/*
 *    Copyright 2012 Jason Miller
 *
 * 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 jj.configuration;

import static java.util.concurrent.TimeUnit.SECONDS;
import static jj.application.AppLocation.AppBase;
import static jj.configuration.ConfigurationScriptEnvironmentCreator.CONFIG_SCRIPT_NAME;
import static jj.server.ServerLocation.Virtual;
import static jj.configuration.ConfigurationScriptEnvironmentCreator.CONFIG_NAME;

import java.nio.file.Path;
import java.util.concurrent.CountDownLatch;

import javax.inject.Inject;
import javax.inject.Singleton;

import jj.ServerStarting;
import jj.ServerStarting.Priority;
import jj.event.Listener;
import jj.event.Subscriber;
import jj.execution.ServerTask;
import jj.resource.FileCreation;
import jj.resource.PathResolver;
import jj.resource.ResourceLoader;

/**
 * ensures that the configuration file for the application
 * is available to the system on startup and thereafter
 * 
 * @author jason
 *
 */
@Singleton
@Subscriber
class ConfigurationEventManager {
	
	private final ResourceLoader resourceLoader;
	private final Path configFilePath;
	private final CountDownLatch latch = new CountDownLatch(1);
	
	@Inject
	ConfigurationEventManager(ResourceLoader resourceFinder, PathResolver pathResolver) {
		this.resourceLoader = resourceFinder;
		configFilePath = pathResolver.resolvePath(AppBase, CONFIG_SCRIPT_NAME);
	}

	/**
	 * When the server is started, try to load the configuration
	 */
	@Listener
	void on(ServerStarting event) {
		event.registerStartupTask(Priority.Middle, new ServerTask("initial load of configuration script") {
			
			@Override
			protected void run() throws Exception {
				load();
				boolean success = latch.await(3, SECONDS);
				assert success : "configuration didn't load in 3 seconds";
			}
		});
	}

	/**
	 * If a config file is created, try to load it
	 */
	@Listener
	void on(FileCreation fileCreation) {
		if (configFilePath.equals(fileCreation.path)) {
			load();
		}
	}

	/**
	 * noting that the configuration has been loaded. this only
	 * matters during startup
	 */
	@Listener
	void on(ConfigurationLoaded configurationLoaded) {
		latch.countDown();
	}

	/**
	 * Noting that the configuration has errored, this only
	 * matters during startup
	 */
	@Listener
	void on(ConfigurationErrored event) {
		latch.countDown();
	}
	
	private void load() {
		resourceLoader.loadResource(ConfigurationScriptEnvironment.class, Virtual, CONFIG_NAME);
	}
}