Impersonation system implementation

nonpacks/profiles/views.py

@@ -8,14 +8,16 @@ from django.contrib.auth.decorators import login_required
 from django.contrib.auth.forms import AuthenticationForm, PasswordChangeForm, UserCreationForm
 from django.core.files.base import ContentFile
 from django.core.files.storage import default_storage
-from django.http import JsonResponse
+from django.core.paginator import Paginator
+from django.http import HttpResponse, HttpResponseForbidden, JsonResponse
 from django.shortcuts import get_object_or_404, redirect, render
+from django.utils import timezone
 
 from common.markdown import render_markdown
 from library.models import FileIndex
 
 from .forms import AvatarForm, BioForm, EmailForm, UsernameForm
-from .models import ApiToken, UserProfile
+from .models import ApiToken, ImpersonationLog, UserProfile
 
 
 def register(request):
@@ -47,6 +49,10 @@ def user_login(request):
 def user_logout(request):
     if request.method == 'POST':
         was_authorized = request.session.get('authorized', False)
+        # While impersonating, "logout" returns to the real account instead of
+        # ending the session entirely.
+        if _stop_impersonation(request):
+            return redirect('landing:home')
         logout(request)
         # logout() flushes the session (wiping the gate flag). The gate is a
         # site-wide master password, separate from user accounts — preserve it.
@@ -56,6 +62,85 @@ def user_logout(request):
     return redirect('landing:home')
 
 
+# ---------- Impersonation (staff only) ----------
+
+def _stop_impersonation(request):
+    """Return the session to the original (impersonator) account. Shared by
+    impersonate_stop and user_logout. login() flushes the session, so the gate
+    flag must be restored afterwards."""
+    impersonator_id = request.session.pop('impersonator_id', None)
+    if not impersonator_id:
+        return False
+    original = get_user_model().objects.filter(pk=impersonator_id).first()
+    if original is None:
+        return False
+    ImpersonationLog.objects.filter(
+        impersonator=original, ended_at__isnull=True,
+    ).update(ended_at=timezone.now())
+    login(request, original, backend='django.contrib.auth.backends.ModelBackend')
+    request.session['authorized'] = True
+    return True
+
+
+def user_list(request):
+    """Browse-style directory of every account on the site."""
+    q = request.GET.get('q', '').strip()
+    users = get_user_model().objects.select_related('userprofile').order_by('username')
+    if q:
+        users = users.filter(username__icontains=q)
+    paginator = Paginator(users, 24)
+    page_obj = paginator.get_page(request.GET.get('page'))
+    return render(request, 'profiles/users.html', {
+        'users': page_obj,
+        'q': q,
+    })
+
+
+@login_required
+def impersonate_start(request, user_id):
+    if request.method != 'POST':
+        return HttpResponse(status=405)
+    if not request.user.is_staff:
+        return HttpResponseForbidden('Only staff can impersonate users.')
+    if request.session.get('impersonator_id'):
+        messages.error(request, 'Stop the current impersonation first.')
+        return redirect('profiles:user_profile', username=request.user.username)
+
+    actor = request.user
+    target = get_object_or_404(get_user_model(), pk=user_id)
+
+    if target.pk == actor.pk:
+        messages.error(request, 'You cannot impersonate yourself.')
+        return redirect('profiles:user_profile', username=target.username)
+
+    if target.is_superuser:
+        messages.error(request, 'Superusers cannot be impersonated.')
+        return redirect('profiles:user_profile', username=target.username)
+
+    if target.is_staff and actor.pk >= target.pk:
+        # Staff-to-staff: only an older (lower PK) account may impersonate.
+        messages.error(request, 'You cannot impersonate a more senior staff member.')
+        return redirect('profiles:user_profile', username=target.username)
+
+    reason = request.POST.get('reason', '')[:255]
+    ImpersonationLog.objects.create(impersonator=actor, target=target, reason=reason)
+
+    login(request, target, backend='django.contrib.auth.backends.ModelBackend')
+    request.session['authorized'] = True
+    request.session['impersonator_id'] = actor.pk
+    messages.success(request, f'Now acting as {target.username}.')
+    return redirect('profiles:user_profile', username=target.username)
+
+
+@login_required
+def impersonate_stop(request):
+    if request.method != 'POST':
+        return HttpResponse(status=405)
+    _stop_impersonation(request)
+    messages.success(request, 'Impersonation stopped.')
+    return redirect('landing:home')
+
+
 @login_required
 def settings_page(request):
     tokens = request.user.api_tokens.all()
@@ -186,6 +271,14 @@ def user_profile(request, username):
     user = get_object_or_404(User, username__iexact=username)
     profile, created = UserProfile.objects.get_or_create(user=user)
     is_owner = request.user.is_authenticated and request.user.pk == user.pk
+    can_impersonate = (
+        request.user.is_authenticated
+        and request.user.is_staff
+        and not request.session.get('impersonator_id')
+        and request.user.pk != user.pk
+        and not user.is_superuser
+        and (not user.is_staff or request.user.pk < user.pk)
+    )
     bio_form = None
     if is_owner:
         if request.method == 'POST' and request.POST.get('action') == 'bio':
@@ -201,6 +294,7 @@ def user_profile(request, username):
         'profile': profile,
         'profile_user': user,
         'is_owner': is_owner,
+        'can_impersonate': can_impersonate,
         'bio_form': bio_form,
         'projects': user.projects.select_related('owner', 'thumbnail').prefetch_related(
             'tag_links__tag__category', 'versions',