Watchlist × Emacs org-mode

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+---
+title: "Watchlist × Emacs org-mode"
+date: 2025-04-19T12:29:00-07:00
+---
+
+Watch progress websites exist for [anime](https://myanimelist.net) and [film](https://letterboxd.com). They work great. Socialization is great.
+
+But they don't record the _exact time_ at which I finished each episode. I find such statistics amusing to dig through in some kind of a year-end review. I also found it tremendously helpful to know which episodes were most recently watched, and in what order. Helps with recollecting the context of each show, especially when chasing more than a couple of shows at the same time.
+Depending on your judgment, using Letterboxd and MyAnimeList may also constitute giving private information to 3rd parties.
+
+So I ended with an organization system that's, effectively, top layer of bullet points for the show, and inner layer for the episodes. Something like:
+
+```org
+* STRT SHIROBAKO
+** [2025-04-01 Tue 11:11] E01
+** [2025-04-16 Wed 22:22] E02
+* TODO Do It Yourself!!
+* DONE ゆるキャンプ
+** [2025-03-20 Thu 20:21] E10
+** [2025-03-21 Fri 20:59] E11
+** [2025-04-14 Mon 21:36] E12
+* STRT mono
+** [2025-04-13 Sun 16:56] E01
+```
+
+I want to be able to run a command, and get it as a linear timeline:
+
+```org
+* [2025-03-20 Thu 20:21] ゆるキャンプ E10
+* [2025-03-21 Fri 20:59] ゆるキャンプ E11
+* [2025-04-01 Tue 11:11] SHIROBAKO E01
+* [2025-04-13 Sun 16:56] mono E01
+* [2025-04-14 Mon 21:36] ゆるキャンプ E12
+* [2025-04-16 Wed 22:22] SHIROBAKO E02
+```
+
+Which turns out to be a pretty easy simple regex-based forward parsing algorithm. I thought about using `org-element-map`, but it seemed like a bit of an overkill?
+
+To use, I do <kbd>g g M-x org-category->timeline</kbd> (evidently, I use evil-mode), bringing me to a new buffer `*Category Timeline*` filled out appropriately.
+
+```emacs-lisp
+(defun org-category->timeline ()
+  "Collect category-timestamp tree into a single, chronologically
+ordered timestamp list. Starting at point."
+  (interactive)
+  (let ((pt (point))
+        (curr-category nil)
+        (curr-pt (search-forward "\n* " nil t))
+        (items '()))
+    ;; Collect items
+    (while curr-pt
+      (goto-char curr-pt)
+      ;; Skip org-todo marker
+      (forward-word) (forward-char)
+      (setq curr-category (buffer-substring-no-properties (point) (line-end-position))
+            curr-pt (save-excursion (search-forward "\n* " nil t)))
+      (while-let ((i (re-search-forward (rx "\n** ["
+                                            (group (* (not "]")))
+                                            "] ")
+                                        curr-pt t)))
+        (let ((time (match-string-no-properties 1))
+              (comment (buffer-substring-no-properties (point) (line-end-position))))
+          (push (list (encode-time (org-parse-time-string time))
+                      time curr-category comment)
+                items))))
+    ;; Sort by time
+    (sort items (lambda (a b) (time-less-p (car a) (car b))))
+    ;; Restore to starting point in the source buffer
+    (goto-char pt)
+    ;; Print items into a new buffer
+    (switch-to-buffer "*Category Timeline*")
+    (erase-buffer)
+    (dolist (i items)
+      (let ((time (cadr i))
+            (category (caddr i))
+            (comment (cadddr i)))
+        (insert "* [" time "] " category " " comment ?\n)))))
+```