lang/org: add +org-attach/sync (attachment management)

lang/org now supports the attach:* link abbreviation. Running
+org/attach-sync will index all such links across org files in +org-dir
and delete any files in org-attach-directory that aren't referenced.

TODO: have a separate directory for attach:* attachments and vanilla
attachments?

modules/lang/org/autoload/org-attach.el

@@ -14,35 +14,58 @@
      ((or "zip" "gz" "tar" "7z" "rar") ?)
      (_ ?))))
 
-;; (defun +org-attach-cleanup ()
-;;   ;; "Deletes any attachments that are no longer present in the org-mode buffer."
-;;   (let* ((attachments-local (+org-attachments))
-;;          (attachments (directory-files org-attach-directory t "^[^.]" t))
-;;          (to-delete (cl-set-difference attachments-local attachments)))
-;;     ;; TODO
-;;     to-delete))
 
-;; (defun +org-attachments ()
-;;   "List all attachments in the current buffer."
-;;   (unless (eq major-mode 'org-mode)
-;;     (user-error "Not an org buffer"))
-;;   (org-save-outline-visibility nil
-;;     (let ((attachments '())
-;;           element)
-;;       (when (and (file-directory-p org-attach-directory)
-;;                  (> (length (file-expand-wildcards (expand-file-name "*" org-attach-directory))) 0))
-;;         (save-excursion
-;;           (goto-char (point-min))
-;;           (while (progn (org-next-link) (not org-link-search-failed))
-;;             (setq element (org-element-context))
-;;             (when-let* (file (and (eq (org-element-type element) 'link)
-;;                                   (expand-file-name (org-element-property :path element))))
-;;               (when (and (string= (org-element-property :type element) "file")
-;;                          (string= (concat (file-name-base (directory-file-name (file-name-directory file))) "/")
-;;                                   org-attach-directory)
-;;                          (file-exists-p file))
-;;                 (push file attachments))))))
-;;       (cl-remove-duplicates attachments))))
+;;
+(defvar +org-attachments nil
+  "A list of all indexed attachments in `+org-dir'.")
+
+(defvar +org-attachments-files value
+  "A list of all attachments in `org-attach-directory'.")
+
+(defun +org-attachments--list (&optional beg end)
+  "Return a list of all attachment file names in the current buffer between BEG
+and END (defaults to `point-min' and `point-max')."
+  (let ((case-fold-search t)
+        attachments)
+    (or end (setq end (point-max)))
+    (org-save-outline-visibility nil
+      (org-with-wide-buffer
+       (goto-char (or beg (point-min)))
+       (while (search-forward "[[attach:" end t)
+         (let* ((context (save-match-data (org-element-context)))
+                (link (expand-file-name (org-link-unescape (org-element-property :path context))
+                                        org-attach-directory)))
+           (when (and (equal "file" (org-element-property :type context))
+                      (file-in-directory-p link org-attach-directory))
+             (push (file-name-nondirectory link) attachments))))))
+    (cl-delete-duplicates attachments :test #'string=)))
+
+;;;###autoload
+(defun +org-attach/sync (arg)
+  "Reindex all attachments in `+org-dir' and delete orphaned attachments in
+`org-attach-directory'. If ARG (universal arg), conduct a dry run."
+  (declare (interactive-only t))
+  (interactive "P")
+  (message "Reloading")
+  (setq +org-attachments-files (directory-files org-attach-directory nil "^[^.]" t))
+  (with-temp-buffer
+    (delay-mode-hooks (org-mode))
+    (dolist (org-file (directory-files-recursively +org-dir "\\.org$"))
+      (insert-file-contents-literally org-file))
+    (setq +org-attachments (+org-attachments--list)))
+  ;; clean up
+  (dolist (file (cl-set-difference +org-attachments-files +org-attachments
+                                   :test #'string=))
+    (message "Deleting orphaned attachment: %s" file)
+    (unless arg
+      (delete-file (expand-file-name file org-attach-directory))))
+  (message "Buffer's attachments synced"))
+
+;;;###autoload
+(defun +org-attach/find-file ()
+  "Open a file from `org-attach-directory'."
+  (interactive)
+  (doom-project-browse org-attach-directory))
 
 ;;;###autoload
 (defun +org-attach/file (path)
@@ -84,6 +107,11 @@ the cursor."
                              (copy-alist dnd-protocol-alist))))
       (dnd-handle-one-url nil action uri))))
 
+
+;;
+;; Advice
+;;
+
 ;;;###autoload
 (defun +org-attach*insert-link (_link filename)
   "Produces and inserts a link to FILENAME into the document.