;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2023 Tanguy Le Carrour <tanguy@bioneland.org>
;;;
;;; 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 mail)
  #:use-module (guix gexp)
  #:use-module (guix records)
  #:use-module (gnu services)
  #:use-module (gnu services configuration)
  #:use-module (gnu home services)
  #:use-module (gnu home services shepherd)
  #:use-module (gnu home services utils)
  #:use-module (gnu packages mail)
  #:use-module (gnu packages guile)
  #:use-module (ice-9 match)
  #:use-module (ice-9 string-fun)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-26)
  #:export (home-goimapnotify-configuration
            home-goimapnotify-configuration-fields
            home-goimapnotify-configuration?
            home-goimapnotify-configuration-accounts
            home-goimapnotify-service-type
            goimapnotify-account
            goimapnotify-account-fields
            goimapnotify-account-host
            goimapnotify-account-host-cmd
            goimapnotify-account-port
            goimapnotify-account-tls
            goimapnotify-account-tls-options
            goimapnotify-account-username
            goimapnotify-account-username-cmd
            goimapnotify-account-password
            goimapnotify-account-password-cmd
            goimapnotify-account-xoauth2
            goimapnotify-account-on-new-mail
            goimapnotify-account-on-new-mail-post
            goimapnotify-account-wait
            goimapnotify-account-boxes
            goimapnotify-tls-options
            goimapnotify-tls-options-fields
            goimapnotify-tls-options-reject-unauthorized

            home-msmtp-configuration
            home-msmtp-configuration?
            home-msmtp-configuration-defaults
            home-msmtp-configuration-accounts
            home-msmtp-configuration-default-account
            home-msmtp-configuration-extra-content
            home-msmtp-service-type
            msmtp-configuration
            msmtp-configuration-auth?
            msmtp-configuration-tls?
            msmtp-configuration-tls-starttls?
            msmtp-configuration-tls-trust-file
            msmtp-configuration-log-file
            msmtp-configuration-host
            msmtp-configuration-port
            msmtp-configuration-user
            msmtp-configuration-from
            msmtp-configuration-password-eval
            msmtp-configuration-extra-content
            msmtp-account
            msmtp-account-name
            msmtp-account-configuration))

(define-maybe string (prefix msmtp-configuration-))
(define-maybe boolean (prefix msmtp-configuration-))
(define-maybe integer (prefix msmtp-configuration-))

;; Serialization of 'msmtp'.
(define (uglify-symbol field-name)
  (let* ((name (symbol->string field-name))
         (ugly-name (string-replace-substring name "-" "_")))
    (if (string-suffix? "?" ugly-name)
      (string-drop-right ugly-name 1)
      ugly-name)))

(define (msmtp-configuration-serialize-boolean field-name value)
  #~(string-append #$(uglify-symbol field-name) " "
                   (if #$value "on" "off") "\n"))

(define (msmtp-configuration-serialize-string field-name value)
  #~(string-append #$(uglify-symbol field-name) " " #$value "\n"))

(define (msmtp-configuration-serialize-maybe-string-no-underscore field-name value)
  #~(if #$(maybe-value-set? value)
      (string-append
        #$(string-replace-substring (uglify-symbol field-name) "_" "") " " #$value "\n")
      ""))

(define (msmtp-configuration-serialize-integer field-name value)
  #~(string-append #$(uglify-symbol field-name) " "
                   (number->string #$value) "\n"))

(define (msmtp-configuration-serialize-extra-content field-name value)
  #~(if (string=? #$value "") "" (string-append #$value "\n")))

(define (msmtp-account-serialize-name field-name value)
  #~(string-append "\naccount " #$value "\n"))

(define (msmtp-account-serialize-msmtp-configuration field-name value)
  #~(string-append #$(serialize-configuration value msmtp-configuration-fields)))

(define (home-msmtp-configuration-serialize-list-of-msmtp-accounts field-name value)
  #~(string-append #$@(map (cut serialize-configuration <> msmtp-account-fields)
                           value)))

(define (home-msmtp-configuration-serialize-msmtp-configuration field-name value)
  #~(string-append "defaults\n"
                   #$(serialize-configuration value msmtp-configuration-fields)))

(define (home-msmtp-configuration-serialize-default-account field-name value)
  #~(if #$(maybe-value-set? value)
      (string-append "\naccount default : " #$value "\n")
      ""))

(define (home-msmtp-configuration-serialize-extra-content field-name value)
  #~(if (string=? #$value "") "" (string-append #$value "\n")))

;; Configuration of 'msmtp'.
;; Source <https://marlam.de/msmtp/msmtp.html#Configuration-files>.
(define-configuration msmtp-configuration
  (auth?
   maybe-boolean
   "Enable or disable authentication.")

  (tls?
   maybe-boolean
   "Enable or disable TLS (also known as SSL) for secured connections.")

  (tls-starttls?
   maybe-boolean
   "Choose the TLS variant: start TLS from within the session (‘on’, default),
or tunnel the session through TLS (‘off’).")

  (tls-trust-file
   maybe-string
   "Activate server certificate verification using a list of
trusted Certification Authorities (CAs).")

  (log-file
   maybe-string
   "Enable logging to the specified file. An empty argument disables logging.
The file name ‘-’ directs the log information to standard output."
   (serializer msmtp-configuration-serialize-maybe-string-no-underscore))

  (host
    maybe-string
    "The SMTP server to send the mail to.")

  (port
    maybe-integer
    "The port that the SMTP server listens on. The default is 25 (\"smtp\"),
unless TLS without STARTTLS is used, in which case it is 465 (\"smtps\").")

  (user
    maybe-string
    "Set the user name for authentication.")

  (from
    maybe-string
    "Set the envelope-from address.")

  (password-eval
    maybe-string
    "Set the password for authentication to the output (stdout) of the command cmd."
    (serializer msmtp-configuration-serialize-maybe-string-no-underscore))

  (extra-content
   (string "")
   "Extra content appended as-is to the configuration block.  Run
@command{man msmtp} for more information about the configuration file
format."
   (serializer msmtp-configuration-serialize-extra-content))

  (prefix msmtp-configuration-))

(define-configuration msmtp-account
  (name
   (string)
   "The unique name of the account."
   (serializer msmtp-account-serialize-name))

  (configuration
   (msmtp-configuration)
   "The configuration for this given account.")

  (prefix msmtp-account-))

(define (list-of-msmtp-accounts? lst)
  (every msmtp-account? lst))

(define-configuration home-msmtp-configuration
  (defaults
   (msmtp-configuration (msmtp-configuration))
   "The configuration that will be set as default for all accounts.")

  (accounts
   (list-of-msmtp-accounts '())
   "A list of @code{msmtp-account} records which contain
information about all your accounts.")

  (default-account
   maybe-string
   "Set the default account."
   (serializer home-msmtp-configuration-serialize-default-account))

  (extra-content
   (string "")
   "Extra content appended as-is to the configuration file.  Run
@command{man msmtp} for more information about the configuration file
format."
   (serializer home-msmtp-configuration-serialize-extra-content))

  (prefix home-msmtp-configuration-))

(define (home-msmtp-files config)
  (list
   `(".config/msmtp/config"
     ,(mixed-text-file "msmtp-config"
                       (serialize-configuration config home-msmtp-configuration-fields)))))

(define (home-msmtp-profile-entries config)
  (list msmtp))

(define home-msmtp-service-type
  (service-type (name 'home-msmtp)
                (extensions
                 (list (service-extension home-profile-service-type
                                          home-msmtp-profile-entries)
                       (service-extension home-files-service-type
                                          home-msmtp-files)))
                (default-value (home-msmtp-configuration))
                (description "Configure msmtp, a simple
@acronym{SMTP, Simple Mail Transfer Protocol} client that can relay email
to SMTP servers.")))

; Configuration for goimapnotify from (gnu packages mail)

(define-maybe string)
(define-maybe integer)
(define-maybe boolean)
(define-maybe list-of-strings)
(define-maybe string-or-file-like)

(define (string-or-file-like? value)
  (or (string? value)
      (file-like? value)))

(define (goimapnotify-format-field field-name)
  (object->camel-case-string
    (string-trim-right
      (object->string field-name)
      #\?)))

(define (goimapnotify-serialize-field field-name value)
  "This is converted to JSON later, so we don't return a string here"
  #~(#$(goimapnotify-format-field field-name) . #$value))

(define (goimapnotify-serialize-string-or-file-like field-name value)
  (goimapnotify-serialize-string field-name value))

(define (goimapnotify-maybe-serialize field-name value serialization-function)
  (if (maybe-value-set? value)
    (serialization-function field-name value)
    ""))

(define (goimapnotify-serialize-maybe-string-or-file-like field-name value)
 (goimapnotify-maybe-serialize field-name value
                               goimapnotify-serialize-string-or-file-like))

(define goimapnotify-serialize-string goimapnotify-serialize-field)
(define (goimapnotify-serialize-maybe-string field-name value)
 (goimapnotify-maybe-serialize field-name value goimapnotify-serialize-string))

(define (goimapnotify-serialize-maybe-integer field-name value)
 (goimapnotify-maybe-serialize field-name value goimapnotify-serialize-integer))
(define goimapnotify-serialize-integer goimapnotify-serialize-field)

(define (goimapnotify-serialize-maybe-boolean field-name value)
  (goimapnotify-maybe-serialize field-name value goimapnotify-serialize-boolean))
(define goimapnotify-serialize-boolean goimapnotify-serialize-field)

(define (goimapnotify-serialize-maybe-list-of-strings field-name value)
  (goimapnotify-maybe-serialize field-name value goimapnotify-serialize-list-of-strings))
(define (goimapnotify-serialize-list-of-strings field-name value)
  (goimapnotify-serialize-field field-name (list->array 1 value)))

(define (goimapnotify-serialize-maybe-goimapnotify-tls-options field-name config)
  (goimapnotify-maybe-serialize field-name config
                                goimapnotify-serialize-goimapnotify-tls-options))

(define (goimapnotify-serialize-goimapnotify-tls-options field-name config)
  (goimapnotify-serialize-field
    field-name
    (prepare-configuration-for-json config goimapnotify-tls-options-fields)))

(define (prepare-configuration-for-json config fields)
  "Convert the configuration to the format expected by guile-json.
  Unset maybe-values do not appear in the configuration file."
  (fold
    (lambda (field accu)
      (let ((value ((configuration-field-getter field) config)))
        (append accu
          (if (maybe-value-set? value)
            (list ((configuration-field-serializer field)
                   (configuration-field-name field)
                   value))
            '()))))
    '()
    fields))

(define-configuration goimapnotify-tls-options
                      (reject-unauthorized?
                        maybe-boolean
                        "Skip verifying CA server identify?")
                      (prefix goimapnotify-))

(define-maybe goimapnotify-tls-options)

; See https://gitlab.com/shackra/goimapnotify/-/blob/423f0e65350f7e042edbd2c373f252c5a0d31dc2/config.go#L46-62
(define-configuration goimapnotify-account
                      (host
                        maybe-string
                        "Address of the IMAP server to connect to.")
                      (host-cmd
                        maybe-string-or-file-like
                        "An executable or script that retrieves your host from somewhere,
                        we cannot pass arguments to this command from stdin.")
                      (port
                        maybe-integer
                        "Port of the IMAP server to connect to.")
                      (tls?
                        maybe-boolean
                        "Use TLS?")
                      (tls-options
                        maybe-goimapnotify-tls-options
                        "Option(s) for the TLS connection. Currently, only one option is
                        supported.")
                      (username
                        maybe-string
                        "Username for authentication.")
                      (username-cmd
                        maybe-string-or-file-like
                        "An executable or script that retrieves your username from
                        somewhere, we cannot pass arguments to this command from stdin.")
                      (password
                        maybe-string
                        "Password for authentication.")
                      (password-cmd
                        maybe-string-or-file-like
                        "An executable or script that retrieves your password from
                        somewhere, we cannot pass arguments to this command from stdin.")
                      (xoauth2?
                        maybe-boolean
                        "You can also use xoauth2 instead of password based authentication
                        by setting the xoauth2 option to true and the output of a tool
                        which can provide xoauth2 encoded tokens in passwordCmd.
                        Examples: @url{https://github.com/google/oauth2l, Google oauth2l}
                        or
                        @url{https://github.com/harishkrupo/oauth2ms, xoauth2 fetcher for O365}.")
                      (on-new-mail
                        maybe-string-or-file-like
                        "An executable or script to run when new mail has arrived.")
                      (on-new-mail-post
                        maybe-string-or-file-like
                        "An executable or script to run after on-new-mail has ran.")
                      (wait
                        maybe-integer
                        "The delay in seconds before the mail syncing is triggered.")
                      (boxes
                        maybe-list-of-strings
                        "Mailboxes to watch.")
                      (prefix goimapnotify-))

(define (list-of-goimapnotify-accounts? lst)
  "List is in the form of '((file-name file-like))"
  (every (compose goimapnotify-account? second) lst))

(define-configuration/no-serialization home-goimapnotify-configuration
                                       (accounts
                                         (list-of-goimapnotify-accounts '())
                                         "List of accounts that goimapnotify should watch.
                                         For each account, a separate configuration file
                                         will be generated."))

(define (home-goimapnotify-extension old-config extensions)
  (match-record old-config <home-goimapnotify-configuration>
                (accounts)
                (home-goimapnotify-configuration
                  (inherit old-config)
                  (accounts (append accounts
                                    (append-map
                                      home-goimapnotify-configuration-accounts
                                      extensions))))))

(define (goimapnotify-files config)
  (define* (account->json account-config-and-path)
    (match
      account-config-and-path
      ((path account-config)
       (let ((prepared-config
               (prepare-configuration-for-json
                 account-config
                 goimapnotify-account-fields)))
         `((,path
            ,(computed-file
               (string-append
                 "mail-imapnotify-config-"
                 (goimapnotify-account-host account-config))
               (with-extensions (list guile-json-4)
                   #~(begin
                       (use-modules (json builder))

                       (with-output-to-file #$output
                         (lambda ()
                           (scm->json '(#$@prepared-config)
                                      #:pretty #t))))))))))))

  (match-record config <home-goimapnotify-configuration>
                (accounts)
                (append-map
                  (cut account->json <>)
                  accounts)))

(define home-goimapnotify-service-type
  (service-type
    (name 'home-goimapnotify-service)
    (extensions
      (list (service-extension
              home-files-service-type
              goimapnotify-files)))
    (compose identity)
    (extend home-goimapnotify-extension)
    (default-value (home-goimapnotify-configuration))
    (description "Configure goimapnotify to execute scripts on IMAP
                 mailbox changes.")))