content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.calcite.adapter.mongodb;
  
  import org.apache.calcite.adapter.java.AbstractQueryableTable;
  import org.apache.calcite.linq4j.AbstractEnumerable;
  import org.apache.calcite.linq4j.Enumerable;
  import org.apache.calcite.linq4j.Enumerator;
  import org.apache.calcite.linq4j.QueryProvider;
  import org.apache.calcite.linq4j.Queryable;
  import org.apache.calcite.linq4j.function.Function1;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelOptTable;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.schema.SchemaPlus;
  import org.apache.calcite.schema.TranslatableTable;
  import org.apache.calcite.schema.impl.AbstractTableQueryable;
  import org.apache.calcite.sql.type.SqlTypeName;
  import org.apache.calcite.util.Util;
  
  import com.mongodb.client.FindIterable;
  import com.mongodb.client.MongoCollection;
  import com.mongodb.client.MongoDatabase;
  
  import org.bson.BsonDocument;
  import org.bson.Document;
  import org.bson.conversions.Bson;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  /**
   * Table based on a MongoDB collection.
   */
  public class MongoTable extends AbstractQueryableTable
      implements TranslatableTable {
    private final String collectionName;
  
    /** Creates a MongoTable. */
    MongoTable(String collectionName) {
      super(Object[].class);
      this.collectionName = collectionName;
    }
  
    @Override public String toString() {
      return "MongoTable {" + collectionName + "}";
    }
  
    @Override public RelDataType getRowType(RelDataTypeFactory typeFactory) {
      final RelDataType mapType =
          typeFactory.createMapType(
              typeFactory.createSqlType(SqlTypeName.VARCHAR),
              typeFactory.createTypeWithNullability(
                  typeFactory.createSqlType(SqlTypeName.ANY), true));
      return typeFactory.builder().add("_MAP", mapType).build();
    }
  
    @Override public <T> Queryable<T> asQueryable(QueryProvider queryProvider,
        SchemaPlus schema, String tableName) {
      return new MongoQueryable<>(queryProvider, schema, this, tableName);
    }
  
    @Override public RelNode toRel(
        RelOptTable.ToRelContext context,
        RelOptTable relOptTable) {
      final RelOptCluster cluster = context.getCluster();
      return new MongoTableScan(cluster, cluster.traitSetOf(MongoRel.CONVENTION),
          relOptTable, this, null);
    }
  
    /** Executes a "find" operation on the underlying collection.
     *
     * <p>For example,
     * <code>zipsTable.find("{state: 'OR'}", "{city: 1, zipcode: 1}")</code>
     *
     * @param mongoDb MongoDB connection
     * @param filterJson Filter JSON string, or null
     * @param projectJson Project JSON string, or null
     * @param fields List of fields to project; or null to return map
     * @return Enumerator of results
     */
    private Enumerable<Object> find(MongoDatabase mongoDb, String filterJson,
        String projectJson, List<Map.Entry<String, Class>> fields) {
      final MongoCollection collection =
          mongoDb.getCollection(collectionName);
      final Bson filter =
          filterJson == null ? null : BsonDocument.parse(filterJson);
      final Bson project =
          projectJson == null ? null : BsonDocument.parse(projectJson);
      final Function1<Document, Object> getter = MongoEnumerator.getter(fields);
      return new AbstractEnumerable<Object>() {
        @Override public Enumerator<Object> enumerator() {
          @SuppressWarnings("unchecked") final FindIterable<Document> cursor =
              collection.find(filter).projection(project);
          return new MongoEnumerator(cursor.iterator(), getter);
        }
      };
    }
  
    /** Executes an "aggregate" operation on the underlying collection.
     *
     * <p>For example:
     * <code>zipsTable.aggregate(
     * "{$filter: {state: 'OR'}",
     * "{$group: {_id: '$city', c: {$sum: 1}, p: {$sum: '$pop'}}}")
     * </code>
     *
     * @param mongoDb MongoDB connection
     * @param fields List of fields to project; or null to return map
     * @param operations One or more JSON strings
     * @return Enumerator of results
     */
    private Enumerable<Object> aggregate(final MongoDatabase mongoDb,
        final List<Map.Entry<String, Class>> fields,
        final List<String> operations) {
      final List<Bson> list = new ArrayList<>();
      for (String operation : operations) {
        list.add(BsonDocument.parse(operation));
      }
      final Function1<Document, Object> getter =
          MongoEnumerator.getter(fields);
      return new AbstractEnumerable<Object>() {
        @Override public Enumerator<Object> enumerator() {
          final Iterator<Document> resultIterator;
          try {
            resultIterator = mongoDb.getCollection(collectionName)
                .aggregate(list).iterator();
          } catch (Exception e) {
            throw new RuntimeException("While running MongoDB query "
                + Util.toString(operations, "[", ",\n", "]"), e);
          }
          return new MongoEnumerator(resultIterator, getter);
        }
      };
    }
  
    /** Implementation of {@link org.apache.calcite.linq4j.Queryable} based on
     * a {@link org.apache.calcite.adapter.mongodb.MongoTable}.
     *
     * @param <T> element type */
    public static class MongoQueryable<T> extends AbstractTableQueryable<T> {
      MongoQueryable(QueryProvider queryProvider, SchemaPlus schema,
          MongoTable table, String tableName) {
        super(queryProvider, schema, table, tableName);
      }
  
      @Override public Enumerator<T> enumerator() {
        //noinspection unchecked
        final Enumerable<T> enumerable =
            (Enumerable<T>) getTable().find(getMongoDb(), null, null, null);
        return enumerable.enumerator();
      }
  
      private MongoDatabase getMongoDb() {
        return schema.unwrap(MongoSchema.class).mongoDb;
      }
  
      private MongoTable getTable() {
        return (MongoTable) table;
      }
  
      /** Called via code-generation.
       *
       * @see org.apache.calcite.adapter.mongodb.MongoMethod#MONGO_QUERYABLE_AGGREGATE
       */
      @SuppressWarnings("UnusedDeclaration")
      public Enumerable<Object> aggregate(List<Map.Entry<String, Class>> fields,
          List<String> operations) {
        return getTable().aggregate(getMongoDb(), fields, operations);
      }
  
      /** Called via code-generation.
       *
       * @param filterJson Filter document
       * @param projectJson Projection document
       * @param fields List of expected fields (and their types)
       * @return result of mongo query
       *
       * @see org.apache.calcite.adapter.mongodb.MongoMethod#MONGO_QUERYABLE_FIND
       */
      @SuppressWarnings("UnusedDeclaration")
      public Enumerable<Object> find(String filterJson,
          String projectJson, List<Map.Entry<String, Class>> fields) {
        return getTable().find(getMongoDb(), filterJson, projectJson, fields);
      }
    }
  }
  