(require 'ox-hugo)
(require 'cl)

;; Predicate for if 'el' is a headline that has some tag.
(defun element-has-tag-p (el tag)
  (if (not (eq (org-element-type el) 'headline))
      nil 
    (let* ((tags     (org-element-property :tags el))
           (match_fn (lambda (tag_test) (string= tag tag_test)))
           (match    (mapcar match_fn tags)))
      (some 'identity match))))

;; Creates a new buffer of the given name, and write the contents of
;; some org mode AST into it (e.g. from org-element-parse-buffer)
(defun interpret-to-buffer (name tree)
  (let ((buf (generate-new-buffer name)))
    (with-current-buffer buf
      (org-mode)
      (mapc 'insert (org-element-interpret-data tree)))
    buf))

;; Modifies 'tree' destructively to remove any headline that contains
;; 'tag'.
(defun filter-out-tag (tree tag)
  (if (let ((el-type (org-element-type tree)))
        (not (or (eq el-type 'headline)
                 (eq el-type 'org-data))))
      tree
    (if (element-has-tag-p tree tag)
        ;; has tag - stop recursing here:
        nil
      ;; lacks tag - keep searching:
      (org-element-set-contents
       tree (mapcar (lambda (el) (filter-out-tag el tag))
                    (org-element-contents tree))))))

;; Produce a new buffer
(defun filter-buffer (fname newbuf tag)
  (let* ((buf (find-file-noselect fname))
         (tree (with-current-buffer buf (org-element-parse-buffer)))
         (tree (filter-out-tag tree tag)))
    (interpret-to-buffer newbuf tree)))

(defun filter-org-tag (tag src-name dst-name)
  (with-current-buffer (filter-buffer src-name "tmp.org" tag)
    (write-file dst-name)))

;; (filter-out-tag-from-file "/Users/hodapp/log_tmp2.org" "tmp.org" "dream")
;; (filter-org-tag "dream" "/Users/hodapp/log_tmp2.org" "/Users/hodapp/log_tmp_filter.org")

(defun filter-org ()
  (let ((fname "/mnt/share/syncthing/notes/log.org")
        (tag "private"))
    (princ (format "Filtering %s...\n" fname))
    (with-current-buffer (filter-buffer fname "tmp.org" tag)
      (write-file "./_tmp_filtered.org"))))

(defun export-run ()
  (find-file "./_tmp_filtered2.org")
  (princ "Exporting with ox-hugo...\n")
  (org-hugo-export-as-md)
  (write-file "./log.md"))
;; TODO: use command-line-args so that I can pass in the filename
;; instead of hard-code it