views: Implement a view to uninstall an app

- Take backup of the app before uninstall.

- Allow selecting the backup repository for backup.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/templates/uninstall.html

@@ -0,0 +1,39 @@
+{% extends "base.html" %}
+{% comment %}
+# SPDX-License-Identifier: AGPL-3.0-or-later
+{% endcomment %}
+
+{% load bootstrap %}
+{% load i18n %}
+
+{% block content %}
+  <h2>
+    {% blocktrans trimmed with app_name=app_info.name %}
+      Uninstall App <em>{{ app_name }}</em>?
+    {% endblocktrans %}
+  </h2>
+
+  <div class="alert alert-warning" role="alert">
+    {% blocktrans trimmed %}
+      Uninstalling an app is an exprimental feature.
+    {% endblocktrans %}
+  </div>
+
+  <p>
+    {% blocktrans trimmed %}
+      All app data and configuration will be permanently lost. App may be
+      installed freshly again.
+    {% endblocktrans %}
+  </p>
+
+  <p>
+    <form class="form form-uninstall" method="post">
+      {% csrf_token %}
+
+      {{ form|bootstrap }}
+
+      <input type="submit" class="btn btn-danger" name="uninstall_confirm"
+             value="{% trans 'Uninstall' %}"/>
+    </form>
+  </p>
+{% endblock %}

plinth/urls.py

@@ -15,6 +15,8 @@ urlpatterns = [
             name='language-selection'),
     re_path(r'^apps/$', views.AppsIndexView.as_view(), name='apps'),
     re_path(r'^sys/$', views.system_index, name='system'),
+    re_path(r'^uninstall/(?P<app_id>[1-9a-z\-_]+)/$',
+            views.UninstallView.as_view(), name='uninstall'),
 
     # captcha urls are public
     re_path(r'^captcha/image/(?P<key>\w+)/$', public(cviews.captcha_image),

plinth/views.py

@@ -3,6 +3,7 @@
 Main FreedomBox views.
 """
 
+import datetime
 import time
 import urllib.parse
 
@@ -349,6 +350,57 @@ class SetupView(TemplateView):
                    if component.has_unavailable_packages())
 
 
+class UninstallView(FormView):
+    """View to uninstall apps."""
+
+    form_class = forms.UninstallForm
+    template_name = 'uninstall.html'
+
+    def dispatch(self, request, *args, **kwargs):
+        """Don't allow the view to be used on essential apps."""
+        app_id = self.kwargs['app_id']
+        app = app_module.App.get(app_id)
+        if app.info.is_essential:
+            raise Http404
+
+        return super().dispatch(request, *args, **kwargs)
+
+    def get_context_data(self, *args, **kwargs):
+        """Add app information to the context data."""
+        context = super().get_context_data(*args, **kwargs)
+        app_id = self.kwargs['app_id']
+        app = app_module.App.get(app_id)
+        context['app_info'] = app.info
+        return context
+
+    def get_success_url(self):
+        """Return the URL to redirect to after uninstall."""
+        return reverse(self.kwargs['app_id'] + ':index')
+
+    def form_valid(self, form):
+        """Uninstall the app."""
+        app_id = self.kwargs['app_id']
+
+        # Backup the app
+        if form.cleaned_data['should_backup']:
+            repository_id = form.cleaned_data['repository']
+
+            import plinth.modules.backups.repository as repository_module
+            repository = repository_module.get_instance(repository_id)
+            if repository.flags.get('mountable'):
+                repository.mount()
+
+            name = datetime.datetime.now().strftime(
+                '%Y-%m-%d:%H:%M:%S') + ' ' + str(
+                    _('before uninstall of {app_id}')).format(app_id=app_id)
+            repository.create_archive(name, [app_id])
+
+        # Uninstall
+        setup.run_uninstall_on_app(app_id)
+
+        return super().form_valid(form)
+
+
 def notification_dismiss(request, id):
     """Dismiss a notification."""
     from .notification import Notification