Apply a penalty if table sizes are not honored

app/services/tables/discomfort_calculator.rb

@@ -3,16 +3,38 @@
 module Tables
   class DiscomfortCalculator
     private attr_reader :table
-    def initialize(table)
+    def initialize(table:)
       @table = table
     end
 
     def calculate
-      cohesion_penalty
+      table_size_penalty + cohesion_penalty
     end
 
     private
 
+    #
+    # Calculates the penalty associated with violating the table size constraints. The penalty is
+    # zero when the limits are honored, and it increases linearly as the number of guests deviates
+    # from the limits. Overcapacity is penalized more severely than undercapacity.
+    #
+    # @return [Number] The penalty associated with violating the table size constraints.
+    #
+    def table_size_penalty
+      case table.size
+      when 0...table.min_per_table then 2 * (table.min_per_table - table.size)
+      when table.min_per_table..table.max_per_table then 0
+      else 5 * (table.size - table.max_per_table)
+      end
+    end
+
+    #
+    # Calculates the discomfort of the table based on the cohesion of the guests. The total discomfort
+    # is calculated as the sum of the discomfort of each pair of guests. The discomfort of a pair of
+    # guests is a rational number between 1 (unrelated groups) and 0 (same group).
+    #
+    # @return [Number] Total discomfort of the table.
+    #
     def cohesion_penalty
       table.map(&:group_id).tally.to_a.combination(2).sum do |(a, count_a), (b, count_b)|
         distance = AffinityGroupsHierarchy.instance.distance(a, b)

app/services/tables/distribution.rb

@@ -4,7 +4,7 @@ require_relative '../../extensions/tree_node_extension'
 
 module Tables
   class Distribution
-    attr_accessor :tables
+    attr_accessor :tables, :min_per_table, :max_per_table
 
     def initialize(min_per_table:, max_per_table:)
       @min_per_table = min_per_table
@@ -17,6 +17,8 @@ module Tables
       max_tables = (people.count * 1.0 / @min_per_table).ceil
       @tables = people.in_groups(rand(min_tables..max_tables), false)
                       .map { |group| Table.new(group) }
+                      .each { |table| table.min_per_table = @min_per_table }
+                      .each { |table| table.max_per_table = @max_per_table }
     end
 
     def discomfort
@@ -62,7 +64,7 @@ module Tables
     private
 
     def local_discomfort(table)
-      table.discomfort ||= DiscomfortCalculator.new(table).calculate
+      table.discomfort ||= DiscomfortCalculator.new(table:).calculate
     end
   end
 end

app/services/tables/table.rb

@@ -2,7 +2,8 @@
 
 module Tables
   class Table < Array
-    attr_accessor :discomfort
+    attr_accessor :discomfort, :min_per_table, :max_per_table
+
     def initialize(*args)
       super
       reset
@@ -14,4 +15,4 @@ module Tables
       original_discomfort
     end
   end
-end
+end

spec/services/tables/discomfort_calculator_spec.rb

@@ -3,13 +3,61 @@
 require 'rails_helper'
 module Tables
   RSpec.describe DiscomfortCalculator do
-    let(:calculator) { described_class.new(table) }
+    let(:calculator) { described_class.new(table:) }
 
     let(:family) { create(:group, name: 'family') }
     let(:friends) { create(:group, name: 'friends') }
     let(:work) { create(:group, name: 'work') }
     let(:school) { create(:group, name: 'school') }
 
+    describe '#table_size_penalty' do
+      before do
+        table.min_per_table = 5
+        table.max_per_table = 7
+      end
+      context 'when the number of guests is in the lower bound' do
+        let(:table) { Table.new(create_list(:guest, 5)) }
+
+        it { expect(calculator.send(:table_size_penalty)).to eq(0) }
+      end
+
+      context 'when the number of guests is within the table size limits' do
+        let(:table) { Table.new(create_list(:guest, 6)) }
+
+        it { expect(calculator.send(:table_size_penalty)).to eq(0) }
+      end
+
+      context 'when the number of guests is in the upper bound' do
+        let(:table) { Table.new(create_list(:guest, 7)) }
+
+        it { expect(calculator.send(:table_size_penalty)).to eq(0) }
+      end
+
+      context 'when the number of guests is one unit below the lower bound' do
+        let(:table) { Table.new(create_list(:guest, 4)) }
+
+        it { expect(calculator.send(:table_size_penalty)).to eq(2) }
+      end
+
+      context 'when the number of guests is two units below the lower bound' do
+        let(:table) { Table.new(create_list(:guest, 3)) }
+
+        it { expect(calculator.send(:table_size_penalty)).to eq(4) }
+      end
+
+      context 'when the number of guests is one unit above the upper bound' do
+        let(:table) { Table.new(create_list(:guest, 8)) }
+
+        it { expect(calculator.send(:table_size_penalty)).to eq(5) }
+      end
+
+      context 'when the number of guests is two units above the upper bound' do
+        let(:table) { Table.new(create_list(:guest, 9)) }
+
+        it { expect(calculator.send(:table_size_penalty)).to eq(10) }
+      end
+    end
+
     describe '#cohesion_penalty' do
       before do
         # Overridden in each test except trivial cases