/*
 *  $Id$
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * and is licensed under the LGPL. For more information, see
 * <http://www.phpdoctrine.com>.
 */
Doctrine::autoload('Doctrine_Expression');
/**
 * Doctrine_Expression_Pgsql
 *
 * @package     Doctrine ORM
 * @url         www.phpdoctrine.com
 * @license     LGPL
 */
class Doctrine_Expression_Pgsql extends Doctrine_Expression {
    /**
     * Returns the md5 sum of a field.
     *
     * Note: Not SQL92, but common functionality
     *
     * md5() works with the default PostgreSQL 8 versions.
     *
     * If you are using PostgreSQL 7.x or older you need
     * to make sure that the digest procedure.
     * If you use RPMS (Redhat and Mandrake) install the postgresql-contrib
     * package. You must then install the procedure by running this shell command:
     * <code>
     * psql [dbname] < /usr/share/pgsql/contrib/pgcrypto.sql
     * </code>
     * You should make sure you run this as the postgres user.
     *
     * @return string
     */
    public function md5($column) {
        $column = $this->getIdentifier($column);

        if ($this->version > 7)
            return 'MD5(' . $column . ')';
        else
            return 'encode(digest(' . $column .', md5), hex)';
    }

    /**
     * Returns part of a string.
     *
     * Note: Not SQL92, but common functionality.
     *
     * @param string $value the target $value the string or the string column.
     * @param int $from extract from this characeter.
     * @param int $len extract this amount of characters.
     * @return string sql that extracts part of a string.
     */
    public function subString($value, $from, $len = null) {
        $value = $this->getIdentifier($value);

        if ($len === null) {
            $len = $this->getIdentifier($len);
            return 'SUBSTR(' . $value . ', ' . $from . ')';
        } else
            return 'SUBSTR(' . $value . ', ' . $from . ', ' . $len . ')';
    }

    /**
     * Returns a series of strings concatinated
     *
     * concat() accepts an arbitrary number of parameters. Each parameter
     * must contain an expression or an array with expressions.
     *
     * @param string|array(string) strings that will be concatinated.
     * @return string
     */
    public function concat($arg1, $arg2) {
        $args = func_get_args();
        $cols = $this->getIdentifiers($cols);

        return join(' || ' , $cols);
    }
    /**
     * regexp
     *
     * @return string           the regular expression operator
     */
    public function regexp() {
        return 'SIMILAR TO';
    }
    /**
     * return string to call a function to get random value inside an SQL statement
     *
     * @return return string to generate float between 0 and 1
     * @access public
     */
    public function random() {
        return 'RANDOM()';
    }
}