# SPDX-License-Identifier: AGPL-3.0-or-later
"""
Main FreedomBox views.
"""

import sys
import time
import urllib.parse

from django.contrib import messages
from django.core.exceptions import ImproperlyConfigured
from django.http import Http404, HttpResponseBadRequest, HttpResponseRedirect
from django.template.response import TemplateResponse
from django.urls import reverse
from django.utils.translation import gettext as _
from django.views.generic import TemplateView
from django.views.generic.edit import FormView
from stronghold.decorators import public

from plinth import app as app_module
from plinth import package
from plinth.daemon import app_is_running
from plinth.modules.config import get_advanced_mode
from plinth.modules.firewall.components import get_port_forwarding_info
from plinth.package import Packages
from plinth.translation import get_language_from_request, set_language

from . import forms, frontpage

REDIRECT_FIELD_NAME = 'next'


def is_safe_url(url):
    """Check if the URL is safe to redirect to.

    Based on Django internal utility removed in Django 4.0.

    """
    if url is not None:
        url = url.strip()

    if not url:
        return False

    if '\\' in url or url.startswith('///'):
        return False

    try:
        result = urllib.parse.urlparse(url)
    except ValueError:
        return False

    # Only accept URLs to the same site and scheme.
    if result.scheme or result.netloc:
        return False

    return True


def _get_redirect_url_from_param(request):
    """Return the redirect URL from 'next' GET/POST param."""
    redirect_to = request.GET.get(REDIRECT_FIELD_NAME, '')
    redirect_to = request.POST.get(REDIRECT_FIELD_NAME, redirect_to)
    if is_safe_url(redirect_to):
        return redirect_to

    return reverse('index')


@public
def index(request):
    """Serve the main index page."""
    username = str(request.user) if request.user.is_authenticated else None
    shortcuts = frontpage.Shortcut.list(username)
    selected = request.GET.get('selected')

    selected_shortcut = [
        shortcut for shortcut in shortcuts if shortcut.component_id == selected
    ]
    selected_shortcut = selected_shortcut[0] if selected_shortcut else None

    return TemplateResponse(
        request, 'index.html', {
            'title': _('FreedomBox'),
            'shortcuts': shortcuts,
            'selected_shortcut': selected_shortcut,
        })


class AppsIndexView(TemplateView):
    """View for apps index"""
    template_name = 'apps.html'

    def get_context_data(self, *args, **kwargs):
        context = super().get_context_data(*args, **kwargs)
        context['show_disabled'] = True
        context['advanced_mode'] = get_advanced_mode()
        return context


def system_index(request):
    """Serve the system index page."""
    return TemplateResponse(request, 'system.html',
                            {'advanced_mode': get_advanced_mode()})


class LanguageSelectionView(FormView):
    """View for language selection"""
    form_class = forms.LanguageSelectionForm
    template_name = 'language-selection.html'

    def get_initial(self):
        """Return the initial values for the form."""
        return {'language': get_language_from_request(self.request)}

    def form_valid(self, form):
        """Set or reset the current language."""
        response = super().form_valid(form)
        set_language(self.request, response, form.cleaned_data['language'])
        return response

    def get_success_url(self):
        """Return the URL in the next parameter or home page."""
        return _get_redirect_url_from_param(self.request)


class AppView(FormView):
    """A generic view for showing an app's main page.

    The view and it's template may be customized but by default show the
    following:

    * Icon for the app
    * Name of the app
    * Description of the app
    * Link to the manual page for the app
    * A button to enable/disable the app
    * A toolbar with common actions such as 'Run diagnostics'
    * A status section showing the running status of the app
    * A form for configuring the app

    The following class properties are available on the view:

    'app_id' is the mandatory property to set the ID of the app. It is used to
    retrieve the App instance for the app that is needed for basic information
    and operations such as enabling/disabling the app.

    'form_class' is the Django form class that is used by this view. It may be
    None if the app does not have a configuration form. Default is None.

    'template_name' is the template used to render this view. By default it is
    app.html. It may be overridden with a template that derives from app.html
    to customize the appearance of the app to achieve more complex presentation
    instead of the simple appearance provided by default.

    """
    form_class = None
    app_id = None
    template_name = 'app.html'

    def __init__(self, *args, **kwargs):
        """Initialize the view."""
        super().__init__(*args, **kwargs)
        self._common_status = None

    def post(self, request, *args, **kwargs):
        """Handle app enable/disable button separately."""
        if 'app_enable_disable_button' not in request.POST:
            return super().post(request, *args, **kwargs)

        form = forms.AppEnableDisableForm(data=self.request.POST)
        if form.is_valid():
            return self.enable_disable_form_valid(form)

        return HttpResponseBadRequest('Invalid form submission')

    @property
    def success_url(self):
        return self.request.path

    @property
    def app(self):
        """Return the app for which this view is configured."""
        if not self.app_id:
            raise ImproperlyConfigured('Missing attribute: app_id')

        return app_module.App.get(self.app_id)

    def get_form(self, *args, **kwargs):
        """Return an instance of this view's form.

        Also the form_class for this view to be None.

        """
        if not self.form_class:
            return None

        return super().get_form(*args, **kwargs)

    def _get_common_status(self):
        """Return the status needed for form and template.

        Avoid multiple queries to expensive operations such as
        app.is_enabled().

        """
        if self._common_status:
            return self._common_status

        self._common_status = {'is_enabled': self.app.is_enabled()}
        return self._common_status

    def get_initial(self):
        """Return the status of the app to fill in the form."""
        initial = super().get_initial()
        initial.update(self._get_common_status())
        return initial

    def form_valid(self, form):
        """Enable/disable a service and set messages."""
        if not self.request._messages._queued_messages:
            messages.info(self.request, _('Setting unchanged'))

        return super().form_valid(form)

    def get_enable_disable_form(self):
        """Return an instance of the app enable/disable form.

        If the app can't be disabled by the user, return None.

        """
        if not self.app.can_be_disabled:
            return None

        initial = {
            'should_enable': not self._get_common_status()['is_enabled']
        }
        return forms.AppEnableDisableForm(initial=initial)

    def enable_disable_form_valid(self, form):
        """Form handling for enabling / disabling apps."""
        should_enable = form.cleaned_data['should_enable']
        if should_enable != self.app.is_enabled():
            if should_enable:
                self.app.enable()
            else:
                self.app.disable()

        return HttpResponseRedirect(self.request.path)

    def get_context_data(self, *args, **kwargs):
        """Add service to the context data."""
        context = super().get_context_data(*args, **kwargs)
        context.update(self._get_common_status())
        context['app_id'] = self.app.app_id
        context['is_running'] = app_is_running(self.app)
        context['app_info'] = self.app.info
        context['has_diagnostics'] = self.app.has_diagnostics()
        context['port_forwarding_info'] = get_port_forwarding_info(self.app)
        context['app_enable_disable_form'] = self.get_enable_disable_form()

        from plinth.modules.firewall.components import Firewall
        context['firewall'] = self.app.get_components_of_type(Firewall)

        return context


class SetupView(TemplateView):
    """View to prompt and setup applications."""
    template_name = 'setup.html'

    def get_context_data(self, **kwargs):
        """Return the context data rendering the template."""
        context = super().get_context_data(**kwargs)
        app_id = self.kwargs['app_id']
        app = app_module.App.get(app_id)

        context['app_info'] = app.info

        # Report any installed conflicting packages that will be removed.
        package_conflicts, package_conflicts_action = \
            self._get_app_package_conflicts(app)
        context['package_conflicts'] = package_conflicts
        context['package_conflicts_action'] = package_conflicts_action

        # Reuse the value of setup_state throughout the view for consistency.
        context['setup_state'] = app.get_setup_state()
        setup_helper = sys.modules[app.__module__].setup_helper
        context['setup_current_operation'] = setup_helper.current_operation

        # Perform expensive operation only if needed.
        if not context['setup_current_operation']:
            context[
                'package_manager_is_busy'] = package.is_package_manager_busy()
            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
        elif context['setup_current_operation']:
            context['refresh_page_sec'] = 3

        return context

    def dispatch(self, request, *args, **kwargs):
        if request.method == 'POST':
            if 'install' in request.POST:
                # Handle installing/upgrading applications.
                # Start the application setup, and refresh the page every few
                # seconds to keep displaying the status.
                app = app_module.App.get(self.kwargs['app_id'])
                setup_helper = sys.modules[app.__module__].setup_helper
                setup_helper.run_in_thread()

                # Give a moment for the setup process to start and show
                # meaningful status.
                time.sleep(1)
                response = self.render_to_response(self.get_context_data())
                # Post/Response/Get pattern for reloads
                response.status_code = 303
                return response

            if 'refresh-packages' in request.POST:
                # Refresh apt package lists
                package.refresh_package_lists()
                return self.render_to_response(self.get_context_data())

        return super().dispatch(request, *args, **kwargs)

    @staticmethod
    def _get_app_package_conflicts(app_):
        """Return packages that may conflict with packages of an app."""
        components = app_.get_components_of_type(Packages)
        conflicts = []
        conflicts_action = None
        for component in components:
            component_conflicts = component.find_conflicts()
            if component_conflicts:
                conflicts += component_conflicts
                if conflicts_action in (None, Packages.ConflictsAction.IGNORE):
                    conflicts_action = component.conflicts_action

        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 notification_dismiss(request, id):
    """Dismiss a notification."""
    from .notification import Notification
    notes = Notification.list(key=id, user=request.user)
    if not notes:
        raise Http404

    notes[0].dismiss()

    return HttpResponseRedirect(_get_redirect_url_from_param(request))
