;;; Guix --- Nix package management from Guile.         -*- coding: utf-8 -*-
;;; Copyright (C) 2012 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of Guix.
;;;
;;; 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.
;;;
;;; 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 Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (guix build utils)
  #:use-module (srfi srfi-1)
  #:export (directory-exists?
            set-path-environment-variable))

(define (directory-exists? dir)
  "Return #t if DIR exists and is a directory."
  (let ((s (stat dir #f)))
    (and s
         (eq? 'directory (stat:type s)))))

(define (search-path-as-list sub-directories input-dirs)
  "Return the list of directories among SUB-DIRECTORIES that exist in
INPUT-DIRS.  Example:

  (search-path-as-list '(\"share/emacs/site-lisp\" \"share/emacs/24.1\")
                       (list \"/package1\" \"/package2\" \"/package3\"))
  => (\"/package1/share/emacs/site-lisp\"
      \"/package3/share/emacs/site-lisp\")

"
  (append-map (lambda (input)
                (filter-map (lambda (dir)
                              (let ((dir (string-append input "/"
                                                        dir)))
                                (and (directory-exists? dir)
                                     dir)))
                            sub-directories))
              input-dirs))

(define (list->search-path-as-string lst separator)
  (string-join lst separator))

(define* (set-path-environment-variable env-var sub-directories input-dirs
                                        #:key (separator ":"))
  "Look for each of SUB-DIRECTORIES in INPUT-DIRS.  Set ENV-VAR to a
SEPARATOR-separated path accordingly.  Example:

  (set-path-environment-variable \"PKG_CONFIG\"
                                 '(\"lib/pkgconfig\")
                                 (list package1 package2))
"
  (setenv env-var
          (list->search-path-as-string (search-path-as-list sub-directories
                                                            input-dirs)
                                       separator)))