lifetime_insights method to get metrics by each post

CHANGELOG.md

@@ -11,6 +11,7 @@ For more information about changelogs, check
 
 * [IMPROVEMENT] Return UTC time for String value of `created_time`, `backdated_time`,
 `end_time`, etc from Facebook to have exact time.
+* [FEATURE] Add Fb::Post#lifetime_insights` method to get metrics of each post.
 
 ## 1.0.0.beta10  - 2018/05/01
 

lib/fb/page.rb

@@ -13,6 +13,8 @@ class Page < Resource
     # @option [String] the page’s category.
     attr_reader :category
 
+    attr_reader :access_token
+
     # @param [Hash] options to initialize a Page object.
     # @option [String] :id The page’s unique ID.
     # @option [String] :name The page’s name.

lib/fb/post.rb

@@ -5,7 +5,7 @@ module Fb
   #   :id, :url, :created_at, :type, :message, :length, engaged_users,
   #   video_views, video_views_organic, video_views_paid, and so on.
   # @see https://developers.facebook.com/docs/graph-api/reference/v2.10/post
-  class Post
+  class Post < Resource
     attr_accessor :custom_labels
 
     # @option [String] the post’s unique ID.
@@ -300,6 +300,20 @@ def initialize(options = {})
       @video_view_time_organic = options[:post_video_view_time_organic]
     end
 
+    # @return [Hash] a hash of metrics mapped to their values.
+    # @param [Array<String, Symbol>] :metrics the metrics to fetch.
+    # @param [String] :page_access_token page access token of its page.
+    def lifetime_insights(metrics, page_access_token)
+      params = { metric: Array(metrics).join(","), access_token: page_access_token, period: "lifetime", ids: id }
+      request = HTTPRequest.new path: "/v2.9/insights", params: params
+      insights = request.run.body
+
+      data = insights[id]['data'].map do |metric|
+        [metric['name'], metric['values'].last.fetch('value', 0)]
+      end.to_h
+      symbolize_keys data
+    end
+
     # @return [String] the representation of the post.
     def to_s
       %Q(#<#{self.class.name} #{@id} "#{@type}">)

spec/post/lifetime_insights_spec.rb

@@ -0,0 +1,26 @@
+require 'spec_helper'
+
+RSpec.describe 'Fb::Post#lifetime_insights' do
+  let(:user) { Fb::User.new access_token: ENV['FB_TEST_ACCESS_TOKEN'] }
+  let(:page) { user.pages.first }
+  let(:post) { page.posts.first }
+
+  context 'given a post and valid metrics' do
+    let(:metrics) { %i(post_video_views post_video_view_time) }
+
+    it 'returns a hash of given metrics mapped to their values' do
+      lifetime_insights = post.lifetime_insights metrics, page.access_token
+      expect(lifetime_insights).to be_a(Hash)
+      expect(lifetime_insights.keys).to match_array metrics
+      expect(lifetime_insights.values).to all (be_an Integer)
+    end
+  end
+
+  context 'given a page and invalid metrics' do
+    let(:metrics) { %i(invalid_metric) }
+
+    it 'raises an HTTPError' do
+      expect{post.lifetime_insights metrics, page.access_token}.to raise_error Fb::HTTPError
+    end
+  end
+end