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package com.sun.faces.context;

import com.sun.faces.RIConstants;
import com.sun.faces.application.ApplicationAssociate;
import com.sun.faces.application.ApplicationStateInfo;
import com.sun.faces.util.ComponentStruct;

import javax.faces.component.UIComponent;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;
import javax.faces.event.AbortProcessingException;
import javax.faces.event.PostAddToViewEvent;
import javax.faces.event.PreRemoveFromViewEvent;
import javax.faces.event.SystemEvent;
import javax.faces.event.SystemEventListener;

import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import static com.sun.faces.context.StateHolderSaver.DYNAMIC_COMPONENT;

/**
 * Context for dealing with partial state saving mechanics.
 */
public class StateContext {


    private static final String KEY = StateContext.class.getName() + "_KEY";
    
    private static final String HAS_ONE_OR_MORE_DYNAMIC_CHILD =
            StateContext.class.getName() + "_HAS_ONE_OR_MORE_DYNAMIC_CHILD";


    private boolean partial;
    private boolean partialLocked;
    private boolean trackMods = true;
    private AddRemoveListener modListener;
    private ApplicationStateInfo stateInfo;
    private WeakReference viewRootRef = new WeakReference(null);


    // ------------------------------------------------------------ Constructors


    private StateContext(ApplicationStateInfo stateInfo) {

        this.stateInfo = stateInfo;

    }


    // ---------------------------------------------------------- Public Methods


    /**
     * @param ctx the FacesContext for the current request
     * @return StateContext for this request
     */
    public static StateContext getStateContext(FacesContext ctx) {

        StateContext stateCtx = (StateContext) ctx.getAttributes().get(KEY);
        if (stateCtx == null) {
            ApplicationAssociate associate = ApplicationAssociate.getCurrentInstance();
            ApplicationStateInfo info = associate.getApplicationStateInfo();
            stateCtx = new StateContext(info);
            ctx.getAttributes().put(KEY, stateCtx);
        }
        return stateCtx;

    }

    /**
     * @param current FacesContext.
     * @param viewId the view ID to check or null if viewId is unknown.
     * @return true if partial state saving should be used for the
     *  specified view ID, otherwise false
     */
    public boolean partialStateSaving(FacesContext ctx, String viewId) {
        // track UIViewRoot changes
        UIViewRoot root = ctx.getViewRoot();
        UIViewRoot refRoot = viewRootRef.get();
        if (root != refRoot) {
          // set weak reference to current viewRoot
          this.viewRootRef = new WeakReference(root);

          // On first call in restore phase, viewRoot is null, so we treat the first 
          // change to not null not as a changing viewRoot.
          if (refRoot != null) {
            // view root changed in request processing - force usage of a 
            // new AddRemoveListener instance for the new viewId ...
            modListener = null;
            // ... and also force check for partial state saving for the new viewId
            partialLocked = false;
          }
        }

        if (!partialLocked) {
                  if (viewId == null) {
                          if (root != null) {
                                  viewId = root.getViewId();
                          } else {
                                  // View root has not yet been initialized.  Check to see whether
                                  // the target view id has been stashed away for us.
                                  viewId = (String)ctx.getAttributes().get(RIConstants.VIEWID_KEY_NAME);
                                }
                  }
        
                  partial = stateInfo.usePartialStateSaving(viewId);
                  partialLocked = true;
        }
        return partial;

    }


    /**
     * @return true if view modifications outside of the initial
     *  construction of the view are being tracked.
     */
    public boolean trackViewModifications() {

        return trackMods;

    }


    /**
     * Installs a SystemEventListener on the UIViewRoot
     * to track components added to or removed from the view.
     */
    public void startTrackViewModifications(FacesContext ctx, UIViewRoot root) {
      
        if (modListener == null) {
            modListener = new AddRemoveListener(ctx);
            root.subscribeToViewEvent(PostAddToViewEvent.class, modListener);
            root.subscribeToViewEvent(PreRemoveFromViewEvent.class, modListener);
        }
        setTrackViewModifications(true);
        
    }


    /**
     * Toggles the current modification tracking status.
     * @param trackMods if true and the listener installed by
     *  {@link #startTrackViewModifications()} is present, then view modifications
     *  will be tracked.  If false, then modification events
     *  will be ignored.
     */
    public void setTrackViewModifications(boolean trackMods) {

        this.trackMods = trackMods;

    }


    /**
     * @param c the UIComponent to check
     * @return true if the component was added after the initial
     *  view construction
     */
    public boolean componentAddedDynamically(UIComponent c) {

        return c.getAttributes().containsKey(DYNAMIC_COMPONENT);

    }

    public int getIndexOfDynamicallyAddedChildInParent(UIComponent c) {
        int result = -1;
        Map attrs = c.getAttributes();
        if (attrs.containsKey(DYNAMIC_COMPONENT)) {
            result = (Integer) attrs.get(DYNAMIC_COMPONENT);
        }
        return result;
    }

    public boolean hasOneOrMoreDynamicChild(UIComponent parent) {
        return parent.getAttributes().containsKey(HAS_ONE_OR_MORE_DYNAMIC_CHILD);
    }

    private int incrementDynamicChildCount(UIComponent parent) {
        int result = 0;
        Map attrs = parent.getAttributes();
        Integer cur = (Integer) attrs.get(HAS_ONE_OR_MORE_DYNAMIC_CHILD);
        if (null != cur) {
            result = cur++;
        } else {
            result = 1;
        }
        attrs.put(HAS_ONE_OR_MORE_DYNAMIC_CHILD, (Integer) result);

        return result;
    }

    private int decrementDynamicChildCount(UIComponent parent) {
        int result = 0;
        Map attrs = parent.getAttributes();
        Integer cur = (Integer) attrs.get(HAS_ONE_OR_MORE_DYNAMIC_CHILD);
        if (null != cur) {
            result = (0 < cur) ? cur-- : 0;

        }
        if (0 == result && null != cur){
            attrs.remove(HAS_ONE_OR_MORE_DYNAMIC_CHILD);
        }

        return result;
    }

    /**
     * @return a Map containing information about all components
     *  added after the initial view construction.
     */
    public Map getDynamicAdds() {

        return ((modListener != null) ? modListener.getDynamicAdds() : null);

    }


    /**
     * @return a List of client IDs that have been removed after
     *  the initial view construction.
     */
    public List getDynamicRemoves() {

        return ((modListener != null) ? modListener.dynamicRemoves : null);

    }


    // ---------------------------------------------------------- Nested Classes


    public class AddRemoveListener implements SystemEventListener {

        private StateContext stateCtx;
        private LinkedHashMap dynamicAdds;
        private List dynamicRemoves;


        // -------------------------------------------------------- Constructors


        public AddRemoveListener(FacesContext ctx) {
            stateCtx = StateContext.getStateContext(ctx);
        }

        // -------------------------------------------------------- Getters

        public Map getDynamicAdds() {
            if (null == dynamicAdds) {
                dynamicAdds = new LinkedHashMap();
            }

            return dynamicAdds;
        }

        // ------------------------------------ Methods From SystemEventListener


        public void processEvent(SystemEvent event)
              throws AbortProcessingException {
            FacesContext ctx = FacesContext.getCurrentInstance();
            if (event instanceof PreRemoveFromViewEvent) {
                if (stateCtx.trackViewModifications()) {
                    handleRemoveEvent(ctx, (PreRemoveFromViewEvent) event);
                }
            } else {
                if (stateCtx.trackViewModifications()) {
                    handleAddEvent(ctx, (PostAddToViewEvent) event);
                }
            }
        }

        public boolean isListenerForSource(Object source) {
            return (source instanceof UIComponent);
        }


        // ----------------------------------------------------- Private Methods


        private void handleRemoveEvent(FacesContext context,
                                       PreRemoveFromViewEvent event) {

            UIComponent removed = event.getComponent();
            if (removed.isTransient()) {
                return;
            }
            
            // this component, while not transient may be a child or facet
            // of component that is.  We'll have to search the parent hierarchy
            // to the root to confirm.
            UIComponent parent = removed.getParent();
            while (parent != null) {
                if (parent.isTransient()) {
                    return;
                }
                parent = parent.getParent();
            }
            
            if (dynamicRemoves == null) {
                dynamicRemoves = new ArrayList();
            }
            String clientId = event.getComponent().getClientId(context);
            if (dynamicAdds != null && dynamicAdds.containsKey(clientId)) {
                dynamicAdds.remove(clientId);
            }
            StateContext.this.decrementDynamicChildCount(removed.getParent());
            dynamicRemoves.add(clientId);
        }


        private void handleAddEvent(FacesContext context,
                                    PostAddToViewEvent event) {

            // if the root is transient, then no action is ever needed here
            if (context.getViewRoot().isTransient()) {
                return;
            }

            UIComponent added = event.getComponent();
            if (added.isTransient() || added instanceof UIViewRoot) {
                return;
            }

            // this component, while not transient may be a child or facet
            // of component that is.  We'll have to search the parent hierarchy
            // to the root to confirm.
            UIComponent parent = added.getParent();
            while (parent != null) {
                if (parent.isTransient()) {
                    return;
                }
                parent = parent.getParent();
            }

            parent = added.getParent();
            StateContext.this.incrementDynamicChildCount(parent);
            ComponentStruct toAdd = new ComponentStruct();
            toAdd.absorbComponent(context, added);

            if (dynamicRemoves != null) {
                dynamicRemoves.remove(toAdd.clientId);
            }
            added.getAttributes().put(DYNAMIC_COMPONENT, new Integer(toAdd.indexOfChildInParent));
            getDynamicAdds().put(toAdd.clientId, toAdd);

        }

    } // END AddRemoveListener

} // END StateContext




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