package org.kuali.common.dns.util;
   
   import static java.lang.String.format;
   import static org.kuali.common.util.base.Precondition.checkNotNull;
   import static org.kuali.common.util.log.Loggers.newLogger;
   
   import org.kuali.common.dns.api.DnsService;
   import org.kuali.common.dns.model.CNAMEContext;
   import org.kuali.common.dns.model.SimpleDnsRecord;
  import org.kuali.common.util.execute.Executable;
  import org.slf4j.Logger;
  
  import com.google.common.base.Optional;
  
  public final class CreateOrReplaceCNAME implements Executable {
  
  	private static final Logger logger = newLogger();
  
  	public CreateOrReplaceCNAME(DnsService service, CNAMEContext context) {
  		this(service, context, false);
  	}
  
  	public CreateOrReplaceCNAME(DnsService service, CNAMEContext context, boolean skip) {
  		this.service = checkNotNull(service, "service");
  		this.context = checkNotNull(context, "context");
  		this.skip = skip;
  	}
  
  	private final DnsService service;
  	private final CNAMEContext context;
  	private final boolean skip;
  
  	@Override
  	public void execute() {
  
  		// Might be skipping execution all together
  		if (skip) {
  			return;
  		}
  
  		// Extract the DNS record corresponding to the alias FQDN
  		Optional<SimpleDnsRecord> record = service.getCNAMERecord(context.getAliasFQDN());
  
  		// If this is true, we are good to go, DNS is already setup correctly
  		if (existsAndMatches(record)) {
  			return;
  		}
  
  		// Otherwise, check to see if there is an existing record
  		if (record.isPresent()) {
  
  			// There is an existing record but it doesn't match, we must delete it
  			logger.info(format("deleting cname record for [%s]", context.getAliasFQDN()));
  			service.deleteCNAMERecord(context.getAliasFQDN());
  		}
  
  		// There may have never been a DNS record OR we just deleted one
  		// Either way, need to create a new one
  		logger.info(format("creating cname record for [%s] -> [%s]", context.getAliasFQDN(), context.getCanonicalFQDN()));
  		service.createCNAMERecord(context.getAliasFQDN(), context.getCanonicalFQDN(), context.getTimeToLiveInSeconds());
  	}
  
  	private boolean existsAndMatches(Optional<SimpleDnsRecord> record) {
  		if (!record.isPresent()) {
  			return false;
  		}
  		String existingValue = record.get().getValue();
  		String cnameRecordValue = service.getCNAMERecordValueFromFQDN(context.getCanonicalFQDN());
  		return cnameRecordValue.equals(existingValue);
  	}
  
  	public DnsService getService() {
  		return service;
  	}
  
  	public boolean isSkip() {
  		return skip;
  	}
  
  	public CNAMEContext getContext() {
  		return context;
  	}
  
  }