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.validate;
  
  import org.apache.calcite.sql.SqlIdentifier;
  import org.apache.calcite.util.Util;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  import static java.util.Objects.hash;
  
  /**
   * Fully-qualified identifier.
   *
   * <p>The result of calling
   * {@link org.apache.calcite.sql.validate.SqlValidatorScope#fullyQualify(org.apache.calcite.sql.SqlIdentifier)},
   * a fully-qualified identifier contains the name (in correct case),
   * parser position, type, and scope of each component of the identifier.
   *
   * <p>It is immutable.
   */
  public class SqlQualified {
    public final int prefixLength;
    public final @Nullable SqlValidatorNamespace namespace;
    public final SqlIdentifier identifier;
  
    private SqlQualified(@Nullable SqlValidatorScope scope, int prefixLength,
        @Nullable SqlValidatorNamespace namespace, SqlIdentifier identifier) {
      Util.discard(scope);
      this.prefixLength = prefixLength;
      this.namespace = namespace;
      this.identifier = identifier;
    }
  
    @Override public int hashCode() {
      return hash(identifier.names, prefixLength);
    }
  
    @Override public boolean equals(@Nullable Object obj) {
      // Two SqlQualified instances are equivalent if they are of the same
      // identifier and same prefix length. Thus, in
      //
      //  SELECT e.address, e.address.zipcode
      //  FROM employees AS e
      //
      // "e.address" is {identifier=[e, address], prefixLength=1}
      // and is distinct from "e.address.zipcode".
      //
      // We assume that all SqlQualified instances being compared are resolved
      // from the same SqlValidatorScope, and therefore we do not need to look
      // at namespace to distinguish them.
      return this == obj
          || obj instanceof SqlQualified
          && prefixLength == ((SqlQualified) obj).prefixLength
          && identifier.names.equals(((SqlQualified) obj).identifier.names);
    }
  
    @Override public String toString() {
      return "{id: " + identifier + ", prefix: " + prefixLength + "}";
    }
  
    public static SqlQualified create(@Nullable SqlValidatorScope scope, int prefixLength,
        @Nullable SqlValidatorNamespace namespace, SqlIdentifier identifier) {
      return new SqlQualified(scope, prefixLength, namespace, identifier);
    }
  
    public final List<String> prefix() {
      return identifier.names.subList(0, prefixLength);
    }
  
    public final List<String> suffix() {
      return Util.skip(identifier.names, prefixLength);
    }
  }
  