home-services: Add utils module.

* gnu/home-services/utils.scm (maybe-object->string object->snake-case-string)
(object->snake-case-string): New variables.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add home-services/utils.scm.

Signed-off-by: Oleg Pykhalov <go.wigust@gmail.com>

gnu/home-services/shells.scm

@@ -20,6 +20,7 @@
 (define-module (gnu home-services shells)
   #:use-module (gnu services configuration)
   #:use-module (gnu home-services configuration)
+  #:use-module (gnu home-services utils)
   #:use-module (gnu home-services)
   #:use-module (gnu packages shells)
   #:use-module (gnu packages bash)

gnu/home-services/utils.scm

@@ -0,0 +1,77 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;;
+;;; 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 (gnu home-services utils)
+  #:use-module (ice-9 string-fun)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+
+  #:export (maybe-object->string
+            object->snake-case-string
+            object->camel-case-string))
+
+(define (maybe-object->string object)
+  "Like @code{object->string} but don't do anyting if OBJECT already is
+a string."
+  (if (string? object)
+      object
+      (object->string object)))
+
+;; Snake case: <https://en.wikipedia.org/wiki/Snake_case>
+(define* (object->snake-case-string object #:optional (style 'lower))
+  "Convert the object OBJECT to the equivalent string in ``snake
+case''.  STYLE can be three `@code{lower}', `@code{upper}', or
+`@code{capitalize}', defaults to `@code{lower}'.
+
+@example
+(object->snake-case-string 'variable-name 'upper)
+@result{} \"VARIABLE_NAME\" @end example"
+  (if (not (member style '(lower upper capitalize)))
+      (error 'invalid-style (format #f "~a is not a valid style" style))
+      (let ((stringified (maybe-object->string object)))
+        (string-replace-substring
+         (cond
+          ((equal? style 'lower) stringified)
+          ((equal? style 'upper) (string-upcase stringified))
+          (else (string-capitalize stringified)))
+         "-" "_"))))
+
+(define* (object->camel-case-string object #:optional (style 'lower))
+  "Convert the object OBJECT to the equivalent string in ``camel case''.
+STYLE can be three `@code{lower}', `@code{upper}', defaults to
+`@code{lower}'.
+
+@example
+(object->camel-case-string 'variable-name 'upper)
+@result{} \"VariableName\"
+@end example"
+  (if (not (member style '(lower upper)))
+      (error 'invalid-style (format #f "~a is not a valid style" style))
+      (let ((stringified (maybe-object->string object)))
+        (cond
+         ((eq? style 'upper)
+          (string-concatenate
+           (map string-capitalize
+                (string-split stringified (cut eqv? <> #\-)))))
+         ((eq? style 'lower)
+          (let ((splitted-string (string-split stringified (cut eqv? <> #\-))))
+            (string-concatenate
+             (cons (first splitted-string)
+                   (map string-capitalize
+                        (cdr splitted-string))))))))))

gnu/local.mk

@@ -79,6 +79,7 @@ GNU_SYSTEM_MODULES =				\
   %D%/home-services/fontutils.scm               \
   %D%/home-services/configuration.scm           \
   %D%/home-services/shells.scm                  \
+  %D%/home-services/utils.scm                   \
   %D%/home-services/xdg.scm                     \
   %D%/image.scm					\
   %D%/packages.scm				\