import: Add 'cran' importer.

* guix/import/cran.scm: New file.
* guix/scripts/import.scm: Add "cran" to 'importers'.
* guix/scripts/import/cran.scm: New file.
* tests/cran.scm: New file.
* Makefile.am (MODULES): Add 'guix/import/cran.scm' and
  'guix/scripts/import/cran.scm'.
  (SCM_TESTS): Add 'tests/cran.scm'.
* doc/guix.texi (Invoking guix import): Document it.
* po/guix/POTFILES.in: Add 'guix/scripts/import/cran.scm'.

3 files changed, 281 insertions, 1 deletions

diff --git a/guix/import/cran.scm b/guix/import/cran.scm
new file mode 100644
index 0000000000..8ed5e5407f
--- /dev/null
+++ b/guix/import/cran.scm
@@ -0,0 +1,188 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2015 Ricardo Wurmus <rekado@elephly.net>
+;;;
+;;; 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 (guix import cran)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
+  #:use-module (srfi srfi-1)
+  #:use-module (sxml simple)
+  #:use-module (sxml match)
+  #:use-module (sxml xpath)
+  #:use-module (guix http-client)
+  #:use-module (guix hash)
+  #:use-module (guix store)
+  #:use-module (guix base32)
+  #:use-module ((guix download) #:select (download-to-store))
+  #:use-module (guix import utils)
+  #:export (cran->guix-package))
+
+;;; Commentary:
+;;;
+;;; Generate a package declaration template for the latest version of an R
+;;; package on CRAN, using the HTML description downloaded from
+;;; cran.r-project.org.
+;;;
+;;; Code:
+
+(define string->license
+  (match-lambda
+   ("AGPL-3" 'agpl3+)
+   ("Artistic-2.0" 'artistic2.0)
+   ("Apache License 2.0" 'asl2.0)
+   ("BSD_2_clause" 'bsd-2)
+   ("BSD_3_clause" 'bsd-3)
+   ("GPL-2" 'gpl2+)
+   ("GPL-3" 'gpl3+)
+   ("LGPL-2" 'lgpl2.0+)
+   ("LGPL-2.1" 'lgpl2.1+)
+   ("LGPL-3" 'lgpl3+)
+   ("MIT" 'x11)
+   ((x) (string->license x))
+   ((lst ...) `(list ,@(map string->license lst)))
+   (_ #f)))
+
+(define (format-inputs names)
+  "Generate a sorted list of package inputs from a list of package NAMES."
+  (map (lambda (name)
+         (list name (list 'unquote (string->symbol name))))
+       (sort names string-ci<?)))
+
+(define* (maybe-inputs package-inputs #:optional (type 'inputs))
+  "Given a list of PACKAGE-INPUTS, tries to generate the TYPE field of a
+package definition."
+  (match package-inputs
+    (()
+     '())
+    ((package-inputs ...)
+     `((,type (,'quasiquote ,(format-inputs package-inputs)))))))
+
+(define (table-datum tree label)
+  "Extract the datum node following a LABEL in the sxml table TREE.  Only the
+first cell of a table row is considered a label cell."
+  ((node-pos 1)
+   ((sxpath `(xhtml:tr
+              (xhtml:td 1)        ; only first cell can contain label
+              (equal? ,label)
+              ,(node-parent tree) ; go up to label cell
+              ,(node-parent tree) ; go up to matching row
+              (xhtml:td 2)))      ; select second cell
+    tree)))
+
+(define %cran-url "http://cran.r-project.org/web/packages/")
+
+(define (cran-fetch name)
+  "Return an sxml representation of the CRAN page for the R package NAME,
+or #f on failure.  NAME is case-sensitive."
+  ;; This API always returns the latest release of the module.
+  (let ((cran-url (string-append %cran-url name)))
+    (false-if-exception
+     (xml->sxml (http-fetch cran-url)
+                #:trim-whitespace? #t
+                #:namespaces '((xhtml . "http://www.w3.org/1999/xhtml"))
+                #:default-entity-handler
+                (lambda (port name)
+                  (case name
+                    ((nbsp) " ")
+                    ((ge) ">=")
+                    ((gt) ">")
+                    ((lt) "<")
+                    (else
+                     (format (current-warning-port)
+                             "~a:~a:~a: undefined entitity: ~a\n"
+                             cran-url (port-line port) (port-column port)
+                             name)
+                     (symbol->string name))))))))
+
+(define (cran-sxml->sexp sxml)
+  "Return the `package' s-expression for a CRAN package from the SXML
+representation of the package page."
+  (define (nodes->text nodeset)
+    (string-join ((sxpath '(// *text*)) nodeset) " "))
+
+  (define (guix-name name)
+    (if (string-prefix? "r-" name)
+        (string-downcase name)
+        (string-append "r-" (string-downcase name))))
+
+  (sxml-match-let*
+   (((*TOP* (xhtml:html
+             ,head
+             (xhtml:body
+              (xhtml:h2 ,name-and-synopsis)
+              (xhtml:p ,description)
+              ,summary
+              (xhtml:h4 "Downloads:") ,downloads
+              . ,rest)))
+     sxml))
+   (let* ((name       (match:prefix (string-match ": " name-and-synopsis)))
+          (synopsis   (match:suffix (string-match ": " name-and-synopsis)))
+          (version    (nodes->text (table-datum summary "Version:")))
+          (license    ((compose string->license nodes->text)
+                       (table-datum summary "License:")))
+          (home-page  (nodes->text ((sxpath '((xhtml:a 1)))
+                                    (table-datum summary "URL:"))))
+          (source-url (string-append "mirror://cran/"
+                                     ;; Remove double dots, because we want an
+                                     ;; absolute path.
+                                     (regexp-substitute/global
+                                      #f "\\.\\./"
+                                      (string-join
+                                       ((sxpath '((xhtml:a 1) @ href *text*))
+                                        (table-datum downloads
+                                                     " Package source: ")))
+                                      'pre 'post)))
+          (tarball    (with-store store (download-to-store store source-url)))
+          (sysdepends (map match:substring
+                           (list-matches
+                            "[^ ]+"
+                            ;; Strip off comma and parenthetical
+                            ;; expressions.
+                            (regexp-substitute/global
+                             #f "(,|\\([^\\)]+\\))"
+                             (nodes->text (table-datum summary
+                                                       "SystemRequirements:"))
+                             'pre 'post))))
+          (imports    (map guix-name
+                           ((sxpath '(// xhtml:a *text*))
+                            (table-datum summary "Imports:")))))
+     `(package
+        (name ,(guix-name name))
+        (version ,version)
+        (source (origin
+                  (method url-fetch)
+                  (uri (string-append ,@(factorize-uri source-url version)))
+                  (sha256
+                   (base32
+                    ,(bytevector->nix-base32-string (file-sha256 tarball))))))
+        (build-system r-build-system)
+        ,@(maybe-inputs sysdepends)
+        ,@(maybe-inputs imports 'propagated-inputs)
+        (home-page ,(if (string-null? home-page)
+                        (string-append %cran-url name)
+                        home-page))
+        (synopsis ,synopsis)
+        ;; Use double spacing
+        (description ,(regexp-substitute/global #f "\\. \\b" description
+                                                'pre ".  " 'post))
+        (license ,license)))))
+
+(define (cran->guix-package package-name)
+  "Fetch the metadata for PACKAGE-NAME from cran.r-project.org, and return the
+`package' s-expression corresponding to that package, or #f on failure."
+  (let ((module-meta (cran-fetch package-name)))
+    (and=> module-meta cran-sxml->sexp)))
diff --git a/guix/scripts/import.scm b/guix/scripts/import.scm
index 6cd762a537..7b29794e8f 100644
--- a/guix/scripts/import.scm
+++ b/guix/scripts/import.scm
@@ -73,7 +73,7 @@ rather than \\n."
 ;;; Entry point.
 ;;;
 
-(define importers '("gnu" "nix" "pypi" "cpan" "hackage" "elpa" "gem"))
+(define importers '("gnu" "nix" "pypi" "cpan" "hackage" "elpa" "gem" "cran"))
 
 (define (resolve-importer name)
   (let ((module (resolve-interface
diff --git a/guix/scripts/import/cran.scm b/guix/scripts/import/cran.scm
new file mode 100644
index 0000000000..f11fa1004f
--- /dev/null
+++ b/guix/scripts/import/cran.scm
@@ -0,0 +1,92 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
+;;; Copyright © 2015 Ricardo Wurmus <rekado@elephly.net>
+;;;
+;;; 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 (guix scripts import cran)
+  #:use-module (guix ui)
+  #:use-module (guix utils)
+  #:use-module (guix import cran)
+  #:use-module (guix scripts import)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-37)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 format)
+  #:export (guix-import-cran))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  '())
+
+(define (show-help)
+  (display (_ "Usage: guix import cran PACKAGE-NAME
+Import and convert the CRAN package for PACKAGE-NAME.\n"))
+  (display (_ "
+  -h, --help             display this help and exit"))
+  (display (_ "
+  -V, --version          display version information and exit"))
+  (newline)
+  (show-bug-report-information))
+
+(define %options
+  ;; Specification of the command-line options.
+  (cons* (option '(#\h "help") #f #f
+                 (lambda args
+                   (show-help)
+                   (exit 0)))
+         (option '(#\V "version") #f #f
+                 (lambda args
+                   (show-version-and-exit "guix import cran")))
+         %standard-import-options))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-import-cran . args)
+  (define (parse-options)
+    ;; Return the alist of option values.
+    (args-fold* args %options
+                (lambda (opt name arg result)
+                  (leave (_ "~A: unrecognized option~%") name))
+                (lambda (arg result)
+                  (alist-cons 'argument arg result))
+                %default-options))
+
+  (let* ((opts (parse-options))
+         (args (filter-map (match-lambda
+                            (('argument . value)
+                             value)
+                            (_ #f))
+                           (reverse opts))))
+    (match args
+      ((package-name)
+       (let ((sexp (cran->guix-package package-name)))
+         (unless sexp
+           (leave (_ "failed to download description for package '~a'~%")
+                  package-name))
+         sexp))
+      (()
+       (leave (_ "too few arguments~%")))
+      ((many ...)
+       (leave (_ "too many arguments~%"))))))