;; -*- lexical-binding: t -*-
;;; desktop-registry.el --- Keep a central registry of desktop files

;; Copyright (C) 2013  Tom Willemse

;; Author: Tom Willemse <tom@ryuslash.org>
;; Keywords: convenience
;; Version: 1.0.0

;; 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 <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This module provides functions and a global minor mode that lets
;; you track a central registry of desktop files.  This is useful when
;; you use desktop files as project files and want to be able to
;; switch between them quickly.

(require 'desktop)

;;; Code:

(defgroup desktop-registry nil
  "Customization group for desktop-registry."
  :group 'desktop
  :prefix 'desktop-registry)

(defcustom desktop-registry-registry nil
  "The registry of desktop files."
  :group 'desktop-registry
  :type '(repeat (cons string directory)))

(defvar desktop-registry--history nil
  "History variable for `desktop-registry'.")

(defun desktop-registry--canonicalize-dir (dir)
  "Canonicalize DIR for use."
  (directory-file-name (expand-file-name dir)))

;;;###autoload
(defun desktop-registry-current-desktop (&optional default)
  "Get the name of the currently loaded desktop.

Returns DEFAULT when `desktop-dirname' is nil."
  (if desktop-dirname
      (let ((canonical
             (desktop-registry--canonicalize-dir desktop-dirname)))
        (car (cl-find-if (lambda (d) (equal (cdr d) canonical))
                         desktop-registry-registry)))
    default))

;;;###autoload
(defun desktop-registry-add-directory (dir)
  "Add DIR to the desktop registry."
  (interactive "DDirectory: ")
  (let* ((clean-dir (desktop-registry--canonicalize-dir dir))
         (label (file-name-base clean-dir)))
    (unless (assoc label desktop-registry-registry)
      (customize-save-variable
       'desktop-registry-registry
       (cons (cons label clean-dir) desktop-registry-registry)))))

;;;###autoload
(defun desktop-registry-add-current-desktop ()
  "Add the currently opened desktop file to `desktop-registry-registry'."
  (interactive)
  (unless desktop-dirname
    (error "No desktop loaded"))
  (desktop-registry-add-directory desktop-dirname))

(defun desktop-registry--completing-read (&optional prompt
                                                    default-current)
  "Ask the user to pick a desktop directory.

PROMPT specifies the prompt to use when asking, which defaults to
\"Desktop: \". DEFAULT-CURRENT specifies whether to use the
current desktop as default value."
  (let ((prompt (or prompt "Desktop: "))
        (default (and default-current
                      (desktop-registry-current-desktop))))
    (completing-read prompt desktop-registry-registry nil nil nil
                     'desktop-registry--history default)))

;;;###autoload
(defun desktop-registry-remove-desktop (desktop)
  "Remove DESKTOP from the desktop registry."
  (interactive (list (desktop-registry--completing-read "Remove: " t)))
  (let ((spec (assoc desktop desktop-registry-registry)))
    (if spec
        (customize-save-variable
         'desktop-registry-registry
         (delete spec desktop-registry-registry))
      (error "Unknown desktop: %s" desktop))))

;;;###autoload
(defun desktop-registry-rename-desktop (old new)
  "Rename desktop OLD to NEW."
  (interactive (list (desktop-registry--completing-read "Rename: " t)
                     (read-string "to: ")))
  (let ((spec (assoc old desktop-registry-registry)))
    (if (not spec)
        (error "Unknown desktop: %s" old)
      (setf (car spec) new)
      (customize-save-variable 'desktop-registry-registry
                               desktop-registry-registry))))

;;;###autoload
(defun desktop-registry-change-desktop (name)
  "Change to the desktop named NAME."
  (interactive (list (desktop-registry--completing-read "Switch to: ")))
  (desktop-change-dir (cdr (assoc name desktop-registry-registry))))

;;;###autoload
(define-minor-mode desktop-registry-auto-register
  "Automatically add saved desktops to the registry."
  :global t
  (if desktop-registry-auto-register
      (add-hook 'desktop-save-hook
                'desktop-registry-add-current-desktop)
    (remove-hook 'desktop-save-hook
                 'desktop-registry-add-current-desktop)))

(provide 'desktop-registry)
;;; desktop-registry.el ends here