;;; gnus-mock.el --- Mock Gnus installation for testing  -*- lexical-binding: t; -*-

;; Copyright (C) 2018  Free Software Foundation

;; Author: Eric Abrahamsen <address@hidden>

;; This program 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.

;; This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This module provides a reproducible mock Gnus installation,
;; including dummy data, that can be used for Gnus development and
;; testing.  Start the mock Gnus session with either `gnus-mock' or
;; `gnus-mock-unplugged'.  Nothing in the mock sessions will make a
;; network connection, and mail sending is stubbed out using
;; `gnus-mock-sendmail-program'.

;; The mock session starts with a predefined nnmaildir server, as well
;; as some dummy mail data.  Other predefined servers may be added in
;; the future.  At startup, all dummy data is copied into a temporary
;; directory.  At shutdown, the temporary directory is deleted.

;; A special config file is used for the mock session; users may add
;; to this config, or shadow its options, by setting
;; `gnus-mock-settings-file' to the name of an additional config file.

;;; Code:

(require 'gnus)
(require 'message)

(defgroup gnus-mock nil
  "Options for the mock Gnus installation."
  :group 'gnus
  :version "27.1")

(defcustom gnus-mock-settings-file nil
  "Path to an additional config file for mock Gnus.
The contents of this file will be appended to gnus-mock's own
config file before Gnus startup, in effect shadowing config
values in the default file."
  :group 'gnus-mock
  :type 'file)

(defcustom gnus-mock-data-dir
  (expand-file-name "test/data/gnus/mock" source-directory)
  "Source directory for Gnus mock data."
  :group 'gnus-mock
  :type 'string)

(defcustom gnus-mock-cleanup-p t
  "When non-nil, delete temporary files after shutdown.
Each Gnus mock session will create a new temporary directory, so
multiple sessions will not conflict if this option is nil."
  :group 'gnus-mock
  :type 'boolean)

(defcustom gnus-mock-sendmail-program
  (nnheader-concat gnus-mock-data-dir "fakesendmail.py")
  "Program used as the value of `sendmail-program'."
  :group 'gnus-mock
  :type 'string)

;; Regular Gnus can also check this, in case of a "dirty" mock
;; session.
(defvar gnus-mock-p nil
  "Non-nil during a mocked Gnus session.")

(defun gnus-mock-setup ()
  "Set up mock data and config."
  (let ((mock-tmp-dir (make-temp-file "emacs-gnus-mock-" t)))
    (setq gnus-home-directory mock-tmp-dir
	  gnus-directory (nnheader-concat gnus-home-directory "News")
	  gnus-agent-directory (nnheader-concat gnus-directory "agent/")
	  nndraft-directory (nnheader-concat gnus-directory "drafts/")
	  gnus-init-file (nnheader-concat gnus-home-directory ".gnus")
	  gnus-startup-file (nnheader-concat gnus-home-directory ".newsrc")
	  message-directory gnus-home-directory
	  sendmail-program gnus-mock-sendmail-program
	  ;; If Emacs was started with -Q, as it should have been,
	  ;; `init-file-user' will be nil which will prevent reading of
	  ;; `gnus-init-file'.
	  init-file-user "gnus-mock")
    ;; Put our data and config in place.
    (copy-directory
     gnus-mock-data-dir
     (file-name-as-directory gnus-home-directory) nil nil t)
    ;; Possibly insert additional config.
    (when gnus-mock-settings-file
      (with-temp-buffer
	(insert-file-contents gnus-mock-settings-file)
	(append-to-file
	 (point-min) (point-max) gnus-init-file)))))

;;;###autoload
(defun gnus-mock-unplugged ()
  "Start an unplugged mock Gnus session."
  (interactive)
  (gnus-mock t))

;;;###autoload
(defun gnus-mock (&optional unplugged)
  "Start a mock Gnus session."
  (interactive)
  (when (gnus-alive-p)
    (error "First save and quit your running Gnus session"))
  (gnus-mock-setup)
  (when unplugged
    (setq gnus-plugged nil))
  (setq gnus-mock-p t)
  (gnus)
  (add-hook 'gnus-after-exiting-gnus-hook #'gnus-mock-restore))

(defun gnus-mock-restore ()
  "Restore after quitting a mock Gnus session."
  (when gnus-mock-p
    (when gnus-mock-cleanup-p
      (delete-directory gnus-home-directory t))
    (setq gnus-mock-p nil)
    (remove-hook 'gnus-after-exiting-gnus-hook #'gnus-mock-restore)))

(provide 'gnus-mock)
;;; gnus-mock.el ends here