;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017, 2019, 2021 Ludovic Courtès <ludo@gnu.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 gnome)
  #:use-module (guix upstream)
  #:use-module (guix utils)
  #:use-module (guix packages)
  #:use-module (guix http-client)
  #:use-module (json)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-11)
  #:use-module (srfi srfi-34)
  #:use-module (web uri)
  #:use-module (ice-9 match)
  #:export (%gnome-updater))

;;; Commentary:
;;;
;;; This package provides not an actual importer but simply an updater for
;;; GNOME packages.  It grabs package meta-data from 'cache.json' files
;;; available on ftp.gnome.org.
;;;
;;; Code:

(define (jsonish->upstream-source name jsonish)
  "Return an <upstream-source> object for package NAME, using JSONISH as the
source for metadata."
  (match jsonish
    ((version . dictionary)
     (upstream-source
      (package name)
      (version version)
      (urls (filter-map (lambda (extension)
                          (match (assoc-ref dictionary extension)
                            (#f
                             #f)
                            ((? string? relative-url)
                             (string-append "mirror://gnome/sources/"
                                            name "/" relative-url))))
                        '("tar.lz" "tar.xz" "tar.bz2" "tar.gz")))))))

(define (latest-gnome-release package)
  "Return the latest release of PACKAGE, a GNOME package, or #f if it could
not be determined."
  (define %not-dot
    (char-set-complement (char-set #\.)))

  (define (even-minor-version? version)
    (match (string-tokenize version %not-dot)
      (((= string->number major) (= string->number minor) (= string->number micro))
       ;; This is for things like GLib, with version strings like "2.72.3".
       (and minor (even? minor) micro))
      (((= string->number major) (= string->number minor))
       ;; GNOME applications have version strings like "42.1" (only two
       ;; integers) and are not subject to the odd/even policy.  MAJOR and
       ;; MINOR should be valid numbers though; "43.alpha" is rejected.
       (and major minor))
      (_
       #f)))

  (define upstream-name
    ;; Some packages like "NetworkManager" have camel-case names.
    (package-upstream-name package))

  (guard (c ((http-get-error? c)
             (if (= 404 (http-get-error-code c))
                 #f
                 (raise c))))
    (let* ((port (http-fetch/cached
                  (string->uri (string-append
                                "https://ftp.gnome.org/pub/gnome/sources/"
                                upstream-name "/cache.json"))

                  ;; ftp.gnome.org supports 'if-Modified-Since', so the local
                  ;; cache can expire early.
                  #:ttl (* 60 10)

                  ;; Hide messages about URL redirects.
                  #:log-port (%make-void-port "w")))
           (json (json->scm port)))
      (close-port port)
      (match json
        (#(4 releases _ ...)
         (let* ((releases (assoc-ref releases upstream-name))
                (latest   (fold (match-lambda*
                                  (((key . value) result)
                                   (cond ((even-minor-version? key)
                                          (match result
                                            (#f
                                             (cons key value))
                                            ((newest . _)
                                             (if (version>? key newest)
                                                 (cons key value)
                                                 result))))
                                         (else
                                          result))))
                                #f
                                releases)))
           (and latest
                (jsonish->upstream-source upstream-name latest))))))))

(define %gnome-updater
  (upstream-updater
   (name 'gnome)
   (description "Updater for GNOME packages")
   (pred (url-prefix-predicate "mirror://gnome/"))
   (latest latest-gnome-release)))
