Markdown で [[WikiLink]] を開きたい

md-wiki-link.el

;; Markdown で [[WikiLink]] を開きたい
(defun open-wiki-link (link-name)
  (let ((directories '("." "books"))
        (file-found nil))
    (dolist (dir directories)
      (let ((path (concat dir "/" link-name ".md")))
        (when (and (not file-found) (file-exists-p path))
          (setq file-found t)
          (find-file path))))
    (unless file-found
      (message "File not found for link: %s" link-name))))

(defun open-wiki-link-at-point ()
  (interactive)
  (let ((start nil)
        (end nil)
        (link-name nil)
        (line-start (line-beginning-position))
        (line-end (line-end-position)))
    (save-excursion
      (goto-char (point))
      (when (search-backward "[[" line-start t)
        (setq start (point)))
      (goto-char (point))
      (when (search-forward "]]" line-end t)
        (setq end (point))))
    (when (and start end (> end start))
      (setq link-name (buffer-substring-no-properties (+ start 2) (- end 2)))
      (open-wiki-link link-name))))

(defun markdown-wiki-link-setup ()
  (setq markdown-wiki-link-regexp "\\[\\[\\(.*?\\)\\]\\]")
  (add-to-list 'markdown-mode-font-lock-keywords
               (cons markdown-wiki-link-regexp '(1 'link)))

  (defun open-wiki-link-at-point-conditional ()
    "Open wiki link at point if on a link, otherwise execute default return key action."
    (interactive)
    (if (eq (get-text-property (point) 'face) 'link)
        (open-wiki-link-at-point)
      (markdown-enter-key)))

  (local-set-key (kbd "<return>") 'open-wiki-link-at-point-conditional))

(add-hook 'markdown-mode-hook 'markdown-wiki-link-setup)