class SqliteDateSql

class SqliteDateSql implements DateSqlInterface {
    use DependencySerializationTrait;
    
    /**
     * The database connection.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $database;
    
    /**
     * An array of PHP-to-SQLite date replacement patterns.
     *
     * @var array
     */
    protected static $replace = [
        'Y' => '%Y',
        // No format for 2 digit year number.
'y' => '%Y',
        // No format for 3 letter month name.
'M' => '%m',
        'm' => '%m',
        // No format for month number without leading zeros.
'n' => '%m',
        // No format for full month name.
'F' => '%m',
        // No format for 3 letter day name.
'D' => '%d',
        'd' => '%d',
        // No format for full day name.
'l' => '%d',
        // no format for day of month number without leading zeros.
'j' => '%d',
        'W' => '%W',
        'H' => '%H',
        // No format for 12 hour with leading zeros.
'h' => '%H',
        'i' => '%M',
        's' => '%S',
        // No format for AM/PM.
'A' => '',
    ];
    
    /**
     * Constructs the SQLite-specific date sql class.
     *
     * @param \Drupal\Core\Database\Connection $database
     *   The database connection.
     */
    public function __construct(Connection $database) {
        $this->database = $database;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDateField($field, $string_date) {
        if ($string_date) {
            $field = "strftime('%s', {$field})";
        }
        return $field;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDateFormat($field, $format) {
        $format = strtr($format, static::$replace);
        // SQLite does not have an ISO week substitution string, so it needs special
        // handling.
        // @see http://wikipedia.org/wiki/ISO_week_date#Calculation
        // @see http://stackoverflow.com/a/15511864/1499564
        if ($format === '%W') {
            $expression = "((strftime('%j', date(strftime('%Y-%m-%d', {$field}, 'unixepoch'), '-3 days', 'weekday 4')) - 1) / 7 + 1)";
        }
        else {
            $expression = "strftime('{$format}', {$field}, 'unixepoch')";
        }
        // The expression yields a string, but the comparison value is an integer in
        // case the comparison value is a float, integer, or numeric. All of the
        // above SQLite format tokens only produce integers. However, the given
        // $format may contain 'Y-m-d', which results in a string.
        // @see \Drupal\sqlite\Driver\Database\sqlite\Connection::expandArguments()
        // @see http://www.sqlite.org/lang_datefunc.html
        // @see http://www.sqlite.org/lang_expr.html#castexpr
        if (preg_match('/^(?:%\\w)+$/', $format)) {
            $expression = "CAST({$expression} AS NUMERIC)";
        }
        return $expression;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setTimezoneOffset($offset) {
        // Nothing to do here.
    }
    
    /**
     * {@inheritdoc}
     */
    public function setFieldTimezoneOffset(&$field, $offset, $string_date = FALSE) {
        if (!empty($offset)) {
            $field = "({$field} + {$offset})";
        }
    }

}