Move modules to new backend/frontend directories (#668)

# Description

This is a yet another refactoring PR (I promise this will be the last
_major_ one), this time I based it on a codebase structure used by
Bottles project. The new structure should be more readable, and easier
to navigate. Also, as a nice small bonus, I've included `struct.md`
files inside `frontend/` and `backend/` directories with small
descriptions for subdirectories.

## Type of change

<!-- What type of change does your pull request introduce? Put an `x` in
the box that apply. -->
- [x] Refactor
- [ ] Bugfix (Change which fixes a issue)
- [ ] New feature (Change which adds new functionality)
- [ ] Enhancement (Change which slightly improves existing code)
- [ ] Breaking change (This change will introduce incompatibility with
existing functionality)

## Changelog <!-- This is optional, but highly appreciated. -->

- Rename `utils/css.py` to `utils/css_parser.py` and
`utils/custom_presets.py` to `utils/preset_downloader.py`,
- Move modules to new backend/frontend directories,
- Change module name from `utils.py` to `common.py`,
- Format some modules for better readability

## Testing

- [x] I have tested my changes and verified that they work as expected
<!-- Required, your PR won't be accepted if you don't do this step. -->

### How to test the changes

Just check if everything is working as expected in every build method
(I've tested this PR with manual and Flatpak methods)

Author: tfuxu

.gitignore

@@ -431,5 +431,5 @@ $RECYCLE.BIN/
 # The flatpak pip generator (needed for GH-Actions)
 flatpak-pip-generator
 
-# Don't include constants.py in VCS since that's a generated file 
-gradience/constants.py
+# Don't include constants.py in VCS since that's a generated file
+gradience/backend/constants.py

gradience/Structure.md

@@ -1,17 +0,0 @@
-# __init__.py
-#
-# Change the look of Adwaita, with ease
-# Copyright (C) 2022 Gradience Team
-#
-# This program 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.
-#
-# This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

gradience/__init__.py

@@ -1,4 +1,4 @@
-# css.py
+# css_parser.py
 #
 # Change the look of Adwaita, with ease
 # Copyright (C) 2022 Gradience Team
@@ -20,7 +20,7 @@
 
 
 # Adwaita named palette colors dict
-COLORS = [
+adw_colors = [
     "blue_",
     "green_",
     "yellow_",
@@ -41,7 +41,7 @@ def parse_css(path):
     variables = {}
     palette = {}
 
-    for color in COLORS:
+    for color in adw_colors:
         palette[color] = {}
 
     with open(path, "r", encoding="utf-8") as sheet:
@@ -51,7 +51,7 @@ def parse_css(path):
             if cdefine_match != None: # If @define-color variable declarations were found
                 palette_part = cdefine_match.__getitem__(1) # Get the second item of the re.Match object
                 name, color = palette_part.split(" ", 1)[1].split(" ", 1)
-                for color_name in COLORS:
+                for color_name in adw_colors:
                     if name.startswith(color_name): # Palette colors
                         palette[name[:-1]][name[-1:]] = color[:-1]
                         break

gradience/backend/__init__.py

@@ -20,7 +20,7 @@
 
 from gi.repository import GLib, Gio, Adw
 
-from gradience.utils.utils import buglog
+from gradience.backend.utils.common import buglog
 
 
 """ Custom exception class """

gradience/constants.py.in gradience/backend/constants.py.ingradience/constants.py.in renamed to gradience/backend/constants.py.in

@@ -0,0 +1,31 @@
+backenddir = 'gradience/backend'
+
+configure_file(
+  input: 'constants.py.in',
+  output: 'constants.py',
+  configuration: configuration_data({
+    'APP_ID': APPLICATION_ID,
+    'RELEASE_VER': meson.project_version(),
+    'VERSION': meson.project_version() + VERSION_SUFFIX,
+    'BUILD_TYPE': get_option('buildtype'),
+    'PROJECT_URL': PROJECT_URL,
+    'BUGTRACKER_URL': BUGTRACKER_URL,
+    'HELP_URL': HELP_URL,
+    'TRANSLATE_URL': TRANSLATE_URL,
+    'PKGDATA_DIR': PKGDATA_DIR,
+    'LOCALE_DIR': conf.get('LOCALE_DIR'),
+  }),
+  install: true,
+  install_dir: PY_INSTALLDIR.get_install_dir() / backenddir,
+)
+
+subdir('models')
+subdir('utils')
+
+gradience_sources = [
+    '__init__.py',
+    'css_parser.py',
+    'flatpak_overrides.py',
+    'preset_downloader.py'
+]
+PY_INSTALLDIR.install_sources(gradience_sources, subdir: backenddir)

gradience/utils/css.py gradience/backend/css_parser.pygradience/utils/css.py renamed to gradience/backend/css_parser.py

@@ -0,0 +1,8 @@
+modelsdir = 'gradience/backend/models'
+
+gradience_sources = [
+    '__init__.py',
+    'preset.py',
+    'repo.py'
+]
+PY_INSTALLDIR.install_sources(gradience_sources, subdir: modelsdir)