Limit the number of asignees on a card

app/controllers/cards/assignments_controller.rb

@@ -8,11 +8,16 @@ def new
   end
 
   def create
-    @card.toggle_assignment @board.users.active.find(params[:assignee_id])
-
-    respond_to do |format|
-      format.turbo_stream
-      format.json { head :no_content }
+    if @card.toggle_assignment @board.users.active.find(params[:assignee_id])
+      respond_to do |format|
+        format.turbo_stream
+        format.json { head :no_content }
+      end
+    else
+      respond_to do |format|
+        format.turbo_stream
+        format.json { head :unprocessable_entity }
+      end
     end
   end
 end

app/javascript/controllers/assignment_limit_controller.js

@@ -0,0 +1,26 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static values = { limit: Number, count: Number }
+  static targets = ["unassigned", "limitMessage"]
+
+  connect() {
+    this.updateState()
+  }
+
+  countValueChanged() {
+    this.updateState()
+  }
+
+  updateState() {
+    const atLimit = this.countValue >= this.limitValue
+
+    this.unassignedTargets.forEach(el => {
+      el.hidden = atLimit
+    })
+
+    if (this.hasLimitMessageTarget) {
+      this.limitMessageTarget.hidden = !atLimit
+    }
+  }
+}

app/models/assignment.rb

@@ -1,7 +1,18 @@
 class Assignment < ApplicationRecord
+  LIMIT = 10
+
   belongs_to :account, default: -> { card.account }
   belongs_to :card, touch: true
 
   belongs_to :assignee, class_name: "User"
   belongs_to :assigner, class_name: "User"
+
+  validate :within_limit, on: :create
+
+  private
+    def within_limit
+      if card.assignments.count >= LIMIT
+        errors.add(:base, "Card already has the maximum of #{LIMIT} assignees")
+      end
+    end
 end

app/models/card/assignable.rb

@@ -24,10 +24,12 @@ def assigned?
 
   private
     def assign(user)
-      assignments.create! assignee: user, assigner: Current.user
-      watch_by user
+      assignment = assignments.create assignee: user, assigner: Current.user
 
-      track_event :assigned, assignee_ids: [ user.id ]
+      if assignment.persisted?
+        watch_by user
+        track_event :assigned, assignee_ids: [ user.id ]
+      end
     rescue ActiveRecord::RecordNotUnique
       # Already assigned
     end

app/views/cards/assignments/new.html.erb

@@ -1,10 +1,12 @@
 <%= turbo_frame_tag @card, :assignment do %>
   <%= tag.div class: "max-width full-width", data: {
 				action: "turbo:before-cache@document->dialog#close dialog:show@document->navigable-list#reset keydown->navigable-list#navigate filter:changed->navigable-list#reset",
-				controller: "filter navigable-list",
+				controller: "filter navigable-list assignment-limit",
 				dialog_target: "dialog",
 				navigable_list_focus_on_selection_value: false,
-				navigable_list_actionable_items_value: true } do %>
+				navigable_list_actionable_items_value: true,
+				assignment_limit_limit_value: Assignment::LIMIT,
+				assignment_limit_count_value: @card.assignments.count } do %>
 
     <div class="flex align-start justify-space-between">
       <strong class="popup__title">Assign this to…</strong>
@@ -19,7 +21,14 @@
         <span class="visually-hidden"><%= Current.user.name %></span>
       <% end %>
       <%= render collection: @assigned_to, partial: "user", locals: { card: @card } %>
-      <%= render collection: @users, partial: "user", locals: { card: @card } %>
+      <li class="popup__item txt-small color-tint" hidden data-assignment-limit-target="limitMessage">
+        You can't have more than <%= Assignment::LIMIT %> assignees
+      </li>
+      <% @users.each do |user| %>
+        <span data-assignment-limit-target="unassigned">
+          <%= render "user", card: @card, user: user %>
+        </span>
+      <% end %>
     </ul>
   <% end %>
 <% end %>

test/models/assignment_test.rb

@@ -1,7 +1,38 @@
 require "test_helper"
 
 class AssignmentTest < ActiveSupport::TestCase
-  # test "the truth" do
-  #   assert true
-  # end
+  test "create" do
+    card = cards(:text)
+    assignment = card.assignments.create!(assignee: users(:david), assigner: users(:jason))
+
+    assert_equal users(:david), assignment.assignee
+    assert_equal users(:jason), assignment.assigner
+    assert_equal card, assignment.card
+  end
+
+  test "create cannot exceed assignee limit" do
+    card = cards(:logo)
+    board = card.board
+    account = card.account
+
+    card.assignments.delete_all
+
+    Assignment::LIMIT.times do |i|
+      identity = Identity.create!(email_address: "limit_test_#{i}@example.com")
+      user = account.users.create!(identity: identity, name: "Limit Test User #{i}", role: :member)
+      user.accesses.find_or_create_by!(board: board)
+      card.assignments.create!(assignee: user, assigner: users(:david))
+    end
+
+    assert_equal Assignment::LIMIT, card.assignments.count
+
+    identity = Identity.create!(email_address: "[email protected]")
+    extra_user = account.users.create!(identity: identity, name: "Over Limit User", role: :member)
+    extra_user.accesses.find_or_create_by!(board: board)
+
+    assignment = card.assignments.build(assignee: extra_user, assigner: users(:david))
+
+    assert_not assignment.valid?
+    assert_includes assignment.errors[:base], "Card already has the maximum of #{Assignment::LIMIT} assignees"
+  end
 end

test/models/card/assignable_test.rb

@@ -12,4 +12,31 @@ class Card::AssignableTest < ActiveSupport::TestCase
     assert cards(:layout).assigned_to?(users(:kevin))
     assert cards(:layout).watched_by?(users(:kevin))
   end
+
+  test "toggle_assignment does not add assignee when at limit" do
+    card = cards(:logo)
+    board = card.board
+    account = card.account
+
+    card.assignments.delete_all
+
+    Assignment::LIMIT.times do |i|
+      identity = Identity.create!(email_address: "toggle_test_#{i}@example.com")
+      user = account.users.create!(identity: identity, name: "Toggle Test User #{i}", role: :member)
+      user.accesses.find_or_create_by!(board: board)
+      card.assignments.create!(assignee: user, assigner: users(:david))
+    end
+
+    identity = Identity.create!(email_address: "[email protected]")
+    extra_user = account.users.create!(identity: identity, name: "Toggle Over User", role: :member)
+    extra_user.accesses.find_or_create_by!(board: board)
+
+    with_current_user(:david) do
+      assert_no_difference "card.assignments.count" do
+        card.toggle_assignment(extra_user)
+      end
+    end
+
+    assert_not card.reload.assigned_to?(extra_user)
+  end
 end