guix: Add ContentDB importer.

* guix/import/contentdb.scm: New file.
* guix/scripts/import/contentdb.scm: New file.
* tests/contentdb.scm: New file.
* Makefile.am (MODULES, SCM_TESTS): Register them.
* po/guix/POTFILES.in: Likewise.
* doc/guix.texi (Invoking guix import): Document it.

Signed-off-by: Leo Prikler <leo.prikler@student.tugraz.at>

7 files changed, 966 insertions, 1 deletions

diff --git a/Makefile.am b/Makefile.am
index 344b7423c5..327d3f9961 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -262,6 +262,7 @@ MODULES =					\
   guix/import/json.scm				\
   guix/import/kde.scm				\
   guix/import/launchpad.scm   			\
+  guix/import/minetest.scm   			\
   guix/import/opam.scm				\
   guix/import/print.scm				\
   guix/import/pypi.scm				\
@@ -304,6 +305,7 @@ MODULES =					\
   guix/scripts/import/go.scm			\
   guix/scripts/import/hackage.scm		\
   guix/scripts/import/json.scm  		\
+  guix/scripts/import/minetest.scm  		\
   guix/scripts/import/opam.scm			\
   guix/scripts/import/pypi.scm			\
   guix/scripts/import/stackage.scm		\
@@ -470,6 +472,7 @@ SCM_TESTS =					\
   tests/import-utils.scm			\
   tests/inferior.scm				\
   tests/lint.scm				\
+  tests/minetest.scm				\
   tests/modules.scm				\
   tests/monads.scm				\
   tests/nar.scm				\
diff --git a/doc/guix.texi b/doc/guix.texi
index d6197d3743..241a1824ec 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -11314,6 +11314,38 @@ and generate package expressions for all those packages that are not yet
 in Guix.
 @end table
 
+@item contentdb
+@cindex minetest
+@cindex ContentDB
+Import metadata from @uref{https://content.minetest.net, ContentDB}.
+Information is taken from the JSON-formatted metadata provided through
+@uref{https://content.minetest.net/help/api/, ContentDB's API} and
+includes most relevant information, including dependencies.  There are
+some caveats, however.  The license information is often incomplete.
+The commit hash is sometimes missing.  The descriptions are in the
+Markdown format, but Guix uses Texinfo instead.  Texture packs and
+subgames are unsupported.
+
+The command below imports metadata for the Mesecons mod by Jeija:
+
+@example
+guix import minetest Jeija/mesecons
+@end example
+
+The author name can also be left out:
+
+@example
+guix import minetest mesecons
+@end example
+
+@table @code
+@item --recursive
+@itemx -r
+Traverse the dependency graph of the given upstream package recursively
+and generate package expressions for all those packages that are not yet
+in Guix.
+@end table
+
 @item cpan
 @cindex CPAN
 Import metadata from @uref{https://www.metacpan.org/, MetaCPAN}.
diff --git a/guix/import/minetest.scm b/guix/import/minetest.scm
new file mode 100644
index 0000000000..e1f8487b75
--- /dev/null
+++ b/guix/import/minetest.scm
@@ -0,0 +1,456 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
+;;;
+;;; 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 minetest)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 receive)
+  #:use-module (ice-9 threads)
+  #:use-module (ice-9 hash-table)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-2)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-26)
+  #:use-module (guix utils)
+  #:use-module (guix ui)
+  #:use-module (guix i18n)
+  #:use-module (guix memoization)
+  #:use-module (guix serialization)
+  #:use-module (guix import utils)
+  #:use-module (guix import json)
+  #:use-module ((gcrypt hash) #:select (open-sha256-port port-sha256))
+  #:use-module (json)
+  #:use-module (guix base32)
+  #:use-module (guix git)
+  #:use-module (guix store)
+  #:export (%default-sort-key
+            %contentdb-api
+            json->package
+            contentdb-fetch
+            elaborate-contentdb-name
+            minetest->guix-package
+            minetest-recursive-import
+            sort-packages))
+
+;; The ContentDB API is documented at
+;; <https://content.minetest.net>.
+
+(define %contentdb-api
+  (make-parameter "https://content.minetest.net/api/"))
+
+(define (string-or-false x)
+  (and (string? x) x))
+
+(define (natural-or-false x)
+  (and (exact-integer? x) (>= x 0) x))
+
+;; Descriptions on ContentDB use carriage returns, but Guix doesn't.
+(define (delete-cr text)
+  (string-delete #\cr text))
+
+
+
+;;;
+;;; JSON mappings
+;;;
+
+;; Minetest package.
+;;
+;; API endpoint: /packages/AUTHOR/NAME/
+(define-json-mapping <package> make-package package?
+  json->package
+  (author            package-author) ; string
+  (creation-date     package-creation-date ; string
+                     "created_at")
+  (downloads         package-downloads) ; integer
+  (forums            package-forums "forums" natural-or-false)
+  (issue-tracker     package-issue-tracker "issue_tracker") ; string
+  (license           package-license) ; string
+  (long-description  package-long-description "long_description") ; string
+  (maintainers       package-maintainers ; list of strings
+                     "maintainers" vector->list)
+  (media-license     package-media-license "media_license") ; string
+  (name              package-name) ; string
+  (provides          package-provides ; list of strings
+                     "provides" vector->list)
+  (release           package-release) ; integer
+  (repository        package-repository "repo" string-or-false)
+  (score             package-score) ; flonum
+  (screenshots       package-screenshots "screenshots" vector->list) ; list of strings
+  (short-description package-short-description "short_description") ; string
+  (state             package-state) ; string
+  (tags              package-tags "tags" vector->list) ; list of strings
+  (thumbnail         package-thumbnail) ; string
+  (title             package-title) ; string
+  (type              package-type) ; string
+  (url               package-url) ; string
+  (website           package-website "website" string-or-false))
+
+(define-json-mapping <release> make-release release?
+  json->release
+  ;; If present, a git commit identified by its hash
+  (commit               release-commit "commit" string-or-false)
+  (downloads            release-downloads) ; integer
+  (id                   release-id) ; integer
+  (max-minetest-version release-max-minetest-version string-or-false)
+  (min-minetest-version release-min-minetest-version string-or-false)
+  (release-date         release-data) ; string
+  (title                release-title) ; string
+  (url                  release-url)) ; string
+
+(define-json-mapping <dependency> make-dependency dependency?
+  json->dependency
+  (optional? dependency-optional? "is_optional") ; bool
+  (name dependency-name) ; string
+  (packages dependency-packages "packages" vector->list)) ; list of strings
+
+;; A structure returned by the /api/packages/?fmt=keys endpoint
+(define-json-mapping <package-keys> make-package-keys package-keys?
+  json->package-keys
+  (author package-keys-author) ; string
+  (name package-keys-name)     ; string
+  (type package-keys-type))    ; string
+
+(define (package-mod? package)
+  "Is the ContentDB package PACKAGE a mod?"
+  ;; ContentDB also has ‘games’ and ‘texture packs’.
+  (string=? (package-type package) "mod"))
+
+
+
+;;;
+;;; Manipulating names of packages
+;;;
+;;; There are three kind of names:
+;;;
+;;;   * names of guix packages, e.g. minetest-basic-materials.
+;;;   * names of mods on ContentDB, e.g. basic_materials
+;;;   * a combination of author and mod name on ContentDB, e.g. VanessaE/basic_materials
+;;;
+
+(define (%construct-full-name author name)
+  (string-append author "/" name))
+
+(define (package-full-name package)
+  "Given a <package> object, return the corresponding AUTHOR/NAME string."
+  (%construct-full-name (package-author package) (package-name package)))
+
+(define (package-keys-full-name package)
+  "Given a <package-keys> object, return the corresponding AUTHOR/NAME string."
+  (%construct-full-name (package-keys-author package)
+                        (package-keys-name package)))
+
+(define (contentdb->package-name author/name)
+  "Given the AUTHOR/NAME of a package on ContentDB, return a Guix-compliant
+name for the package."
+  ;; The author is not included, as the names of popular mods
+  ;; tend to be unique.
+  (string-append "minetest-" (snake-case (author/name->name author/name))))
+
+(define (author/name->name author/name)
+  "Extract NAME from the AUTHOR/NAME string, or raise an error if AUTHOR/NAME
+is ill-formatted."
+  (match (string-split author/name #\/)
+    ((author name)
+     (when (string-null? author)
+       (leave
+        (G_ "In ~a: author names must consist of at least a single character.~%")
+        author/name))
+     (when (string-null? name)
+       (leave
+        (G_ "In ~a: mod names must consist of at least a single character.~%")
+        author/name))
+     name)
+    ((too many . components)
+     (leave
+      (G_ "In ~a: author names and mod names may not contain forward slashes.~%")
+      author/name))
+    ((name)
+     (if (string-null? name)
+         (leave (G_ "mod names may not be empty.~%"))
+         (leave (G_ "The name of the author is missing in ~a.~%")
+                author/name)))))
+
+(define* (elaborate-contentdb-name name #:key (sort %default-sort-key))
+  "If NAME is an AUTHOR/NAME string, return it.  Otherwise, try to determine
+the author and return an appropriate AUTHOR/NAME string.  If that fails,
+raise an exception."
+  (if (or (string-contains name "/") (string-null? name))
+      ;; Call 'author/name->name' to verify that NAME seems reasonable
+      ;; and raise an appropriate exception if it isn't.
+      (begin
+        (author/name->name name)
+        name)
+      (let* ((package-keys (contentdb-query-packages name #:sort sort))
+             (correctly-named
+              (filter (lambda (package-key)
+                        (string=? name (package-keys-name package-key)))
+                      package-keys)))
+        (match correctly-named
+          ((one) (package-keys-full-name one))
+          ((too . many)
+           (warning (G_ "~a is ambigious, presuming ~a (other options include: ~a)~%")
+                    name (package-keys-full-name too)
+                    (map package-keys-full-name many))
+           (package-keys-full-name too))
+          (()
+           (leave (G_ "No mods with name ~a were found.~%") name))))))
+
+
+
+;;;
+;;; API endpoints
+;;;
+
+(define contentdb-fetch
+  (mlambda (author/name)
+    "Return a <package> record for package AUTHOR/NAME, or #f on failure."
+    (and=> (json-fetch
+            (string-append (%contentdb-api) "packages/" author/name "/"))
+           json->package)))
+
+(define (contentdb-fetch-releases author/name)
+  "Return a list of <release> records for package NAME by AUTHOR, or #f
+on failure."
+  (and=> (json-fetch (string-append (%contentdb-api) "packages/" author/name
+                                    "/releases/"))
+         (lambda (json)
+           (map json->release (vector->list json)))))
+
+(define (latest-release author/name)
+  "Return the latest source release for package NAME by AUTHOR,
+or #f if this package does not exist."
+  (and=> (contentdb-fetch-releases author/name)
+         car))
+
+(define (contentdb-fetch-dependencies author/name)
+  "Return an alist of lists of <dependency> records for package NAME by AUTHOR
+and possibly some other packages as well, or #f on failure."
+  (define url (string-append (%contentdb-api) "packages/" author/name
+                             "/dependencies/"))
+  (and=> (json-fetch url)
+         (lambda (json)
+           (map (match-lambda
+                  ((key . value)
+                   (cons key (map json->dependency (vector->list value)))))
+                json))))
+
+(define* (contentdb-query-packages q #:key
+                                   (type "mod")
+                                   (limit 50)
+                                   (sort %default-sort-key)
+                                   (order "desc"))
+  "Search ContentDB for Q (a string).  Sort by SORT, in ascending order
+if ORDER is \"asc\" or descending order if ORDER is \"desc\".  TYPE must
+be \"mod\", \"game\" or \"txp\", restricting thes search results to
+respectively mods, games and texture packs.  Limit to at most LIMIT
+results.  The return value is a list of <package-keys> records."
+  ;; XXX does Guile have something for constructing (and, when necessary,
+  ;; escaping) query strings?
+  (define url (string-append (%contentdb-api) "packages/?type=" type
+                             "&q=" q "&fmt=keys"
+                             "&limit=" (number->string limit)
+                             "&order=" order
+                             "&sort=" sort))
+  (let ((json (json-fetch url)))
+    (if json
+        (map json->package-keys (vector->list json))
+        (leave
+         (G_ "The package search API doesn't exist anymore.~%")))))
+
+
+
+;; XXX copied from (guix import elpa)
+(define* (download-git-repository url ref)
+  "Fetch the given REF from the Git repository at URL."
+  (with-store store
+    (latest-repository-commit store url #:ref ref)))
+
+;; XXX adapted from (guix scripts hash)
+(define (file-hash file)
+  "Compute the hash of FILE."
+  (let-values (((port get-hash) (open-sha256-port)))
+    (write-file file port)
+    (force-output port)
+    (get-hash)))
+
+(define (make-minetest-sexp author/name version repository commit
+                            inputs home-page synopsis
+                            description media-license license)
+  "Return a S-expression for the minetest package with the given author/NAME,
+VERSION, REPOSITORY, COMMIT, INPUTS, HOME-PAGE, SYNOPSIS, DESCRIPTION,
+MEDIA-LICENSE and LICENSE."
+  `(package
+     (name ,(contentdb->package-name author/name))
+     (version ,version)
+     (source
+       (origin
+         (method git-fetch)
+         (uri (git-reference
+                (url ,repository)
+                (commit ,commit)))
+         (sha256
+          (base32
+           ;; The git commit is not always available.
+           ,(and commit
+                 (bytevector->nix-base32-string
+                  (file-hash
+                   (download-git-repository repository
+                                            `(commit . ,commit)))))))
+         (file-name (git-file-name name version))))
+     (build-system minetest-mod-build-system)
+     ,@(maybe-propagated-inputs (map contentdb->package-name inputs))
+     (home-page ,home-page)
+     (synopsis ,(delete-cr synopsis))
+     (description ,(delete-cr description))
+     (license ,(if (eq? media-license license)
+                   license
+                   `(list ,media-license ,license)))
+     ;; The Minetest updater (not yet in Guix; it requires not-yet-submitted
+     ;; patches to (guix upstream) that require some work) needs to know both
+     ;; the author name and mod name for efficiency.
+     (properties ,(list 'quasiquote `((upstream-name . ,author/name))))))
+
+(define (package-home-page package)
+  "Guess the home page of the ContentDB package PACKAGE.
+
+In order of preference, try the 'website', the forum topic on the
+official Minetest forum and the Git repository (if any)."
+  (define (topic->url-sexp topic)
+    ;; 'minetest-topic' is a procedure defined in (gnu packages minetest)
+    `(minetest-topic ,topic))
+  (or (package-website package)
+      (and=> (package-forums package) topic->url-sexp)
+      (package-repository package)))
+
+;; If the default sort key is changed, make sure to modify 'show-help'
+;; in (guix scripts import minetest) appropriately as well.
+(define %default-sort-key "score")
+
+(define* (sort-packages packages #:key (sort %default-sort-key))
+  "Sort PACKAGES by SORT, in descending order."
+  (define package->key
+    (match sort
+      ("score" package-score)
+      ("downloads" package-downloads)))
+  (define (greater x y)
+    (> (package->key x) (package->key y)))
+  (sort-list packages greater))
+
+(define builtin-mod?
+  (let ((%builtin-mods
+         (alist->hash-table
+          (map (lambda (x) (cons x #t))
+               '("beds" "binoculars" "boats" "bones" "bucket" "butterflies"
+                 "carts" "creative" "default" "doors" "dungeon_loot" "dye"
+                 "env_sounds" "farming" "fire" "fireflies" "flowers"
+                 "game_commands" "give_initial_stuff" "map" "mtg_craftguide"
+                 "player_api" "screwdriver" "sethome" "sfinv" "spawn" "stairs"
+                 "tnt" "vessels" "walls" "weather" "wool" "xpanes")))))
+    (lambda (mod)
+      "Is MOD provided by the default minetest subgame?"
+      (hash-ref %builtin-mods mod))))
+
+(define* (important-dependencies dependencies author/name
+                                 #:key (sort %default-sort-key))
+  "Return the hard dependencies of AUTHOR/NAME in the association list
+DEPENDENCIES as a list of AUTHOR/NAME strings."
+  (define dependency-list
+    (assoc-ref dependencies author/name))
+  (filter-map
+   (lambda (dependency)
+     (and (not (dependency-optional? dependency))
+          (not (builtin-mod? (dependency-name dependency)))
+          ;; The dependency information contains symbolic names
+          ;; that can be ‘provided’ by multiple mods, so we need to choose one
+          ;; of the implementations.
+          (let* ((implementations
+                  (par-map contentdb-fetch (dependency-packages dependency)))
+                 ;; Fetching package information about the packages is racy:
+                 ;; some packages might be removed from ContentDB between the
+                 ;; construction of DEPENDENCIES and the call to
+                 ;; 'contentdb-fetch'.  So filter out #f.
+                 ;;
+                 ;; Filter out ‘games’ that include the requested mod -- it's
+                 ;; the mod itself we want.
+                 (mods (filter (lambda (p) (and=> p package-mod?))
+                               implementations))
+                 (sorted-mods (sort-packages mods #:sort sort)))
+            (match sorted-mods
+              ((package) (package-full-name package))
+              ((too . many)
+               (warning
+                (G_ "The dependency ~a of ~a has multiple different implementations ~a.~%")
+                (dependency-name dependency)
+                author/name
+                (map package-full-name sorted-mods))
+               (match sort
+                 ("score"
+                  (warning
+                   (G_ "The implementation with the highest score will be choosen!~%")))
+                 ("downloads"
+                  (warning
+                   (G_ "The implementation that has been downloaded the most will be choosen!~%"))))
+               (package-full-name too))
+              (()
+               (warning
+                (G_ "The dependency ~a of ~a does not have any implementation.  It will be ignored!~%")
+                (dependency-name dependency) author/name)
+               #f)))))
+   dependency-list))
+
+(define* (%minetest->guix-package author/name #:key (sort %default-sort-key))
+  "Fetch the metadata for AUTHOR/NAME from https://content.minetest.net, and
+return the 'package' S-expression corresponding to that package, or raise an
+exception on failure.  On success, also return the upstream dependencies as a
+list of AUTHOR/NAME strings."
+  ;; Call 'author/name->name' to verify that AUTHOR/NAME seems reasonable.
+  (author/name->name author/name)
+  (define package (contentdb-fetch author/name))
+  (unless package
+    (leave (G_ "no package metadata for ~a on ContentDB~%") author/name))
+  (define dependencies (contentdb-fetch-dependencies author/name))
+  (unless dependencies
+    (leave (G_ "no dependency information for ~a on ContentDB~%") author/name))
+  (define release (latest-release author/name))
+  (unless release
+    (leave (G_ "no release of ~a on ContentDB~%") author/name))
+  (define important-upstream-dependencies
+    (important-dependencies dependencies author/name #:sort sort))
+  (values (make-minetest-sexp author/name
+                              (release-title release) ; version
+                              (package-repository package)
+                              (release-commit release)
+                              important-upstream-dependencies
+                              (package-home-page package)
+                              (package-short-description package)
+                              (package-long-description package)
+                              (spdx-string->license
+                               (package-media-license package))
+                              (spdx-string->license
+                               (package-license package)))
+          important-upstream-dependencies))
+
+(define minetest->guix-package
+  (memoize %minetest->guix-package))
+
+(define* (minetest-recursive-import author/name #:key (sort %default-sort-key))
+  (define* (minetest->guix-package* author/name #:key repo version)
+    (minetest->guix-package author/name #:sort sort))
+  (recursive-import author/name
+                    #:repo->guix-package minetest->guix-package*
+                    #:guix-name contentdb->package-name))
diff --git a/guix/scripts/import.scm b/guix/scripts/import.scm
index f53d1ac1f4..b369a362d0 100644
--- a/guix/scripts/import.scm
+++ b/guix/scripts/import.scm
@@ -77,7 +77,8 @@ rather than \\n."
 ;;;
 
 (define importers '("gnu" "pypi" "cpan" "hackage" "stackage" "egg" "elpa"
-                    "gem" "go" "cran" "crate" "texlive" "json" "opam"))
+                    "gem" "go" "cran" "crate" "texlive" "json" "opam"
+                    "minetest"))
 
 (define (resolve-importer name)
   (let ((module (resolve-interface
diff --git a/guix/scripts/import/minetest.scm b/guix/scripts/import/minetest.scm
new file mode 100644
index 0000000000..5f204d90fc
--- /dev/null
+++ b/guix/scripts/import/minetest.scm
@@ -0,0 +1,117 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 David Thompson <davet@gnu.org>
+;;; Copyright © 2018 Ricardo Wurmus <rekado@elephly.net>
+;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
+;;;
+;;; 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 minetest)
+  #:use-module (guix ui)
+  #:use-module (guix utils)
+  #:use-module (guix scripts)
+  #:use-module (guix import minetest)
+  #:use-module (guix import utils)
+  #: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-minetest))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  `((sort . ,%default-sort-key)))
+
+(define (show-help)
+  (display (G_ "Usage: guix import minetest AUTHOR/NAME
+Import and convert the Minetest mod NAME by AUTHOR from ContentDB.\n"))
+  (display (G_ "
+  -h, --help             display this help and exit"))
+  (display (G_ "
+  -r, --recursive        import packages recursively"))
+  (display (G_ "
+  -V, --version          display version information and exit"))
+  (display (G_ "
+      --sort=KEY         when choosing between multiple implementations,
+                         choose the one with the highest value for KEY
+                         (one of \"score\" (standard) or \"downloads\")"))
+  (newline)
+  (show-bug-report-information))
+
+(define (verify-sort-order sort)
+  "Verify SORT can be used to sort mods by."
+  (unless (member sort '("score" "downloads" "reviews"))
+    (leave (G_ "~a: not a valid key to sort by~%") sort))
+  sort)
+
+(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 minetest")))
+         (option '(#\r "recursive") #f #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'recursive #t result)))
+         (option '("sort") #t #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'sort (verify-sort-order arg) result)))
+         %standard-import-options))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-import-minetest . args)
+  (define (parse-options)
+    ;; Return the alist of option values.
+    (args-fold* args %options
+                (lambda (opt name arg result)
+                  (leave (G_ "~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
+      ((name)
+       (with-error-handling
+         (let* ((sort (assoc-ref opts 'sort))
+                (author/name (elaborate-contentdb-name name #:sort sort)))
+           (if (assoc-ref opts 'recursive)
+               ;; Recursive import
+               (filter-map package->definition
+                           (minetest-recursive-import author/name #:sort sort))
+               ;; Single import
+               (minetest->guix-package author/name #:sort sort)))))
+      (()
+       (leave (G_ "too few arguments~%")))
+      ((many ...)
+       (leave (G_ "too many arguments~%"))))))
diff --git a/po/guix/POTFILES.in b/po/guix/POTFILES.in
index 14324b25de..1eee82be53 100644
--- a/po/guix/POTFILES.in
+++ b/po/guix/POTFILES.in
@@ -60,6 +60,7 @@ guix/scripts/git.scm
 guix/scripts/git/authenticate.scm
 guix/scripts/hash.scm
 guix/scripts/import.scm
+guix/scripts/import/contentdb.scm
 guix/scripts/import/cran.scm
 guix/scripts/import/elpa.scm
 guix/scripts/pull.scm
diff --git a/tests/minetest.scm b/tests/minetest.scm
new file mode 100644
index 0000000000..6ae476fe5f
--- /dev/null
+++ b/tests/minetest.scm
@@ -0,0 +1,355 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
+;;;
+;;; 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 (test-minetest)
+  #:use-module (guix memoization)
+  #:use-module (guix import minetest)
+  #:use-module (guix import utils)
+  #:use-module (guix tests)
+  #:use-module (json)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:use-module (srfi srfi-34)
+  #:use-module (srfi srfi-64))
+
+
+;; Some procedures for populating a ‘fake’ ContentDB server.
+
+(define* (make-package-sexp #:key
+                            (guix-name "minetest-foo")
+                            (home-page "https://example.org/foo")
+                            (repo "https://example.org/foo.git")
+                            (synopsis "synopsis")
+                            (guix-description "description")
+                            (guix-license
+                             '(list license:cc-by-sa4.0 license:lgpl3+))
+                            (inputs '())
+                            (upstream-name "Author/foo")
+                            #:allow-other-keys)
+  `(package
+     (name ,guix-name)
+     ;; This is not a proper version number but ContentDB does not include
+     ;; version numbers.
+     (version "2021-07-25")
+     (source
+      (origin
+        (method git-fetch)
+        (uri (git-reference
+              (url ,(and (not (eq? repo 'null)) repo))
+              (commit #f)))
+        (sha256
+         (base32 #f))
+        (file-name (git-file-name name version))))
+     (build-system minetest-mod-build-system)
+     ,@(maybe-propagated-inputs inputs)
+     (home-page ,home-page)
+     (synopsis ,synopsis)
+     (description ,guix-description)
+     (license ,guix-license)
+     (properties
+      ,(list 'quasiquote
+             `((upstream-name . ,upstream-name))))))
+
+(define* (make-package-json #:key
+                            (author "Author")
+                            (name "foo")
+                            (media-license "CC-BY-SA-4.0")
+                            (license "LGPL-3.0-or-later")
+                            (short-description "synopsis")
+                            (long-description "description")
+                            (repo "https://example.org/foo.git")
+                            (website "https://example.org/foo")
+                            (forums 321)
+                            (score 987.654)
+                            (downloads 123)
+                            (type "mod")
+                            #:allow-other-keys)
+  `(("author" . ,author)
+    ("content_warnings" . #())
+    ("created_at" . "2018-05-23T19:58:07.422108")
+    ("downloads" . ,downloads)
+    ("forums" . ,forums)
+    ("issue_tracker" . "https://example.org/foo/issues")
+    ("license" . ,license)
+    ("long_description" . ,long-description)
+    ("maintainers" . #("maintainer"))
+    ("media_license" . ,media-license)
+    ("name" . ,name)
+    ("provides" . #("stuff"))
+    ("release" . 456)
+    ("repo" . ,repo)
+    ("score" . ,score)
+    ("screenshots" . #())
+    ("short_description" . ,short-description)
+    ("state" . "APPROVED")
+    ("tags" . #("some" "tags"))
+    ("thumbnail" . null)
+    ("title" . "The name")
+    ("type" . ,type)
+    ("url" . ,(string-append "https://content.minetest.net/packages/"
+                             author "/" name "/download/"))
+    ("website" . ,website)))
+
+(define* (make-releases-json #:key (commit #f) (title "") #:allow-other-keys)
+  `#((("commit" . ,commit)
+      ("downloads" . 469)
+      ("id" . 8614)
+      ("max_minetest_version" . null)
+      ("min_minetest_version" . null)
+      ("release_date" . "2021-07-25T01:10:23.207584")
+      ("title" . "2021-07-25"))))
+
+(define* (make-dependencies-json #:key (author "Author")
+                                 (name "foo")
+                                 (requirements '(("default" #f ())))
+                                 #:allow-other-keys)
+  `((,(string-append author "/" name)
+     . ,(list->vector
+         (map (match-lambda
+                ((symbolic-name optional? implementations)
+                 `(("is_optional" . ,optional?)
+                   ("name" . ,symbolic-name)
+                   ("packages" . ,(list->vector implementations)))))
+              requirements)))
+    ("something/else" . #())))
+
+(define* (make-packages-keys-json #:key (author "Author")
+                                  (name "Name")
+                                  (type "mod"))
+  `(("author" . ,author)
+    ("name" . ,name)
+    ("type" . ,type)))
+
+(define (call-with-packages thunk . argument-lists)
+  ;; Don't reuse results from previous tests.
+  (invalidate-memoization! contentdb-fetch)
+  (invalidate-memoization! minetest->guix-package)
+  (define (scm->json-port scm)
+    (open-input-string (scm->json-string scm)))
+  (define (handle-package url requested-author requested-name . rest)
+    (define relevant-argument-list
+      (any (lambda (argument-list)
+             (apply (lambda* (#:key (author "Author") (name "foo")
+                              #:allow-other-keys)
+                      (and (equal? requested-author author)
+                           (equal? requested-name name)
+                           argument-list))
+                    argument-list))
+           argument-lists))
+    (when (not relevant-argument-list)
+      (error "the package ~a/~a should be irrelevant, but ~a is fetched"
+             requested-author requested-name url))
+    (scm->json-port
+     (apply (match rest
+              (("") make-package-json)
+              (("dependencies" "") make-dependencies-json)
+              (("releases" "") make-releases-json)
+              (_ (error "TODO ~a" rest)))
+            relevant-argument-list)))
+  (define (handle-mod-search sort)
+    ;; Produce search results, sorted by SORT in descending order.
+    (define arguments->key
+      (match sort
+        ("score" (lambda* (#:key (score 987.654) #:allow-other-keys)
+                   score))
+        ("downloads" (lambda* (#:key (downloads 123) #:allow-other-keys)
+                       downloads))))
+    (define argument-list->key (cut apply arguments->key <>))
+    (define (greater x y)
+      (> (argument-list->key x) (argument-list->key y)))
+    (define sorted-argument-lists (sort-list argument-lists greater))
+    (define* (arguments->json #:key (author "Author") (name "Foo") (type "mod")
+                              #:allow-other-keys)
+      (and (string=? type "mod")
+           `(("author" . ,author)
+             ("name" . ,name)
+             ("type" . ,type))))
+    (define argument-list->json (cut apply arguments->json <>))
+    (scm->json-port
+     (list->vector (filter-map argument-list->json sorted-argument-lists))))
+  (mock ((guix http-client) http-fetch
+         (lambda* (url #:key headers)
+           (unless (string-prefix? "mock://api/packages/" url)
+             (error "the URL ~a should not be used" url))
+           (define resource
+             (substring url (string-length "mock://api/packages/")))
+           (define components (string-split resource #\/))
+           (match components
+             ((author name . rest)
+              (apply handle-package url author name rest))
+             (((? (cut string-prefix? "?type=mod&q=" <>) query))
+              (handle-mod-search
+               (cond ((string-contains query "sort=score") "score")
+                     ((string-contains query "sort=downloads") "downloads")
+                     (#t (error "search query ~a has unknown sort key"
+                                query)))))
+             (_
+              (error "the URL ~a should have an author and name component"
+                     url)))))
+        (parameterize ((%contentdb-api "mock://api/"))
+          (thunk))))
+
+(define* (minetest->guix-package* #:key (author "Author") (name "foo")
+                                  (sort %default-sort-key)
+                                  #:allow-other-keys)
+  (minetest->guix-package (string-append author "/" name) #:sort sort))
+
+(define (imported-package-sexp* primary-arguments . secondary-arguments)
+  "Ask the importer to import a package specified by PRIMARY-ARGUMENTS,
+during a dynamic where that package and the packages specified by
+SECONDARY-ARGUMENTS are available on ContentDB."
+  (apply call-with-packages
+         (lambda ()
+           ;; The memoization cache is reset by call-with-packages
+           (apply minetest->guix-package* primary-arguments))
+   primary-arguments
+   secondary-arguments))
+
+(define (imported-package-sexp . extra-arguments)
+  "Ask the importer to import a package specified by EXTRA-ARGUMENTS,
+during a dynamic extent where that package is available on ContentDB."
+  (imported-package-sexp* extra-arguments))
+
+(define-syntax-rule (test-package test-case . extra-arguments)
+  (test-equal test-case
+    (make-package-sexp . extra-arguments)
+    (imported-package-sexp . extra-arguments)))
+
+(define-syntax-rule (test-package* test-case primary-arguments extra-arguments
+                                   ...)
+  (test-equal test-case
+    (apply make-package-sexp primary-arguments)
+    (imported-package-sexp* primary-arguments extra-arguments ...)))
+
+(test-begin "minetest")
+
+
+;; Package names
+(test-package "minetest->guix-package")
+(test-package "minetest->guix-package, _ → - in package name"
+              #:name "foo_bar"
+              #:guix-name "minetest-foo-bar"
+              #:upstream-name "Author/foo_bar")
+
+(test-equal "elaborate names, unambigious"
+  "Jeija/mesecons"
+  (call-with-packages
+   (cut elaborate-contentdb-name "mesecons")
+   '(#:name "mesecons" #:author "Jeija")
+   '(#:name "something" #:author "else")))
+
+(test-equal "elaborate name, ambigious (highest score)"
+  "Jeija/mesecons"
+  (call-with-packages
+   ;; #:sort "score" is the default
+   (cut elaborate-contentdb-name "mesecons")
+   '(#:name "mesecons" #:author "Jeijc" #:score 777)
+   '(#:name "mesecons" #:author "Jeijb" #:score 888)
+   '(#:name "mesecons" #:author "Jeija" #:score 999)))
+
+
+(test-equal "elaborate name, ambigious (most downloads)"
+  "Jeija/mesecons"
+  (call-with-packages
+   (cut elaborate-contentdb-name "mesecons" #:sort "downloads")
+   '(#:name "mesecons" #:author "Jeijc" #:downloads 777)
+   '(#:name "mesecons" #:author "Jeijb" #:downloads 888)
+   '(#:name "mesecons" #:author "Jeija" #:downloads 999)))
+
+
+;; Determining the home page
+(test-package "minetest->guix-package, website is used as home page"
+              #:home-page "web://site"
+              #:website "web://site")
+(test-package "minetest->guix-package, if absent, the forum is used"
+              #:home-page '(minetest-topic 628)
+              #:forums 628
+              #:website 'null)
+(test-package "minetest->guix-package, if absent, the git repo is used"
+              #:home-page "https://github.com/minetest-mods/mesecons"
+              #:forums 'null
+              #:website 'null
+              #:repo "https://github.com/minetest-mods/mesecons")
+(test-package "minetest->guix-package, all home page information absent"
+              #:home-page #f
+              #:forums 'null
+              #:website 'null
+              #:repo 'null)
+
+
+
+;; Dependencies
+(test-package* "minetest->guix-package, unambigious dependency"
+  (list #:requirements '(("mesecons" #f
+                          ("Jeija/mesecons"
+                           "some-modpack/containing-mese")))
+        #:inputs '("minetest-mesecons"))
+  (list #:author "Jeija" #:name "mesecons")
+  (list #:author "some-modpack" #:name "containing-mese" #:type "modpack"))
+
+(test-package* "minetest->guix-package, ambigious dependency (highest score)"
+  (list #:name "frobnicate"
+        #:guix-name "minetest-frobnicate"
+        #:upstream-name "Author/frobnicate"
+        #:requirements '(("frob" #f
+                          ("Author/foo" "Author/bar")))
+        ;; #:sort "score" is the default
+        #:inputs '("minetest-bar"))
+  (list #:author "Author" #:name "foo" #:score 0)
+  (list #:author "Author" #:name "bar" #:score 9999))
+
+(test-package* "minetest->guix-package, ambigious dependency (most downloads)"
+  (list #:name "frobnicate"
+        #:guix-name "minetest-frobnicate"
+        #:upstream-name "Author/frobnicate"
+        #:requirements '(("frob" #f
+                          ("Author/foo" "Author/bar")))
+        #:inputs '("minetest-bar")
+        #:sort "downloads")
+  (list #:author "Author" #:name "foo" #:downloads 0)
+  (list #:author "Author" #:name "bar" #:downloads 9999))
+
+(test-package "minetest->guix-package, optional dependency"
+              #:requirements '(("mesecons" #t
+                                ("Jeija/mesecons"
+                                 "some-modpack/containing-mese")))
+              #:inputs '())
+
+
+;; License
+(test-package "minetest->guix-package, identical licenses"
+              #:guix-license 'license:lgpl3+
+              #:license "LGPL-3.0-or-later"
+              #:media-license "LGPL-3.0-or-later")
+
+;; Sorting
+(let* ((make-package
+        (lambda arguments
+          (json->package (apply make-package-json arguments))))
+       (x (make-package #:score 0))
+       (y (make-package #:score 1))
+       (z (make-package #:score 2)))
+  (test-equal "sort-packages, already sorted"
+    (list z y x)
+    (sort-packages (list z y x)))
+  (test-equal "sort-packages, reverse"
+    (list z y x)
+    (sort-packages (list x y z))))
+
+(test-end "minetest")