package com.netflix.astyanax.contrib.eureka;

import java.util.List;

import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.base.Supplier;
import com.google.common.collect.Collections2;
import com.google.common.collect.Lists;
import com.netflix.appinfo.AmazonInfo;
import com.netflix.appinfo.AmazonInfo.MetaDataKey;
import com.netflix.appinfo.InstanceInfo;
import com.netflix.appinfo.MyDataCenterInstanceConfig;
import com.netflix.astyanax.connectionpool.Host;
import com.netflix.discovery.DefaultEurekaClientConfig;
import com.netflix.discovery.DiscoveryClient;
import com.netflix.discovery.DiscoveryManager;
import com.netflix.discovery.shared.Application;

/**
 * Simple class that implements {@link Supplier}<{@link List}<{@link Host}>>. It provides a List<{@link Host}>
 * using the {@link DiscoveryManager} which is the eureka client. 
 * 
 * Note that the class needs the eureka application name to discover all instances for that application. 
 * 
 * @author poberai
 */
public class EurekaBasedHostSupplier implements Supplier<List<Host>> {

    private static final Logger LOG = LoggerFactory.getLogger(EurekaBasedHostSupplier.class);

    // The C* cluster name for discovering nodes
    private final String applicationName;

    public EurekaBasedHostSupplier(String applicationName) {
        this.applicationName = applicationName.toUpperCase();
        // initialize eureka client.  make sure eureka properties are properly configured in config.properties
        DiscoveryManager.getInstance().initComponent(new MyDataCenterInstanceConfig(), new DefaultEurekaClientConfig());
    }

    @Override
    public List<Host> get() {

        DiscoveryClient discoveryClient = DiscoveryManager.getInstance().getDiscoveryClient();
        if (discoveryClient == null) {
            LOG.error("Error getting discovery client");
            throw new RuntimeException("Failed to create discovery client");
        }

        Application app = discoveryClient.getApplication(applicationName);
        List<Host> hosts = Lists.newArrayList();
        
        if (app == null) {
            return hosts;
        }
        
        List<InstanceInfo> ins = app.getInstances();
        
        if (ins == null || ins.isEmpty()) {
            return hosts;
        }
        
        hosts = Lists.newArrayList(Collections2.transform(
                Collections2.filter(ins, new Predicate<InstanceInfo>() {
                    @Override
                    public boolean apply(InstanceInfo input) {
                        return input.getStatus() == InstanceInfo.InstanceStatus.UP;
                    }
                }), new Function<InstanceInfo, Host>() {
                    @Override
                    public Host apply(InstanceInfo info) {
                        String[] parts = StringUtils.split(
                                StringUtils.split(info.getHostName(), ".")[0], '-');

                        Host host = new Host(info.getHostName(), info.getPort())
                        .addAlternateIpAddress(
                                StringUtils.join(new String[] { parts[1], parts[2], parts[3],
                                        parts[4] }, "."))
                                        .addAlternateIpAddress(info.getIPAddr())
                                        .setId(info.getId());

                        try {
                            if (info.getDataCenterInfo() instanceof AmazonInfo) {
                                AmazonInfo amazonInfo = (AmazonInfo)info.getDataCenterInfo();
                                host.setRack(amazonInfo.get(MetaDataKey.availabilityZone));
                            }
                        }
                        catch (Throwable t) {
                            LOG.error("Error getting rack for host " + host.getName(), t);
                        }

                        return host;
                    }
                }));


        return hosts;
    }
}