asdf.rkt

;; Remove a given tag from a set of file ids.
;;  If any of the file ids is not tagged with the given tag, they are silently skipped
;;  without hassling the user.  If a tag is empty after this operation, it is deleted.
;;
;;  TODO: This procedure performs up to three database writes.   If those writes
;;         happened to be interleaved with other writes which are associated with
;;         the same tag, screwy things might happen.   Therefore these two/three
;;         writes should be performed in a single transaction.
(define (untag-files tag . file-ids)
  (let* ([tag-id (get-tag-id tag)]
	 [files-with-tags (map cons file-ids (apply get-tags-for-files file-ids))]
	 [files-with-our-tag (filter (lambda (f) (member? tag (cdr f))) files-with-tags)])
    (for ([f files-with-our-tag])
      (sql-write 'exec "DELETE FROM FileTags WHERE file_id=? AND tag_id=? AND probability=1" (car f) tag-id)
      (sql-write 'exec "UPDATE Files SET num_tags = num_tags - 1 WHERE file_id=?" (car f)))

    (invalidate-memo/partial get-tag-size tag)
    (when (zero? (get-tag-size tag))
      (sql-write 'exec "DELETE FROM Tags WHERE tag_id=?" tag-id))

    ;; TODO: fire plugins with tag and `files-with-our-tag` (which now do not have it.)
    ))