Log changes from DB migration to CSV file

db/migrate/20181128054803_simplify_variant_override_stock_settings.rb

@@ -13,42 +13,112 @@
 # validation rules.
 class SimplifyVariantOverrideStockSettings < ActiveRecord::Migration
   class VariantOverride < ActiveRecord::Base
+    belongs_to :variant
+    belongs_to :hub, class_name: "Enterprise"
+
     scope :with_count_on_hand, -> { where("count_on_hand IS NOT NULL") }
     scope :without_count_on_hand, -> { where(count_on_hand: nil) }
   end
 
+  class Variant < ActiveRecord::Base
+    self.table_name = "spree_variants"
+
+    belongs_to :product
+
+    def name
+      namer = OpenFoodNetwork::OptionValueNamer.new(self)
+      namer.name
+    end
+  end
+
+  class Product < ActiveRecord::Base
+    self.table_name = "spree_products"
+
+    belongs_to :supplier, class_name: "Enterprise"
+  end
+
+  class Enterprise < ActiveRecord::Base; end
+
   def up
-    update_use_producer_stock_settings_with_count_on_hand
-    update_on_demand_with_count_on_hand
-    update_limited_stock_without_count_on_hand
+    CSV.open(csv_path, "w") do |csv|
+      csv << csv_header_row
+
+      update_use_producer_stock_settings_with_count_on_hand(csv)
+      update_on_demand_with_count_on_hand(csv)
+      update_limited_stock_without_count_on_hand(csv)
+    end
   end
 
   def down; end
 
   private
 
+  def csv_path
+    Rails.root.join("reports", "SimplifyVariantOverrideStockSettings-changed_variant_overrides.csv")
+  end
+
   # When on_demand is nil but count_on_hand is set, force limited stock.
-  def update_use_producer_stock_settings_with_count_on_hand
+  def update_use_producer_stock_settings_with_count_on_hand(csv)
     variant_overrides = VariantOverride.where(on_demand: nil).with_count_on_hand
-    variant_overrides.find_each do |variant_override|
+    update_variant_overrides_and_log(csv, variant_overrides) do |variant_override|
       variant_override.update_attributes!(on_demand: false)
     end
   end
 
   # Clear count_on_hand if forcing on demand.
-  def update_on_demand_with_count_on_hand
+  def update_on_demand_with_count_on_hand(csv)
     variant_overrides = VariantOverride.where(on_demand: true).with_count_on_hand
-    variant_overrides.find_each do |variant_override|
+    update_variant_overrides_and_log(csv, variant_overrides) do |variant_override|
       variant_override.update_attributes!(count_on_hand: nil)
     end
   end
 
   # When on_demand is false but count on hand is not specified, set this to use producer stock
   # settings.
-  def update_limited_stock_without_count_on_hand
+  def update_limited_stock_without_count_on_hand(csv)
     variant_overrides = VariantOverride.where(on_demand: false).without_count_on_hand
-    variant_overrides.find_each do |variant_override|
+    update_variant_overrides_and_log(csv, variant_overrides) do |variant_override|
       variant_override.update_attributes!(on_demand: nil)
     end
   end
+
+  def update_variant_overrides_and_log(csv, variant_overrides)
+    variant_overrides.find_each do |variant_override|
+      csv << variant_override_log_row(variant_override) do
+        yield variant_override
+      end
+    end
+  end
+
+  def csv_header_row
+    %w(
+      variant_override_id
+      distributor_name distributor_id
+      producer_name producer_id
+      product_name product_id
+      variant_description variant_id
+      previous_on_demand previous_count_on_hand
+      updated_on_demand updated_count_on_hand
+    )
+  end
+
+  def variant_override_log_row(variant_override)
+    variant = variant_override.variant
+    distributor = variant_override.hub
+    product = variant.andand.product
+    supplier = product.andand.supplier
+
+    row = [
+      variant_override.id,
+      distributor.andand.name, distributor.andand.id,
+      supplier.andand.name, supplier.andand.id,
+      product.andand.name, product.andand.id,
+      variant.andand.name, variant.andand.id,
+      variant_override.on_demand, variant_override.count_on_hand
+    ]
+
+    yield variant_override
+
+    row + [variant_override.on_demand, variant_override.count_on_hand]
+  end
 end