import: Add CPAN importer.

* guix/import/cpan.scm, guix/scripts/import/cpan.scm, tests/cpan.scm:
  New files.
* Makefile.am (MODULE)[HAVE_GUILE_JSON]: Add them.
* guix/scripts/import.scm (importers): Add cpan.
* doc/guix.texi (Requirements): Mention `guix import cpan` as a user
  of guile-json.
  (Invoking guix import): Document new `guix import cpan` command.

3 files changed, 259 insertions, 1 deletions

diff --git a/guix/import/cpan.scm b/guix/import/cpan.scm
new file mode 100644
index 0000000000..5f4602a8d2
--- /dev/null
+++ b/guix/import/cpan.scm
@@ -0,0 +1,167 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.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 (guix import cpan)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
+  #:use-module (srfi srfi-1)
+  #:use-module (json)
+  #: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)
+  #:use-module (guix import json)
+  #:export (cpan->guix-package))
+
+;;; Commentary:
+;;;
+;;; Generate a package declaration template for the latest version of a CPAN
+;;; module, using meta-data from metacpan.org.
+;;;
+;;; Code:
+
+(define string->license
+  (match-lambda
+   ;; List of valid values from https://metacpan.org/pod/CPAN::Meta::Spec.
+   ;; Some licenses are excluded based on their absense from (guix licenses).
+   ("agpl_3" 'agpl3)
+   ;; apache_1_1
+   ("apache_2_0" 'asl2.0)
+   ;; artistic_1_0
+   ;; artistic_2_0
+   ("bsd" 'bsd-3)
+   ("freebsd" 'bsd-2)
+   ;; gfdl_1_2
+   ("gfdl_1_3" 'fdl1.3+)
+   ("gpl_1" 'gpl1)
+   ("gpl_2" 'gpl2)
+   ("gpl_3" 'gpl3)
+   ("lgpl_2_1" 'lgpl2.1)
+   ("lgpl_3_0" 'lgpl3)
+   ("mit" 'x11)
+   ;; mozilla_1_0
+   ("mozilla_1_1" 'mpl1.1)
+   ("openssl" 'openssl)
+   ("perl_5" 'gpl1+)                    ;and Artistic 1
+   ("qpl_1_0" 'qpl)
+   ;; ssleay
+   ;; sun
+   ("zlib" 'zlib)
+   ((x) (string->license x))
+   ((lst ...) `(list ,@(map string->license lst)))
+   (_ #f)))
+
+(define (module->name module)
+  "Transform a 'module' name into a 'release' name"
+  (regexp-substitute/global #f "::" module 'pre "-" 'post))
+
+(define (cpan-fetch module)
+  "Return an alist representation of the CPAN metadata for the perl module MODULE,
+or #f on failure.  MODULE should be e.g. \"Test::Script\""
+  ;; This API always returns the latest release of the module.
+  (json-fetch (string-append "http://api.metacpan.org/release/"
+                             ;; XXX: The 'release' api requires the "release"
+                             ;; name of the package.  This substitution seems
+                             ;; reasonably consistent across packages.
+                             (module->name module))))
+
+(define (cpan-home name)
+  (string-append "http://search.cpan.org/dist/" name))
+
+(define (cpan-module->sexp meta)
+  "Return the `package' s-expression for a CPAN module from the metadata in
+META."
+  (define name
+    (assoc-ref meta "distribution"))
+
+  (define (guix-name name)
+    (if (string-prefix? "perl-" name)
+        (string-downcase name)
+        (string-append "perl-" (string-downcase name))))
+
+  (define version
+    (assoc-ref meta "version"))
+
+  (define (convert-inputs phases)
+    ;; Convert phase dependencies into a list of name/variable pairs.
+    (match (flatten
+            (map (lambda (ph)
+                   (filter-map (lambda (t)
+                                 (assoc-ref* meta "metadata" "prereqs" ph t))
+                               '("requires" "recommends" "suggests")))
+                 phases))
+      (#f
+       '())
+      ((inputs ...)
+       (delete-duplicates
+        ;; Listed dependencies may include core modules.  Filter those out.
+        (filter-map (match-lambda
+                     ((or (module . "0") ("perl" . _))
+                      ;; TODO: A stronger test might to run MODULE through
+                      ;; `corelist' from our perl package.  This current test
+                      ;; seems to be only a loose convention.
+                      #f)
+                     ((module . _)
+                      (let ((name (guix-name (module->name module))))
+                        (list name
+                              (list 'unquote (string->symbol name))))))
+                    inputs)))))
+
+  (define (maybe-inputs guix-name inputs)
+    (match inputs
+      (()
+       '())
+      ((inputs ...)
+       (list (list guix-name
+                   (list 'quasiquote inputs))))))
+
+  (define source-url
+    (assoc-ref meta "download_url"))
+
+  (let ((tarball (with-store store
+                   (download-to-store store source-url))))
+    `(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 perl-build-system)
+       ,@(maybe-inputs 'native-inputs
+                       ;; "runtime" and "test" may also be needed here.  See
+                       ;; https://metacpan.org/pod/CPAN::Meta::Spec#Phases,
+                       ;; which says they are required during building.  We
+                       ;; have not yet had a need for cross-compiled perl
+                       ;; modules, however, so we leave them out.
+                       (convert-inputs '("configure" "build")))
+       ,@(maybe-inputs 'inputs
+                       (convert-inputs '("runtime")))
+       (home-page ,(string-append "http://search.cpan.org/dist/" name))
+       (synopsis ,(assoc-ref meta "abstract"))
+       (description fill-in-yourself!)
+       (license ,(string->license (assoc-ref meta "license"))))))
+
+(define (cpan->guix-package module-name)
+  "Fetch the metadata for PACKAGE-NAME from metacpan.org, and return the
+`package' s-expression corresponding to that package, or #f on failure."
+  (let ((module-meta (cpan-fetch module-name)))
+    (and=> module-meta cpan-module->sexp)))
diff --git a/guix/scripts/import.scm b/guix/scripts/import.scm
index 86ef05bc2c..7e75c10b3e 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"))
+(define importers '("gnu" "nix" "pypi" "cpan"))
 
 (define (resolve-importer name)
   (let ((module (resolve-interface
diff --git a/guix/scripts/import/cpan.scm b/guix/scripts/import/cpan.scm
new file mode 100644
index 0000000000..1f4dedf23f
--- /dev/null
+++ b/guix/scripts/import/cpan.scm
@@ -0,0 +1,91 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.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 (guix scripts import cpan)
+  #:use-module (guix ui)
+  #:use-module (guix utils)
+  #:use-module (guix import cpan)
+  #: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-cpan))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  '())
+
+(define (show-help)
+  (display (_ "Usage: guix import cpan PACKAGE-NAME
+Import and convert the CPAN 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 cpan")))
+         %standard-import-options))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-import-cpan . 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 (cpan->guix-package package-name)))
+         (unless sexp
+           (leave (_ "failed to download meta-data for package '~a'~%")
+                  package-name))
+         sexp))
+      (()
+       (leave (_ "too few arguments~%")))
+      ((many ...)
+       (leave (_ "too many arguments~%"))))))