Use a series with recent data

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2020-01-01 01:01:20 -0500 using RuboCop version 0.78.0.
+# on 2020-01-08 20:39:50 -0500 using RuboCop version 0.78.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new

cpi_fetcher.rb

@@ -6,30 +6,40 @@ require 'net/https'
 require 'uri'
 
 class CPIFetcher
-  DEFAULT_CPI_SERIES_URL = File.join(
-    'https://api.bls.gov',
-    'publicAPI/v2/timeseries/data/CUUSA210SA0'
-  )
-  private_constant :DEFAULT_CPI_SERIES_URL
-  attr_reader :url, :bls_token
-  private :url, :bls_token
-
-  def initialize
-    @url = URI(ENV['CPI_SERIES_URL'] || DEFAULT_CPI_SERIES_URL)
-    @bls_token = ENV.fetch('BLS_TOKEN')
-  end
-
   def cpi
     resp = fetch_raw_response
     return nil unless resp['Results']['series']
 
-    last_cpi_value(resp['Results']['series'].first['data'])
+    latest_cpi_value(resp['Results']['series'].first['data'])
   end
 
-  private def last_cpi_value(data)
-    data
-      .sort { |a, b| a['year'] <=> b['year'] }
-      .then { |d| d.last['value'] }
+  private def url
+    @url ||= URI(ENV['CPI_SERIES_URL'] || File.join(
+      'https://api.bls.gov',
+      'publicAPI/v2/timeseries/data/'
+    ))
+  end
+
+  private def series_id
+    @series_id ||= ENV.fetch(
+      'CPI_SERIES_ID', 'CUURS000SA0,CUUSS000SA0'
+    ).split(/[, ]/).map(&:strip).reject(&:empty?)
+  end
+
+  private def start_year
+    @start_year ||= ENV.fetch('CPI_SERIES_START_YEAR', '2014')
+  end
+
+  private def end_year
+    @end_year ||= ENV.fetch('CPI_SERIES_END_YEAR', Time.now.year.to_s)
+  end
+
+  private def bls_token
+    @bls_token ||= ENV.fetch('BLS_TOKEN')
+  end
+
+  private def latest_cpi_value(data)
+    data.find { |d| d['latest'] == 'true' }.fetch('value')
   end
 
   private def fetch_raw_response
@@ -40,8 +50,18 @@ class CPIFetcher
   end
 
   private def build_request
-    Net::HTTP::Get.new(url)
+    Net::HTTP::Post.new(url)
       .tap { |r| r['Authorization'] = "token #{bls_token}" }
+      .tap { |r| r['Content-Type'] = 'application/json' }
+      .tap { |r| r.body = JSON.generate(build_request_body) }
+  end
+
+  private def build_request_body
+    {
+      'seriesid' => series_id,
+      'startyear' => start_year,
+      'endyear' => end_year
+    }
   end
 end