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  package org.apache.cayenne.lifecycle.id;
  
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.cayenne.ObjectContext;
  import org.apache.cayenne.exp.Expression;
  import org.apache.cayenne.exp.ExpressionFactory;
  import org.apache.cayenne.map.DataMap;
  import org.apache.cayenne.map.DbEntity;
  import org.apache.cayenne.map.EntityResolver;
  import org.apache.cayenne.map.ObjEntity;
  import org.apache.cayenne.map.Procedure;
  import org.apache.cayenne.query.ObjectSelect;
  import org.apache.cayenne.query.PrefetchTreeNode;
  import org.apache.cayenne.query.Query;
  import org.apache.cayenne.query.QueryCacheStrategy;
  import org.apache.cayenne.query.QueryChain;
  import org.apache.cayenne.query.QueryMetadata;
  import org.apache.cayenne.query.QueryRouter;
  import org.apache.cayenne.query.SQLAction;
  import org.apache.cayenne.query.SQLActionVisitor;
  import org.apache.cayenne.reflect.ClassDescriptor;
  
  /**
   * A query that allows to fetch objects based on one or more String IDs. The returned
   * objects do not have to be of the same type, be related via inheritance, or come from
   * the same DB table. Note that if you expect multiple types of objects, use
   * {@link ObjectContext#performGenericQuery(Query)}. The returned QueryResponse will
   * contain separate lists of DataRows for each type in no particular order.
   * <p>
   * As of this writing, a limitation of this query is that it returns DataRows that need to
   * be manually converted to objects if needed. In that it is similar to {@link QueryChain}.
   * 
   * @since 3.1
   */
  public class StringIdQuery implements Query {
  
      private static Collection<String> toCollection(String... stringIds) {
  
          if (stringIds == null) {
              throw new NullPointerException("Null stringIds");
          }
  
          return Arrays.asList(stringIds);
      }
  
      protected Collection<String> stringIds;
  
      protected transient Map<String, ObjectSelect> idQueriesByEntity;
  
      public StringIdQuery(String... stringIds) {
          this(toCollection(stringIds));
      }
  
      public StringIdQuery(Collection<String> stringIds) {
          // using a Set to ensure that duplicates do not result in a longer invariant
          // qualifier
          this.stringIds = new HashSet<String>(stringIds);
      }
  
      public Collection<String> getStringIds() {
          return stringIds;
      }
  
      public void addStringIds(String... ids) {
          if (ids == null) {
              throw new NullPointerException("Null ids");
          }
  
          boolean changed = false;
          for (String id : ids) {
              if (stringIds.add(id)) {
                  changed = true;
              }
          }
  
          if (changed) {
              idQueriesByEntity = null;
          }
      }
  
      protected Map<String, ObjectSelect> getIdQueriesByEntity(EntityResolver resolver) {
          if (this.idQueriesByEntity == null) {
  
              Map<String, ObjectSelect> idQueriesByEntity = new HashMap<>();
              Map<String, EntityIdCoder> codersByEntity = new HashMap<>();
  
              for (String id : stringIds) {
                  String entityName = EntityIdCoder.getEntityName(id);
                  EntityIdCoder coder = codersByEntity.get(entityName);
                  ObjectSelect query;
  
                  if (coder == null) {
                      coder = new EntityIdCoder(resolver.getObjEntity(entityName));
  
                      query = ObjectSelect.query(Object.class, entityName);
  
                      codersByEntity.put(entityName, coder);
                      idQueriesByEntity.put(entityName, query);
                  }
                  else {
                      query = idQueriesByEntity.get(entityName);
                  }
  
                  Expression idExp = ExpressionFactory.matchAllDbExp(coder
                          .toObjectId(id)
                          .getIdSnapshot(), Expression.EQUAL_TO);
                  query.or(idExp);
              }
  
              this.idQueriesByEntity = idQueriesByEntity;
          }
  
          return this.idQueriesByEntity;
      }
  
      public QueryMetadata getMetaData(EntityResolver resolver) {
  
          // Cayenne doesn't know how to handle multiple root entities, so this
          // QueryMetadata, just like QueryChain's metadata is not very precise and won't
          // result in correct PersistentObjects...
          return new QueryMetadata() {
  
              public DataMap getDataMap() {
                  return null;
              }
  
              public List<Object> getResultSetMapping() {
                  return null;
              }
  
              @Override
              public boolean isSingleResultSetMapping() {
                  return false;
              }
  
              public Query getOriginatingQuery() {
                  return null;
              }
  
              public QueryCacheStrategy getCacheStrategy() {
                  return QueryCacheStrategy.getDefaultStrategy();
              }
  
              public DbEntity getDbEntity() {
                  return null;
              }
  
              public ObjEntity getObjEntity() {
                  return null;
              }
  
              public ClassDescriptor getClassDescriptor() {
                  return null;
              }
  
              public Procedure getProcedure() {
                  return null;
              }
  
              public String getCacheKey() {
                  return null;
              }
  
              public String getCacheGroup() {
                  return null;
              }
  
              public boolean isFetchingDataRows() {
                  // overriding this... Can't fetch objects until DataDomainQueryAction
                  // starts converting multiple ResultSets to object... Same as QueryChain
                  // essentially.
                  return true;
              }
  
              public boolean isRefreshingObjects() {
                  return true;
              }
  
              public int getPageSize() {
                  return QueryMetadata.PAGE_SIZE_DEFAULT;
              }
  
              public int getFetchOffset() {
                  return -1;
              }
  
              public int getFetchLimit() {
                  return QueryMetadata.FETCH_LIMIT_DEFAULT;
              }
  
              public PrefetchTreeNode getPrefetchTree() {
                  return null;
              }
  
              public Map<String, String> getPathSplitAliases() {
                  return Collections.emptyMap();
              }
  
              public int getStatementFetchSize() {
                  return QueryMetadata.STATEMENT_FETCH_SIZE_DEFAULT;
              }
  
              @Override
              public int getQueryTimeout() {
                  return QueryMetadata.QUERY_TIMEOUT_DEFAULT;
              }
  
              @Override
              public boolean isSuppressingDistinct() {
                  return false;
              }
          };
      }
  
      public void route(QueryRouter router, EntityResolver resolver, Query substitutedQuery) {
  
          Map<String, ObjectSelect> queries = getIdQueriesByEntity(resolver);
          for (ObjectSelect query : queries.values()) {
              query.route(router, resolver, this);
          }
      }
  
      public SQLAction createSQLAction(SQLActionVisitor visitor) {
          throw new UnsupportedOperationException(
                  "This query was supposed to be replace with a set of SelectQueries during the route phase");
      }
  }
  