installation scripting: turn steps into Enum

Fixes backward navigation by not trying to advance further than the
prepare step upon reaching disks page.

src/ui/pages/confirm.py

@@ -3,7 +3,7 @@
 from gi.repository import Gtk
 
 from .global_state import global_state
-from .installation_scripting import installation_scripting
+from .installation_scripting import installation_scripting, Step
 from .page import Page
 
 
@@ -24,7 +24,7 @@ class ConfirmPage(Gtk.Box, Page):
     ### callbacks ###
 
     def _on_clicked_confirm(self, button):
-        installation_scripting.start_next_step()
+        installation_scripting.set_ok_to_start_step(Step.install)
         global_state.advance_without_return(self.__gtype_name__)
 
     ### public methods ###

src/ui/pages/disk.py

@@ -6,7 +6,7 @@ from gi.repository import Gio, Gtk
 
 from .disk_provider import disk_provider
 from .global_state import global_state
-from .installation_scripting import installation_scripting
+from .installation_scripting import installation_scripting, Step
 from .page import Page
 from .system_calls import is_booted_with_uefi, open_disks
 from .widgets import DeviceRow, NoPartitionsRow
@@ -132,7 +132,7 @@ class DiskPage(Gtk.Box, Page):
 
     def load_once(self):
         # start prepare script
-        installation_scripting.start_next_step()
+        installation_scripting.set_ok_to_start_step(Step.prepare)
 
         with self.lock:
             self._setup_disk_list()

src/ui/pages/locale.py

@@ -3,7 +3,7 @@
 from gi.repository import Gio, Gtk, GWeather
 
 from .global_state import global_state
-from .installation_scripting import installation_scripting
+from .installation_scripting import installation_scripting, Step
 from .locale_provider import get_current_formats, get_formats, get_timezone
 from .page import Page
 from .system_calls import set_system_formats, set_system_timezone
@@ -121,7 +121,7 @@ class LocalePage(Gtk.Box, Page):
     ### callbacks ###
 
     def _on_clicked_confirm_button(self, button):
-        installation_scripting.start_next_step()
+        installation_scripting.set_ok_to_start_step(Step.configure)
         global_state.advance_without_return(self.__gtype_name__)
 
     def _on_formats_row_activated(self, list_box, row):

src/util/installation_scripting.py

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
+from enum import Enum
 from threading import Lock
 import time
 
@@ -8,7 +9,12 @@ from gi.repository import Gio, GLib, GObject, Vte
 from .global_state import global_state
 
 
-steps = [None, 'prepare', 'install', 'configure']
+class Step(Enum):
+    none = 0
+    prepare = 1
+    install = 2
+    configure = 3
+    done = 4
 
 
 class InstallationScripting():
@@ -23,8 +29,8 @@ class InstallationScripting():
     cancel = Gio.Cancellable()
 
     lock = Lock()
-    current_step = 0
-    step_ready = 0
+    current_step = Step.none
+    step_ready = Step.none
     script_running = False
 
     # set by installation page
@@ -39,16 +45,19 @@ class InstallationScripting():
         self.terminal.connect('child-exited', self._on_child_exited)
 
     def _start_next_script(self):
-        if self.current_step < self.step_ready and not self.script_running:
-            self.current_step += 1
-            script_name = steps[self.current_step]
-            print(f'Starting step "{script_name}"...')
-            envs = global_state.create_envs(self.current_step >= 2, self.current_step == 3)
-            global_state.installation_running = self.current_step >= 2
+        if self.current_step.value < self.step_ready.value and not self.script_running:
+            self.current_step = Step(self.current_step.value + 1)
+            print(f'Starting step "{self.current_step.name}"...')
+
+            is_installing = self.current_step is Step.install or self.current_step is Step.configure
+            is_configuring = self.current_step is Step.configure
+            envs = global_state.create_envs(is_installing, is_configuring)
+
+            global_state.installation_running = is_installing
 
             # check config
             if envs == None:
-                print(f'Not all config options set for "{script_name}". Please report this bug.')
+                print(f'Not all config options set for "{self.current_step.name}". Please report this bug.')
                 print('############################')
                 print(global_state.config)
                 print('############################')
@@ -67,12 +76,11 @@ class InstallationScripting():
     def _on_child_exited(self, terminal, status):
         with self.lock:
             self.script_running = False
-            script_name = steps[self.current_step]
-            print(f'Finished step "{script_name}".')
+            print(f'Finished step "{self.current_step.name}".')
 
             if not status == 0 and not global_state.demo_mode:
                 global_state.installation_failed()
-            elif self.current_step == 3:
+            elif self.current_step is Step.configure:
                 global_state.installation_running = False
                 if global_state.demo_mode:
                     # allow returning in demo
@@ -84,10 +92,11 @@ class InstallationScripting():
 
     ### public methods ###
 
-    def start_next_step(self):
+    def set_ok_to_start_step(self, step: Step):
         with self.lock:
-            self.step_ready += 1
-            self._start_next_script()
+            if self.step_ready.value < step.value:
+                self.step_ready = step
+                self._start_next_script()
 
 
 installation_scripting = InstallationScripting()