Add VariantTagRuleFilterer to filter variants by tag rule

app/services/variant_tag_rules_filterer.rb

@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+# Takes a Spree::Variant AR object and filters results based on applicable tag rules.
+# Tag rules exists in the context of enterprise, customer, and variants.
+# Returns a Spree::Variant AR object.
+
+# The filtering is somewhat not intuitive when they are conflicting rules in play:
+#  * When a variant is hidden by a default rule, It will apply the "show rule" if any
+#  * When there is no default rule, it will apply the "show rule" over any "hide rule"
+#
+class VariantTagRulesFilterer
+  def initialize(distributor:, customer:, variants_relation: )
+    @distributor = distributor
+    @customer = customer
+    @variants_relation = variants_relation
+  end
+
+  def call
+    return variants_relation unless distributor_rules.any?
+
+    filter(variants_relation)
+  end
+
+  private
+
+  attr_accessor :distributor, :customer, :variants_relation
+
+  def distributor_rules
+    @distributor_rules ||= TagRule::FilterVariants.for(distributor).all
+  end
+
+  def filter(variants_relation)
+    return variants_relation unless variants_to_hide.any?
+
+    variants_relation.where(query_with_tag_rules)
+  end
+
+  def query_with_tag_rules
+    "#{variant_not_hidden_by_rule} OR #{variant_shown_by_rule}"
+  end
+
+  def variant_not_hidden_by_rule
+    return "FALSE" unless variants_to_hide.any?
+
+    "spree_variants.id NOT IN (#{variants_to_hide.join(',')})"
+  end
+
+  def variant_shown_by_rule
+    return "FALSE" unless variants_to_show.any?
+
+    "spree_variants.id IN (#{variants_to_show.join(',')})"
+  end
+
+  def variants_to_hide
+    @variants_to_hide ||= Spree::Variant.where(supplier: distributor)
+      .tagged_with(default_rule_tags + hide_rule_tags, any: true)
+      .pluck(:id)
+  end
+
+  def variants_to_show
+    @variants_to_show ||= Spree::Variant.where(supplier: distributor)
+      .tagged_with(show_rule_tags, any: true)
+      .pluck(:id)
+  end
+
+  def default_rule_tags
+    default_rules.map(&:preferred_variant_tags)
+  end
+
+  def hide_rule_tags
+    hide_rules.map(&:preferred_variant_tags)
+  end
+
+  def show_rule_tags
+    show_rules.map(&:preferred_variant_tags)
+  end
+
+  def default_rules
+    # These rules hide a variant with tag X and apply to all customers
+    distributor_rules.select(&:is_default?)
+  end
+
+  def non_default_rules
+    # These rules show or hide a variant with tag X for customer with tag Y
+    distributor_rules.reject(&:is_default?)
+  end
+
+  def customer_applicable_rules
+    # Rules which apply specifically to the current customer
+    @customer_applicable_rules ||= non_default_rules.select{ |rule| customer_tagged?(rule) }
+  end
+
+  def hide_rules
+    @hide_rules ||= customer_applicable_rules
+      .select{ |rule| rule.preferred_matched_variants_visibility == 'hidden' }
+  end
+
+  def show_rules
+    customer_applicable_rules - hide_rules
+  end
+
+  def customer_tagged?(rule)
+    customer_tag_list.include? rule.preferred_customer_tags
+  end
+
+  def customer_tag_list
+    customer&.tag_list || []
+  end
+end