enumerator_builder.rb in job-iteration-1.4.0

- old
+ new

@@ -2,10 +2,11 @@
 
 require_relative "./active_record_batch_enumerator"
 require_relative "./active_record_enumerator"
 require_relative "./csv_enumerator"
 require_relative "./throttle_enumerator"
+require_relative "./nested_enumerator"
 require "forwardable"
 
 module JobIteration
   class EnumeratorBuilder
     extend Forwardable
@@ -17,14 +18,16 @@
     # Enumerators without wrapping them in
     # `enumerator_builder.wrap(custom_enum)`. We don't do this yet for backwards
     # compatibility with raw calls to EnumeratorBuilder. Think of these wrappers
     # the way you should a middleware.
     class Wrapper < Enumerator
-      def self.wrap(_builder, enum)
-        new(-> { enum.size }) do |yielder|
-          enum.each do |*val|
-            yielder.yield(*val)
+      class << self
+        def wrap(_builder, enum)
+          new(-> { enum.size }) do |yielder|
+            enum.each do |*val|
+              yielder.yield(*val)
+            end
           end
         end
       end
     end
 
@@ -97,11 +100,11 @@
     # again. Similarly, if the value gets updated to a lesser value than the curor's value, it will get skipped.
     def build_active_record_enumerator_on_records(scope, cursor:, **args)
       enum = build_active_record_enumerator(
         scope,
         cursor: cursor,
-        **args
+        **args,
       ).records
       wrap(self, enum)
     end
 
     # Builds Enumerator from Active Record Relation and enumerates on batches of records.
@@ -112,48 +115,83 @@
     # For the rest of arguments, see documentation for #build_active_record_enumerator_on_records
     def build_active_record_enumerator_on_batches(scope, cursor:, **args)
       enum = build_active_record_enumerator(
         scope,
         cursor: cursor,
-        **args
+        **args,
       ).batches
       wrap(self, enum)
     end
 
     # Builds Enumerator from Active Record Relation and enumerates on batches, yielding Active Record Relations.
     # See documentation for #build_active_record_enumerator_on_batches.
     def build_active_record_enumerator_on_batch_relations(scope, wrap: true, cursor:, **args)
       enum = JobIteration::ActiveRecordBatchEnumerator.new(
         scope,
         cursor: cursor,
-        **args
+        **args,
       ).each
       enum = wrap(self, enum) if wrap
       enum
     end
 
     def build_throttle_enumerator(enum, throttle_on:, backoff:)
       JobIteration::ThrottleEnumerator.new(
         enum,
         @job,
         throttle_on: throttle_on,
-        backoff: backoff
+        backoff: backoff,
       ).to_enum
     end
 
     def build_csv_enumerator(enumerable, cursor:)
       CsvEnumerator.new(enumerable).rows(cursor: cursor)
     end
 
+    # Builds Enumerator for nested iteration.
+    #
+    # @param enums [Array<Proc>] an Array of Procs, each should return an Enumerator.
+    #   Each proc from enums should accept the yielded items from the parent enumerators
+    #     and the `cursor` as its arguments.
+    #   Each proc's `cursor` argument is its part from the `build_enumerator`'s `cursor` array.
+    # @param cursor [Array<Object>] array of offsets for each of the enums to start iteration from
+    #
+    # @example
+    #   def build_enumerator(cursor:)
+    #     enumerator_builder.nested(
+    #       [
+    #         ->(cursor) {
+    #           enumerator_builder.active_record_on_records(Shop.all, cursor: cursor)
+    #         },
+    #         ->(shop, cursor) {
+    #           enumerator_builder.active_record_on_records(shop.products, cursor: cursor)
+    #         },
+    #         ->(_shop, product, cursor) {
+    #           enumerator_builder.active_record_on_batch_relations(product.product_variants, cursor: cursor)
+    #         }
+    #       ],
+    #       cursor: cursor
+    #     )
+    #   end
+    #
+    #   def each_iteration(product_variants_relation)
+    #     # do something
+    #   end
+    #
+    def build_nested_enumerator(enums, cursor:)
+      NestedEnumerator.new(enums, cursor: cursor).each
+    end
+
     alias_method :once, :build_once_enumerator
     alias_method :times, :build_times_enumerator
     alias_method :array, :build_array_enumerator
     alias_method :active_record_on_records, :build_active_record_enumerator_on_records
     alias_method :active_record_on_batches, :build_active_record_enumerator_on_batches
     alias_method :active_record_on_batch_relations, :build_active_record_enumerator_on_batch_relations
     alias_method :throttle, :build_throttle_enumerator
     alias_method :csv, :build_csv_enumerator
+    alias_method :nested, :build_nested_enumerator
 
     private
 
     def build_active_record_enumerator(scope, cursor:, **args)
       unless scope.is_a?(ActiveRecord::Relation)
@@ -161,10 +199,10 @@
       end
 
       JobIteration::ActiveRecordEnumerator.new(
         scope,
         cursor: cursor,
-        **args
+        **args,
       )
     end
   end
 end