/**
 * Copyright (C) 2010 hprange <hprange@gmail.com>
 * 
 * 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.woinject;

import com.google.inject.Key;
import com.google.inject.OutOfScopeException;
import com.google.inject.Provider;
import com.google.inject.Scope;
import com.webobjects.appserver.WOSession;
import com.webobjects.foundation.NSKeyValueCoding;

import er.extensions.appserver.ERXSession;

/**
 * WOSession scope.
 * 
 * @author <a href="mailto:hprange@gmail.com">Henrique Prange</a>
 * @since 1.0
 */
class WOSessionScope implements Scope {
    WOSessionScope() {
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.google.inject.Scope#scope(com.google.inject.Key,
     * com.google.inject.Provider)
     */
    public <T> Provider<T> scope(final Key<T> key, final Provider<T> creator) {
        final String name = key.toString();

        return new Provider<T>() {
            public T get() {
                WOSession session = session();

                if (session == null) {
                    throw new OutOfScopeException("Cannot access scoped object. Either the session has not been initialized yet, or it has expired.");
                }

                synchronized (session) {
                    Object object = session.objectForKey(name);

                    if (object == NSKeyValueCoding.NullValue) {
                        return null;
                    }

                    @SuppressWarnings("unchecked")
                    T t = (T) object;

                    if (t == null) {
                        t = creator.get();

                        session.setObjectForKey(t != null ? t : NSKeyValueCoding.NullValue, name);
                    }

                    return t;
                }
            }
        };
    }

    protected WOSession session() {
        return ERXSession.session();
    }
}