;;; mspools.el --- show mail spools waiting to be read  -*- lexical-binding: t; -*-

;; Copyright (C) 1997, 2001-2021 Free Software Foundation, Inc.

;; Author: Stephen Eglen <stephen@gnu.org>
;; Created: 22 Jan 1997
;; Keywords: mail
;; location: http://www.anc.ed.ac.uk/~stephen/emacs/

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; If you use a mail filter (e.g. procmail, filter) to put mail messages in
;; folders, this file will let you see which folders have mail waiting
;; to be read in them.  It assumes that new mail for the file `folder'
;; is written by the filter to a file called `folder.spool'.  (If the
;; file writes directly to `folder' you may lose mail if new mail
;; arrives whilst you are reading the folder in emacs, hence the use
;; of a spool file.)  For example, the following procmail recipe puts
;; any mail with `emacs' in the subject line into the spool file
;; `emacs.spool', ready to go into the folder `emacs'.
;:0:
;* ^Subject.*emacs
;emacs.spool

;; It also assumes that all of your spool files and mail folders live
;; in the directory pointed to by `mspools-folder-directory', so you must
;; set this (see Installation).

;; When you run `mspools-show', it creates a *spools* buffer containing
;; all of the spools in the folder directory that are waiting to be
;; read.  On each line is the spool name and its size in bytes.  Move
;; to the line of the folder that you would like to read, and then
;; press return or space.  The mailer (VM or RMAIL) should then read
;; that folder and get the new mail for you.  When you return to the
;; *spools* buffer, you will either see "*" to indicate that the spool
;; has been read, or the remaining unread spools, depending on the
;; value of `mspools-update'.

;; This file should work with both VM and RMAIL.  See the variable
;; `mspools-using-vm' for details.

;;; Basic installation.
;; (autoload 'mspools-show "mspools" "Show outstanding mail spools." t)
;; (setq mspools-folder-directory "~/MAIL/")
;;
;; If you use VM, mspools-folder-directory will default to vm-folder-directory
;; unless you have already given it a value.

;; Extras.
;;
;; (global-set-key '[S-f1] 'mspools-show) ;Bind mspools-show to Shift F1.
;; (setq mspools-update t)                ;Automatically update buffer.

;; Interface with the mail filter.
;; We assume that the mail filter drops new mail into the spool
;; `folder.spool'.  If your spool files are something like folder.xyz
;; for inbox `folder', then do:
;; (setq mspools-suffix "xyz")
;; If you use other conventions for your spool files, this code will
;; need rewriting.

;; Warning for VM users
;; Don't use if you are not sure what you are doing.  The value of
;; vm-spool-files is altered, so you may not be able to read incoming
;; mail with VM if this is incorrectly set.

;; Useful settings for VM
;; vm-auto-get-new-mail should be t (the default).

;; Acknowledgments
;; Thanks to jond@mitre.org (Jonathan Doughty) for help with code for
;; setting up vm-spool-files.

;;; TODO

;; What if users have mail spools in more than one directory?  Extend
;; mspools-folder-directory to be a list of directories?  Currently,
;; if mail spools are in other directories, the way to read them is to
;; put a symbolic link to the spool into the mspools-folder-directory.

;; I was going to add mouse support so that you could click on a line
;; to visit the buffer.  Tell me if you want it, and I can put the
;; code in (I don't use the mouse much, so I haven't bothered with it
;; so far).

;; Rather than showing size in bytes, could we see the number of msgs
;; waiting?  (Could be more time demanding / system dependent).
;; Maybe just call a perl script to do all the hard work, and
;; visualize the results in the buffer.

;; Shrink wrap the buffer to remove excess white-space?

;;; Code:

(defvar rmail-inbox-list)
(defvar vm-crash-box)
(defvar vm-folder-directory)
(defvar vm-init-file)
(defvar vm-init-file-loaded)
(defvar vm-primary-inbox)
(defvar vm-spool-files)

;;; User Variables

(defgroup mspools nil
  "Show mail spools waiting to be read."
  :group 'mail
  :link '(emacs-commentary-link :tag "Commentary" "mspools.el")
)

(defcustom mspools-update nil
  "Non-nil means update *spools* buffer after visiting any folder."
  :type 'boolean)

(defcustom mspools-suffix "spool"
  "Extension used for spool files (not including full stop)."
  :type 'string)

(defcustom mspools-using-vm  (fboundp 'vm)
  "Non-nil if VM is used as mail reader, otherwise RMAIL is used."
  :type 'boolean)

(defcustom mspools-folder-directory
  (if (boundp 'vm-folder-directory)
      vm-folder-directory
    "~/MAIL/")
  "Directory where mail folders are kept.  Ensure it has a trailing /.
Defaults to `vm-folder-directory' if bound else to ~/MAIL/."
  :type 'directory)

(defcustom mspools-vm-system-mail (or (getenv "MAIL")
				      (concat rmail-spool-directory
					      (user-login-name)))
  "Spool file for main mailbox.  Only used by VM.
This needs to be set to your primary mail spool - mspools will not run
without it.  By default this will be set to the environment variable
$MAIL.  Otherwise it will use `rmail-spool-directory' to guess where
your primary spool is.  If this fails, set it to something like
/usr/spool/mail/login-name."
  :type 'file)

;;; Internal Variables

(defvar mspools-files nil
  "List of entries (SPOOL . SIZE) giving spool name and file size.")

(defvar mspools-files-len nil
  "Length of `mspools-files' list.")

(defvar mspools-buffer "*spools*"
  "Name of buffer for displaying spool info.")

(defvar mspools-mode-map
  (let ((map (make-sparse-keymap)))
    (define-key map "\C-c\C-c" #'mspools-visit-spool)
    (define-key map "\C-m" #'mspools-visit-spool)
    (define-key map " " #'mspools-visit-spool)
    (define-key map "n" #'next-line)
    (define-key map "p" #'previous-line)
    map)
  "Keymap for the *spools* buffer.")

;;; Code

;;; VM Specific code
(if mspools-using-vm
    ;; set up vm if not already loaded.
    (progn
      (require 'vm-vars)
      (if (and (not vm-init-file-loaded) (file-readable-p vm-init-file))
	  (load-file vm-init-file))
      (if (not mspools-folder-directory)
	  (setq mspools-folder-directory vm-folder-directory))
      ))

(defun mspools-set-vm-spool-files ()
  "Set value of `vm-spool-files'.  Only needed for VM."
  (if (not (file-readable-p mspools-vm-system-mail))
      (error "Need to set mspools-vm-system-mail to the spool for primary inbox"))
  (if (null mspools-folder-directory)
      (error "Set `mspools-folder-directory' to where the spool files are"))
  (setq
   vm-spool-files
   (append
    (list
     ;; Main mailbox
     (list vm-primary-inbox
	   mspools-vm-system-mail	; your mailbox
	   vm-crash-box			;crash for mailbox
	   ))

    ;; Mailing list inboxes
    ;; must have VM already loaded to get vm-folder-directory.
    (mapcar (lambda (s)
              "make the appropriate entry for vm-spool-files"
              (list
               (concat mspools-folder-directory s)
               (concat mspools-folder-directory s "." mspools-suffix)
               (concat mspools-folder-directory s ".crash")))
	    ;; So I create a vm-spool-files entry for each of those mail drops
	    (mapcar #'file-name-sans-extension
		    (directory-files mspools-folder-directory nil
				     (format "\\`[^.]+\\.%s" mspools-suffix)))
	    ))
   ))

;;; MSPOOLS-SHOW -- the main function
;;;###autoload
(defun mspools-show (&optional noshow)
  "Show the list of non-empty spool files in the *spools* buffer.
Buffer is not displayed if SHOW is non-nil."
  (interactive)
  (if (get-buffer mspools-buffer)
      ;; buffer exists
      (progn
	(set-buffer mspools-buffer)
	(setq buffer-read-only nil)
	(erase-buffer))
    ;; else buffer doesn't exist so create it
    (get-buffer-create mspools-buffer))

  ;; generate the list of spool files
  (if mspools-using-vm
      (mspools-set-vm-spool-files))

  (mspools-get-spool-files)
  (if (not noshow) (pop-to-buffer mspools-buffer))

  (setq buffer-read-only t)
  (mspools-mode)
  )

(declare-function rmail-get-new-mail "rmail" (&optional file-name))

;; External.
(declare-function vm-visit-folder "ext:vm-startup" (folder &optional read-only))

(defun mspools-visit-spool ()
  "Visit the folder on the current line of the *spools* buffer."
  (interactive)
  (let ((spool-name (mspools-get-spool-name))
        folder-name)
    (if (null spool-name)
	(message "No spool on current line")

      (setq folder-name (mspools-get-folder-from-spool spool-name))

      ;; put in a little "*" to indicate spool file has been read.
      (if (not mspools-update)
	  (save-excursion
	    (beginning-of-line)
	    (let ((inhibit-read-only t))
	      (insert "*")
	      (delete-char 1))))

      (message "folder %s spool %s" folder-name spool-name)
      (forward-line (if (eq (count-lines (point-min) (point-at-eol))
	                    mspools-files-len)
	                ;; FIXME: Why use `mspools-files-len' instead
                        ;; of looking if we're on the last line and
                        ;; jumping to the first one if so?
	                (- 1 mspools-files-len) ;back to top of list
	              ;; else just on to next line
	              1))

      ;; Choose whether to use VM or RMAIL for reading folder.
      (if mspools-using-vm
	  (vm-visit-folder (concat mspools-folder-directory folder-name))
	;; else using RMAIL
	(rmail (concat mspools-folder-directory folder-name))
	(setq rmail-inbox-list
	      (list (concat mspools-folder-directory spool-name)))
	(rmail-get-new-mail))


      (if mspools-update
	  ;; generate new list of spools.
	  (save-excursion ;;FIXME: Why?
	    (mspools-revert-buffer))))))

(defun mspools-get-folder-from-spool (name)
  "Return folder name corresponding to the spool file NAME."
  ;; Simply strip of the extension.
  (file-name-sans-extension name))

;; Alternative version if you have more complicated mapping of spool name
;; to file name.
;(defun get-folder-from-spool-safe (name)
;  "Return the folder name corresponding to the spool file NAME."
;  (if (string-match "^\\(.*\\)\\.spool$" name)
;      (substring name (match-beginning 1) (match-end 1))
;    (error "Could not extract folder name from spool name %s" name)))

; test
;(mspools-get-folder-from-spool "happy.spool")
;(mspools-get-folder-from-spool "happy.sp")

(defun mspools-get-spool-name ()
  "Return the name of the spool on the current line."
  (let ((line-num (1- (count-lines (point-min) (point-at-eol)))))
    ;; FIXME: Why not extract the name directly from the current line's text?
    (car (nth line-num mspools-files))))

;;; Spools mode functions

(defun mspools-revert-buffer (&optional _ignore _noconfirm)
  "Re-run `mspools-show' to revert the *spools* buffer."
  (mspools-show 'noshow))

(defun mspools-show-again (&optional noshow)
  "Update the *spools* buffer.
This is useful if `mspools-update' is nil."
  (declare (obsolete revert-buffer "28.1"))
  (interactive)
  (mspools-show noshow))

(defun mspools-help ()
  "Show help for `mspools-mode'."
  (declare (obsolete describe-mode "28.1"))
  (interactive)
  (describe-function 'mspools-mode))

(defun mspools-quit ()
  "Quit the *spools* buffer."
  (declare (obsolete quit-window "28.1"))
  (interactive)
  (kill-buffer mspools-buffer))

(define-derived-mode mspools-mode special-mode "MSpools"
  "Major mode for output from mspools-show.
\\<mspools-mode-map>Move point to one of the items in this buffer, then use
\\[mspools-visit-spool] to go to the spool that the current line refers to.
\\[revert-buffer] to regenerate the list of spools.
\\{mspools-mode-map}"
  (setq-local revert-buffer-function 'mspools-revert-buffer))

(defun mspools-get-spool-files ()
  "Find the list of spool files and display them in *spools* buffer."
  (if (null mspools-folder-directory)
      (error "Set `mspools-folder-directory' to where the spool files are"))
  (let* ((folders (directory-files mspools-folder-directory nil
				   (format "\\`[^.]+\\.%s\\'" mspools-suffix)))
	 (folders (delq nil (mapcar #'mspools-size-folder folders)))
	 ;; beg end
	 )
    (setq mspools-files folders)
    (setq mspools-files-len (length mspools-files))
    (with-current-buffer mspools-buffer
      (pcase-dolist (`(,spool . ,len) folders)
        ;; (setq beg (point))
        (insert (format " %10d %s" len spool))
        ;; (setq end (point))
        (insert "\n")
        ;;(put-text-property beg end 'mouse-face 'highlight)
        )
      (if (not (bolp))
	  (delete-char -1))			;delete last RET
      (goto-char (point-min)))))

(defun mspools-size-folder (spool)
  "Return (SPOOL . SIZE ), if SIZE of spool file is non-zero."
  ;; 7th file attribute is the size of the file in bytes.
  (let ((file (concat mspools-folder-directory spool))
	size)
    (setq file (or (file-symlink-p file) file))
    (setq size (file-attribute-size (file-attributes file)))
    ;; size could be nil if the sym-link points to a non-existent file
    ;; so check this first.
    (if (and size  (> size 0))
	(cons spool  size)
      ;; else SPOOL is empty
      nil)))

(provide 'mspools)

;;; mspools.el ends here