class ImportConstituenciesJob < ApplicationJob

  HOST = "http://data.parliament.uk"

  ENDPOINT = "/membersdataplatform/services/mnis/ReferenceData/Constituencies/"

  TIMEOUT = 30

  UTF_BOM = /\A\xEF\xBB\xBF/

  rescue_from StandardError do |exception|

    Appsignal.send_exception exception

   end

  def perform

    current_constituencies.each do |row|

      constituency = Constituency.find_or_initialize_by(external_id: row["Constituency_Id"])

      constituency.name = row["Name"]

      constituency.ons_code = row["ONSCode"]

      constituency.example_postcode = example_postcodes[row["ONSCode"]]

      if constituency.changed? || constituency.new_record?

        constituency.save!

      end

    end

  end

  private

  def constituencies

    response = fetch_constituencies

    # The response from the Parliament API includes a BOM (byte-order mark)

    # and JSON.parse barfs on this so remove it if it is present

    body = response.body.force_encoding("utf-8")

    body = body[1..-1] if body =~ UTF_BOM

    json = JSON.parse(body)

    json["Constituencies"]["Constituency"]

  end

  def current_constituencies

    constituencies.select { |c| c["EndDate"].nil? }

  end

  def faraday

    Faraday.new(HOST) do |f|

      f.response :follow_redirects

      f.response :raise_error

      f.adapter :net_http_persistent

    end

  end

  def fetch_constituencies

    faraday.get(ENDPOINT) do |request|

      request.headers["Accept"] = "application/json"

      request.options[:timeout] = TIMEOUT

      request.options[:open_timeout] = TIMEOUT

    end

  end

  def example_postcodes

    @example_postcodes ||= YAML.load_file(Rails.root.join("data", "example_postcodes.yml"))

  end

end