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;
  
  import org.apache.calcite.adapter.java.JavaTypeFactory;
  import org.apache.calcite.linq4j.QueryProvider;
  import org.apache.calcite.linq4j.tree.Expressions;
  import org.apache.calcite.linq4j.tree.ParameterExpression;
  import org.apache.calcite.rel.type.TimeFrameSet;
  import org.apache.calcite.schema.SchemaPlus;
  import org.apache.calcite.sql.advise.SqlAdvisor;
  
  import com.google.common.base.CaseFormat;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.lang.reflect.Modifier;
  import java.util.Locale;
  import java.util.TimeZone;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  /**
   * Runtime context allowing access to the tables in a database.
   *
   * @see DataContexts
   */
  public interface DataContext {
    ParameterExpression ROOT =
        Expressions.parameter(Modifier.FINAL, DataContext.class, "root");
  
    /**
     * Returns a sub-schema with a given name, or null.
     */
    @Nullable SchemaPlus getRootSchema();
  
    /**
     * Returns the type factory.
     */
    JavaTypeFactory getTypeFactory();
  
    /**
     * Returns the query provider.
     */
    QueryProvider getQueryProvider();
  
    /**
     * Returns a context variable.
     *
     * <p>Supported variables include: "sparkContext", "currentTimestamp",
     * "localTimestamp".
     *
     * @param name Name of variable
     */
    @Nullable Object get(String name);
  
    /** Variable that may be asked for in a call to {@link DataContext#get}. */
    enum Variable {
      UTC_TIMESTAMP("utcTimestamp", Long.class),
  
      /** The time at which the current statement started executing. In
       * milliseconds after 1970-01-01 00:00:00, UTC. Required. */
      CURRENT_TIMESTAMP("currentTimestamp", Long.class),
  
      /** The time at which the current statement started executing. In
       * milliseconds after 1970-01-01 00:00:00, in the time zone of the current
       * statement. Required. */
      LOCAL_TIMESTAMP("localTimestamp", Long.class),
  
      /** The time in the operating system time zone of the database server. In
       * milliseconds after 1970-01-01 00:00:00, in the time zone of the database
       * server. Required. */
      SYS_TIMESTAMP("sysTimestamp", Long.class),
  
      /** The Spark engine. Available if Spark is on the class path. */
      SPARK_CONTEXT("sparkContext", Object.class),
  
      /** A mutable flag that indicates whether user has requested that the
       * current statement be canceled. Cancellation may not be immediate, but
       * implementations of relational operators should check the flag fairly
       * frequently and cease execution (e.g. by returning end of data). */
      CANCEL_FLAG("cancelFlag", AtomicBoolean.class),
  
      /** Query timeout in milliseconds.
       * When no timeout is set, the value is 0 or not present. */
      TIMEOUT("timeout", Long.class),
  
      /** Advisor that suggests completion hints for SQL statements. */
      SQL_ADVISOR("sqlAdvisor", SqlAdvisor.class),
  
      /** Writer to the standard error (stderr). */
      STDERR("stderr", OutputStream.class),
  
      /** Reader on the standard input (stdin). */
      STDIN("stdin", InputStream.class),
  
      /** Writer to the standard output (stdout). */
      STDOUT("stdout", OutputStream.class),
  
      /** Locale in which the current statement is executing.
       * Affects the behavior of functions such as {@code DAYNAME} and
       * {@code MONTHNAME}. Required; defaults to the root locale if the
       * connection does not specify a locale. */
      LOCALE("locale", Locale.class),
  
      /** Time zone in which the current statement is executing. Required;
       * defaults to the time zone of the JVM if the connection does not specify a
       * time zone. */
      TIME_ZONE("timeZone", TimeZone.class),
  
      /** Set of built-in and custom time frames for use in functions such as
       * {@code FLOOR} and {@code EXTRACT}. Required; defaults to
       * {@link org.apache.calcite.rel.type.TimeFrames#CORE}. */
      TIME_FRAME_SET("timeFrameSet", TimeFrameSet.class),
  
      /** The query user.
       *
       * <p>Default value is "sa". */
      USER("user", String.class),
  
      /** The system user.
       *
       * <p>Default value is "user.name" from
       * {@link System#getProperty(String)}. */
      SYSTEM_USER("systemUser", String.class);
  
      public final String camelName;
      public final Class clazz;
  
      Variable(String camelName, Class clazz) {
        this.camelName = camelName;
        this.clazz = clazz;
        assert camelName.equals(
            CaseFormat.UPPER_UNDERSCORE.to(CaseFormat.LOWER_CAMEL, name()));
      }
  
      /** Returns the value of this variable in a given data context. */
      public <T> T get(DataContext dataContext) {
        //noinspection unchecked
        return (T) clazz.cast(dataContext.get(camelName));
      }
    }
  }
  