Allow stats to be nested_on resources

lib/graphiti.rb

@@ -145,6 +145,7 @@ def self.setup!
 require "graphiti/scoping/filter"
 require "graphiti/stats/dsl"
 require "graphiti/stats/payload"
+require "graphiti/stats/nested_payload"
 require "graphiti/delegates/pagination"
 require "graphiti/util/include_params"
 require "graphiti/util/field_params"

lib/graphiti/resource_proxy.rb

@@ -83,6 +83,18 @@ def stats
       end
     end
 
+    def nested_stats
+      @nested_stats ||= if @query.hash[:stats]
+        payload = Stats::NestedPayload.new @resource,
+          @query,
+          @scope.unpaginated_object,
+          data
+        payload.generate
+      else
+        {}
+      end
+    end
+
     def pagination
       @pagination ||= Delegates::Pagination.new(self)
     end

lib/graphiti/serializer.rb

@@ -26,6 +26,7 @@ def as_jsonapi(*)
       super.tap do |hash|
         strip_relationships!(hash) if strip_relationships?
         add_links!(hash)
+        add_meta!(hash)
       end
     end
 
@@ -62,6 +63,15 @@ def strip_relationships!(hash)
       end
     end
 
+    def add_meta!(hash)
+      return if @resource.try(:type).nil?
+
+      resource_stats = @_exposures[:proxy].nested_stats.fetch(@resource.type, {})
+      nested_stats = resource_stats[@object.id]
+
+      hash[:meta] = {stats: nested_stats} if nested_stats.present?
+    end
+
     def strip_relationships?
       return false unless Graphiti.config.links_on_demand
       params = Graphiti.context[:object].params || {}

lib/graphiti/stats/dsl.rb

@@ -25,7 +25,7 @@ module Stats
     # @attr_reader [Symbol] name the stat, e.g. :total
     # @attr_reader [Hash] calculations procs for various metrics
     class DSL
-      attr_reader :name, :calculations
+      attr_reader :name, :calculations, :nested_on
 
       # @param [Adapters::Abstract] adapter the Resource adapter
       # @param [Symbol, Hash] config example: +:total+ or +{ total: [:count] }+
@@ -35,6 +35,8 @@ def initialize(adapter, config)
         @adapter = adapter
         @calculations = {}
         @name = config.keys.first
+        @nested_on = config[:nested_on]
+
         Array(config.values.first).each { |c| send(:"#{c}!") }
       end
 

lib/graphiti/stats/nested_payload.rb

@@ -0,0 +1,66 @@
+module Graphiti
+  module Stats
+    # Generate the nested stats payload so we can return it in the response for each record i.e.
+    #
+    #   {
+    #     data: [
+    #       {
+    #         id: "1",
+    #         type: "employee",
+    #         attributes: {},
+    #         relationships: {},
+    #         meta: { stats: { total: { count: 100 } } }
+    #       }
+    #     ],
+    #     meta: {}
+    #   }
+
+    class NestedPayload
+      def initialize(resource, query, scope, data)
+        @resource = resource
+        @query = query
+        @scope = scope
+        @data = data
+      end
+
+      # Generate the payload for +{ meta: { stats: { ... } } }+
+      # Loops over all calculations, computes then, and gives back
+      # a hash of stats and their results.
+      # @return [Hash] the generated payload
+      def generate
+        {}.tap do |stats|
+          @query.stats.each_pair do |name, calculation|
+            nested_on = @resource.stats[name].nested_on
+            next if nested_on.blank?
+
+            stats[nested_on] ||= {}
+
+            each_calculation(name, calculation) do |calc, function|
+              data_arr = @data.is_a?(Enumerable) ? @data : [@data]
+
+              data_arr.each do |object|
+                args = [@scope, name]
+                args << @resource.context if function.arity >= 3
+                args << object if function.arity == 4
+                result = function.call(*args)
+
+                stats[nested_on][object.id] ||= {}
+                stats[nested_on][object.id][name] ||= {}
+                stats[nested_on][object.id][name][calc] = result
+              end
+            end
+          end
+        end
+      end
+
+      private
+
+      def each_calculation(name, calculations)
+        calculations.each do |calc|
+          function = @resource.stat(name, calc)
+          yield calc, function
+        end
+      end
+    end
+  end
+end

lib/graphiti/stats/payload.rb

@@ -28,6 +28,9 @@ def initialize(resource, query, scope, data)
       def generate
         {}.tap do |stats|
           @query.stats.each_pair do |name, calculation|
+            nested_on = @resource.stats[name]&.nested_on
+            next if nested_on.present?
+
             stats[name] = {}
 
             each_calculation(name, calculation) do |calc, function|

spec/boolean_attribute_spec.rb

@@ -10,7 +10,8 @@
   end
 
   let(:author) { double(id: 1) }
-  let(:resource) { klass.new(object: author) }
+  let(:proxy) { double(nested_stats: {}) }
+  let(:resource) { klass.new(resource: double(type: "klass"), object: author, proxy: proxy) }
 
   subject { resource.as_jsonapi[:attributes] }
 

spec/fixtures/poro.rb

@@ -304,7 +304,8 @@ def sum(scope, attr)
     end
 
     def average(scope, attr)
-      "poro_average_#{attr}"
+      items = ::PORO::DB.all(scope)
+      items.map(&attr).sum / items.count
     end
 
     def maximum(scope, attr)

spec/stats/payload_spec.rb

@@ -18,6 +18,9 @@ def stub_stat(attr, calc, result)
       stub_stat(:attr1, :count, 2)
       stub_stat(:attr1, :average, 1)
       stub_stat(:attr2, :maximum, 3)
+
+      stats_obj = double(nested_on: false)
+      allow(dsl).to receive(:stats).and_return({attr1: stats_obj, attr2: stats_obj})
     end
 
     it "generates the correct payload for each requested stat" do

spec/stats/resource_with_nested_stats_spec.rb

@@ -0,0 +1,58 @@
+require "spec_helper"
+
+RSpec.describe "A resource with nested stats" do
+  include_context "resource testing"
+
+  let!(:employee1) { PORO::Employee.create first_name: "Alice", age: 25 }
+  let!(:employee2) { PORO::Employee.create first_name: "Bob", age: 40 }
+
+  let!(:position1) { PORO::Position.create employee_id: employee1.id, rank: 4 }
+  let!(:position2) { PORO::Position.create employee_id: employee1.id, rank: 8 }
+  let!(:position3) { PORO::Position.create employee_id: employee2.id, rank: 10 }
+  let!(:position4) { PORO::Position.create employee_id: employee2.id, rank: 22 }
+
+  let(:state_group_count) { [{id: 10, count: 3}, {id: 11, count: 0}] }
+
+  def jsonapi
+    JSON.parse(proxy.to_jsonapi)
+  end
+
+  describe "has_many" do
+    context "with include directive" do
+      let(:resource) do
+        Class.new(PORO::EmployeeResource) do
+          def self.name
+            "PORO::EmployeeResource"
+          end
+
+          has_many :positions
+
+          stat age: [:squared], nested_on: :employees do
+            squared do |scope, attr, context, employee|
+              employee.age * employee.age
+            end
+          end
+        end
+      end
+
+      before do
+        allow_any_instance_of(PORO::Employee).to receive(:applications_by_state_group_count).and_return(state_group_count)
+
+        params[:include] = "positions"
+        params[:stats] = {age: "squared"}
+        render
+      end
+
+      it "includes the top-level stats" do
+        expect(jsonapi["meta"]["stats"]).to be_nil
+      end
+
+      it "includes the stats nested on employees" do
+        jsonapi["data"].each do |record|
+          expect(record["meta"]["stats"]).to_not be_nil
+          expect(record["meta"]["stats"]["age"]).to_not be_nil
+        end
+      end
+    end
+  end
+end

spec/stats_spec.rb

@@ -68,7 +68,7 @@
       it "responds with average in meta stats" do
         render
         expect(json["meta"]["stats"])
-          .to eq({"age" => {"average" => "poro_average_age"}})
+          .to eq({"age" => {"average" => 0}})
       end
     end
 
@@ -190,7 +190,7 @@ def resolve(scope)
       render
       expect(json["meta"]["stats"]).to eq({
         "total" => {"count" => "poro_count_total"},
-        "age" => {"sum" => "poro_sum_age", "average" => "poro_average_age"}
+        "age" => {"sum" => "poro_sum_age", "average" => 0}
       })
     end
   end