package com.trendmicro.grid.acl.ds.jpa.util;
   
   import com.trendmicro.grid.acl.l0.datatypes.FileIdentifier;
   import static net.sf.tinyjee.util.Assert.assertNotNull;
   
   import javax.persistence.EntityManager;
   import javax.persistence.Query;
   import javax.persistence.TypedQuery;
   
  /**
   * Is a helper class that configures and caches queries that fetch results by FileIdentifier.
   * <p/>
   * Note: Instanes of this class are meant to be short lived for the time of a single transaction.
   *
   * @param <T> The type of the expected result.
   */
  public class FileQueryConfigurator<T> {
  
  	private final EntityManager em;
  	private final String sha1QueryName;
  	private final String md5QueryName;
  	private final String fullQueryName;
  	private final Class<T> resultType;
  
  	private Query md5Query, sha1Query, fullQuery;
  
  	/**
  	 * Creates a new configurator.
  	 *
  	 * @param em			the entitymanager to use for retrieving the queries.
  	 * @param resultType	the result type of the queries.
  	 * @param queryBaseName the common base name for both queries.
  	 */
  	public FileQueryConfigurator(EntityManager em, Class<T> resultType, String queryBaseName) {
  		this(em, resultType, queryBaseName.concat("ByMD5"), queryBaseName.concat("BySHA1"), queryBaseName.concat("BySHA1AndMD5"));
  	}
  
  	/**
  	 * Creates a new configurator.
  	 *
  	 * @param em			the entitymanager to use for retrieving the queries.
  	 * @param resultType	the result type of the queries.
  	 * @param sha1QueryName	 the name of the named sha1-only query
  	 * @param fullQueryName the name of the named sha1+md5 query.
  	 */
  	public FileQueryConfigurator(EntityManager em, Class<T> resultType, String md5QueryName, String sha1QueryName, String fullQueryName) {
  		this.em = em;
  		this.resultType = resultType;
  		this.md5QueryName = md5QueryName;
  		this.sha1QueryName = sha1QueryName;
  		this.fullQueryName = fullQueryName;
  	}
  
  	/**
  	 * Returns the configured query.
  	 *
  	 * @param file the identifier specifying the file to ask for.
  	 * @return the configured query.
  	 */
  	@SuppressWarnings("unchecked")
  	public TypedQuery<T> getQuery(FileIdentifier file) {
  		if (resultType == null) throw new IllegalStateException("Result type cannot be 'null' for typed queries.");
  
  		return (TypedQuery<T>) getUntypedQuery(file);
  	}
  
  	/**
  	 * Returns the configured query.
  	 *
  	 * @param file the identifier specifying the file to ask for.
  	 * @return the configured query.
  	 */
  	public Query getUntypedQuery(FileIdentifier file) {
  		assertNotNull("FileIdentifier", file);
  
  		final Query q;
  		final byte[] md5 = file.getMD5Hash();
  		final byte[] sha1 = file.getSHA1Hash();
  
  		if (sha1 == null) {
  			if (md5Query == null) {
  				if (resultType == null)
  					md5Query = em.createNamedQuery(md5QueryName).setMaxResults(1);
  				else
  					md5Query = em.createNamedQuery(md5QueryName, resultType).setMaxResults(1);
  			}
  			q = md5Query.setParameter("md5", md5);
  		} else if (md5 == null) {
  			if (sha1Query == null) {
  				if (resultType == null)
  					sha1Query = em.createNamedQuery(sha1QueryName).setMaxResults(1);
  				else
  					sha1Query = em.createNamedQuery(sha1QueryName, resultType).setMaxResults(1);
  			}
  			q = sha1Query.setParameter("sha1", sha1);
  		} else {
  			if (fullQuery == null) {
  				if (resultType == null)
  					fullQuery = em.createNamedQuery(fullQueryName).setMaxResults(1);
 				else
 					fullQuery = em.createNamedQuery(fullQueryName, resultType).setMaxResults(1);
 			}
 			q = fullQuery.setParameter("md5", md5).setParameter("sha1", sha1);
 		}
 
 		return q;
 	}
 }