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<?php

    namespace CzProject\SqlGenerator\Statements;

    use CzProject\SqlGenerator\DuplicateException;
    use CzProject\SqlGenerator\Drivers;
    use CzProject\SqlGenerator\Helpers;
    use CzProject\SqlGenerator\IDriver;
    use CzProject\SqlGenerator\IStatement;


    class DropIndex implements IStatement
    {
        /** @var string|NULL */
        private $index;


        /**
         * @param  string|NULL
         */
        public function __construct($index)
        {
            $this->index = $index;
        }


        /**
         * @return string
         */
        public function toSql(IDriver $driver)
        {
            if ($this->index === NULL) { // PRIMARY KEY
                if ($driver instanceof Drivers\MysqlDriver) {
                    return 'DROP PRIMARY KEY';

                } else {
                    throw new \CzProject\SqlGenerator\NotImplementedException('Drop of primary key is not implemented for driver ' . get_class($driver) . '.');
                }
            }

            return 'DROP INDEX ' . $driver->escapeIdentifier($this->index);
        }
    }