feat(calendar-sync): dispatch Google calendars through API helper

The Python helper from d6a995b could fetch and render on its own, but nothing in Emacs called it. This wires it in. Each entry in calendar-sync-calendars now takes a :fetcher key. 'api routes through the helper, and the default 'ics keeps the existing curl + Elisp parser path. Proton and any plain .ics feed work unchanged because the key defaults to 'ics.

The 'api path reads :account and :calendar-id off the calendar plist, builds the helper command (honoring the past/future window and the calendar-sync-skip-declined toggle), and runs it through make-process. The script writes the org file directly, so the sentinel only handles state bookkeeping and failure reporting, the same as the .ics worker.

I split the old --sync-calendar body into --sync-calendar-ics and turned --sync-calendar into a dispatcher. The command builder and script-path resolution are pure functions, tested directly. The dispatch routing is tested with both leaf syncers stubbed, so no process runs. I added 14 tests across the two new files, and the full suite is green.

Running the 'api path still needs the one-time OAuth bootstrap from docs/calendar-sync-api-setup.org.

1 files changed, 110 insertions, 6 deletions

diff --git a/modules/calendar-sync.el b/modules/calendar-sync.el
index 2f2b8b4f..2fb1df03 100644
--- a/modules/calendar-sync.el
+++ b/modules/calendar-sync.el
@@ -87,15 +87,26 @@
 
 (defvar calendar-sync-calendars nil
   "List of calendars to sync.
-Each calendar is a plist with the following keys:
-  :name - Display name for the calendar (used in logs and prompts)
-  :url  - URL to fetch .ics file from
-  :file - Output file path for org format
+Each calendar is a plist.  Common keys:
+  :name    - Display name for the calendar (used in logs and prompts)
+  :file    - Output file path for org format
+  :fetcher - Fetch path: \\='ics (default) or \\='api
+
+For the default \\='ics fetcher (Proton, plain .ics feeds):
+  :url     - URL to fetch the .ics file from
+
+For the \\='api fetcher (Google Calendar, sees per-occurrence response
+status so OOO auto-declines on recurring events can be filtered):
+  :account     - OAuth account nickname (work, personal, ...) matching the
+                 token file under ~/.config/calendar-sync/
+  :calendar-id - Calendar ID (\"primary\" or a long calendar address)
 
 Example:
   (setq calendar-sync-calendars
         \\='((:name \"google\"
-           :url \"https://calendar.google.com/calendar/ical/.../basic.ics\"
+           :fetcher api
+           :account \"work\"
+           :calendar-id \"primary\"
            :file gcal-file)
           (:name \"proton\"
            :url \"https://calendar.proton.me/api/calendar/v1/url/.../calendar.ics\"
@@ -141,6 +152,11 @@ Default: 3 months. This keeps recent history visible in org-agenda.")
   "Number of months in the future to include when expanding recurring events.
 Default: 12 months. This provides a full year of future events.")
 
+(defvar calendar-sync-python-command "python3"
+  "Executable used to run the Google Calendar API helper script.
+Only the API fetch path (a calendar with `:fetcher' \\='api) uses it; the
+default .ics path shells out to curl instead.")
+
 (defvar calendar-sync-fetch-timeout 120
   "Maximum time in seconds for a calendar fetch to complete.
 This is the total time allowed for the entire transfer (connect + download).
@@ -1388,14 +1404,102 @@ Checks `cj/debug-modules' for symbol `calendar-sync' or t (all)."
        (or (eq cj/debug-modules t)
            (memq 'calendar-sync cj/debug-modules))))
 
+;;; Google Calendar API Fetch Path
+
+(defun calendar-sync--api-script ()
+  "Return the absolute path to the Google Calendar API helper script.
+Resolved relative to this module so batch workers and tests don't depend
+on `user-emacs-directory'."
+  (let ((module-dir (file-name-directory calendar-sync--module-file)))
+    (expand-file-name "calendar_sync_api.py"
+                      (expand-file-name "scripts"
+                                        (file-name-parent-directory module-dir)))))
+
+(defun calendar-sync--api-command (account calendar-id output-file)
+  "Build the command list that runs the API helper.
+ACCOUNT and CALENDAR-ID select the OAuth account and calendar; OUTPUT-FILE
+is where the helper writes rendered org content.  The past/future window
+mirrors the .ics path's `calendar-sync-past-months' /
+`calendar-sync-future-months'.  When `calendar-sync-skip-declined' is nil,
+passes --keep-declined so the API path honors the same toggle."
+  (append
+   (list calendar-sync-python-command
+         (calendar-sync--api-script)
+         "--account" account
+         "--calendar-id" calendar-id
+         "--output" output-file
+         "--past-months" (number-to-string calendar-sync-past-months)
+         "--future-months" (number-to-string calendar-sync-future-months))
+   (unless calendar-sync-skip-declined
+     (list "--keep-declined"))))
+
+(defun calendar-sync--sync-calendar-api (calendar)
+  "Sync a single Google CALENDAR via the API helper script.
+CALENDAR is a plist with :name, :account, :calendar-id, and :file keys.
+The helper fetches, filters, and renders org in one pass and writes :file
+directly, so it runs in a single external process off the interactive thread."
+  (let* ((name (plist-get calendar :name))
+         (account (plist-get calendar :account))
+         (calendar-id (plist-get calendar :calendar-id))
+         (file (plist-get calendar :file))
+         (fetch-start (float-time)))
+    (calendar-sync--set-calendar-state name '(:status syncing))
+    (calendar-sync--log-silently "calendar-sync: [%s] Syncing (API)..." name)
+    (condition-case err
+        (let ((buffer (generate-new-buffer " *calendar-sync-api*")))
+          (make-process
+           :name "calendar-sync-api"
+           :buffer buffer
+           :command (calendar-sync--api-command account calendar-id file)
+           :sentinel
+           (lambda (process _event)
+             (when (memq (process-status process) '(exit signal))
+               (let* ((buf (process-buffer process))
+                      (success (and (eq (process-status process) 'exit)
+                                    (= (process-exit-status process) 0)))
+                      (output (when (buffer-live-p buf)
+                                (with-current-buffer buf
+                                  (string-trim (buffer-string))))))
+                 (when (buffer-live-p buf)
+                   (kill-buffer buf))
+                 (if (not success)
+                     (calendar-sync--mark-sync-failed
+                      name (if (or (null output) (string-empty-p output))
+                               "API helper failed"
+                             output))
+                   (calendar-sync--set-calendar-state
+                    name
+                    (list :status 'ok
+                          :last-sync (current-time)
+                          :last-error nil))
+                   (setq calendar-sync--last-timezone-offset
+                         (calendar-sync--current-timezone-offset))
+                   (calendar-sync--save-state)
+                   (let ((total-elapsed (- (float-time) fetch-start)))
+                     (message "calendar-sync: [%s] Sync complete (%.1fs total) → %s"
+                              name total-elapsed file))))))))
+      (error
+       (calendar-sync--log-silently "calendar-sync: [%s] API helper error: %s"
+                                    name (error-message-string err))
+       (calendar-sync--mark-sync-failed name (error-message-string err))))))
+
 ;;; Single Calendar Sync
 
 (defun calendar-sync--sync-calendar (calendar)
   "Sync a single CALENDAR asynchronously.
-CALENDAR is a plist with :name, :url, and :file keys.
+CALENDAR is a plist with :name, :file, and either :url (the default \\='ics
+fetcher) or :account + :calendar-id (the \\='api fetcher).  Dispatches on the
+:fetcher key, defaulting to the .ics path.
 Updates calendar state and saves to disk on completion.
 The fetch and conversion run in external processes so parsing and writing large
 calendar files do not block the interactive Emacs thread."
+  (if (eq (plist-get calendar :fetcher) 'api)
+      (calendar-sync--sync-calendar-api calendar)
+    (calendar-sync--sync-calendar-ics calendar)))
+
+(defun calendar-sync--sync-calendar-ics (calendar)
+  "Sync a single CALENDAR from its :url .ics feed asynchronously.
+CALENDAR is a plist with :name, :url, and :file keys."
   (let ((name (plist-get calendar :name))
         (url (plist-get calendar :url))
         (file (plist-get calendar :file))