stats: fix exception when HelpScout env vars are missing

This fixes the stats page, which used to raise an exception when
HelpScout env vars are not present.

app/controllers/stats_controller.rb

@@ -168,7 +168,12 @@ class StatsController < ApplicationController
     from = Date.new(2018, 1)
     to = Date.today.prev_month
 
-    Helpscout::UserConversationsAdapter.new(from, to)
+    adapter = Helpscout::UserConversationsAdapter.new(from, to)
+    if !adapter.can_fetch_reports?
+      return nil
+    end
+
+    adapter
       .reports
       .map do |monthly_report|
         start_date = monthly_report[:start_date].to_time.localtime

app/lib/helpscout/api.rb

@@ -7,6 +7,15 @@ class Helpscout::API
   PHONES = 'phones'
   OAUTH2_TOKEN = 'oauth2/token'
 
+  def ready?
+    required_secrets = [
+      Rails.application.secrets.helpscout[:mailbox_id],
+      Rails.application.secrets.helpscout[:client_id],
+      Rails.application.secrets.helpscout[:client_secret]
+    ]
+    required_secrets.all?(&:present?)
+  end
+
   def add_tags(conversation_id, tags)
     call_api(:put, "#{CONVERSATIONS}/#{conversation_id}/#{TAGS}", {
       tags: tags

app/lib/helpscout/user_conversations_adapter.rb

@@ -7,6 +7,10 @@ class Helpscout::UserConversationsAdapter
     @to = to
   end
 
+  def can_fetch_reports?
+    api_client.ready?
+  end
+
   # Return an array of monthly reports
   def reports
     @reports ||= (@from..@to)
@@ -35,15 +39,17 @@ class Helpscout::UserConversationsAdapter
     }
   end
 
+  def api_client
+    @api_client ||= Helpscout::API.new
+  end
+
   def fetch_conversations_report(year, month)
     if year == Date.today.year && month == Date.today.month
       raise ArgumentError, 'The report for the current month will change in the future, and cannot be cached.'
     end
 
-    @helpscout_api ||= Helpscout::API.new
-
     Rails.cache.fetch("helpscout-conversation-report-#{year}-#{month}") do
-      @helpscout_api.conversations_report(year, month)
+      api_client.conversations_report(year, month)
     end
   end
 end

spec/lib/helpscout/user_conversations_adapter_spec.rb

@@ -1,10 +1,30 @@
 require 'spec_helper'
 
 describe Helpscout::UserConversationsAdapter do
-  describe '#reports', vcr: { cassette_name: 'helpscout_conversations_reports' } do
-    let(:from) { Date.new(2017, 11) }
-    let(:to)   { Date.new(2017, 12) }
+  let(:from) { Date.new(2017, 11) }
+  let(:to)   { Date.new(2017, 12) }
 
+  describe '#can_fetch_reports?' do
+    context 'when a required secret is missing' do
+      before do
+        Rails.application.secrets.helpscout[:mailbox_id] = nil
+      end
+
+      it { expect(described_class.new(from, to).can_fetch_reports?).to be false }
+    end
+
+    context 'when all required secrets are present' do
+      before do
+        Rails.application.secrets.helpscout[:mailbox_id] = '9999'
+        Rails.application.secrets.helpscout[:client_id] = '1234'
+        Rails.application.secrets.helpscout[:client_secret] = '5678'
+      end
+
+      it { expect(described_class.new(from, to).can_fetch_reports?).to be true }
+    end
+  end
+
+  describe '#reports', vcr: { cassette_name: 'helpscout_conversations_reports' } do
     before { Rails.cache.clear }
 
     subject { described_class.new(from, to) }