Álvaro Ramírez

17 November 2018 Quickly swapping elfeed filters

I seem to be more efficient in getting through rss feeds by individually browsing through related content. That is, I can get through all Emacs entries a lot faster if I look at Emacs content exclusively, instead of mixing with say BBC news. Elfeed filters are great for filtering related content.

I wanted a way to easily switch through my typical categories of related content by quickly changing elfeed filters using a completion framework.

Emacs's completing-read plays nicely with your favorite completing framework (mine is ivy). With a couple of functions, we can get Emacs to ask us for the filtering category using human-readable options and quickly presenting related content. Binding the new functionality to <tab> is working well for me.

(use-package elfeed :ensure t
  :commands elfeed
  :bind (:map elfeed-search-mode-map
              ("<tab>" . ar/elfeed-completing-filter))
  :config
  (defun ar/elfeed-filter-results-count (search-filter)
    "Count results for SEARCH-FILTER."
    (let* ((filter (elfeed-search-parse-filter search-filter))
           (head (list nil))
           (tail head)
           (count 0))
      (let ((lexical-binding t)
            (func (byte-compile (elfeed-search-compile-filter filter))))
        (with-elfeed-db-visit (entry feed)
          (when (funcall func entry feed count)
            (setf (cdr tail) (list entry)
                  tail (cdr tail)
                  count (1+ count)))))
      count))

  (defun ar/elfeed-completing-filter ()
    "Completing filter."
    (interactive)
    (let ((categories (-filter
                       (lambda (item)
                         (> (ar/elfeed-filter-results-count (cdr item))
                            0))
                       '(("All" . "@6-months-ago +unread")
                         ("BBC" . "@6-months-ago +unread +bbc")
                         ("Dev" . "@6-months-ago +unread +dev")
                         ("Emacs" . "@6-months-ago +unread +emacs")
                         ("Health" . "@6-months-ago +unread +health")
                         ("Hacker News" . "@6-months-ago +unread +hackernews")
                         ("iOS" . "@6-months-ago +unread +ios")
                         ("Money" . "@6-months-ago +unread +money")))))
      (if (> (length categories) 0)
          (progn
            (ar/elfeed-view-filtered (cdr (assoc (completing-read "Categories: " categories)
                                                 categories)))
            (goto-char (window-start)))
        (message "All caught up \\o/")))))

We don't actually need two functions, but ar/elfeed-filter-results-count enables us to list only those feeds that actually have new content. The list will shrink as we get through our content. When no content is left, we get a little celebratory message.

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