Integrate gnus and notmuch with multiple accounts

gnus-notmuch.el

;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Gnus and notmuch ....
;; - Sets up searching with notmuch, when looking at the message it's possible
;; to switch to gnus article view with C-c C-c 
;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(require 'notmuch)
(add-hook 'gnus-group-mode-hook 'lch-notmuch-shortcut)
(require 'org-gnus)

(defun lch-notmuch-shortcut ()
  (define-key gnus-group-mode-map "GG" 'notmuch-search)
  )

(defun notmuch-file-to-group (file)
  "Calculate the Gnus group name from the given file name."

  (let ((group (file-name-directory (directory-file-name (file-name-directory file)))))

    (if (string-match ".*/Maildir/Silverbullet" file)
        (setq group (replace-regexp-in-string ".*/Maildir/Account1/\." "nnimap+account2:" group))
        )
    (if (string-match ".*/Maildir/Private" file)
        (setq group (replace-regexp-in-string ".*/Maildir/Account2/\." "nnimap+account2:" group))
        )

    (setq group (replace-regexp-in-string "/$" "" group))
    (if (string-match ":$" group)
        (concat group "INBOX")
      (replace-regexp-in-string ":\\." ":" group))))

(defun notmuch-goto-message-in-gnus ()
       "Open a summary buffer containing the current notmuch
     article."
       (interactive)
       (unless (gnus-alive-p) (with-temp-buffer (gnus)))
       (let ((group (notmuch-file-to-group (notmuch-show-get-filename)))
     	(message-id
     	 (replace-regexp-in-string "\"" ""
     	  (replace-regexp-in-string "^id:" ""
     				    (notmuch-show-get-message-id)))))
         (if (and group message-id)
     	(progn
     	  (gnus-summary-read-group group 1) ; have to show at least one old message
     	  (gnus-summary-refer-article message-id)) ; simpler than org-gnus method?
           (message "Couldn't get relevant infos for switching to Gnus."))))

(define-key notmuch-show-mode-map (kbd "C-c C-c") 'notmuch-goto-message-in-gnus)