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package com.sun.faces.component.behavior;

import java.io.Serializable;

import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.faces.application.Application;
import javax.faces.component.behavior.AjaxBehavior;
import javax.faces.component.behavior.ClientBehavior;
import javax.faces.component.behavior.ClientBehaviorHint;
import javax.faces.component.behavior.ClientBehaviorHolder;
import javax.faces.context.FacesContext;

/**
 * An instance of the class is used to 
 * manage {@link AjaxBehavior} instances.
 *
 * @since 2.0
 */
public class AjaxBehaviors implements Serializable {

    private static final String AJAX_BEHAVIORS = "javax.faces.component.AjaxBehaviors";

    private LinkedList behaviorStack = null;

    public AjaxBehaviors() {
        behaviorStack = new LinkedList();
    }

    // Returns the AjaxBehaviors instance, creating it if necessary.
    public static AjaxBehaviors getAjaxBehaviors(FacesContext context,
                                                 boolean createIfNull) {

        Map attrs = context.getAttributes();
        AjaxBehaviors ajaxBehaviors = (AjaxBehaviors)attrs.get(AJAX_BEHAVIORS);

        if ((ajaxBehaviors == null) && createIfNull) {
            ajaxBehaviors = new AjaxBehaviors();
            attrs.put(AJAX_BEHAVIORS, ajaxBehaviors);
        }

        return ajaxBehaviors;
    }

    // Adds AjaxBehaviors to the specified ClientBehaviorHolder
    public void addBehaviors(FacesContext context,
                             ClientBehaviorHolder behaviorHolder) {

        if ((behaviorStack == null) || behaviorStack.isEmpty()){
            return;
        }

        // Loop over pushed Behaviors and add to the ClientBehaviorHolder.
        // Note that we add most recently pushed behaviors first.  That
        // way the nearest behaviors take precedence.  Behaviors that were
        // pushed earlier won't be added since we'll already have a 
        // submitting behavior attached.
        int count = behaviorStack.size();
        for (int i = count - 1; i >= 0; i--) {
            behaviorStack.get(i).addBehavior(context, behaviorHolder);
        }
    }


    /**
     * Push the {@link AjaxBehavior} into scope making it available 
     * for subsequent calls to {@link #getBehaviorForEvent}.
     *
     * @param ajaxBehavior the {@link AjaxBehavior} instance
     * @param eventName the name of the event that the behavior is associated
     *     with.
     *
     * @since 2.0
     */ 
    public void pushBehavior(FacesContext context,
                             AjaxBehavior ajaxBehavior,
                             String eventName) {
        behaviorStack.add(new BehaviorInfo(context, ajaxBehavior, eventName));
    }

    /**
     * Pop the last {@link AjaxBehavior} instance 
     * from the List.
     *
     * @since 2.0
     */
    public void popBehavior() {
         if (behaviorStack.size() > 0) {
             behaviorStack.removeLast();
         }
    }   

    // Helper class for storing and creating/applying inherited
    // AjaxBehaviors
    public static class BehaviorInfo {
        private String eventName;
        private Object behaviorState;

        public BehaviorInfo(FacesContext context,
                            AjaxBehavior ajaxBehavior,
                            String eventName) {
            this.eventName = eventName;

            // We don't actually need the AjaxBehavior - just
            // its state.
            behaviorState = ajaxBehavior.saveState(context);
        }

        public void addBehavior(FacesContext context,
                                ClientBehaviorHolder behaviorHolder) {

            String eventName = this.eventName;
            if (eventName == null) {
                eventName = behaviorHolder.getDefaultEventName();

                // No event name, default or otherwise - we're done
                if (eventName == null) {
                    return;
                }
            }

            // We only add the 
            if (shouldAddBehavior(behaviorHolder, eventName)) {
                ClientBehavior behavior = createBehavior(context);
                behaviorHolder.addClientBehavior(eventName, behavior);
            }

        }

        // Tests whether we should add an AjaxBehavior to the specified
        // ClientBehaviorHolder/event name.
        private boolean shouldAddBehavior(ClientBehaviorHolder behaviorHolder,
                                          String eventName) {

            // First need to make sure that this ClientBehaviorHolder
            // supports the specified event type.
            if (!behaviorHolder.getEventNames().contains(eventName)) {
                return false;
            }

            // Check for a submitting behavior already attached.
            // If we've already got one, we don't add another.
            Map> allBehaviors =
                behaviorHolder.getClientBehaviors();
            List eventBehaviors = allBehaviors.get(eventName);

            if ((eventBehaviors == null) || (eventBehaviors.isEmpty())) {
                return true;
            }

            for (ClientBehavior behavior : eventBehaviors) {
                Set hints = behavior.getHints();

                if (hints.contains(ClientBehaviorHint.SUBMITTING)) {
                    return false;
                }
            }

            return true;
        }

        // Creates the AjaxBehavior
        private ClientBehavior createBehavior(FacesContext context) {
            Application application = context.getApplication();

            // Re-create the instance via the Application
            AjaxBehavior behavior = (AjaxBehavior)application.createBehavior(
                                                    AjaxBehavior.BEHAVIOR_ID);

            // And re-initialize its state
            behavior.restoreState(context, behaviorState);

            return behavior;
        }

        private BehaviorInfo() {
        }
    }

}