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/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or .
 */
package org.hibernate.dialect;

import java.sql.Types;
import java.util.Locale;

import org.hibernate.LockOptions;
import org.hibernate.dialect.pagination.AbstractLimitHandler;
import org.hibernate.dialect.pagination.LimitHandler;
import org.hibernate.dialect.pagination.LimitHelper;
import org.hibernate.engine.spi.RowSelection;
import org.hibernate.sql.ANSICaseFragment;
import org.hibernate.sql.CaseFragment;

/**
 * A dialect for Oracle 9i databases.
 * 
 * Specifies to not use "ANSI join syntax" because 9i does not seem to properly handle it in all cases.
 *
 * @author Steve Ebersole
 */
public class Oracle9iDialect extends Oracle8iDialect {

	private static final AbstractLimitHandler LIMIT_HANDLER = new AbstractLimitHandler() {
		@Override
		public String processSql(String sql, RowSelection selection) {
			final boolean hasOffset = LimitHelper.hasFirstRow( selection );
			sql = sql.trim();
			String forUpdateClause = null;
			boolean isForUpdate = false;
			final int forUpdateIndex = sql.toLowerCase(Locale.ROOT).lastIndexOf( "for update" );
			if (forUpdateIndex > -1) {
				// save 'for update ...' and then remove it
				forUpdateClause = sql.substring( forUpdateIndex );
				sql = sql.substring( 0, forUpdateIndex - 1 );
				isForUpdate = true;
			}

			final StringBuilder pagingSelect = new StringBuilder( sql.length() + 100 );
			if (hasOffset) {
			pagingSelect.append( "select * from ( select row_.*, rownum rownum_ from ( " );
			}
			else {
				pagingSelect.append( "select * from ( " );
			}
			pagingSelect.append( sql );
			if (hasOffset) {
				pagingSelect.append( " ) row_ where rownum <= ?) where rownum_ > ?" );
			}
			else {
				pagingSelect.append( " ) where rownum <= ?" );
			}

			if (isForUpdate) {
				pagingSelect.append( " " );
				pagingSelect.append( forUpdateClause );
			}

			return pagingSelect.toString();
		}

		@Override
		public boolean supportsLimit() {
			return true;
		}

		@Override
		public boolean bindLimitParametersInReverseOrder() {
			return true;
		}

		@Override
		public boolean useMaxForLimit() {
			return true;
		}
	};

	@Override
	protected void registerCharacterTypeMappings() {
		registerColumnType( Types.CHAR, "char(1 char)" );
		registerColumnType( Types.VARCHAR, 4000, "varchar2($l char)" );
		registerColumnType( Types.VARCHAR, "long" );
		registerColumnType( Types.NVARCHAR, "nvarchar2($l)" );
		registerColumnType( Types.LONGNVARCHAR, "nvarchar2($l)" );
	}

	@Override
	protected void registerDateTimeTypeMappings() {
		registerColumnType( Types.DATE, "date" );
		registerColumnType( Types.TIME, "date" );
		registerColumnType( Types.TIMESTAMP, "timestamp" );
	}

	@Override
	public CaseFragment createCaseFragment() {
		// Oracle did add support for ANSI CASE statements in 9i
		return new ANSICaseFragment();
	}

	@Override
	public LimitHandler getLimitHandler() {
		return LIMIT_HANDLER;
	}

	@Override
	public String getLimitString(String sql, boolean hasOffset) {
		sql = sql.trim();
		String forUpdateClause = null;
		boolean isForUpdate = false;
		final int forUpdateIndex = sql.toLowerCase(Locale.ROOT).lastIndexOf( "for update") ;
		if ( forUpdateIndex > -1 ) {
			// save 'for update ...' and then remove it
			forUpdateClause = sql.substring( forUpdateIndex );
			sql = sql.substring( 0, forUpdateIndex-1 );
			isForUpdate = true;
		}

		final StringBuilder pagingSelect = new StringBuilder( sql.length() + 100 );
		if (hasOffset) {
			pagingSelect.append( "select * from ( select row_.*, rownum rownum_ from ( " );
		}
		else {
			pagingSelect.append( "select * from ( " );
		}
		pagingSelect.append( sql );
		if (hasOffset) {
			pagingSelect.append( " ) row_ where rownum <= ?) where rownum_ > ?" );
		}
		else {
			pagingSelect.append( " ) where rownum <= ?" );
		}

		if ( isForUpdate ) {
			pagingSelect.append( " " );
			pagingSelect.append( forUpdateClause );
		}

		return pagingSelect.toString();
	}

	@Override
	public String getSelectClauseNullString(int sqlType) {
		return getBasicSelectClauseNullString( sqlType );
	}

	@Override
	public String getCurrentTimestampSelectString() {
		return "select systimestamp from dual";
	}

	@Override
	public String getCurrentTimestampSQLFunctionName() {
		// the standard SQL function name is current_timestamp...
		return "current_timestamp";
	}

	@Override
	public String getForUpdateString() {
		return " for update";
	}

	@Override
	public String getWriteLockString(int timeout) {
		if ( timeout == LockOptions.NO_WAIT ) {
			return " for update nowait";
		}
		else if ( timeout > 0 ) {
			// convert from milliseconds to seconds
			final float seconds = timeout / 1000.0f;
			timeout = Math.round( seconds );
			return " for update wait " + timeout;
		}
		else {
			return " for update";
		}
	}

	@Override
	public String getReadLockString(int timeout) {
		return getWriteLockString( timeout );
	}

	/**
	 * HHH-4907, I don't know if oracle 8 supports this syntax, so I'd think it is better add this 
	 * method here. Reopen this issue if you found/know 8 supports it.
	 * 
	 * {@inheritDoc}
	 */
	@Override
	public boolean supportsRowValueConstructorSyntaxInInList() {
		return true;
	}

	@Override
	public boolean supportsTupleDistinctCounts() {
		return false;
	}	
}