Define a hierarchy of groups

app/controllers/groups_controller.rb

@@ -1,5 +1,5 @@
 class GroupsController < ApplicationController
   def index
-    render jsonapi: Group.all
+    render jsonapi: Group.where(parent_id: nil), include: [children: [children: [:children]]]
   end
 end

app/models/group.rb

@@ -1,4 +1,7 @@
 class Group < ApplicationRecord
     validates :name, uniqueness: true
     validates :name, :order, presence: true
+
+    has_many :children, class_name: 'Group', foreign_key: 'parent_id'
+    belongs_to :parent, class_name: 'Group', optional: true
 end

app/serializers/serializable_group.rb

@@ -2,4 +2,6 @@ class SerializableGroup < JSONAPI::Serializable::Resource
   type 'group'
 
   attributes :name, :icon
+
+  has_many :children
 end

db/migrate/20240811143801_add_parent_to_group.rb

@@ -0,0 +1,5 @@
+class AddParentToGroup < ActiveRecord::Migration[7.1]
+  def change
+    add_reference :groups, :parent, type: :uuid, index: true, foreign_key: { to_table: :groups }
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2024_08_11_142121) do
+ActiveRecord::Schema[7.1].define(version: 2024_08_11_143801) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -32,7 +32,9 @@ ActiveRecord::Schema[7.1].define(version: 2024_08_11_142121) do
     t.integer "order", default: 1, null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.uuid "parent_id"
     t.index ["name"], name: "index_groups_on_name", unique: true
+    t.index ["parent_id"], name: "index_groups_on_parent_id"
   end
 
   create_table "guests", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|
@@ -91,6 +93,7 @@ ActiveRecord::Schema[7.1].define(version: 2024_08_11_142121) do
     t.index ["name"], name: "index_tags_on_name", unique: true
   end
 
+  add_foreign_key "groups", "groups", column: "parent_id"
   add_foreign_key "seats", "guests"
   add_foreign_key "seats", "tables_arrangements", on_delete: :cascade
   add_foreign_key "taggings", "tags"

db/seeds.rb

@@ -22,6 +22,35 @@ Expense.create!(name: 'Transportation', amount: 3000, pricing_type: 'fixed')
 Expense.create!(name: 'Invitations', amount: 200, pricing_type: 'fixed')
 Expense.create!(name: 'Cake', amount: 500, pricing_type: 'fixed')
 
+Group.create!(name: "Jim's guests", icon: "pi pi-heart").tap do |parent|
+  parent.children.create!(name: "Jim's family", icon: "pi pi-users").tap do |family|
+    family.children.create!(name: "Jim's close family", icon: "pi pi-home")
+    family.children.create!(name: "Jim's cousins", icon: "pi pi-home")
+    family.children.create!(name: "Jim's relatives", icon: "pi pi-home")
+  end
+  parent.children.create!(name: "Jim's friends", icon: "pi pi-bullseye")
+  parent.children.create!(name: "Jim's work", icon: "pi pi-desktop").tap do |work|
+    work.children.create!(name: "Jim's besties at work", icon: "pi pi-briefcase")
+  end  
+end
+
+Group.create!(name: "Pam's guests", icon: "pi pi-heart-fill").tap do |parent|
+  parent.children.create!(name: "Pam's family", icon: "pi pi-users").tap do |family|
+    family.children.create!(name: "Pam's close family", icon: "pi pi-home")
+    family.children.create!(name: "Pam's cousins", icon: "pi pi-home")
+    family.children.create!(name: "Pam's relatives", icon: "pi pi-home")
+  end
+  parent.children.create!(name: "Pam's friends", icon: "pi pi-bullseye")
+  parent.children.create!(name: "Pam's work", icon: "pi pi-desktop").tap do |work|
+    work.children.create!(name: "Pam's besties at work", icon: "pi pi-briefcase")
+  end  
+end
+
+Group.create!(name: "Common guests", icon: "pi pi-users").tap do |parent|
+  parent.children.create!(name: "College friends", icon: "pi pi-calculator")
+  parent.children.create!(name: "High school friends", icon: "pi pi-crown")
+  parent.children.create!(name: "Childhood friends", icon: "pi pi-envelope")
+end
 
 samples = {
   close_family_a: 10,
@@ -44,7 +73,6 @@ samples = {
   football_team_a: 15,
   dance_club: 10
 }.each_with_object([]) do |(affinity_group, count), acc|
-  Group.find_or_create_by!(name: affinity_group.to_s.humanize)
   count.times { acc << affinity_group }
 end