From 1f98dfcad195d9fff0a44d7b6d1995375bae353b Mon Sep 17 00:00:00 2001
From: Sunil Mohan Adapa <sunil@medhas.org>
Date: Wed, 30 Jul 2025 19:14:21 -0700
Subject: [PATCH] setup: Perform a check for app availability after the page
 loads

- Using AJAX request instead of loading the initial page slowly.

Tests:

- Unit tests passes.

- Deluge app is not available in bookworm and is available in Trixie.

- When app is available, no message is shown. Install button is enabled.

- When app is not available a proper warning alert message is shown. Install
button is disabled.

- During check for the availability, the progress message is shown. Install
button is disabled.

- When Javascript is disabled on the page, no availability check is performed.
Install button is enabled.

- When an exception is raised in the is-available view, error message is shown.
Install button is enabled.

- When is-available view return HTML response, error message is shown. Install
button is enabled.

- When is-available view invalid JSON response, error message is shown. Install
button is enabled.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Joseph Nuthalapati <njoseph@riseup.net>
---
 plinth/app.py                     | 12 ++++++
 plinth/modules/deluge/__init__.py |  6 +--
 plinth/package.py                 | 17 ++++----
 plinth/templates/setup.html       | 46 +++++++++++++--------
 plinth/tests/test_app.py          | 20 +++++++++
 plinth/tests/test_package.py      | 10 ++---
 plinth/urls.py                    |  2 +
 plinth/views.py                   | 24 +++++------
 static/themes/default/js/main.js  | 69 +++++++++++++++++++++++++++++++
 9 files changed, 158 insertions(+), 48 deletions(-)

diff --git a/plinth/app.py b/plinth/app.py
index f9d562e91..0d4a62f4b 100644
--- a/plinth/app.py
+++ b/plinth/app.py
@@ -140,6 +140,14 @@ class App:
         """
         return self.get_component(self.app_id + '-info')
 
+    def is_available(self) -> bool:
+        """Return whether the app is available to install."""
+        for component in self.components.values():
+            if not component.is_available():
+                return False
+
+        return True
+
     def setup(self, old_version):
         """Install and configure the app and its components."""
         for component in self.components.values():
@@ -330,6 +338,10 @@ class Component:
         """
         return App.get(self.app_id)
 
+    def is_available(self) -> bool:
+        """Return whether the app is available to install."""
+        return True
+
     def setup(self, old_version):
         """Run operations to install and configure the component."""
 
diff --git a/plinth/modules/deluge/__init__.py b/plinth/modules/deluge/__init__.py
index 58d25ea69..e9215fc8c 100644
--- a/plinth/modules/deluge/__init__.py
+++ b/plinth/modules/deluge/__init__.py
@@ -34,11 +34,11 @@ class DelugePackages(Packages):
     https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1031593
     """
 
-    def has_unavailable_packages(self) -> bool | None:
+    def is_available(self) -> bool:
         if get_current_release()[1] == 'bookworm':
-            return True
+            return False
 
-        return super().has_unavailable_packages()
+        return super().is_available()
 
 
 class DelugeApp(app_module.App):
diff --git a/plinth/package.py b/plinth/package.py
index 8abe8ba7d..e4cfcf551 100644
--- a/plinth/package.py
+++ b/plinth/package.py
@@ -249,27 +249,26 @@ class Packages(app_module.FollowerComponent):
 
         return packages_installed(self.conflicts)
 
-    def has_unavailable_packages(self) -> bool | None:
-        """Return whether any of the packages are not available.
+    def is_available(self) -> bool:
+        """Return whether all of the packages are available.
 
-        Returns True if one or more of the packages is not available in the
-        user's Debian distribution or False otherwise. Returns None if it
-        cannot be reliably determined whether the packages are available or
-        not.
+        Returns True if all of the packages are available in the user's Debian
+        distribution or False otherwise. Returns True if it cannot be reliably
+        determined whether the packages are available or not.
         """
         apt_lists_dir = pathlib.Path('/var/lib/apt/lists/')
         num_files = len(
             [child for child in apt_lists_dir.iterdir() if child.is_file()])
         if num_files < 2:  # not counting the lock file
-            return None
+            return True  # Don't know, package cache is not available
 
         # List of all packages from all Package components
         try:
             self.get_actual_packages()
         except MissingPackageError:
-            return True
+            return False
 
-        return False
+        return True
 
     def _filter_packages_to_keep(self, packages: list[str]) -> list[str]:
         """Filter out the list of packages to keep from given list.
diff --git a/plinth/templates/setup.html b/plinth/templates/setup.html
index b9feb345d..cbf6e316f 100644
--- a/plinth/templates/setup.html
+++ b/plinth/templates/setup.html
@@ -33,24 +33,36 @@
       {% endif %}
     </p>
 
+    <div class="app-unavailable d-none">
+      <div class="alert alert-warning d-flex align-items-center" role="alert">
+        <div class="me-2">
+          <span class="fa fa-exclamation-triangle" aria-hidden="true"></span>
+          <span class="visually-hidden">{% trans "Caution:" %}</span>
+        </div>
+        <div>
+          {% blocktrans trimmed %}
+            This application is currently not available in your distribution.
+          {% endblocktrans %}
+        </div>
+      </div>
+    </div>
+    <p class="app-checking-availability d-none" data-app-id="{{ app_id }}"
+       data-setup-state="{{ setup_state.value }}">
+      {% blocktrans trimmed %}
+        Checking app availability...
+      {% endblocktrans %}
+      <span class="spinner-border spinner-border-sm" role="status"></span>
+    </p>
+    <p class="app-checking-availability-error d-none">
+      {% blocktrans trimmed %}
+        Error checking app availability. Please refresh page.
+      {% endblocktrans %}
+    </p>
+
     <form class="form-install" action="" method="post">
       {% csrf_token %}
 
       {% if has_unavailable_packages %}
-        <div class="alert alert-warning d-flex align-items-center" role="alert">
-          <div class="me-2">
-            <span class="fa fa-exclamation-triangle" aria-hidden="true"></span>
-            <span class="visually-hidden">{% trans "Caution:" %}</span>
-          </div>
-          <div>
-            {% blocktrans trimmed %}
-              This application is currently not available in your distribution.
-            {% endblocktrans %}
-            <button type="submit" class="btn btn-default btn-sm" name="refresh-packages">
-              <span class="fa fa-refresh"></span> {% trans "Check again" %}
-            </button>
-          </div>
-        </div>
       {% elif package_conflicts and package_conflicts_action.value != 'ignore' %}
         <div class="alert alert-warning d-flex align-items-center" role="alert">
           <div class="me-2">
@@ -70,10 +82,8 @@
         </div>
       {% endif %}
 
-      <input type="submit" class="btn btn-md btn-primary" name="install"
-             {% if has_unavailable_packages %}
-             disabled="disabled"
-             {% endif %}
+      <input type="submit" class="btn btn-md btn-primary install-button"
+             name="install"
              {% if setup_state.value == 'needs-setup' %}
              value="{% trans "Install" %}"
              {% elif setup_state.value == 'needs-update' %}
diff --git a/plinth/tests/test_app.py b/plinth/tests/test_app.py
index 048bd4ae6..7512aeffd 100644
--- a/plinth/tests/test_app.py
+++ b/plinth/tests/test_app.py
@@ -132,6 +132,20 @@ def test_get_components_of_type(app_with_components):
     assert list(components) == leader_components
 
 
+def test_app_is_available(app_with_components):
+    """Test checking if an app is available for setup."""
+    for component in app_with_components.components.values():
+        component.is_available = Mock(return_value=True)
+
+    assert app_with_components.is_available()
+    for component in app_with_components.components.values():
+        component.is_available.assert_has_calls([call()])
+
+    component = list(app_with_components.components.values())[0]
+    component.is_available.return_value = False
+    assert not app_with_components.is_available()
+
+
 def test_app_setup(app_with_components):
     """Test that running setup on an app runs setup on components."""
     for component in app_with_components.components.values():
@@ -333,6 +347,12 @@ def test_component_app_property():
     assert component.app == app
 
 
+def test_component_is_available():
+    """Test checking if a component is available for setup."""
+    component = Component('test-component')
+    assert component.is_available()
+
+
 def test_component_setup():
     """Test running setup on component."""
     component = Component('test-component')
diff --git a/plinth/tests/test_package.py b/plinth/tests/test_package.py
index f220480a5..e553f644b 100644
--- a/plinth/tests/test_package.py
+++ b/plinth/tests/test_package.py
@@ -340,21 +340,21 @@ def test_packages_find_conflicts(packages_installed_):
 
 @patch('apt.Cache')
 @patch('pathlib.Path')
-def test_packages_has_unavailable_packages(path_class, cache):
-    """Test checking for unavailable packages."""
+def test_packages_is_available(path_class, cache):
+    """Test checking for available packages."""
     path = Mock()
     path_class.return_value = path
     path.iterdir.return_value = [Mock()]
 
     component = Packages('test-component', ['package1', 'package2'])
-    assert component.has_unavailable_packages() is None
+    assert component.is_available()
 
     path.iterdir.return_value = [Mock(), Mock()]
     cache.return_value = ['package1', 'package2']
-    assert not component.has_unavailable_packages()
+    assert component.is_available()
 
     cache.return_value = ['package1']
-    assert component.has_unavailable_packages()
+    assert not component.is_available()
 
 
 def test_packages_installed():
diff --git a/plinth/urls.py b/plinth/urls.py
index a1bc7bfb1..0114b3cc0 100644
--- a/plinth/urls.py
+++ b/plinth/urls.py
@@ -26,6 +26,8 @@ urlpatterns = [
     re_path(r'', include((system_urlpatterns, 'system'))),
     re_path(r'^uninstall/(?P<app_id>[1-9a-z\-_]+)/$',
             views.UninstallView.as_view(), name='uninstall'),
+    re_path(r'^is-available/(?P<app_id>[1-9a-z\-_]+)/$',
+            views.is_available_view, name='is-available'),
     re_path(r'^rerun-setup/(?P<app_id>[1-9a-z\-_]+)/$', views.rerun_setup_view,
             name='rerun-setup'),
 
diff --git a/plinth/views.py b/plinth/views.py
index 97128ad1f..15c0d739a 100644
--- a/plinth/views.py
+++ b/plinth/views.py
@@ -12,7 +12,7 @@ from django.contrib import messages
 from django.core.exceptions import ImproperlyConfigured
 from django.forms import Form
 from django.http import (Http404, HttpRequest, HttpResponseBadRequest,
-                         HttpResponseRedirect)
+                         HttpResponseRedirect, JsonResponse)
 from django.shortcuts import redirect
 from django.template.response import TemplateResponse
 from django.urls import reverse
@@ -513,12 +513,6 @@ class SetupView(TemplateView):
         context['show_uninstall'] = (not app.info.is_essential and setup_state
                                      != app_module.App.SetupState.NEEDS_SETUP)
 
-        # Perform expensive operation only if needed.
-        if not context['operations']:
-            context[
-                'has_unavailable_packages'] = self._has_unavailable_packages(
-                    app)
-
         context['refresh_page_sec'] = None
         if context['setup_state'] == app_module.App.SetupState.UP_TO_DATE:
             context['refresh_page_sec'] = 0
@@ -565,12 +559,16 @@ class SetupView(TemplateView):
 
         return conflicts, conflicts_action
 
-    @staticmethod
-    def _has_unavailable_packages(app_):
-        """Return whether the app has unavailable packages."""
-        components = app_.get_components_of_type(Packages)
-        return any(component for component in components
-                   if component.has_unavailable_packages())
+
+def is_available_view(request, app_id):
+    """Return whether an app is available.
+
+    This check may take quite some time, so don't perform this check when
+    loading the app's setup page.
+    """
+    app = app_module.App.get(app_id)
+    data = {'is_available': app.is_available()}
+    return JsonResponse(data)
 
 
 @require_POST
diff --git a/static/themes/default/js/main.js b/static/themes/default/js/main.js
index 07c533a69..dbb4e8bd6 100644
--- a/static/themes/default/js/main.js
+++ b/static/themes/default/js/main.js
@@ -206,3 +206,72 @@ function setSelectAllValue(parent) {
 
     parent.querySelector('.select-all').checked = enableSelectAll;
 }
+
+/*
+ * Check whether an app is available on its setup page.
+ */
+document.addEventListener('DOMContentLoaded', function(event) {
+    const checkingElement = document.querySelector('.app-checking-availability');
+    if (!checkingElement)
+        return;
+
+    // App does not need setup, it likely needs upgrade
+    const setupState = checkingElement.getAttribute('data-setup-state');
+    if (setupState !== 'needs-setup')
+        return;
+
+    const appId = checkingElement.getAttribute('data-app-id');
+    checkingElement.classList.remove('d-none');
+
+    function setInstallButtonState(enable) {
+        const installButton = document.querySelector('.install-button');
+        if (enable) {
+            installButton.removeAttribute('disabled');
+        } else {
+            installButton.setAttribute('disabled', 'disabled');
+        }
+    }
+
+    function unavailable() {
+        document.querySelector('.app-unavailable').classList.remove('d-none');
+        setInstallButtonState(false);
+    }
+
+    function error() {
+        const element = document.querySelector('.app-checking-availability-error');
+        element.classList.remove('d-none');
+        checkingElement.classList.add('d-none');
+        setInstallButtonState(true);  // Allow trying installation
+    }
+
+    let request = new XMLHttpRequest();
+    request.timeout = 2 * 60 * 1000;  // 2 minutes
+    request.onload = function() {
+        // Remove the progress spinner
+        checkingElement.classList.add('d-none');
+
+        let available = false;
+        if (this.status === 200) {
+            try {
+                const response = JSON.parse(this.responseText);
+                if (response.is_available === true) {
+                    setInstallButtonState(true);
+                } else if (response.is_available === false) {
+                    unavailable();
+                } else {
+                    error();
+                }
+            } catch (e) {
+                error();
+            }
+        } else {
+            error();
+        }
+    };
+    request.onerror = error;
+    request.ontimeout = error;
+
+    request.open('GET', `/plinth/is-available/${appId}/`, true);
+    setInstallButtonState(false);
+    request.send();
+});