;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.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 (wrap-program)
  #:use-module (guix packages)
  #:use-module (guix store)
  #:use-module (srfi srfi-26)
  #:export (store-location
            wrap-program))

(define (store-location package output rest)
  "Return a PACKAGE-related location."
  (string-append (package-output (open-connection) package output)
                 rest))

(define (wrap-program program prefix? variable var-dir)
  "Copy PROGRAM to .PROGRAM-real and make PROGRAM a wrapper."
  (let* ((bin-location (store-location program "out"
                                       (string-append "/bin"))) ; not safe
         (program-name (package-name program))
         (old (string-append bin-location "/" program-name))
         (new (string-append bin-location "/." program-name "-real"))
         (tmp (string-append bin-location "/." program-name "-tmp")))

    (define (change-variable)
      ;; Prepend VAR-DIR to VARIABLE or return VAR-DIR.
      (if prefix?
          (string-append var-dir ":$" variable)
          var-dir))

    (copy-file old new)

    (call-with-output-file
        tmp
      (cut format <> "#!/bin/sh~%export ~a=\"~a\"~%exec ./~a \"$@\"~%"
           variable (change-variable) (basename new)))

    (chmod tmp #o755)
    (rename-file tmp old)))