[gnunet-scheme] 280/324: config/fs: Locate the user and system configuration.

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commit f11480492afc4b14554360f53f58cd89fcb1f50a
Author: Maxime Devos <maximedevos@telenet.be>
AuthorDate: Sun Sep 12 21:47:10 2021 +0200

    config/fs: Locate the user and system configuration.
    
    * Makefile.am (modules): Add new module.
      (SCM_TESTS): Add new tests.
    * doc/scheme-gnunet.tm (Locating configuration files): New section.
    * gnu/gnunet/config/fs.scm: New module.
    * tests/config-fs.scm: New test file.
---
 Makefile.am              |  2 ++
 doc/scheme-gnunet.tm     | 58 ++++++++++++++++++++++++++++++++++++++++++
 gnu/gnunet/config/fs.scm | 64 +++++++++++++++++++++++++++++++++++++++++++++++
 tests/config-fs.scm      | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 189 insertions(+)

diff --git a/Makefile.am b/Makefile.am
index 8ed4ab5..536c705 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -59,6 +59,7 @@ modules = \
   gnu/gnunet/config/value-parser.scm \
   gnu/gnunet/config/expand.scm \
   gnu/gnunet/config/db.scm \
+  gnu/gnunet/config/fs.scm \
   \
   gnu/gnunet/util/cmsg.scm \
   gnu/gnunet/util/time.scm \
@@ -161,6 +162,7 @@ SCM_TESTS = \
   tests/config-value-parser.scm \
   tests/config-expand.scm \
   tests/config-db.scm \
+  tests/config-fs.scm \
   tests/netstruct.scm \
   tests/time.scm \
   tests/tokeniser.scm
diff --git a/doc/scheme-gnunet.tm b/doc/scheme-gnunet.tm
index 01234b1..a6c2ad2 100644
--- a/doc/scheme-gnunet.tm
+++ b/doc/scheme-gnunet.tm
@@ -93,6 +93,64 @@
 
   <section|Configuration>
 
+  <subsection|Locating configuration files>
+
+  There are two \U possibly non-existent \U configuration files: the
+  <with|font-shape|italic|user> configuration and the
+  <with|font-shape|italic|system> configuration.<space|1em>The
+  <with|font-shape|italic|system> configuration typically contains the paths
+  for services like NSE, CORE, <text-dots><space|1em>A user may choose not to
+  use the services by the system and instead use their own.<space|1em>To do
+  so, the user needs to override the paths in the
+  <with|font-shape|italic|user> configuration.<space|1em><todo|defaults?> The
+  module <scm|(gnu gnunet config fs)> is responsible for determining the
+  location of the configuration files to load and actually load configuration
+  files.<space|1em>For determining the location of the configuration files,
+  the procedures <scm|locate-user-configuration> and
+  <scm|locate-system-configuration> can be used.
+
+  <\warning>
+    The C implementation's mechanism for user-system separation seems to work
+    differently.
+  </warning>
+
+  <\explain>
+    <scm|(locate-user-configuration <scm|#:getenv=getenv>)>
+  <|explain>
+    This procedure determines the location of the user configuration file, as
+    a string, or <scm|#false> if it could not be determined.<space|1em>If the
+    location of the user configuration file is known, but the file does not
+    exist, it is returned anyway, as a string.
+
+    If the environment variable <shell|XDG_CONFIG_HOME> is set, the location
+    of the file <verbatim|gnunet.conf> in the directory
+    <shell|$XDG_CONFIG_HOME> is returned.<space|1em>If the environment
+    variable is not set, the location of the file at
+    <verbatim|.config/gnunet.conf> in the home directory specified by the
+    environment variable <verbatim|HOME> is returned, if that environment
+    variable exists.<space|1em>If both are unset, <scm|#false> is returned.
+
+    The values of environment variables is determined with the procedure
+    <scm|getenv>.
+  </explain>
+
+  <\explain>
+    <scm|(locate-system-configuration)>
+  <|explain>
+    This procedure determines the location of the system configuration file,
+    as a string.
+
+    Currently, this is always <verbatim|/etc/gnunet.conf>.
+  </explain>
+
+  <subsection|Loading configuration files>
+
+  TODO: loading configurations from the disk
+
+  <subsection|Value types>
+
+  TODO
+
   <section|Manipulation of network structures>
 
   <index|network structure><index|netstruct>The modules <scm|(gnu gnunet
diff --git a/gnu/gnunet/config/fs.scm b/gnu/gnunet/config/fs.scm
new file mode 100644
index 0000000..0a39679
--- /dev/null
+++ b/gnu/gnunet/config/fs.scm
@@ -0,0 +1,64 @@
+;; This file is part of scheme-GNUnet, a partial Scheme port of GNUnet.
+;; Copyright (C) 2021 Maxime Devos <maximedevos@telenet.be>
+;;
+;; scheme-GNUnet is free software: you can redistribute it and/or modify it
+;; under the terms of the GNU Affero General Public License as published
+;; by the Free Software Foundation, either version 3 of the License,
+;; or (at your option) any later version.
+;;
+;; scheme-GNUnet 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
+;; Affero General Public License for more details.
+;;
+;; You should have received a copy of the GNU Affero General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+;;
+;; SPDX-License-Identifier: AGPL-3.0-or-later
+
+(define-library (gnu gnunet config fs)
+  (export locate-system-configuration
+         locate-user-configuration)
+  (import (only (rnrs base)
+               begin define and not or)
+         (only (ice-9 optargs)
+               define*)
+         (only (guile)
+               getenv in-vicinity string-null?)
+         (only (gnu gnunet utils hat-let)
+               let^))
+  (begin
+    (define (locate-system-configuration)
+      "/etc/gnunet.conf")
+
+    (define* (locate-user-configuration #:key (getenv getenv))
+      "Determine the location of the user configuration file,
+as a string, or @code{#false} if it could not be determined.
+If the location of the user configuration file is known,
+but the file does not exist, it is returned anyway, as a string.
+
+If the environment variable @code{XDG_CONFIG_HOME} is set, the
+location of the file @code{gnunet.conf} in the directory
+@code{XDG_CONFIG_HOME} is returned.  If the environment variable
+is not set, the location of the file at @code{.config/gnunet.conf}
+in the home directory specified by the environment variable
+@code{HOME} is returned, if that environment variable exist.
+If both are unset, @code{#false} is returned.
+
+The values of environment variables is determined with the procedure
+@var{getenv}."
+      (define (locate/HOME)
+       (define HOME (getenv "HOME"))
+       ;; It is possible, though inadvisable, for HOME
+       ;; to be unset.
+       (and HOME (not (string-null? HOME))
+            (in-vicinity HOME (in-vicinity ".config" "gnunet.conf"))))
+      (let^ ((! XDG_CONFIG_HOME (getenv "XDG_CONFIG_HOME"))
+            ;; If the environment variable is unset, fall-back to
+            ;; $HOME.
+            (? (or (not XDG_CONFIG_HOME)
+                   (string-null? XDG_CONFIG_HOME))
+               (locate/HOME)))
+           (in-vicinity XDG_CONFIG_HOME "gnunet.conf")))
+    ;; TODO actually load the configuration, defaults, ...
+    ))
diff --git a/tests/config-fs.scm b/tests/config-fs.scm
new file mode 100644
index 0000000..f44770f
--- /dev/null
+++ b/tests/config-fs.scm
@@ -0,0 +1,65 @@
+;; This file is part of scheme-GNUnet.
+;; Copyright (C) 2021 Maxime Devos
+;;
+;; scheme-GNUnet is free software: you can redistribute it and/or modify it
+;; under the terms of the GNU Affero General Public License as published
+;; by the Free Software Foundation, either version 3 of the License,
+;; or (at your option) any later version.
+;;
+;; scheme-GNUnet 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
+;; Affero General Public License for more details.
+;;
+;; You should have received a copy of the GNU Affero General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+;;
+;; SPDX-License-Identifier: AGPL3.0-or-later
+
+(import (gnu gnunet config fs)
+       (srfi srfi-64))
+(test-begin "config-fs")
+
+(define (alist->getenv alist)
+  (lambda (x)
+    (assoc-ref alist x)))
+
+(test-equal "locate-user-configuraton, XDG_CONFIG_HOME + HOME"
+  "/somewhere/unusual/gnunet.conf"
+  (locate-user-configuration
+   #:getenv
+   (alist->getenv '(("HOME" . "/a/home")
+                   ("XDG_CONFIG_HOME" . "/somewhere/unusual")))))
+
+(test-equal "locate-user-configuraton, XDG_CONFIG_HOME without HOME"
+  "/somewhere/unusual/gnunet.conf"
+  (locate-user-configuration
+   #:getenv
+   (alist->getenv '(("XDG_CONFIG_HOME" . "/somewhere/unusual")))))
+
+(test-equal "locate-user-configuration, no XDG_CONFIG_HOME"
+  "/a/home/.config/gnunet.conf"
+  (locate-user-configuration
+   #:getenv
+   (alist->getenv '(("HOME" . "/a/home")))))
+
+(test-equal "locate-user-configuration, empty XDG_CONFIG_HOME"
+  "/a/home/.config/gnunet.conf"
+  (locate-user-configuration
+   #:getenv
+   (alist->getenv '(("HOME" . "/a/home")
+                   ("XDG_CONFIG_HOME" . "")))))
+
+(test-equal "locate-user-configuration, no XDG_CONFIG_HOME, no HOME"
+  #false
+  (locate-user-configuration
+   #:getenv
+   (alist->getenv '())))
+
+(test-equal "locate-user-configuration, no XDG_CONFIG_HOME, empty HOME"
+  #false
+  (locate-user-configuration
+   #:getenv
+   (alist->getenv '(("HOME" . "")))))
+
+(test-end "config-fs")

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