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  package org.apache.cayenne.dba;
  
  import org.apache.cayenne.ObjectContext;
  import org.apache.cayenne.di.Inject;
  import org.apache.cayenne.map.DataMap;
  import org.apache.cayenne.map.EntityResolver;
  import org.apache.cayenne.map.ObjEntity;
  import org.apache.cayenne.query.ObjectSelect;
  import org.apache.cayenne.runtime.CayenneRuntime;
  import org.apache.cayenne.testdo.qualified.Qualified1;
  import org.apache.cayenne.unit.DerbyUnitDbAdapter;
  import org.apache.cayenne.unit.UnitDbAdapter;
  import org.apache.cayenne.unit.di.runtime.CayenneProjects;
  import org.apache.cayenne.unit.di.runtime.RuntimeCase;
  import org.apache.cayenne.unit.di.runtime.UseCayenneRuntime;
  import org.junit.Before;
  import org.junit.Test;
  
  import java.sql.CallableStatement;
  import java.sql.Connection;
  import java.sql.SQLException;
  import java.util.List;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.TimeUnit;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.fail;
  
  @UseCayenneRuntime(CayenneProjects.QUALIFIED_PROJECT)
  public class ConcurrentPkGeneratorIT extends RuntimeCase {
  
      @Inject
      private CayenneRuntime runtime;
  
  	@Inject
  	private UnitDbAdapter unitDbAdapter;
  
  	@Before
  	public void prepareDerbyDb() {
  		//use to fix random test failures on derby db
  		if(unitDbAdapter instanceof DerbyUnitDbAdapter) {
  			try(Connection connection = runtime.getDataDomain().getDataNode("qualified").getDataSource().getConnection()){
  				CallableStatement cs =
  						connection.prepareCall("CALL SYSCS_UTIL.SYSCS_SET_DATABASE_PROPERTY(?, ?)");
  				cs.setString(1, "derby.language.sequence.preallocator");
  				cs.setString(2, "1000");
  				cs.execute();
  				cs.close();
  			} catch (SQLException ex) {
  				throw new RuntimeException(ex);
  			}
  		}
  	}
  
      /*
       * Attempts to discover any problems regarding thread locking in the PkGenerator
       */
      @Test
      public void testConcurrentInserts() {
      	if(!unitDbAdapter.supportsPKGeneratorConcurrency()) {
      		return;
  		}
  
  		final DataMap dataMap = runtime.getDataDomain().getDataMap("qualified");
  		
  		// clear out the table
  		ObjectContext context = runtime.newContext();
  		List<Qualified1> qualified1s = context.select(ObjectSelect.query(Qualified1.class));
  		context.deleteObjects(qualified1s);
  		context.commitChanges();
  		
  		// perform concurrent inserts
  		int numThreads = 2;
  		int insertsPerThread = 100;
  
  		ExecutorService executor = Executors.newFixedThreadPool(numThreads);
  		Runnable task = () -> {
              try {
                  ObjectContext context1 = runtime.newContext();
  				EntityResolver entityResolver = context1.getEntityResolver();
  				for (ObjEntity entity : dataMap.getObjEntities()) {
                      context1.newObject(entityResolver.getObjectFactory().getJavaClass(entity.getJavaClassName()));
                  }
                  context1.commitChanges();
              } catch (Exception e) {
                  e.printStackTrace();
              }
          };
  		
  		for (int j = 0; j < insertsPerThread; j++) {
  			for (int i = 0; i < numThreads; i++) {
  				executor.submit(task);
  			}
  		}
  		
  		// check for completion or deadlock
  		executor.shutdown();
  		try {
  			// normally this completes in less than 2 seconds. If it takes 30 then it failed.
  			boolean didFinish = executor.awaitTermination(30, TimeUnit.SECONDS);
  			if (!didFinish) {
  				fail("Concurrent inserts either deadlocked or contended over the lock too long.");
  			}
  		} catch (InterruptedException e) {
  			throw new RuntimeException(e);
  		}
  		
  		// check for gaps in the generated sequence numbers
  		qualified1s = context.select(ObjectSelect.query(Qualified1.class));
  		assertEquals(insertsPerThread * numThreads, qualified1s.size());
  
  		// PKs will be used in order most of the time, but the implementation doesn't guarantee it.
  //		qualified1s.sort(Comparator.comparing(Cayenne::intPKForObject));
  //
  //		int lastPk = Cayenne.intPKForObject(qualified1s.get(0)) - 1;
  //		for (Qualified1 qualified1 : qualified1s) {
  //			if (lastPk+1 != Cayenne.intPKForObject(qualified1)) {
  //				fail("Found gap in sequence number: " + lastPk + " - " + Cayenne.intPKForObject(qualified1));
  //			}
  //			lastPk++;
  //		}
      }
      
  }
  