/*
    * Copyright (c) 2002-2026 Gargoyle Software Inc.
    *
    * 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
    * https://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 org.htmlunit.javascript.host.event;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.commons.lang3.StringUtils;
  import org.htmlunit.Page;
  import org.htmlunit.ScriptResult;
  import org.htmlunit.corejs.javascript.Function;
  import org.htmlunit.corejs.javascript.Scriptable;
  import org.htmlunit.html.DomElement;
  import org.htmlunit.html.DomNode;
  import org.htmlunit.html.HtmlElement;
  import org.htmlunit.html.HtmlLabel;
  import org.htmlunit.javascript.HtmlUnitScriptable;
  import org.htmlunit.javascript.JavaScriptEngine;
  import org.htmlunit.javascript.configuration.JsxClass;
  import org.htmlunit.javascript.configuration.JsxConstructor;
  import org.htmlunit.javascript.configuration.JsxFunction;
  import org.htmlunit.javascript.host.Window;
  import org.htmlunit.javascript.host.dom.Document;
  
  /**
   * JavaScript host object for {@code EventTarget}.
   *
   * @author Ahmed Ashour
   * @author Ronald Brill
   * @author Atsushi Nakagawa
   *
   * @see <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventTarget">MDN Documentation</a>
   */
  @JsxClass
  public class EventTarget extends HtmlUnitScriptable {
  
      private EventListenersContainer eventListenersContainer_;
  
      /**
       * Creates an instance of this object.
       */
      @JsxConstructor
      public void jsConstructor() {
          // nothing to do
      }
  
      /**
       * Registers an event listener on this event target.
       *
       * @param type the event type to listen for (e.g. {@code "click"})
       * @param listener the event listener
       * @param useCapture if {@code true}, indicates that the listener should be added for the capture phase
       * @see <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener">MDN Documentation</a>
       */
      @JsxFunction
      public void addEventListener(final String type, final Scriptable listener, final boolean useCapture) {
          getEventListenersContainer().addEventListener(type, listener, useCapture);
      }
  
      /**
       * Returns the container for event listeners, creating it if necessary.
       *
       * @return the event listeners container
       */
      public final EventListenersContainer getEventListenersContainer() {
          if (eventListenersContainer_ == null) {
              eventListenersContainer_ = new EventListenersContainer(this);
          }
          return eventListenersContainer_;
      }
  
      /**
       * Executes the event on this object only (needed for instance for {@code onload} on {@code (i)frame} tags).
       *
       * @param event the event to execute
       * @see #fireEvent(Event)
       */
      public void executeEventLocally(final Event event) {
          final EventListenersContainer eventListenersContainer = getEventListenersContainer();
          final Window window = getWindow();
          final Object[] args = {event};
  
          final Event previousEvent = window.getCurrentEvent();
          window.setCurrentEvent(event);
          try {
              event.setEventPhase(Event.AT_TARGET);
             eventListenersContainer.executeAtTargetListeners(event, args);
         }
         finally {
             window.setCurrentEvent(previousEvent); // reset event
         }
     }
 
     /**
      * Fires the event on this node with capturing and bubbling phases.
      *
      * @param event the event to fire
      * @return the script result
      */
     public ScriptResult fireEvent(final Event event) {
         final Window window = getWindow();
 
         event.startFire();
         final Event previousEvent = window.getCurrentEvent();
         window.setCurrentEvent(event);
 
         try {
             // These can be null if we aren't tied to a DOM node
             final DomNode ourNode = getDomNodeOrNull();
             final DomNode ourParentNode = (ourNode != null) ? ourNode.getParentNode() : null;
 
             // Determine the propagation path which is fixed here and not affected by
             // DOM tree modification from intermediate listeners (tested in Chrome)
             final List<EventTarget> propagationPath = new ArrayList<>();
 
             // We're added to the propagation path first
             propagationPath.add(this);
 
             // Then add all our parents if we have any (pure JS object such as XMLHttpRequest
             // and MessagePort, etc. will not have any parents)
             for (DomNode parent = ourParentNode; parent != null; parent = parent.getParentNode()) {
                 // scroll does not bubble into the document/window
                 if (Event.TYPE_SCROLL.equals(event.getType()) && parent instanceof Page) {
                     break;
                 }
 
                 propagationPath.add(parent.getScriptableObject());
             }
 
             // The load event has some unnatural behavior that we need to handle specially
             // The load event for other elements target that element but path only
             // up to Document and not Window, so do nothing here
             // (see Note in https://www.w3.org/TR/DOM-Level-3-Events/#event-type-load)
             if (!Event.TYPE_LOAD.equals(event.getType())) {
                 // Add Window if the propagation path reached Document
                 if (propagationPath.get(propagationPath.size() - 1) instanceof Document) {
                     propagationPath.add(window);
                 }
             }
 
             // capturing phase
             event.setEventPhase(Event.CAPTURING_PHASE);
 
             for (int i = propagationPath.size() - 1; i >= 1; i--) {
                 final EventTarget jsNode = propagationPath.get(i);
                 final EventListenersContainer elc = jsNode.eventListenersContainer_;
                 if (elc != null) {
                     elc.executeCapturingListeners(event, new Object[] {event});
                     if (event.isPropagationStopped()) {
                         return new ScriptResult(null);
                     }
                 }
             }
 
             // at target phase
             event.setEventPhase(Event.AT_TARGET);
 
             if (!propagationPath.isEmpty()) {
                 // Note: This element is not always the same as event.getTarget():
                 // e.g. the 'load' event targets Document but "at target" is on Window.
                 final EventTarget jsNode = propagationPath.get(0);
                 final EventListenersContainer elc = jsNode.eventListenersContainer_;
                 if (elc != null) {
                     elc.executeAtTargetListeners(event, new Object[] {event});
                     if (event.isPropagationStopped()) {
                         return new ScriptResult(null);
                     }
                 }
             }
 
             // bubbling phase
             if (event.isBubbles()) {
                 // This belongs here inside the block because events that don't bubble never set
                 // eventPhase = 3 (tested in Chrome)
                 event.setEventPhase(Event.BUBBLING_PHASE);
 
                 final int size = propagationPath.size();
                 for (int i = 1; i < size; i++) {
                     final EventTarget jsNode = propagationPath.get(i);
                     final EventListenersContainer elc = jsNode.eventListenersContainer_;
                     if (elc != null) {
                         elc.executeBubblingListeners(event, new Object[] {event});
                         if (event.isPropagationStopped()) {
                             return new ScriptResult(null);
                         }
                     }
                 }
             }
 
             HtmlLabel label = null;
             if (event.processLabelAfterBubbling()) {
                 for (DomNode parent = ourParentNode; parent != null; parent = parent.getParentNode()) {
                     if (parent instanceof HtmlLabel htmlLabel) {
                         label = htmlLabel;
                         break;
                     }
                 }
             }
 
             if (label != null) {
                 final HtmlElement element = label.getLabeledElement();
                 if (element != null && element != getDomNodeOrNull()) {
                     try {
                         element.click(event.isShiftKey(), event.isCtrlKey(), event.isAltKey(), false, true, true, true);
                     }
                     catch (final IOException ignored) {
                         // ignore for now
                     }
                 }
             }
 
         }
         finally {
             event.endFire();
             window.setCurrentEvent(previousEvent); // reset event
         }
 
         return new ScriptResult(null);
     }
 
     /**
      * Returns whether there are any event handlers for the specified event name.
      *
      * @param eventName the event name (e.g. {@code "onclick"})
      * @return {@code true} if there are any event handlers, {@code false} otherwise
      */
     public boolean hasEventHandlers(final String eventName) {
         if (eventListenersContainer_ == null) {
             return false;
         }
         return eventListenersContainer_.hasEventListeners(StringUtils.substring(eventName, 2));
     }
 
     /**
      * Returns the specified event handler function.
      *
      * @param eventType the event type (e.g. {@code "click"})
      * @return the handler function, or {@code null} if not set
      */
     public Function getEventHandler(final String eventType) {
         if (eventListenersContainer_ == null) {
             return null;
         }
         return eventListenersContainer_.getEventHandler(eventType);
     }
 
     /**
      * Dispatches an event into the event system.
      *
      * @param event the event to be dispatched
      * @return {@code false} if at least one of the event handlers called {@code preventDefault()};
      *         {@code true} otherwise
      * @see <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/dispatchEvent">MDN Documentation</a>
      */
     @JsxFunction
     public boolean dispatchEvent(final Event event) {
         event.setTarget(this);
 
         ScriptResult result = null;
         final DomNode domNode = getDomNodeOrNull();
         if (MouseEvent.TYPE_CLICK.equals(event.getType()) && (domNode instanceof DomElement element)) {
             try {
                 element.click(event, event.isShiftKey(), event.isCtrlKey(), event.isAltKey(), true);
             }
             catch (final IOException e) {
                 throw JavaScriptEngine.reportRuntimeError("Error calling click(): " + e.getMessage());
             }
         }
         else {
             result = fireEvent(event);
         }
         return !event.isAborted(result);
     }
 
     /**
      * Removes a previously registered event listener from this event target.
      *
      * @param type the event type (e.g. {@code "click"})
      * @param listener the listener to remove
      * @param useCapture if {@code true}, the listener is removed from the capture phase
      * @see <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/removeEventListener">MDN Documentation</a>
      */
     @JsxFunction
     public void removeEventListener(final String type, final Scriptable listener, final boolean useCapture) {
         if (eventListenersContainer_ == null) {
             return;
         }
         eventListenersContainer_.removeEventListener(type, listener, useCapture);
     }
 
     /**
      * Defines an event handler (or any other object) for the given event name.
      *
      * @param eventName the event name (e.g. {@code "click"})
      * @param value the handler ({@code null} to reset it)
      */
     public void setEventHandler(final String eventName, final Object value) {
         if (isEventHandlerOnWindow()) {
             getWindow().getEventListenersContainer().setEventHandler(eventName, value);
             return;
         }
         getEventListenersContainer().setEventHandler(eventName, value);
     }
 
     /**
      * Returns whether the event handler property should be set at the window level.
      *
      * @return {@code true} if the event handler should be set at window level
      */
     protected boolean isEventHandlerOnWindow() {
         return false;
     }
 
     /**
      * Clears the event listener container.
      */
     protected void clearEventListenersContainer() {
         eventListenersContainer_ = null;
     }
 }