feat: follow up fixes redesign

CONTEXT.md

@@ -61,6 +61,14 @@ definitions.
 - **pinned (You) group** — the current viewer's own supervisor group in the topics directory, always first with a gray "(You)" suffix. Staff (lecturer/coordinator) only, pinned even at 0 topics; replaces the old "My Topics" section. Students browsing see plain A→Z with no pinned group.
 - **available badge** — on topics-directory rows only, an approved-and-unclaimed topic (`Topic#available?` = `approved? && proposed_project_instances.none?`) renders its pill as green "Available" *in place of* the "Approved" status pill (same approved-green palette — the swap is just the shared `pill_label` local, driven by `_topic_item`'s optional `available_pill:` local, default `false`). Non-available rows keep their real status pill. Always green — the mockup's blue "(You)" rows are an artifact. Display-only; never a substitute authorization gate (ADR 014).
 
+## Course show (browse tables)
+
+- **browse table** — one of the three filterable lists on `courses/show`: Groups, Students (People tab), topics directory. Each is re-rendered wholesale on every filter change, so each has to answer for itself what an absence means.
+- **base list** — a browse table's unfiltered, policy-scoped rows, held alongside its filtered form. The pair is what makes the two kinds of absence separable: the **base list** decides *which* one, never the unscoped list — a student who sees no approved topics has an empty **base list**, not a filtered one, because they filtered nothing out.
+- **empty state** — a **browse table** with nothing in it, ever: no groups created, no students enrolled, nothing available to this viewer. Blames nothing and implies no filter is at fault. Distinct from **no-matches state**; the **profile empty state** below is the same idea on a different page.
+- **no-matches state** — a **browse table** emptied by the active filters while its **base list** still holds rows. One generic pair of lines serves every filter ("No *nouns* match your current filters." + "Try adjusting your search or filters."), so there is no per-filter copy to fall out of date when a filter is added.
+- **filters active** — at least one of a **browse table**'s filters narrows the list; a select's `all` does not count. Reported to the table as a local rather than re-derived, because it outlives the state: a search that *does* match is still **filters active** and must still auto-expand rows.
+
 ## Participant profile
 
 - **participant profile** — the `courses#profile` page for one student or group, reached as `courses/profile/:participant_id/:participant_type` from the People/Groups rows (ADR 0016). Rendered in the **courses/show shell** (`bg-surface-tint`, inline `shared/sidebar` in the page's own `.flex`, `rounded-tl-panel` main — no `border-t border-l`) with content in a centered `max-w-5xl` reading column.

app/controllers/courses_controller.rb

@@ -3,6 +3,11 @@
 
 # Handles CRUD for courses
 class CoursesController < ApplicationController
+  # Params that narrow a list. "all" is the selects' neutral choice and counts
+  # as inactive, as does an absent/blank param.
+  PARTICIPANT_FILTER_KEYS = %w[search_query lecturer_filter status_filter].freeze
+  TOPIC_FILTER_KEYS       = %w[search_query topic_filter].freeze
+
   before_action :set_course, only: %i[show add_students handle_add_students add_lecturers handle_add_lecturers settings handle_settings destroy export_csv profile update_coursecode update_email_domain grouping_preview]
   before_action :set_lecturer_enrolments, only: %i[settings handle_settings]
 
@@ -25,7 +30,7 @@ def show
     # Topics Directory (topics_by_supervisor) data source — policy-scoped with
     # search/filter applied server-side; driving both the initial render and the
     # htmx re-render of _topics_by_supervisor_list.
-    @filtered_topic_list = filtered_topic_list
+    @filtered_topic_list = filtered_topic_list.to_a
     @topics_by_supervisor = topics_by_supervisor
 
     # set students projects
@@ -105,17 +110,28 @@ def show
     @filtered_student_list = filtered_student_list
 
     @show_all = params[:show_all] == 'true'
+    # Counts the matches, taken before the truncation below: the table footer's
+    # "Showing X of Y" is about the current criteria, not the course total.
     @total_group_count   = @filtered_group_list.count
     @total_student_count = @filtered_student_list.count
-    @total_count = @course.grouped? ? @total_group_count : @total_student_count
-    @total_count = @course.grouped? ? @filtered_group_list.count : @filtered_student_list.count
 
     unless @show_all
       @filtered_group_list = @filtered_group_list.first(Rails.application.config.participants_pagination_threshold)
       @filtered_student_list = @filtered_student_list.first(Rails.application.config.participants_pagination_threshold)
     end
 
-    @displayed_count = @course.grouped? ? @filtered_group_list.count : @filtered_student_list.count
+    # Empty vs no-matches, decided here rather than in the partials (ADR 0018).
+    # Each base is the unfiltered, policy-scoped list and is already loaded, so
+    # this costs no extra query. Computed after the truncation so the state and
+    # the list the partial receives can never disagree.
+    @group_list_state   = list_state(@group_list, @filtered_group_list)
+    @student_list_state = list_state(@student_list, @filtered_student_list)
+    @topic_list_state   = list_state(@topic_list, @filtered_topic_list)
+
+    # The filter controls sit outside the htmx-swapped containers, so the
+    # partials are told a filter is active rather than re-deriving it from params.
+    @filters_active       = filters_active?(PARTICIPANT_FILTER_KEYS)
+    @topic_filters_active = filters_active?(TOPIC_FILTER_KEYS)
 
     @capacity_result = SupervisorCapacityCalculator.new(@course).calculate
     @lecturer_capacity_info = @capacity_result.lecturer_capacities.index_by { |lc| lc.enrolment.user_id }
@@ -130,15 +146,19 @@ def show
                projects_by_owner: @projects_by_owner,
                total_count: @total_group_count,
                displayed_count: @filtered_group_list.count,
-               show_all: @show_all
+               show_all: @show_all,
+               state: @group_list_state,
+               filters_active: @filters_active
              }
     elsif params[:section] == 'topics'
       render partial: 'topics_by_supervisor_list',
              locals: {
                course: @course,
                lecturers: @lecturers,
                topics_by_supervisor: @topics_by_supervisor,
-               current_user_enrolment: @current_user_enrolment
+               current_user_enrolment: @current_user_enrolment,
+               state: @topic_list_state,
+               filters_active: @topic_filters_active
              }
     else
       render partial: 'students_table',
@@ -150,7 +170,9 @@ def show
                total_student_count: @student_list.count,
                total_count: @total_student_count,
                displayed_count: @filtered_student_list.count,
-               show_all: @show_all
+               show_all: @show_all,
+               state: @student_list_state,
+               filters_active: @filters_active
              }
     end
     nil
@@ -869,6 +891,29 @@ def groups_by_status(status, group_list, course)
 
   # Participants Table Filters helpers
 
+  # A list renders one of three states, and only the first two are ever
+  # displayed — a non-empty list renders rows and never consults the state:
+  #
+  #   :matched    — the filter returned rows
+  #   :no_matches — the base has rows, the filter returned none
+  #   :empty      — the base itself is empty; nothing has ever existed here
+  #
+  # The base is always the unfiltered, policy-scoped list, so a viewer whose
+  # policy scope hides everything is :empty rather than a false "no matches"
+  # (a student on a course with no approved topics has not filtered anything
+  # out). Both arguments are loaded by the time this runs (ADR 0018).
+  def list_state(base_list, filtered_list)
+    return :matched if filtered_list.any?
+
+    base_list.any? ? :no_matches : :empty
+  end
+
+  # True when any of the given filter params narrows the list. "all" is the
+  # selects' neutral choice, so it does not count.
+  def filters_active?(keys)
+    keys.any? { |key| params[key].present? && params[key] != 'all' }
+  end
+
   def search_groups(group_list, query)
     downcased_query = query.downcase
 

app/controllers/homescreen_controller.rb

@@ -1,5 +1,5 @@
-class HomescreenController < ApplicationController
-  def show
-    @courses = Current.user.courses.uniq
-  end
-end
+class HomescreenController < ApplicationController
+  def show
+    @courses = Current.user.courses_by_earliest_enrolment
+  end
+end

app/models/user.rb

@@ -8,6 +8,14 @@ class User < ApplicationRecord
   has_many :enrolments, dependent: :destroy
   has_many :courses, through: :enrolments
 
+  # sort cards by earliest enrolment (coordinators can have multiple).
+  def courses_by_earliest_enrolment
+    Course.joins(:enrolments)
+          .where(enrolments: { user_id: id })
+          .group('courses.id')
+          .order(Arel.sql('MIN(enrolments.created_at) DESC, courses.id DESC'))
+  end
+
   has_many :project_group_members, dependent: :destroy
   has_many :project_groups, through: :project_group_members
 

app/views/courses/_groups_tab.html.erb

@@ -7,7 +7,7 @@
 
     <div class="flex items-baseline gap-4">
       <h2 class="text-3xl font-normal text-gray-900 tracking-tight" style="font-family: 'DM Sans', Roboto, Arial, sans-serif;">Groups</h2>
-      <span class="text-sm font-medium text-gray-500"><%= pluralize(@total_group_count, "group") %></span>
+      <span class="text-sm font-medium text-gray-500"><%= pluralize(@group_list.size, "group") %></span>
     </div>
 
     <div class="flex flex-col md:flex-row md:items-center justify-between gap-4">
@@ -87,7 +87,9 @@
              projects_by_owner: @projects_by_owner,
              total_count: @total_group_count,
              displayed_count: @filtered_group_list.count,
-             show_all: @show_all %>
+             show_all: @show_all,
+             state: @group_list_state,
+             filters_active: @filters_active %>
 
   <%= render "courses/add_students_modal", course: @course %>
 </section>

app/views/courses/_groups_table.html.erb

@@ -1,4 +1,8 @@
-<%# --- locals: course, groups, projects_by_owner, total_count, displayed_count, show_all %>
+<%# --- locals: course, groups, projects_by_owner, total_count, displayed_count, show_all, state, filters_active %>
+<%# htmx re-render target on the Groups tab, rendered from BOTH the page path and
+    the courses#show htmx branch, so it only ever uses locals. `state` is the
+    controller's :matched / :no_matches / :empty verdict (ADR 0018); the copy
+    for each is chosen here, below. %>
 
 <div id="groups-table-container"
      class="overflow-x-auto pb-8 border border-gray-200 rounded-lg"
@@ -21,9 +25,6 @@
     </thead>
     <tbody class="divide-y divide-gray-200">
       <% if groups.present? %>
-        <% any_filter = params[:search_query].present? ||
-                        (params[:lecturer_filter].present? && params[:lecturer_filter] != 'all') ||
-                        (params[:status_filter].present? && params[:status_filter] != 'all') %>
         <% groups.each do |group| %>
           <% group_project = projects_by_owner[['ProjectGroup', group.id]]
              group_status = group_project&.current_status || 'not_submitted'
@@ -34,14 +35,13 @@
                      project: group_project,
                      status: group_status,
                      supervisor: supervisor,
-                     expanded: any_filter %>
+                     expanded: filters_active %>
         <% end %>
       <% else %>
-        <tr>
-          <td colspan="5" class="px-6 py-12 text-center text-sm text-gray-500 italic">
-            <%= params[:status_filter].present? && params[:status_filter] != 'all' ? "No groups found with #{params[:status_filter].titleize} status." : "No groups have been created yet." %>
-          </td>
-        </tr>
+        <%= render "shared/table_empty_state",
+                   colspan: 5,
+                   heading: state == :no_matches ? "No groups match your current filters." : "No groups have been created yet.",
+                   hint: state == :no_matches ? "Try adjusting your search or filters." : nil %>
       <% end %>
     </tbody>
   </table>

app/views/courses/_people_tab.html.erb

@@ -15,4 +15,6 @@
            total_student_count: @student_list.count,
            total_count: @total_student_count,
            displayed_count: @filtered_student_list.count,
-           show_all: @show_all %>
+           show_all: @show_all,
+           state: @student_list_state,
+           filters_active: @filters_active %>

app/views/courses/_students_section.html.erb

@@ -1,4 +1,4 @@
-<%# --- locals: course, students, student_group_map, student_enrolment_map, total_student_count, total_count, displayed_count, show_all %>
+<%# --- locals: course, students, student_group_map, student_enrolment_map, total_student_count, total_count, displayed_count, show_all, state, filters_active %>
 <%# The students-select controller scopes this whole section: it drives the
     single-select radios, the Actions dropdown dispatch, and survives the
     htmx table swaps (delegated listeners + htmx:afterSwap reset). %>
@@ -82,7 +82,9 @@
              student_enrolment_map: student_enrolment_map,
              total_count: total_count,
              displayed_count: displayed_count,
-             show_all: show_all %>
+             show_all: show_all,
+             state: state,
+             filters_active: filters_active %>
 
   <%= render "courses/add_students_modal", course: course %>
 </section>

app/views/courses/_students_table.html.erb

@@ -1,7 +1,9 @@
-<%# --- locals: course, students, student_group_map, student_enrolment_map, total_count, displayed_count, show_all %>
+<%# --- locals: course, students, student_group_map, student_enrolment_map, total_count, displayed_count, show_all, state, filters_active %>
 <%# htmx re-render target on the People tab — rendered from BOTH the page path and
     the courses#show htmx branch, so it only ever uses locals. Never reach for
-    student_status/student_project_for (see plan §5). %>
+    student_status/student_project_for (see plan §5). `state` is the controller's
+    :matched / :no_matches / :empty verdict (ADR 0018); the copy for each is
+    chosen here, below. %>
 
 <div id="students-table-container" class="overflow-x-auto border border-gray-200 rounded-lg">
   <table class="w-full min-w-[480px] table-fixed">
@@ -24,9 +26,10 @@
                      enrolment: student_enrolment_map[student.id] %>
         <% end %>
       <% else %>
-        <tr>
-          <td colspan="4" class="px-6 py-12 text-center text-sm text-gray-500 italic">No students have been enrolled yet.</td>
-        </tr>
+        <%= render "shared/table_empty_state",
+                   colspan: 4,
+                   heading: state == :no_matches ? "No students match your current filters." : "No students have been enrolled yet.",
+                   hint: state == :no_matches ? "Try adjusting your search or filters." : nil %>
       <% end %>
     </tbody>
   </table>

app/views/courses/_topic_directory_tab.html.erb

@@ -9,7 +9,9 @@
              course: @course,
              lecturers: @lecturers,
              topics_by_supervisor: @topics_by_supervisor,
-             current_user_enrolment: @current_user_enrolment %>
+             current_user_enrolment: @current_user_enrolment,
+             state: @topic_list_state,
+             filters_active: @topic_filters_active %>
 <% else %>
   <%= render "shared/empty_state",
              heading: "Topics are disabled for this course",

app/views/courses/_topics_by_supervisor_list.html.erb

@@ -1,21 +1,26 @@
 <%# Topics Directory body — the htmx-swappable container (mirror of
     _groups_table/_students_table: hx-target + hx-swap="outerHTML" replaces this
-    div). Locals: course, topics_by_supervisor, current_user_enrolment.
-    Supervisor groups: header (name + gray "(You)" for the viewer's own group +
-    topic count + chevron) over a list of _topic_item rows. Groups render
-    expanded by default (mockup). Under an active search/filter, non-matching
-    groups are dropped entirely rather than shown empty. When no supervisors
-    exist at all, the lone empty-state sentence renders. %>
+    div). Locals: course, topics_by_supervisor, current_user_enrolment, state,
+    filters_active. Supervisor groups: header (name + gray "(You)" for the
+    viewer's own group + topic count + chevron) over a list of _topic_item rows.
+    Groups render expanded by default (mockup). Under an active search/filter,
+    non-matching groups are dropped entirely rather than shown empty — so a
+    filter that matches nothing drops every group and the lone empty-state
+    sentence below takes over. `state` is the controller's :matched /
+    :no_matches / :empty verdict (ADR 0018); the copy for each is chosen here. %>
 
-<%
-  any_filter = params[:search_query].present? ||
-               (params[:topic_filter].present? && params[:topic_filter] != 'all')
-  visible = any_filter ? topics_by_supervisor.reject { |_lecturer, topics| topics.empty? } : topics_by_supervisor
-%>
+<% visible = filters_active ? topics_by_supervisor.reject { |_lecturer, topics| topics.empty? } : topics_by_supervisor %>
 
 <div id="topics-by-supervisor-container" class="flex flex-col">
   <% if visible.empty? %>
-    <p class="text-[14px] text-on-surface-variant py-3">No topics are currently available.</p>
+    <div class="py-3">
+      <p class="text-[14px] text-on-surface-variant">
+        <%= state == :no_matches ? "No topics match your current filters." : "No topics are currently available." %>
+      </p>
+      <% if state == :no_matches %>
+        <p class="mt-1 text-[14px] text-on-surface-muted">Try adjusting your search or filters.</p>
+      <% end %>
+    </div>
   <% else %>
     <% visible.each do |lecturer, topics| %>
       <div>

app/views/courses/_topics_section.html.erb

@@ -1,5 +1,6 @@
 <%# Topics Directory — the browse-first Topics panel of courses/show (ADR 0013).
-    Locals: course, lecturers, topics_by_supervisor, current_user_enrolment.
+    Locals: course, lecturers, topics_by_supervisor, current_user_enrolment,
+    state, filters_active.
     The section carries data-controller="expandable-rows" so the supervisor
     header toggles and the Collapse all / Expand all control keep working when
     htmx swaps the inner #topics-by-supervisor-container (mirror of the Groups
@@ -67,5 +68,7 @@
   <%= render "courses/topics_by_supervisor_list",
              course: course,
              topics_by_supervisor: topics_by_supervisor,
-             current_user_enrolment: current_user_enrolment %>
+             current_user_enrolment: current_user_enrolment,
+             state: state,
+             filters_active: filters_active %>
 </section>