views: Add a menu entry and view for showing logs of an app

Tests:

- View logs menu entry is shown only for apps with daemons. It is now shown for
others such as Backups. It does not add menu for apps such as power.

- View logs entry for Date & Time shows show logs for multiple units. View logs
entry for Nextcloud shows many units.

- The textarea occupies full width. It is not editable. It is always scrolled to
the bottom. Control-A and Control-C selects all the text in it. It is re-sizable
vertically.

- The header shows unit name and unit description correctly.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Veiko Aasa <veiko17@disroot.org>

plinth/templates/app-logs.html

@@ -0,0 +1,42 @@
+{% extends "base.html" %}
+{% comment %}
+# SPDX-License-Identifier: AGPL-3.0-or-later
+{% endcomment %}
+
+{% load i18n %}
+
+{% block content %}
+  <h2>{% trans "Logs" %}: {{ app_info.name }}</h2>
+
+  <p>
+    {% blocktrans trimmed %}
+      These are the last lines of the logs for services involved in this app.
+      If you want to report a bug, please use the <a
+      href="https://salsa.debian.org/freedombox-team/freedombox/issues">bug
+      tracker</a> and attach this log to the bug report.
+    {% endblocktrans %}
+  </p>
+
+  <div class="alert alert-warning d-flex align-items-center">
+    <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 %}
+        Please remove any personal information from the log before submitting
+        the bug report.
+      {% endblocktrans %}
+    </div>
+  </div>
+
+  {% for component in logs %}
+    <section id="logs-section-{{ component.unit }}">
+      <h3>{{ component.unit }}: {{ component.description }}</h3>
+      <p>
+        <textarea class="log" readonly rows="10">{{ component.logs }}</textarea>
+      </p>
+    </section>
+  {% endfor %}
+
+{% endblock %}

plinth/templates/toolbar.html

@@ -21,7 +21,7 @@
         </a>
       {% endif %}
 
-      {% if has_diagnostics or show_uninstall or has_backup_restore %}
+      {% if has_diagnostics or has_logs or show_uninstall or has_backup_restore %}
         <!-- Single button -->
         <div class="btn-group button-secondary dropdown">
           <button type="button" class="btn btn-default dropdown-toggle"
@@ -33,6 +33,13 @@
             {% if has_diagnostics %}
               {% include "diagnostics_button.html" with app_id=app_id enabled=is_enabled %}
             {% endif %}
+            {% if has_logs %}
+              <a class="dropdown-item view-logs-item"
+                 href="{% url 'logs' app_id=app_id %}"
+                 title="{% trans "View Logs" %}">
+                {% trans "View Logs" %}
+              </a>
+            {% endif %}
             {% if has_backup_restore %}
               <a class="dropdown-item backup-item"
                  href="{% url 'backups:create' app_id=app_id %}"

plinth/urls.py

@@ -30,6 +30,8 @@ urlpatterns = [
             views.is_available_view, name='is-available'),
     re_path(r'^rerun-setup/(?P<app_id>[1-9a-z\-_]+)/$', views.rerun_setup_view,
             name='rerun-setup'),
+    re_path(r'^logs/(?P<app_id>[1-9a-z\-_]+)/$', views.AppLogsView.as_view(),
+            name='logs'),
 
     # captcha urls are public
     re_path(r'^captcha/image/(?P<key>\w+)/$', public(cviews.captcha_image),

plinth/views.py

@@ -446,6 +446,7 @@ class AppView(FormView):
         context['is_running'] = app_is_running(self.app)
         context['app_info'] = self.app.info
         context['has_diagnostics'] = self.app.has_diagnostics()
+        context['has_logs'] = self.app.has_logs()
         context['port_forwarding_info'] = get_port_forwarding_info(self.app)
         context['app_enable_disable_form'] = self.get_enable_disable_form()
         context['show_rerun_setup'] = True
@@ -647,6 +648,25 @@ class UninstallView(FormView):
         return super().form_valid(form)
 
 
+class AppLogsView(TemplateView):
+    """View for an app's logs.
+
+    This view shows logs for all the daemon units involved the app for easy
+    debugging.
+    """
+    template_name = 'app-logs.html'
+
+    def get_context_data(self, *args, **kwargs):
+        """Add additional context data for template."""
+        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
+        context['logs'] = app.get_logs()
+
+        return context
+
+
 def notification_dismiss(request, id):
     """Dismiss a notification."""
     from .notification import Notification

static/themes/default/css/main.css

@@ -1026,3 +1026,9 @@ img.notification-icon {
 .accordion-header {
     margin: 0;
 }
+
+/* Logs */
+textarea.log {
+    width: 100%;
+    text-wrap: nowrap;
+}

static/themes/default/js/main.js

@@ -263,3 +263,15 @@ document.addEventListener('DOMContentLoaded', async () => {
         error();
     }
 });
+
+/*
+ * Text areas showing log lines have special behavior.
+ */
+document.addEventListener('DOMContentLoaded', function(event) {
+    const logElements = document.querySelectorAll('textarea.log');
+
+    // Scroll the textarea to the bottom so that last lines are visible.
+    for (const element of logElements) {
+        element.scrollTop = element.scrollHeight;
+    }
+});