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SQL Parser and Optimizer
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/*
 * 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 com.hazelcast.org.apache.calcite.sql;

import com.hazelcast.org.apache.calcite.avatica.util.Casing;
import com.hazelcast.org.apache.calcite.config.NullCollation;

import java.sql.DatabaseMetaData;
import java.sql.SQLException;

/**
 * Utilities related to {@link SqlDialect}.
 */
public final class SqlDialects {
  private SqlDialects() {
    // utility class
  }

  /**
   * Extracts information from {@link DatabaseMetaData} into {@link SqlDialect.Context}.
   *
   * @param databaseMetaData the database metadata
   * @return a context with information populated from the database metadata
   */
  public static SqlDialect.Context createContext(DatabaseMetaData databaseMetaData) {
    String databaseProductName;
    int databaseMajorVersion;
    int databaseMinorVersion;
    String databaseVersion;
    try {
      databaseProductName = databaseMetaData.getDatabaseProductName();
      databaseMajorVersion = databaseMetaData.getDatabaseMajorVersion();
      databaseMinorVersion = databaseMetaData.getDatabaseMinorVersion();
      databaseVersion = databaseMetaData.getDatabaseProductVersion();
    } catch (SQLException e) {
      throw new RuntimeException("while detecting database product", e);
    }
    final String quoteString = getIdentifierQuoteString(databaseMetaData);
    final NullCollation nullCollation = getNullCollation(databaseMetaData);
    final Casing unquotedCasing = getCasing(databaseMetaData, false);
    final Casing quotedCasing = getCasing(databaseMetaData, true);
    final boolean caseSensitive = isCaseSensitive(databaseMetaData);
    final SqlDialect.Context c = SqlDialect.EMPTY_CONTEXT
        .withDatabaseProductName(databaseProductName)
        .withDatabaseMajorVersion(databaseMajorVersion)
        .withDatabaseMinorVersion(databaseMinorVersion)
        .withDatabaseVersion(databaseVersion)
        .withIdentifierQuoteString(quoteString)
        .withUnquotedCasing(unquotedCasing)
        .withQuotedCasing(quotedCasing)
        .withCaseSensitive(caseSensitive)
        .withNullCollation(nullCollation);

    return c;
  }

  private static String getIdentifierQuoteString(DatabaseMetaData databaseMetaData) {
    try {
      return databaseMetaData.getIdentifierQuoteString();
    } catch (SQLException e) {
      throw new IllegalArgumentException("cannot deduce identifier quote string", e);
    }
  }

  private static Casing getCasing(DatabaseMetaData databaseMetaData, boolean quoted) {
    try {
      if (quoted
          ? databaseMetaData.storesUpperCaseQuotedIdentifiers()
          : databaseMetaData.storesUpperCaseIdentifiers()) {
        return Casing.TO_UPPER;
      } else if (quoted
          ? databaseMetaData.storesLowerCaseQuotedIdentifiers()
          : databaseMetaData.storesLowerCaseIdentifiers()) {
        return Casing.TO_LOWER;
      } else if (quoted
          ? (databaseMetaData.storesMixedCaseQuotedIdentifiers()
          || databaseMetaData.supportsMixedCaseQuotedIdentifiers())
          : (databaseMetaData.storesMixedCaseIdentifiers()
          || databaseMetaData.supportsMixedCaseIdentifiers())) {
        return Casing.UNCHANGED;
      } else {
        return Casing.UNCHANGED;
      }
    } catch (SQLException e) {
      throw new IllegalArgumentException("cannot deduce casing", e);
    }
  }

  private static boolean isCaseSensitive(DatabaseMetaData databaseMetaData) {
    try {
      return databaseMetaData.supportsMixedCaseIdentifiers()
          || databaseMetaData.supportsMixedCaseQuotedIdentifiers();
    } catch (SQLException e) {
      throw new IllegalArgumentException("cannot deduce case-sensitivity", e);
    }
  }

  private static NullCollation getNullCollation(DatabaseMetaData databaseMetaData) {
    try {
      if (databaseMetaData.nullsAreSortedAtEnd()) {
        return NullCollation.LAST;
      } else if (databaseMetaData.nullsAreSortedAtStart()) {
        return NullCollation.FIRST;
      } else if (databaseMetaData.nullsAreSortedLow()) {
        return NullCollation.LOW;
      } else if (databaseMetaData.nullsAreSortedHigh()) {
        return NullCollation.HIGH;
      } else if (isBigQuery(databaseMetaData)) {
        return NullCollation.LOW;
      } else {
        throw new IllegalArgumentException("cannot deduce null collation");
      }
    } catch (SQLException e) {
      throw new IllegalArgumentException("cannot deduce null collation", e);
    }
  }

  private static boolean isBigQuery(DatabaseMetaData databaseMetaData)
      throws SQLException {
    return databaseMetaData.getDatabaseProductName()
        .equals("Google Big Query");
  }
}