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.sql.advise;
  
  import org.apache.calcite.DataContext;
  import org.apache.calcite.adapter.enumerable.CallImplementor;
  import org.apache.calcite.adapter.enumerable.NullPolicy;
  import org.apache.calcite.adapter.enumerable.RexImpTable;
  import org.apache.calcite.linq4j.Enumerable;
  import org.apache.calcite.linq4j.Linq4j;
  import org.apache.calcite.linq4j.tree.Expression;
  import org.apache.calcite.linq4j.tree.Expressions;
  import org.apache.calcite.linq4j.tree.Types;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.schema.FunctionParameter;
  import org.apache.calcite.schema.ImplementableFunction;
  import org.apache.calcite.schema.TableFunction;
  import org.apache.calcite.schema.impl.ReflectiveFunctionBase;
  import org.apache.calcite.sql.validate.SqlMoniker;
  import org.apache.calcite.util.BuiltInMethod;
  
  import com.google.common.collect.Iterables;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.lang.reflect.Method;
  import java.lang.reflect.Type;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * Table function that returns completion hints for a given SQL statement.
   * This function adds replacement string column to previously existed
   * {@link SqlAdvisorGetHintsFunction}
   */
  public class SqlAdvisorGetHintsFunction2
      implements TableFunction, ImplementableFunction {
    private static final Expression ADVISOR =
        Expressions.convert_(
            Expressions.call(DataContext.ROOT,
                BuiltInMethod.DATA_CONTEXT_GET.method,
                Expressions.constant(DataContext.Variable.SQL_ADVISOR.camelName)),
            SqlAdvisor.class);
  
    private static final Method GET_COMPLETION_HINTS =
        Types.lookupMethod(SqlAdvisorGetHintsFunction2.class, "getCompletionHints",
            SqlAdvisor.class, String.class, int.class);
  
    private static final CallImplementor IMPLEMENTOR =
        RexImpTable.createImplementor(
            (translator, call, operands) ->
                Expressions.call(GET_COMPLETION_HINTS,
                    Iterables.concat(Collections.singleton(ADVISOR), operands)),
            NullPolicy.ANY, false);
  
    private static final List<FunctionParameter> PARAMETERS =
        ReflectiveFunctionBase.builder()
            .add(String.class, "sql")
            .add(int.class, "pos")
            .build();
  
    @Override public CallImplementor getImplementor() {
      return IMPLEMENTOR;
    }
  
    @Override public RelDataType getRowType(RelDataTypeFactory typeFactory,
        List<? extends @Nullable Object> arguments) {
      return typeFactory.createJavaType(SqlAdvisorHint2.class);
    }
  
    @Override public Type getElementType(List<? extends @Nullable Object> arguments) {
      return SqlAdvisorHint2.class;
    }
  
    @Override public List<FunctionParameter> getParameters() {
      return PARAMETERS;
    }
  
    /**
     * Returns completion hints for a given SQL statement.
     *
     * <p>Typically this is called from generated code
     * (via {@link SqlAdvisorGetHintsFunction2#IMPLEMENTOR}).
     *
     * @param advisor Advisor to produce completion hints
     * @param sql     SQL to complete
     * @param pos     Cursor position in SQL
     * @return the table that contains completion hints for a given SQL statement
     */
    public static Enumerable<SqlAdvisorHint2> getCompletionHints(
        final SqlAdvisor advisor, final String sql, final int pos) {
      final String[] replaced = new String[1];
      final List<SqlMoniker> hints =
          advisor.getCompletionHints(sql, pos, replaced);
      final List<SqlAdvisorHint2> res = new ArrayList<>(hints.size() + 1);
      res.add(new SqlAdvisorHint2(replaced[0], null, "MATCH", null));
  
      String word = replaced[0];
      for (SqlMoniker hint : hints) {
        res.add(new SqlAdvisorHint2(hint, advisor.getReplacement(hint, word)));
      }
      return Linq4j.asEnumerable(res).asQueryable();
    }
  }
  