Add service to parse PaaS configuration (#260)

app/services/paas_configuration_service.rb

@@ -0,0 +1,44 @@
+class PaasConfigurationService
+  attr_reader :s3_buckets
+
+  def initialize(logger = Rails.logger)
+    @logger = logger
+    @paas_config = read_pass_config
+    @s3_buckets = read_s3_buckets
+  end
+
+  def config_present?
+    !ENV["VCAP_SERVICES"].nil?
+  end
+
+  def s3_config_present?
+    config_present? && @paas_config.key?(:"aws-s3-bucket")
+  end
+
+private
+
+  def read_pass_config
+    unless config_present?
+      @logger.warn("Could not find VCAP_SERVICES in the environment!")
+      return {}
+    end
+
+    begin
+      JSON.parse(ENV["VCAP_SERVICES"], { symbolize_names: true })
+    rescue StandardError
+      @logger.warn("Could not parse VCAP_SERVICES!")
+    end
+  end
+
+  def read_s3_buckets
+    return [] unless s3_config_present?
+
+    s3_buckets = {}
+    @paas_config[:"aws-s3-bucket"].each do |bucket_config|
+      if bucket_config.key?(:instance_name)
+        s3_buckets[bucket_config[:instance_name].to_sym] = bucket_config
+      end
+    end
+    s3_buckets
+  end
+end

spec/services/paas_configuration_service_spec.rb

@@ -0,0 +1,72 @@
+require "rails_helper"
+
+RSpec.describe "PaasConfigurationService" do
+  context "when the paas configuration is unavailable" do
+    subject { PaasConfigurationService.new(logger) }
+    let(:logger) { double("logger") }
+
+    before { allow(logger).to receive(:warn) }
+
+    it "returns the configuration as not present" do
+      expect(subject.config_present?).to be(false)
+    end
+
+    it "returns the S3 configuration as not present" do
+      expect(subject.s3_config_present?).to be(false)
+    end
+
+    it "does not retrieve any S3 bucket configuration" do
+      expect(subject.s3_buckets).to be_empty
+    end
+  end
+
+  context "when the paas configuration is present with S3 buckets" do
+    subject { PaasConfigurationService.new(double("logger")) }
+    let(:vcap_services) do
+      <<-JSON
+        {"aws-s3-bucket": [{"instance_name": "bucket_1"},{"instance_name": "bucket_2"}]}
+      JSON
+    end
+
+    before do
+      allow(ENV).to receive(:[]).with("VCAP_SERVICES").and_return(vcap_services)
+    end
+
+    it "returns the configuration as present" do
+      expect(subject.config_present?).to be(true)
+    end
+
+    it "returns the S3 configuration as present" do
+      expect(subject.s3_config_present?).to be(true)
+    end
+
+    it "does retrieve the S3 bucket configurations" do
+      s3_buckets = subject.s3_buckets
+
+      expect(s3_buckets).to_not be_empty
+      expect(s3_buckets.count).to be(2)
+      expect(s3_buckets).to have_key(:bucket_1)
+      expect(s3_buckets).to have_key(:bucket_2)
+    end
+  end
+
+  context "when the paas configuration is present without S3 buckets" do
+    subject { PaasConfigurationService.new(double("logger")) }
+
+    before do
+      allow(ENV).to receive(:[]).with("VCAP_SERVICES").and_return("{}")
+    end
+
+    it "returns the configuration as present" do
+      expect(subject.config_present?).to be(true)
+    end
+
+    it "returns the S3 configuration as not present" do
+      expect(subject.s3_config_present?).to be(false)
+    end
+
+    it "does not retrieve any S3 bucket configuration" do
+      expect(subject.s3_buckets).to be_empty
+    end
+  end
+end