;;; mh-identity.el --- multiple identify support for MH-E

;; Copyright (C) 2002-2020 Free Software Foundation, Inc.

;; Author: Peter S. Galbraith <psg@debian.org>
;; Maintainer: Bill Wohler <wohler@newt.com>
;; Keywords: mail
;; See: mh-e.el

;; 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:

;; Multiple identity support for MH-E.

;; Used to easily set different fields such as From and Organization,
;; as well as different signature files.

;; Customize the variable `mh-identity-list' and see the Identity menu
;; in MH-Letter mode. The command `mh-insert-identity' can be used
;; to manually insert an identity.

;;; Change Log:

;;; Code:

(require 'mh-e)

(autoload 'mml-insert-tag "mml")

(defvar mh-identity-pgg-default-user-id nil
  "Holds the GPG key ID to be used by pgg.el.
This is normally set as part of an Identity in
`mh-identity-list'.")
(make-variable-buffer-local 'mh-identity-pgg-default-user-id)

(defvar mh-identity-menu nil
  "The Identity menu.")

(defalias 'mh-identity-make-menu-no-autoload 'mh-identity-make-menu)

;;;###mh-autoload
(defun mh-identity-make-menu ()
  "Build the Identity menu.
This should be called any time `mh-identity-list' or
`mh-auto-fields-list' change.
See `mh-identity-add-menu'."
  (easy-menu-define mh-identity-menu mh-letter-mode-map
    "MH-E identity menu"
    (append
     '("Identity")
     ;; Dynamically render :type corresponding to `mh-identity-list'
     ;; e.g.:
     ;;  ["Home" (mh-insert-identity "Home")
     ;;   :style radio :active (not (equal mh-identity-local "Home"))
     ;;   :selected (equal mh-identity-local "Home")]
     '(["Insert Auto Fields"
        (mh-insert-auto-fields) mh-auto-fields-list]
       "--")

     (mapcar (function
              (lambda (arg)
                `[,arg  (mh-insert-identity ,arg) :style radio
                        :selected (equal mh-identity-local ,arg)]))
             (mapcar 'car mh-identity-list))
     '(["None"
        (mh-insert-identity "None") :style radio
        :selected (not mh-identity-local)]
       "--"
       ["Set Default for Session"
        (setq mh-identity-default mh-identity-local) t]
       ["Save as Default"
        (customize-save-variable 'mh-identity-default mh-identity-local) t]
       ["Customize Identities" (customize-variable 'mh-identity-list) t]
       ))))

;;;###mh-autoload
(defun mh-identity-add-menu ()
  "Add the current Identity menu.
See `mh-identity-make-menu'."
  (if mh-identity-menu
      (easy-menu-add mh-identity-menu)))

(defvar mh-identity-local nil
  "Buffer-local variable that holds the identity currently in use.")
(make-variable-buffer-local 'mh-identity-local)

(defun mh-header-field-delete (field value-only)
  "Delete header FIELD, or only its value if VALUE-ONLY is t.
Return t if anything is deleted."
  (let ((field-colon (if (string-match "^.*:$" field)
                         field
                       (concat field ":"))))
    (when (mh-goto-header-field field-colon)
      (if (not value-only)
          (beginning-of-line)
        (forward-char))
      (delete-region (point)
                     (progn (mh-header-field-end)
                            (if (not value-only) (forward-char 1))
                            (point)))
      t)))

(defvar mh-identity-signature-start nil
  "Marker for the beginning of a signature inserted by `mh-insert-identity'.")
(defvar mh-identity-signature-end nil
  "Marker for the end of a signature inserted by `mh-insert-identity'.")

(defun mh-identity-field-handler (field)
  "Return the handler for header FIELD or nil if none set.
The field name is downcased. If the FIELD begins with the
character \":\", then it must have a special handler defined in
`mh-identity-handlers', else return an error since it is not a
valid header field."
  (or (cdr (mh-assoc-string field mh-identity-handlers t))
      (and (eq (aref field 0) ?:)
           (error "Field %s not found in `mh-identity-handlers'" field))
      (cdr (assoc ":default" mh-identity-handlers))
      'mh-identity-handler-default))

;;;###mh-autoload
(defun mh-select-identity (default)
  "Prompt for and return an identity.
If DEFAULT is non-nil, it will be used if the user doesn't enter a
different identity.

See `mh-identity-list'."
  (let (identity)
    (setq identity
          (completing-read
           "Identity: "
           (cons '("None")
                 (mapcar 'list (mapcar 'car mh-identity-list)))
           nil t default nil default))
    (if (eq identity "None")
        nil
      identity)))

;;;###mh-autoload
(defun mh-identity-field (identity field)
  "Return the specified FIELD of the given IDENTITY.

See `mh-identity-list'."
  (let* ((pers-list (cadr (assoc identity mh-identity-list)))
         (value (cdr (assoc field pers-list))))
    value))

;;;###mh-autoload
(defun mh-insert-identity (identity &optional maybe-insert)
  "Insert fields specified by given IDENTITY.

In a program, do not insert fields if MAYBE-INSERT is non-nil,
`mh-identity-default' is non-nil, and fields have already been
inserted.

See `mh-identity-list'."
  (interactive
   (list (completing-read
          "Identity: "
          (if mh-identity-local
              (cons '("None")
                    (mapcar 'list (mapcar 'car mh-identity-list)))
            (mapcar 'list (mapcar 'car mh-identity-list)))
          nil t)
         nil))

  (when (or (not maybe-insert)
            (and (boundp 'mh-identity-default)
                 mh-identity-default
                 (not mh-identity-local)))
    (save-excursion
      ;;First remove old settings, if any.
      (when mh-identity-local
        (let ((pers-list (cadr (assoc mh-identity-local mh-identity-list))))
          (while pers-list
            (let* ((field (caar pers-list))
                   (handler (mh-identity-field-handler field)))
              (funcall handler field 'remove))
            (setq pers-list (cdr pers-list)))))
      ;; Then insert the replacement
      (when (not (equal "None" identity))
        (let ((pers-list (cadr (assoc identity mh-identity-list))))
          (while pers-list
            (let* ((field (caar pers-list))
                   (value (cdar pers-list))
                   (handler (mh-identity-field-handler field)))
              (funcall handler field 'add value))
            (setq pers-list (cdr pers-list))))))
    ;; Remember what is in use in this buffer
    (if (equal "None" identity)
        (setq mh-identity-local nil)
      (setq mh-identity-local identity))))

;;;###mh-autoload
(defun mh-identity-handler-gpg-identity (_field action &optional value)
  "Process header FIELD \":pgg-default-user-id\".
The ACTION is one of `remove' or `add'. If `add', the VALUE is added.
The buffer-local variable `mh-identity-pgg-default-user-id' is set to
VALUE when action `add' is selected."
  (cond
   ((or (equal action 'remove)
        (not value)
        (string= value ""))
    (setq mh-identity-pgg-default-user-id nil))
   ((equal action 'add)
    (setq mh-identity-pgg-default-user-id value))))

;;;###mh-autoload
(defun mh-identity-handler-signature (_field action &optional value)
  "Process header FIELD \":signature\".
The ACTION is one of `remove' or `add'. If `add', the VALUE is
added."
  (cond
   ((equal action 'remove)
    (when (and (markerp mh-identity-signature-start)
               (markerp mh-identity-signature-end))
      (delete-region mh-identity-signature-start
                     mh-identity-signature-end)))
   (t
    ;; Insert "signature". Nil value means to use `mh-signature-file-name'.
    (when (not (mh-signature-separator-p)) ;...unless already present
      (goto-char (point-max))
      (save-restriction
        (narrow-to-region (point) (point))
        (if (null value)
            (mh-insert-signature)
          (mh-insert-signature value))
        (set (make-local-variable 'mh-identity-signature-start)
             (point-min-marker))
        (set-marker-insertion-type mh-identity-signature-start t)
        (set (make-local-variable 'mh-identity-signature-end)
             (point-max-marker)))))))

(defvar mh-identity-attribution-verb-start nil
  "Marker for the beginning of the attribution verb.")
(defvar mh-identity-attribution-verb-end nil
  "Marker for the end of the attribution verb.")

;;;###mh-autoload
(defun mh-identity-handler-attribution-verb (_field action &optional value)
  "Process header FIELD \":attribution-verb\".
The ACTION is one of `remove' or `add'.  If `add', the VALUE is
added."
  (when (and (markerp mh-identity-attribution-verb-start)
             (markerp mh-identity-attribution-verb-end))
    (delete-region mh-identity-attribution-verb-start
                   mh-identity-attribution-verb-end)
    (goto-char mh-identity-attribution-verb-start)
    (cond
     ((equal action 'remove)              ; Replace with default
      (mh-identity-insert-attribution-verb nil))
     (t                                   ; Insert attribution verb.
      (mh-identity-insert-attribution-verb value)))))

;;;###mh-autoload
(defun mh-identity-insert-attribution-verb (value)
  "Insert VALUE as attribution verb, setting up delimiting markers.
If VALUE is nil, use `mh-extract-from-attribution-verb'."
  (save-restriction
    (narrow-to-region (point) (point))
    (if (null value)
        (insert mh-extract-from-attribution-verb)
      (insert value))
    (set (make-local-variable 'mh-identity-attribution-verb-start)
         (point-min-marker))
    (set-marker-insertion-type mh-identity-attribution-verb-start t)
    (set (make-local-variable 'mh-identity-attribution-verb-end)
         (point-max-marker))))

(defun mh-identity-handler-default (field action top &optional value)
  "Process header FIELD.
The ACTION is one of `remove' or `add'. If TOP is non-nil, add the
field and its VALUE at the top of the header, else add it at the
bottom of the header. If action is `add', the VALUE is added."
  (let ((field-colon (if (string-match "^.*:$" field)
                         field
                       (concat field ":"))))
    (cond
     ((equal action 'remove)
      (mh-header-field-delete field-colon nil))
     (t
      (cond
       ;; No value, remove field
       ((or (not value)
            (string= value ""))
        (mh-header-field-delete field-colon nil))
       ;; Existing field, replace
       ((mh-header-field-delete field-colon t)
        (insert value))
       ;; Other field, add at end or top
       (t
        (goto-char (point-min))
        (if (not top)
            (mh-goto-header-end 0))
        (insert field-colon " " value "\n")))))))

;;;###mh-autoload
(defun mh-identity-handler-top (field action &optional value)
  "Process header FIELD.
The ACTION is one of `remove' or `add'. If `add', the VALUE is
added. If the field wasn't present, it is added to the top of the
header."
  (mh-identity-handler-default field action t value))

;;;###mh-autoload
(defun mh-identity-handler-bottom (field action &optional value)
  "Process header FIELD.
The ACTION is one of `remove' or `add'. If `add', the VALUE is
added. If the field wasn't present, it is added to the bottom of
the header."
  (mh-identity-handler-default field action nil value))

(provide 'mh-identity)

;; Local Variables:
;; indent-tabs-mode: nil
;; sentence-end-double-space: nil
;; End:

;;; mh-identity.el ends here