop() - Window.getScrollTop();
        return WidgetUtil.getTouchOrMouseClientY(event) - relativeTop;
    }

    @Override
    protected void setTargetIndicator(Event event) {
        getTargetRow(((Element) event.getTarget())).ifPresent(target -> {

            // Get required class name
            String className = getTargetClassName(target, (NativeEvent) event);

            // Add or replace class name if changed
            if (!target.hasClassName(className)) {
                if (dragOverClassName != null) {
                    target.removeClassName(dragOverClassName);
                }
                target.addClassName(className);
                dragOverClassName = className;
            }
        });
    }

    private String getTargetClassName(Element target, NativeEvent event) {
        String classSuffix;

        switch (getDropLocation(target, event)) {
        case ABOVE:
            classSuffix = CLASS_SUFFIX_BEFORE;
            break;
        case BELOW:
            classSuffix = CLASS_SUFFIX_AFTER;
            break;
        case ON_TOP:
        default:
            classSuffix = "";
            break;
        }

        return CLASS_DRAG_OVER + classSuffix;
    }

    @Override
    protected void removeTargetIndicator(Event event) {

        // Remove all possible drag over class names
        getTargetRow((Element) event.getTarget()).ifPresent(e -> {
            e.removeClassName(CLASS_DRAG_OVER);
            e.removeClassName(CLASS_DRAG_OVER_BEFORE);
            e.removeClassName(CLASS_DRAG_OVER_AFTER);
        });
    }

    private Optional<TableRowElement> getTargetRow(Element source) {
        while (!Objects.equals(source, getGridBody().getElement())) {
            if (TableRowElement.is(source)) {
                return Optional.of(source.cast());
            }
            source = source.getParentElement();
        }
        return Optional.empty();
    }

    @Override
    protected Element getDropTargetElement() {
        return getGridBody().getElement();
    }

    private Escalator getEscalator() {
        return gridConnector.getWidget().getEscalator();
    }

    private RowContainer.BodyRowContainer getGridBody() {
        return getEscalator().getBody();
    }

    @Override
    public GridDropTargetExtensionState getState() {
        return (GridDropTargetExtensionState) super.getState();
    }
}