;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix 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 Guix 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 Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (gnu home services xdg)
  #:use-module (gnu services configuration)
  #:use-module (gnu home services)
  #:use-module (gnu packages freedesktop)
  #:use-module (gnu home services utils)
  #:use-module (guix gexp)
  #:use-module (guix modules)
  #:use-module (guix records)
  #:use-module (guix i18n)
  #:use-module (guix diagnostics)

  #:use-module (ice-9 match)
  #:use-module (srfi srfi-1)
  #:use-module (rnrs enums)

  #:export (home-xdg-base-directories-service-type
            home-xdg-base-directories-configuration
            home-xdg-base-directories-configuration?

            home-xdg-user-directories-service-type
            home-xdg-user-directories-configuration
            home-xdg-user-directories-configuration?

            xdg-desktop-action
            xdg-desktop-entry
            home-xdg-mime-applications-service-type
            home-xdg-mime-applications-configuration))

;;; Commentary:
;;
;; This module contains services related to XDG directories and
;; applications.
;;
;; - XDG base directories
;; - XDG user directories
;; - XDG MIME applications
;;
;;; Code:


;;;
;;; XDG base directories.
;;;

(define (serialize-path field-name val) "")
(define path? string?)

(define-configuration home-xdg-base-directories-configuration
  (cache-home
   (path "$HOME/.cache")
   "Base directory for programs to store user-specific non-essential
(cached) data.  Files in this directory can be deleted anytime without
loss of important data.")
  (config-home
   (path "$HOME/.config")
   "Base directory for programs to store configuration files.
Some programs store here log or state files, but it's not desired,
this directory should contain static configurations.")
  (data-home
   (path "$HOME/.local/share")
   "Base directory for programs to store architecture independent
read-only shared data, analogus to @file{/usr/share}, but for user.")
  (runtime-dir
   (path "${XDG_RUNTIME_DIR:-/run/user/$UID}")
   "Base directory for programs to store user-specific runtime files,
like sockets.")
  (log-home
   (path "$HOME/.local/var/log")
   "Base directory for programs to store log files, analogus to
@file{/var/log}, but for user.  It is not a part of XDG Base Directory
Specification, but helps to make implementation of home services more
consistent.")
  (state-home
   (path "$HOME/.local/var/lib")
   "Base directory for programs to store state files, like databases,
analogus to @file{/var/lib}, but for user.  It is not a part of XDG
Base Directory Specification, but helps to make implementation of home
services more consistent."))

(define (home-xdg-base-directories-environment-variables-service config)
  (map
   (lambda (field)
     (cons (format
            #f "XDG_~a"
            (object->snake-case-string (configuration-field-name field) 'upper))
           ((configuration-field-getter field) config)))
   home-xdg-base-directories-configuration-fields))

(define (ensure-xdg-base-dirs-on-activation config)
  #~(map (lambda (xdg-base-dir-variable)
           ((@ (guix build utils) mkdir-p)
            (getenv
             xdg-base-dir-variable)))
         '#$(filter-map
             (lambda (field)
               (let ((variable
                      (string-append
                       "XDG_"
                       (object->snake-case-string
                        (configuration-field-name field) 'upper))))
                 ;; XDG_RUNTIME_DIR shouldn't be created during activation
                 ;; and will be provided by elogind or other service.
                 (and (not (string=? "XDG_RUNTIME_DIR" variable))
                      variable)))
             home-xdg-base-directories-configuration-fields)))

(define (last-extension-or-cfg config extensions)
  "Picks configuration value from last provided extension.  If there
are no extensions use configuration instead."
  (or (and (not (null? extensions)) (last extensions)) config))

(define home-xdg-base-directories-service-type
  (service-type (name 'home-xdg-base-directories)
                (extensions
                 (list (service-extension
                        home-environment-variables-service-type
                        home-xdg-base-directories-environment-variables-service)
                       (service-extension
                        home-activation-service-type
                        ensure-xdg-base-dirs-on-activation)))
                (default-value (home-xdg-base-directories-configuration))
                (compose identity)
                (extend last-extension-or-cfg)
                (description "Configure XDG base directories.  This
service introduces two additional variables @env{XDG_STATE_HOME},
@env{XDG_LOG_HOME}.  They are not a part of XDG specification, at
least yet, but are convenient to have, it improves the consistency
between different home services.  The services of this service-type is
instantiated by default, to provide non-default value, extend the
service-type (using @code{simple-service} for example).")))

(define (generate-home-xdg-base-directories-documentation)
  (generate-documentation
   `((home-xdg-base-directories-configuration
      ,home-xdg-base-directories-configuration-fields))
   'home-xdg-base-directories-configuration))


;;;
;;; XDG user directories.
;;;

(define (serialize-string field-name val)
  ;; The path has to be quoted
  (format #f "XDG_~a_DIR=\"~a\"\n"
          (object->snake-case-string field-name 'upper) val))

(define-configuration home-xdg-user-directories-configuration
  (desktop
   (string "$HOME/Desktop")
   "Default ``desktop'' directory, this is what you see on your
desktop when using a desktop environment,
e.g. GNOME (@pxref{XWindow,,,guix.info}).")
  (documents
   (string "$HOME/Documents")
   "Default directory to put documents like PDFs.")
  (download
   (string "$HOME/Downloads")
   "Default directory downloaded files, this is where your Web-broser
will put downloaded files in.")
  (music
   (string "$HOME/Music")
   "Default directory for audio files.")
  (pictures
   (string "$HOME/Pictures")
   "Default directory for pictures and images.")
  (publicshare
   (string "$HOME/Public")
   "Default directory for shared files, which can be accessed by other
users on local machine or via network.")
  (templates
   (string "$HOME/Templates")
   "Default directory for templates.  They can be used by graphical
file manager or other apps for creating new files with some
pre-populated content.")
  (videos
   (string "$HOME/Videos")
   "Default directory for videos."))

(define (home-xdg-user-directories-files-service config)
  `(("user-dirs.conf"
     ,(mixed-text-file
       "user-dirs.conf"
       "enabled=False\n"))
    ("user-dirs.dirs"
     ,(mixed-text-file
       "user-dirs.dirs"
      (serialize-configuration
       config
       home-xdg-user-directories-configuration-fields)))))

(define (home-xdg-user-directories-activation-service config)
  (let ((dirs (map (lambda (field)
                     ((configuration-field-getter field) config))
                   home-xdg-user-directories-configuration-fields)))
    #~(let ((ensure-dir
             (lambda (path)
               ((@ (guix build utils) mkdir-p)
                ((@ (ice-9 string-fun) string-replace-substring)
                 path "$HOME" (getenv "HOME"))))))
        (display "Creating XDG user directories...")
        (map ensure-dir '#$dirs)
        (display " done\n"))))

(define home-xdg-user-directories-service-type
  (service-type (name 'home-xdg-user-directories)
                (extensions
                 (list (service-extension
                        home-xdg-configuration-files-service-type
                        home-xdg-user-directories-files-service)
                       (service-extension
                        home-activation-service-type
                        home-xdg-user-directories-activation-service)))
                (default-value (home-xdg-user-directories-configuration))
                (description "Configure XDG user directories.  To
disable a directory, point it to the $HOME.")))

(define (generate-home-xdg-user-directories-documentation)
  (generate-documentation
   `((home-xdg-user-directories-configuration
     ,home-xdg-user-directories-configuration-fields))
   'home-xdg-user-directories-configuration))


;;;
;;; XDG MIME applications.
;;;

;; Example config
;;
;;  (home-xdg-mime-applications-configuration
;;   (added '((x-scheme-handler/magnet . torrent.desktop)))
;;   (default '((inode/directory . file.desktop)))
;;   (removed '((inode/directory . thunar.desktop)))
;;   (desktop-entries
;;    (list (xdg-desktop-entry
;;           (file "file")
;;           (name "File manager")
;;           (type 'application)
;;           (config
;;            '((exec . "emacsclient -c -a emacs %u"))))
;;          (xdg-desktop-entry
;;           (file "text")
;;           (name "Text editor")
;;           (type 'application)
;;           (config
;;            '((exec . "emacsclient -c -a emacs %u")))
;;           (actions
;;            (list (xdg-desktop-action
;;                   (action 'create)
;;                   (name "Create an action")
;;                   (config
;;                    '((exec . "echo hi"))))))))))

;; See
;; <https://specifications.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-latest.html>
;; <https://specifications.freedesktop.org/mime-apps-spec/mime-apps-spec-latest.html>

(define (serialize-alist field-name val)
  (define (serialize-mimelist-entry key val)
    (let ((val (cond
                ((list? val)
                 (string-join (map maybe-object->string val) ";"))
                ((or (string? val) (symbol? val))
                 val)
                (else (raise (formatted-message
                              (G_ "\
The value of an XDG MIME entry must be a list, string or symbol, was given ~a")
                              val))))))
      (format #f "~a=~a\n" key val)))

  (define (merge-duplicates alist acc)
    "Merge values that have the same key.

@example
(merge-duplicates '((key1 . value1)
                    (key2 . value2)
                    (key1 . value3)
                    (key1 . value4)) '())

@result{} ((key1 . (value4 value3 value1)) (key2 . value2))
@end example"
    (cond
     ((null? alist) acc)
     (else (let* ((head (first alist))
                  (tail (cdr alist))
                  (key (first head))
                  (value (cdr head))
                  (duplicate? (assoc key acc))
                  (ensure-list (lambda (x)
                                 (if (list? x) x (list x)))))
             (if duplicate?
                 ;; XXX: This will change the order of things,
                 ;; though, it shouldn't be a problem for XDG MIME.
                 (merge-duplicates
                  tail
                  (alist-cons key
                              (cons value (ensure-list (cdr duplicate?)))
                              (alist-delete key acc)))
                 (merge-duplicates tail (cons head acc)))))))

  (string-append (if (equal? field-name 'default)
                     "\n[Default Applications]\n"
                     (format #f "\n[~a Associations]\n"
                             (string-capitalize (symbol->string field-name))))
                 (generic-serialize-alist string-append
                                          serialize-mimelist-entry
                                          (merge-duplicates val '()))))

(define xdg-desktop-types (make-enumeration
                           '(application
                             link
                             directory)))

(define (xdg-desktop-type? type)
  (unless (enum-set-member? type xdg-desktop-types)
    (raise (formatted-message
            (G_ "XDG desktop type must be of of ~a, was given: ~a")
            (list->human-readable-list (enum-set->list xdg-desktop-types))
            type))))

;; TODO: Add proper docs for this
;; XXX: 'define-configuration' require that fields have a default
;; value.
(define-record-type* <xdg-desktop-action>
  xdg-desktop-action make-xdg-desktop-action
  xdg-desktop-action?
  (action xdg-desktop-action-action)  ; symbol
  (name   xdg-desktop-action-name)    ; string
  (config xdg-desktop-action-config   ; alist
          (default '())))

(define-record-type* <xdg-desktop-entry>
  xdg-desktop-entry make-xdg-desktop-entry
  xdg-desktop-entry?
  ;; ".desktop" will automatically be added
  (file    xdg-desktop-entry-file)    ; string
  (name    xdg-desktop-entry-name)    ; string
  (type    xdg-desktop-entry-type)    ; xdg-desktop-type
  (config  xdg-desktop-entry-config   ; alist
           (default '()))
  (actions xdg-desktop-entry-actions  ; list of <xdg-desktop-action>
           (default '())))

(define desktop-entries? (list-of xdg-desktop-entry?))
(define (serialize-desktop-entries field-name val) "")

(define (serialize-xdg-desktop-entry entry)
  "Return a tuple of the file name for ENTRY and the serialized
configuration."
  (define (format-config key val)
    (let ((val (cond
                ((list? val)
                 (string-join (map maybe-object->string val) ";"))
                ((boolean? val)
                 (if val "true" "false"))
                (else val)))
          (key (string-capitalize (maybe-object->string key))))
      (list (if (string-suffix? key "?")
                (string-drop-right key (- (string-length key) 1))
                key)
            "=" val "\n")))

  (define (serialize-alist config)
    (generic-serialize-alist append format-config config))

  (define (serialize-xdg-desktop-action action)
    (match action
      (($ <xdg-desktop-action> action name config)
       `(,(format #f "[Desktop Action ~a]\n"
                  (string-capitalize (maybe-object->string action)))
         ,(format #f "Name=~a\n" name)
         ,@(serialize-alist config)))))

  (match entry
    (($ <xdg-desktop-entry> file name type config actions)
     (list (if (string-suffix? file ".desktop")
               file
               (string-append file ".desktop"))
           `("[Desktop Entry]\n"
             ,(format #f "Name=~a\n" name)
             ,(format #f "Type=~a\n"
                      (string-capitalize (symbol->string type)))
             ,@(serialize-alist config)
             ,@(append-map serialize-xdg-desktop-action actions))))))

(define-configuration home-xdg-mime-applications-configuration
  (added
   (alist '())
   "An association list of MIME types and desktop entries which indicate
that the application should used to open the specified MIME type.  The
value has to be string, symbol, or list of strings or symbols, this
applies to the `@code{default}', and `@code{removed}' fields as well.")
  (default
    (alist '())
    "An association list of MIME types and desktop entries which indicate
that the application should be the default for opening the specified
MIME type.")
  (removed
   (alist '())
   "An association list of MIME types and desktop entries which indicate
that the application cannot open the specified MIME type.")
  (desktop-entries
   (desktop-entries '())
   "A list of XDG desktop entries to create.  See
@code{xdg-desktop-entry}."))

(define (home-xdg-mime-applications-files config)
  (define (add-xdg-desktop-entry-file entry)
    (let ((file (first entry))
          (config (second entry)))
      ;; TODO: Use xdg-data-files instead of home-files here
      (list (format #f "applications/~a" file)
          (apply mixed-text-file
                 (format #f "xdg-desktop-~a-entry" file)
                 config))))
  (map (compose add-xdg-desktop-entry-file serialize-xdg-desktop-entry)
       (home-xdg-mime-applications-configuration-desktop-entries config)))

(define (home-xdg-mime-applications-xdg-files config)
  `(("mimeapps.list"
     ,(mixed-text-file
       "xdg-mime-appplications"
       (serialize-configuration
        config
        home-xdg-mime-applications-configuration-fields)))))

(define (home-xdg-mime-applications-extension old-config extension-configs)
  (define (extract-fields config)
    ;; return '(added default removed desktop-entries)
    (list (home-xdg-mime-applications-configuration-added config)
          (home-xdg-mime-applications-configuration-default config)
          (home-xdg-mime-applications-configuration-removed config)
          (home-xdg-mime-applications-configuration-desktop-entries config)))

  (define (append-configs elem acc)
    (list (append (first elem) (first acc))
          (append (second elem) (second acc))
          (append (third elem) (third acc))
          (append (fourth elem) (fourth acc))))

  ;; TODO: Implement procedure to check for duplicates without
  ;; sacrificing performance.
  ;;
  ;; Combine all the alists from 'added', 'default' and 'removed'
  ;; into one big alist.
  (let ((folded-configs (fold append-configs
                              (extract-fields old-config)
                              (map extract-fields extension-configs))))
    (home-xdg-mime-applications-configuration
     (added (first folded-configs))
     (default (second folded-configs))
     (removed (third folded-configs))
     (desktop-entries (fourth folded-configs)))))

(define home-xdg-mime-applications-service-type
  (service-type (name 'home-xdg-mime-applications)
                (extensions
                 (list (service-extension
                        home-xdg-data-files-service-type
                        home-xdg-mime-applications-files)
                       (service-extension
                        home-xdg-configuration-files-service-type
                        home-xdg-mime-applications-xdg-files)))
                (compose identity)
                (extend home-xdg-mime-applications-extension)
                (default-value (home-xdg-mime-applications-configuration))
                (description
                 "Configure XDG MIME applications, and XDG desktop entries.")))