;;;; environment.scm -- interact with the job process environment
;;; Copyright © 2003 Dale Mellor <dale_mellor@users.sourceforge.net>
;;; Copyright © 2015, 2016 Mathieu Lirzin <mthl@gnu.org>
;;;
;;; This file is part of GNU Mcron.
;;;
;;; GNU Mcron 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 Mcron 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 Mcron.  If not, see <http://www.gnu.org/licenses/>.

;;;; Commentary:
;;;
;;; Define the variable current-environment-mods, and the procedures
;;; append-environment-mods (which is available to user configuration files),
;;; clear-environment-mods and modify-environment.  The idea is that the
;;; current-environment-mods is a list of pairs of environment names and
;;; values, and represents the cumulated environment settings in a
;;; configuration file.  When a job definition is seen in a configuration file,
;;; the current-environment-mods are copied into the internal job description,
;;; and when the job actually runs these environment modifications are applied
;;; to the UNIX environment in which the job runs.
;;;
;;;; Code:

(define-module (mcron environment)
  #:export (modify-environment
            clear-environment-mods
            append-environment-mods
            get-current-environment-mods-copy))
            


;; As we parse configuration files, we build up an alist of environment
;; variables here.

(define current-environment-mods '())



;; Each time a job is added to the system, we take a snapshot of the current
;; set of environment modifiers.

(define (get-current-environment-mods-copy)
  (list-copy current-environment-mods))



;; When we start to parse a new configuration file, we want to start with a
;; fresh environment (actually an umodified version of the pervading mcron
;; environment).

(define (clear-environment-mods)
  (set! current-environment-mods '()))



;; Procedure to add another environment setting to the alist above. This is
;; used both implicitly by the Vixie parser, and can be used directly by users
;; in scheme configuration files. The return value is purely for the
;; convenience of the parse-vixie-environment in the vixie-specification module
;; (yuk).

(define (append-environment-mods name value)
  (set! current-environment-mods (append current-environment-mods
                                         (list (cons name value))))
  #t)

(define (modify-environment env passwd-entry)
  "Modify the environment (in the UNIX sense) by setting the variables from
ENV and some default ones which are modulated by PASSWD-ENTRY.  \"LOGNAME\"
and \"USER\" environment variables can't be overided by ENV.  ENV must be an
alist which associate environment variables to their value.  PASSWD-ENTRY must
be an object representing user information which corresponds to a valid entry
in /etc/passwd.  The return value is not specified."
  (for-each (lambda (pair) (setenv (car pair) (cdr pair)))
            (let ((home-dir  (passwd:dir passwd-entry))
                  (user-name (passwd:name passwd-entry)))
              (append
               ;; Default environment variables which can be overided by ENV.
               `(("HOME"    . ,home-dir)
                 ("CWD"     . ,home-dir)
                 ("SHELL"   . ,(passwd:shell passwd-entry))
                 ("TERM"    . #f)
                 ("TERMCAP" . #f))
               env
               ;; Environment variables with imposed values.
               `(("LOGNAME" . ,user-name)
                 ("USER"    . ,user-name))))))