/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2014 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * 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 io.undertow.servlet.core;

import io.undertow.servlet.UndertowServletLogger;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionIdListener;
import javax.servlet.http.HttpSessionListener;
import java.util.ArrayList;
import java.util.List;

import static io.undertow.servlet.core.ApplicationListeners.ListenerState.DECLARED_LISTENER;
import static io.undertow.servlet.core.ApplicationListeners.ListenerState.PROGRAMATIC_LISTENER;

Class that is responsible for invoking application listeners.

This class does not perform any context setup, the context must be setup
before invoking this class.

Note that arrays are used instead of lists for performance reasons.
Author:
Stuart Douglas/**
 * Class that is responsible for invoking application listeners.
 * <p>
 * This class does not perform any context setup, the context must be setup
 * before invoking this class.
 * <p>
 * Note that arrays are used instead of lists for performance reasons.
 *
 * @author Stuart Douglas
 */
public class ApplicationListeners implements Lifecycle {


    private static final ManagedListener[] EMPTY = {};

    private static final Class[] LISTENER_CLASSES = {ServletContextListener.class,
            ServletContextAttributeListener.class,
            ServletRequestListener.class,
            ServletRequestAttributeListener.class,
            javax.servlet.http.HttpSessionListener.class,
            javax.servlet.http.HttpSessionAttributeListener.class,
            HttpSessionIdListener.class};

    private static final ThreadLocal<ListenerState> IN_PROGRAMATIC_SC_LISTENER_INVOCATION = new ThreadLocal<ListenerState>() {
        @Override
        protected ListenerState initialValue() {
            return ListenerState.NO_LISTENER;
        }
    };

    private ServletContext servletContext;
    private final List<ManagedListener> allListeners = new ArrayList<>();
    private ManagedListener[] servletContextListeners;
    private ManagedListener[] servletContextAttributeListeners;
    private ManagedListener[] servletRequestListeners;
    private ManagedListener[] servletRequestAttributeListeners;
    private ManagedListener[] httpSessionListeners;
    private ManagedListener[] httpSessionAttributeListeners;
    private ManagedListener[] httpSessionIdListeners;
    private volatile boolean started = false;

    public ApplicationListeners(final List<ManagedListener> allListeners, final ServletContext servletContext) {
        this.servletContext = servletContext;
        servletContextListeners = EMPTY;
        servletContextAttributeListeners = EMPTY;
        servletRequestListeners = EMPTY;
        servletRequestAttributeListeners = EMPTY;
        httpSessionListeners = EMPTY;
        httpSessionAttributeListeners = EMPTY;
        httpSessionIdListeners = EMPTY;
        for (final ManagedListener listener : allListeners) {
            addListener(listener);
        }
    }

    public void addListener(final ManagedListener listener) {
        if (ServletContextListener.class.isAssignableFrom(listener.getListenerInfo().getListenerClass())) {
            ManagedListener[] old = servletContextListeners;
            servletContextListeners = new ManagedListener[old.length + 1];
            System.arraycopy(old, 0, servletContextListeners, 0, old.length);
            servletContextListeners[old.length] = listener;
        }
        if (ServletContextAttributeListener.class.isAssignableFrom(listener.getListenerInfo().getListenerClass())) {

            ManagedListener[] old = servletContextAttributeListeners;
            servletContextAttributeListeners = new ManagedListener[old.length + 1];
            System.arraycopy(old, 0, servletContextAttributeListeners, 0, old.length);
            servletContextAttributeListeners[old.length] = listener;
        }
        if (ServletRequestListener.class.isAssignableFrom(listener.getListenerInfo().getListenerClass())) {
            ManagedListener[] old = servletRequestListeners;
            servletRequestListeners = new ManagedListener[old.length + 1];
            System.arraycopy(old, 0, servletRequestListeners, 0, old.length);
            servletRequestListeners[old.length] = listener;
        }
        if (ServletRequestAttributeListener.class.isAssignableFrom(listener.getListenerInfo().getListenerClass())) {
            ManagedListener[] old = servletRequestAttributeListeners;
            servletRequestAttributeListeners = new ManagedListener[old.length + 1];
            System.arraycopy(old, 0, servletRequestAttributeListeners, 0, old.length);
            servletRequestAttributeListeners[old.length] = listener;
        }
        if (HttpSessionListener.class.isAssignableFrom(listener.getListenerInfo().getListenerClass())) {
            ManagedListener[] old = httpSessionListeners;
            httpSessionListeners = new ManagedListener[old.length + 1];
            System.arraycopy(old, 0, httpSessionListeners, 0, old.length);
            httpSessionListeners[old.length] = listener;
        }
        if (HttpSessionAttributeListener.class.isAssignableFrom(listener.getListenerInfo().getListenerClass())) {
            ManagedListener[] old = httpSessionAttributeListeners;
            httpSessionAttributeListeners = new ManagedListener[old.length + 1];
            System.arraycopy(old, 0, httpSessionAttributeListeners, 0, old.length);
            httpSessionAttributeListeners[old.length] = listener;
        }
        if (HttpSessionIdListener.class.isAssignableFrom(listener.getListenerInfo().getListenerClass())) {
            ManagedListener[] old = httpSessionIdListeners;
            httpSessionIdListeners = new ManagedListener[old.length + 1];
            System.arraycopy(old, 0, httpSessionIdListeners, 0, old.length);
            httpSessionIdListeners[old.length] = listener;
        }
        this.allListeners.add(listener);
        if(started) {
            try {
                listener.start();
            } catch (ServletException e) {
                throw new RuntimeException(e);
            }
        }
    }

    public void start() throws ServletException {
        started = true;
        for (ManagedListener listener : allListeners) {
            listener.start();
        }
    }

    public void stop() {
        if (started) {
            started = false;
            for (final ManagedListener listener : allListeners) {
                listener.stop();
            }
        }
    }

    @Override
    public boolean isStarted() {
        return started;
    }

    public void contextInitialized() {
        if(!started) {
            return;
        }
        //new listeners can be added here, so we don't use an iterator
        final ServletContextEvent event = new ServletContextEvent(servletContext);
        for (int i = 0; i < servletContextListeners.length; ++i) {
            ManagedListener listener = servletContextListeners[i];
            IN_PROGRAMATIC_SC_LISTENER_INVOCATION.set(listener.isProgramatic() ? PROGRAMATIC_LISTENER : DECLARED_LISTENER);
            try {
                this.<ServletContextListener>get(listener).contextInitialized(event);
            } finally {
                IN_PROGRAMATIC_SC_LISTENER_INVOCATION.remove();
            }
        }
    }

    public void contextDestroyed() {
        if(!started) {
            return;
        }
        final ServletContextEvent event = new ServletContextEvent(servletContext);
        for (int i = servletContextListeners.length - 1; i >= 0; --i) {
            ManagedListener listener = servletContextListeners[i];
            try {
                this.<ServletContextListener>get(listener).contextDestroyed(event);
            } catch (Exception e) {
                UndertowServletLogger.REQUEST_LOGGER.errorInvokingListener("contextDestroyed", listener.getListenerInfo().getListenerClass(), e);
            }
        }
    }

    public void servletContextAttributeAdded(final String name, final Object value) {
        if(!started) {
            return;
        }
        final ServletContextAttributeEvent sre = new ServletContextAttributeEvent(servletContext, name, value);
        for (int i = 0; i < servletContextAttributeListeners.length; ++i) {
            this.<ServletContextAttributeListener>get(servletContextAttributeListeners[i]).attributeAdded(sre);
        }
    }

    public void servletContextAttributeRemoved(final String name, final Object value) {
        if(!started) {
            return;
        }
        final ServletContextAttributeEvent sre = new ServletContextAttributeEvent(servletContext, name, value);
        for (int i = 0; i < servletContextAttributeListeners.length; ++i) {
            this.<ServletContextAttributeListener>get(servletContextAttributeListeners[i]).attributeRemoved(sre);
        }
    }

    public void servletContextAttributeReplaced(final String name, final Object value) {
        if(!started) {
            return;
        }
        final ServletContextAttributeEvent sre = new ServletContextAttributeEvent(servletContext, name, value);
        for (int i = 0; i < servletContextAttributeListeners.length; ++i) {
            this.<ServletContextAttributeListener>get(servletContextAttributeListeners[i]).attributeReplaced(sre);
        }
    }

    public void requestInitialized(final ServletRequest request) {
        if(!started) {
            return;
        }
        if(servletRequestListeners.length > 0) {
            final ServletRequestEvent sre = new ServletRequestEvent(servletContext, request);
            for (int i = 0; i < servletRequestListeners.length; ++i) {
                this.<ServletRequestListener>get(servletRequestListeners[i]).requestInitialized(sre);
            }
        }
    }

    public void requestDestroyed(final ServletRequest request) {
        if(!started) {
            return;
        }
        if(servletRequestListeners.length > 0) {
            final ServletRequestEvent sre = new ServletRequestEvent(servletContext, request);
            for (int i = servletRequestListeners.length - 1; i >= 0; --i) {
                ManagedListener listener = servletRequestListeners[i];
                try {
                    this.<ServletRequestListener>get(listener).requestDestroyed(sre);
                } catch (Exception e) {
                    UndertowServletLogger.REQUEST_LOGGER.errorInvokingListener("requestDestroyed", listener.getListenerInfo().getListenerClass(), e);
                }
            }
        }
    }

    public void servletRequestAttributeAdded(final HttpServletRequest request, final String name, final Object value) {
        if(!started) {
            return;
        }
        final ServletRequestAttributeEvent sre = new ServletRequestAttributeEvent(servletContext, request, name, value);
        for (int i = 0; i < servletRequestAttributeListeners.length; ++i) {
            this.<ServletRequestAttributeListener>get(servletRequestAttributeListeners[i]).attributeAdded(sre);
        }
    }

    public void servletRequestAttributeRemoved(final HttpServletRequest request, final String name, final Object value) {
        if(!started) {
            return;
        }
        final ServletRequestAttributeEvent sre = new ServletRequestAttributeEvent(servletContext, request, name, value);
        for (int i = 0; i < servletRequestAttributeListeners.length; ++i) {
            this.<ServletRequestAttributeListener>get(servletRequestAttributeListeners[i]).attributeRemoved(sre);
        }
    }

    public void servletRequestAttributeReplaced(final HttpServletRequest request, final String name, final Object value) {
        if(!started) {
            return;
        }
        final ServletRequestAttributeEvent sre = new ServletRequestAttributeEvent(servletContext, request, name, value);
        for (int i = 0; i < servletRequestAttributeListeners.length; ++i) {
            this.<ServletRequestAttributeListener>get(servletRequestAttributeListeners[i]).attributeReplaced(sre);
        }
    }

    public void sessionCreated(final HttpSession session) {
        if(!started) {
            return;
        }
        final HttpSessionEvent sre = new HttpSessionEvent(session);
        for (int i = 0; i < httpSessionListeners.length; ++i) {
            this.<HttpSessionListener>get(httpSessionListeners[i]).sessionCreated(sre);
        }
    }

    public void sessionDestroyed(final HttpSession session) {
        if(!started) {
            return;
        }
        final HttpSessionEvent sre = new HttpSessionEvent(session);
        for (int i = httpSessionListeners.length - 1; i >= 0; --i) {
            ManagedListener listener = httpSessionListeners[i];
            this.<HttpSessionListener>get(listener).sessionDestroyed(sre);
        }
    }

    public void httpSessionAttributeAdded(final HttpSession session, final String name, final Object value) {
        if(!started) {
            return;
        }
        final HttpSessionBindingEvent sre = new HttpSessionBindingEvent(session, name, value);
        for (int i = 0; i < httpSessionAttributeListeners.length; ++i) {
            this.<HttpSessionAttributeListener>get(httpSessionAttributeListeners[i]).attributeAdded(sre);
        }
    }

    public void httpSessionAttributeRemoved(final HttpSession session, final String name, final Object value) {
        if(!started) {
            return;
        }
        final HttpSessionBindingEvent sre = new HttpSessionBindingEvent(session, name, value);
        for (int i = 0; i < httpSessionAttributeListeners.length; ++i) {
            this.<HttpSessionAttributeListener>get(httpSessionAttributeListeners[i]).attributeRemoved(sre);
        }
    }

    public void httpSessionAttributeReplaced(final HttpSession session, final String name, final Object value) {
        if(!started) {
            return;
        }
        final HttpSessionBindingEvent sre = new HttpSessionBindingEvent(session, name, value);
        for (int i = 0; i < httpSessionAttributeListeners.length; ++i) {
            this.<HttpSessionAttributeListener>get(httpSessionAttributeListeners[i]).attributeReplaced(sre);
        }
    }

    public void httpSessionIdChanged(final HttpSession session, final String oldSessionId) {
        if(!started) {
            return;
        }
        final HttpSessionEvent sre = new HttpSessionEvent(session);
        for (int i = 0; i < httpSessionIdListeners.length; ++i) {
            this.<HttpSessionIdListener>get(httpSessionIdListeners[i]).sessionIdChanged(sre, oldSessionId);
        }
    }

    private <T> T get(final ManagedListener listener) {
        return (T) listener.instance();
    }

    
returns true if this is in in a
/**
     * returns true if this is in in a
     */
    public static ListenerState listenerState() {
        return IN_PROGRAMATIC_SC_LISTENER_INVOCATION.get();
    }

    
Params:
clazz – The potential listener class
Returns:
true if the provided class is a valid listener class/**
     * @param clazz The potential listener class
     * @return true if the provided class is a valid listener class
     */
    public static boolean isListenerClass(final Class<?> clazz) {
        for (Class c : LISTENER_CLASSES) {
            if (c.isAssignableFrom(clazz)) {
                return true;
            }
        }
        return false;
    }

    public enum ListenerState {
        NO_LISTENER,
        DECLARED_LISTENER,
        PROGRAMATIC_LISTENER,
    }

}