A postgres function that attempts to format phone number to RFC 3966

format_phone_number.sql

CREATE OR REPLACE FUNCTION "public"."format_phone_number"(text)
  RETURNS "pg_catalog"."text" AS $BODY$
    BEGIN
      RETURN 
      regexp_replace(
        regexp_replace(
          regexp_replace(
            regexp_replace(
              regexp_replace(
                regexp_replace(
                  regexp_replace(
                    regexp_replace(
                      $1, 
                      '((?!^\+)\+)|(x(?=.*?x))|([^\+0-9x])', 
                      '', 
                      'g'
                    ),
                    'x$', 
                    '', 
                    'g'
                  ),
                  'x', 
                  ';ext=',
                  'g'
                ),
                '(\d{4}?($|;ext=))', 
                '-\1',
                ''
              ),
              '(\d{3}-\d{4}?($|;ext=))', 
              '-\1',
              ''
            ),
            '(\d{3}-\d{3}-\d{4}?(?:$|;ext=))', 
            '-\1',
            ''
          ),
          '^(\d(.+)?-\d{3}-\d{3}-\d{4}?(?:$|;ext=))',
          '+\1',
          ''
        ),
        '^(\+-|-)',
        '',
        'g'
      );
    END;
  $BODY$
  LANGUAGE plpgsql VOLATILE
  COST 1