(use comparse)

(define whitespace
  (any-of (is #\space) (is #\tab)))
(define nl (is #\newline))
(define headline-marks (sequence (one-or-more (is #\*)) (one-or-more whitespace)))

(define tag-delim (is #\:))
(define tags (preceded-by tag-delim (one-or-more (none-of* (any-of whitespace tag-delim) item))))
(define last-tag (enclosed-by tag-delim (one-or-more (none-of* (any-of whitespace tag-delim) item)) tag-delim))
(define header-tags (followed-by tag-delim (one-or-more tags)))

(define headline-text (repeated item until: (one-or-more header-tags)))

(define headline
  (sequence headline-marks
            headline-text
            (zero-or-more header-tags)
            (none-of item)
            ))

;; Examples:
;;
;; * Hi this is a simple headline
;; * Another one with a :tag:
;; * Two tags :one:two:
;; * This should not be a tag :haha: as its inside the title
;; * Nor is this a tag as it contains whitespaces :aha :