From c7117a5b920a9741eb0b1e0eb96d47ba85efe15e Mon Sep 17 00:00:00 2001
From: Manuel Bustillo <bustikiller@bustikiller.com>
Date: Sun, 10 Nov 2024 12:35:41 +0100
Subject: [PATCH] Implement shift perturbation

---
 app/jobs/table_simulator_job.rb    |  1 +
 app/services/tables/shift.rb       | 30 ++++++++++++++++++++++++++++++
 spec/services/tables/shift_spec.rb |  6 ++++++
 3 files changed, 37 insertions(+)
 create mode 100644 app/services/tables/shift.rb
 create mode 100644 spec/services/tables/shift_spec.rb

diff --git a/app/jobs/table_simulator_job.rb b/app/jobs/table_simulator_job.rb
index 0b90396..ef91719 100644
--- a/app/jobs/table_simulator_job.rb
+++ b/app/jobs/table_simulator_job.rb
@@ -7,6 +7,7 @@ class TableSimulatorJob < ApplicationJob
     engine = VNS::Engine.new
 
     engine.add_perturbation(Tables::Swap)
+    engine.add_perturbation(Tables::Shift)
 
     initial_solution = Tables::Distribution.new(min_per_table: 8, max_per_table: 10)
     initial_solution.random_distribution(Guest.potential.shuffle)
diff --git a/app/services/tables/shift.rb b/app/services/tables/shift.rb
new file mode 100644
index 0000000..8bb962c
--- /dev/null
+++ b/app/services/tables/shift.rb
@@ -0,0 +1,30 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+module Tables
+  class Shift
+    private attr_reader :initial_solution
+    def initialize(initial_solution)
+      @initial_solution = initial_solution
+    end
+
+    def each
+      @initial_solution.tables.permutation(2) do |table_a, table_b|
+        table_a.each do |person|
+          original_discomfort_a = table_a.reset
+          original_discomfort_b = table_b.reset
+
+          table_a.delete(person)
+          table_b << person
+
+          yield(@initial_solution)
+        ensure
+          table_b.delete(person)
+          table_a << person
+
+          table_a.discomfort = original_discomfort_a
+          table_b.discomfort = original_discomfort_b
+        end
+      end
+    end
+  end
+end
diff --git a/spec/services/tables/shift_spec.rb b/spec/services/tables/shift_spec.rb
new file mode 100644
index 0000000..0526884
--- /dev/null
+++ b/spec/services/tables/shift_spec.rb
@@ -0,0 +1,6 @@
+require 'rails_helper'
+
+module Tables
+  RSpec.describe Shift do
+  end
+end