/*
 * This file is part of ELKI:
 * Environment for Developing KDD-Applications Supported by Index-Structures
 *
 * Copyright (C) 2022
 * ELKI Development Team
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package elki.visualization.visualizers.scatterplot;

import org.apache.batik.util.SVGConstants;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.events.Event;
import org.w3c.dom.events.EventListener;
import org.w3c.dom.events.EventTarget;

import elki.database.datastore.DataStoreListener;
import elki.database.ids.DBIDIter;
import elki.database.ids.DBIDRef;
import elki.logging.LoggingUtil;
import elki.visualization.VisualizationTask;
import elki.visualization.VisualizerContext;
import elki.visualization.gui.VisualizationPlot;
import elki.visualization.projections.Projection;
import elki.visualization.style.StyleLibrary;
import elki.visualization.svg.SVGPlot;
import elki.visualization.svg.SVGUtil;

/**
 * General base class for a tooltip visualizer.
 *
 * @author Erich Schubert
 * @since 0.4.0
 */
// TODO: can we improve performance by not adding as many hovers?
public abstract class AbstractTooltipVisualization extends AbstractScatterplotVisualization implements DataStoreListener {
  /**
   * Generic tag to indicate the type of element. Used in IDs, CSS-Classes etc.
   */
  public static final String TOOLTIP_HIDDEN = "tooltip_hidden";

  /**
   * Generic tag to indicate the type of element. Used in IDs, CSS-Classes etc.
   */
  public static final String TOOLTIP_VISIBLE = "tooltip_visible";

  /**
   * Generic tag to indicate the type of element. Used in IDs, CSS-Classes etc.
   */
  public static final String TOOLTIP_STICKY = "tooltip_sticky";

  /**
   * Generic tag to indicate the type of element. Used in IDs, CSS-Classes etc.
   */
  public static final String TOOLTIP_AREA = "tooltip_area";

  /**
   * Our event listener.
   */
  EventListener hoverer = new EventListener() {
    @Override
    public void handleEvent(Event evt) {
      handleHoverEvent(evt);
    }
  };

  /**
   * Constructor.
   *
   * @param context Visualizer context
   * @param task Visualization task
   * @param plot Plot to draw to
   * @param width Embedding width
   * @param height Embedding height
   * @param proj Projection
   */
  public AbstractTooltipVisualization(VisualizerContext context, VisualizationTask task, VisualizationPlot plot, double width, double height, Projection proj) {
    super(context, task, plot, width, height, proj);
  }

  @Override
  public void fullRedraw() {
    setupCanvas();
    setupCSS(svgp);
    final StyleLibrary style = context.getStyleLibrary();
    double dotsize = style.getLineWidth(StyleLibrary.PLOT);

    for(DBIDIter id = sample.getSample().iter(); id.valid(); id.advance()) {
      double[] v = proj.fastProjectDataToRenderSpace(rel.get(id));
      if(v[0] != v[0] || v[1] != v[1]) {
        continue; // NaN!
      }
      Element tooltip = makeTooltip(id, v[0], v[1], dotsize);
      SVGUtil.addCSSClass(tooltip, TOOLTIP_HIDDEN);

      // sensitive area.
      Element area = svgp.svgRect(v[0] - dotsize, v[1] - dotsize, 2 * dotsize, 2 * dotsize);
      SVGUtil.addCSSClass(area, TOOLTIP_AREA);

      EventTarget targ = (EventTarget) area;
      targ.addEventListener(SVGConstants.SVG_MOUSEOVER_EVENT_TYPE, hoverer, false);
      targ.addEventListener(SVGConstants.SVG_MOUSEOUT_EVENT_TYPE, hoverer, false);
      targ.addEventListener(SVGConstants.SVG_CLICK_EVENT_TYPE, hoverer, false);

      // NOTE: do not change the sequence in which these are inserted!
      layer.appendChild(area);
      layer.appendChild(tooltip);
    }
  }

  /**
   * Make a tooltip Element for this id.
   *
   * @param id Id to make a tooltip for
   * @param x X position
   * @param y Y position
   * @param dotsize Size of a dot
   * @return Element
   */
  protected abstract Element makeTooltip(DBIDRef id, double x, double y, double dotsize);

  /**
   * Handle the hover events.
   *
   * @param evt Event.
   */
  protected void handleHoverEvent(Event evt) {
    if(evt.getTarget() instanceof Element) {
      Element e = (Element) evt.getTarget();
      Node next = e.getNextSibling();
      if(next instanceof Element) {
        toggleTooltip((Element) next, evt.getType());
      }
      else {
        LoggingUtil.warning("Tooltip sibling not found.");
      }
    }
    else {
      LoggingUtil.warning("Got event for non-Element?!?");
    }
  }

  /**
   * Toggle the Tooltip of an element.
   *
   * @param elem Element
   * @param type Event type
   */
  protected void toggleTooltip(Element elem, String type) {
    String csscls = elem.getAttribute(SVGConstants.SVG_CLASS_ATTRIBUTE);
    if(SVGConstants.SVG_MOUSEOVER_EVENT_TYPE.equals(type)) {
      if(TOOLTIP_HIDDEN.equals(csscls)) {
        SVGUtil.setAtt(elem, SVGConstants.SVG_CLASS_ATTRIBUTE, TOOLTIP_VISIBLE);
      }
    }
    else if(SVGConstants.SVG_MOUSEOUT_EVENT_TYPE.equals(type)) {
      if(TOOLTIP_VISIBLE.equals(csscls)) {
        SVGUtil.setAtt(elem, SVGConstants.SVG_CLASS_ATTRIBUTE, TOOLTIP_HIDDEN);
      }
    }
    else if(SVGConstants.SVG_CLICK_EVENT_TYPE.equals(type)) {
      if(TOOLTIP_STICKY.equals(csscls)) {
        SVGUtil.setAtt(elem, SVGConstants.SVG_CLASS_ATTRIBUTE, TOOLTIP_HIDDEN);
      }
      if(TOOLTIP_HIDDEN.equals(csscls) || TOOLTIP_VISIBLE.equals(csscls)) {
        SVGUtil.setAtt(elem, SVGConstants.SVG_CLASS_ATTRIBUTE, TOOLTIP_STICKY);
      }
    }
  }

  /**
   * Registers the Tooltip-CSS-Class at a SVGPlot.
   *
   * @param svgp the SVGPlot to register the Tooltip-CSS-Class.
   */
  protected abstract void setupCSS(SVGPlot svgp);
}