API WRAPPER

api_wrapper.rb

require 'net/http'

module APIWrapper
  class ServiceUnavailable < StandardError; end
  class BadGateway < StandardError; end
  class GatewayTimeOut < StandardError; end
  class UnknownResponse < StandardError; end
  class InvalidResponse < StandardError; end
  class ExternalServerError < StandardError; end
  class BadRequest < StandardError; end
  class Unauthorized < StandardError; end

  HTTP_STATUS_TO_ERRORS = {
    400 => BadRequest,
    401 => Unauthorized,
    500 => ExternalServerError,
    502 => BadGateway,
    503 => ServiceUnavailable,
    504 => GatewayTimeOut
  }.freeze

  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def api_root(root)
      class_variable_set :@@root, root
    end

    private

    def get(path, _params: {}, _headers: {})
      uri      = uri_for(path)
      response = Net::HTTP.get_response(uri)

      response_handler(response)
    end

    def post(path, params: {}, _headers: {})
      uri      = uri_for(path)
      response = Net::HTTP.post_form(uri, params)

      response_handler(response)
    end

    def uri_for(path)
      root = class_variable_get :@@root

      raise 'Missing API root' if root.nil?

      URI("#{root}/#{path}")
    end

    def response_handler(response)
      response_code = response.code.to_i
      response_type = response.content_type
      response_body = response.body

      raise(InvalidResponse, response.body) if response_type != 'application/json'

      case response_code
      when 200, 204
        JSON.parse(response_body) if response_body.present?
      when *HTTP_STATUS_TO_ERRORS.keys
        error_class = HTTP_STATUS_TO_ERRORS[response_code]

        raise error_class, response_body
      else
        raise UnknownResponse, response_body
      end
    rescue JSON::ParserError
      raise InvalidResponse, response_body
    end
  end
end