package com.colobu.zkrecipe.discovery;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.test.TestingServer;
import org.apache.curator.utils.CloseableUtils;
import org.apache.curator.x.discovery.ServiceDiscovery;
import org.apache.curator.x.discovery.ServiceDiscoveryBuilder;
import org.apache.curator.x.discovery.ServiceInstance;
import org.apache.curator.x.discovery.ServiceProvider;
import org.apache.curator.x.discovery.details.JsonInstanceSerializer;
import org.apache.curator.x.discovery.strategies.RandomStrategy;

import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

public class DiscoveryExample {
	private static final String PATH = "/discovery/example";

	public static void main(String[] args) throws Exception {
		// This method is scaffolding to get the example up and running
		TestingServer server = new TestingServer();
		CuratorFramework client = null;
		ServiceDiscovery<InstanceDetails> serviceDiscovery = null;
		Map<String, ServiceProvider<InstanceDetails>> providers = Maps.newHashMap();
		try {
			client = CuratorFrameworkFactory.newClient(server.getConnectString(), new ExponentialBackoffRetry(1000, 3));
			client.start();
			JsonInstanceSerializer<InstanceDetails> serializer = new JsonInstanceSerializer<InstanceDetails>(InstanceDetails.class);
			serviceDiscovery = ServiceDiscoveryBuilder.builder(InstanceDetails.class).client(client).basePath(PATH).serializer(serializer).build();
			serviceDiscovery.start();
			processCommands(serviceDiscovery, providers, client);
		} finally {
			for (ServiceProvider<InstanceDetails> cache : providers.values()) {
				CloseableUtils.closeQuietly(cache);
			}
			CloseableUtils.closeQuietly(serviceDiscovery);
			CloseableUtils.closeQuietly(client);
			CloseableUtils.closeQuietly(server);
		}
	}

	private static void processCommands(ServiceDiscovery<InstanceDetails> serviceDiscovery, Map<String, ServiceProvider<InstanceDetails>> providers,
			CuratorFramework client) throws Exception {
		// More scaffolding that does a simple command line processor
		printHelp();
		List<ExampleServer> servers = Lists.newArrayList();
		try {
			BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
			boolean done = false;
			while (!done) {
				System.out.print("> ");
				String line = in.readLine();
				if (line == null) {
					break;
				}
				String command = line.trim();
				String[] parts = command.split("\\s");
				if (parts.length == 0) {
					continue;
				}
				String operation = parts[0];
				String args[] = Arrays.copyOfRange(parts, 1, parts.length);
				if (operation.equalsIgnoreCase("help") || operation.equalsIgnoreCase("?")) {
					printHelp();
				} else if (operation.equalsIgnoreCase("q") || operation.equalsIgnoreCase("quit")) {
					done = true;
				} else if (operation.equals("add")) {
					addInstance(args, client, command, servers);
				} else if (operation.equals("delete")) {
					deleteInstance(args, command, servers);
				} else if (operation.equals("random")) {
					listRandomInstance(args, serviceDiscovery, providers, command);
				} else if (operation.equals("list")) {
					listInstances(serviceDiscovery);
				}
			}
		} finally {
			for (ExampleServer server : servers) {
				CloseableUtils.closeQuietly(server);
			}
		}
	}

	private static void listRandomInstance(String[] args, ServiceDiscovery<InstanceDetails> serviceDiscovery,
			Map<String, ServiceProvider<InstanceDetails>> providers, String command) throws Exception {
		// this shows how to use a ServiceProvider
		// in a real application you'd create the ServiceProvider early for the
		// service(s) you're interested in
		if (args.length != 1) {
			System.err.println("syntax error (expected random <name>): " + command);
			return;
		}
		String serviceName = args[0];
		ServiceProvider<InstanceDetails> provider = providers.get(serviceName);
		if (provider == null) {
			provider = serviceDiscovery.serviceProviderBuilder().serviceName(serviceName).providerStrategy(new RandomStrategy<InstanceDetails>()).build();
			providers.put(serviceName, provider);
			provider.start();
			Thread.sleep(2500); // give the provider time to warm up - in a real
								// application you wouldn't need to do this
		}
		ServiceInstance<InstanceDetails> instance = provider.getInstance();
		if (instance == null) {
			System.err.println("No instances named: " + serviceName);
		} else {
			outputInstance(instance);
		}
	}

	private static void listInstances(ServiceDiscovery<InstanceDetails> serviceDiscovery) throws Exception {
		// This shows how to query all the instances in service discovery
		try {
			Collection<String> serviceNames = serviceDiscovery.queryForNames();
			System.out.println(serviceNames.size() + " type(s)");
			for (String serviceName : serviceNames) {
				Collection<ServiceInstance<InstanceDetails>> instances = serviceDiscovery.queryForInstances(serviceName);
				System.out.println(serviceName);
				for (ServiceInstance<InstanceDetails> instance : instances) {
					outputInstance(instance);
				}
			}
		} finally {
			CloseableUtils.closeQuietly(serviceDiscovery);
		}
	}

	private static void outputInstance(ServiceInstance<InstanceDetails> instance) {
		System.out.println("\t" + instance.getPayload().getDescription() + ": " + instance.buildUriSpec());
	}

	private static void deleteInstance(String[] args, String command, List<ExampleServer> servers) {
		// simulate a random instance going down
		// in a real application, this would occur due to normal operation, a
		// crash, maintenance, etc.
		if (args.length != 1) {
			System.err.println("syntax error (expected delete <name>): " + command);
			return;
		}
		final String serviceName = args[0];
		ExampleServer server = Iterables.find(servers, new Predicate<ExampleServer>() {
			@Override
			public boolean apply(ExampleServer server) {
				return server.getThisInstance().getName().endsWith(serviceName);
			}
		}, null);
		if (server == null) {
			System.err.println("No servers found named: " + serviceName);
			return;
		}
		servers.remove(server);
		CloseableUtils.closeQuietly(server);
		System.out.println("Removed a random instance of: " + serviceName);
	}

	private static void addInstance(String[] args, CuratorFramework client, String command, List<ExampleServer> servers) throws Exception {
		// simulate a new instance coming up
		// in a real application, this would be a separate process
		if (args.length < 2) {
			System.err.println("syntax error (expected add <name> <description>): " + command);
			return;
		}
		StringBuilder description = new StringBuilder();
		for (int i = 1; i < args.length; ++i) {
			if (i > 1) {
				description.append(' ');
			}
			description.append(args[i]);
		}
		String serviceName = args[0];
		ExampleServer server = new ExampleServer(client, PATH, serviceName, description.toString());
		servers.add(server);
		server.start();
		System.out.println(serviceName + " added");
	}

	private static void printHelp() {
		System.out.println("An example of using the ServiceDiscovery APIs. This example is driven by entering commands at the prompt:\n");
		System.out.println("add <name> <description>: Adds a mock service with the given name and description");
		System.out.println("delete <name>: Deletes one of the mock services with the given name");
		System.out.println("list: Lists all the currently registered services");
		System.out.println("random <name>: Lists a random instance of the service with the given name");
		System.out.println("quit: Quit the example");
		System.out.println();
	}
}