module Imgur
  Communication = Struct.new(:session) do

    API_VERSION = 3
    MAX_ATTEMPTS = 3

    # RESTful network call
    def call(method, endpoint, params = nil)
      request do
        session.connection.send method, "/#{API_VERSION}/#{endpoint}.json", params
      end
    end

    private

    # Processes RESTful response according the status code
    def request(attempt = 0, &block)
      if attempt == MAX_ATTEMPTS
        raise "Retried #{MAX_ATTEMPTS} times but could not get an access_token"
      end

      response = yield

      case response.status
      when 200, 404
        return parse_message(response.body)['data']
      when 401, 500
        error_message = parse_message response.body
        raise "Unauthorized: #{error_message['error']['message']}"
      when 403
        get_new_and_reset_token

        request attempt + 1, &block # and retry the request once more
      else
        raise "Response code #{response.status} not recognized"
      end
    end

    def get_new_and_reset_token
      access_token = parse_message(
        session.connection.post(
          '/oauth2/token',
          session.params.merge(grant_type: 'refresh_token')
        ).body
      )['access_token']

      session.access_token = access_token
    end

    # Parses the response as JSON and returns the resulting hash
    def parse_message(message)
      begin
        JSON.parse(message)
      rescue => e
        raise "Failed trying to parse response: #{e}"
      end
    end
  end
end