require 'timeout'

module RailsConnector
class ContentService
  DEFAULT_PROTOCOL = 'https'.freeze
  DEFAULT_TIMEOUT = 10.freeze

  SOCKET_ERRORS = [
    EOFError,
    Errno::ECONNABORTED,
    Errno::ECONNREFUSED,
    Errno::ECONNRESET,
    Errno::EINVAL,
    Errno::EPIPE,
    Errno::ETIMEDOUT,
    IOError,
    SocketError,
    Timeout::Error,
  ].freeze

  class Configuration
    attr_accessor :url
    attr_accessor :login
    attr_accessor :api_key
    attr_accessor :http_host

    def url
      if @url.nil?
        raise RailsConnectorError,
          'ContentService configuration key "url" is missing. '\
          'Set "RailsConnector::Configuration.content_service_url = <url>"'
      end

      @url
    end
  end

  cattr_accessor :configuration do
    Configuration.new
  end

  class RateLimitExceeded < StandardError
    def initialize(retry_after)
      @retry_after = retry_after
    end

    attr_reader :retry_after
  end

  class MaxSleepTimeReached < StandardError
  end

  class Delay
    def initialize
      @sleep_count = 0
      @total_sleep_time = 0
    end

    def next_sleep_time(min_sleep = 0)
      sleep_time = [2 ** @sleep_count * 0.5, min_sleep.to_f].max
      @total_sleep_time += sleep_time
      raise MaxSleepTimeReached if @total_sleep_time > 40
      @sleep_count += 1
      sleep_time
    end
  end

  class << self
    @next_request_not_before = nil

    def query(path, payload, options={})
      timeout = options.fetch(:timeout, DEFAULT_TIMEOUT)
      retry_once_on_socket_error do
        retry_until_timeout_on_rate_limit_exceeded do
          ConnectionManager.ensure_started(uri, timeout)
          request = build_request(path, payload)
          if @next_request_not_before && @next_request_not_before > (now = Time.now)
            sleep @next_request_not_before - now
          end
          handle_response(ConnectionManager.connection(timeout).request(request))
        end
      end
    end

    # for tests only
    def forget_retry_after
      @next_request_not_before = nil
    end

    private

    def retry_once_on_socket_error
      retried = false
      begin
        yield
      rescue *SOCKET_ERRORS => e
        raise BackendNotAvailable.from_socket_error(e) if retried
        ConnectionManager.ensure_finished
        retried = true
        retry
      end
    end

    def retry_until_timeout_on_rate_limit_exceeded
      delay = Delay.new
      begin
        yield
      rescue RateLimitExceeded => e
        begin
          sleep delay.next_sleep_time(e.retry_after)
        rescue MaxSleepTimeReached
          raise BackendNotAvailable.new('rate limit exceeded', 429)
        end
        retry
      end
    end

    def build_request(path, payload)
      request = Net::HTTP::Post.new("#{uri.path}/#{path}".squeeze('/'), request_headers)
      request.basic_auth(configuration.login, configuration.api_key)
      request.body = MultiJson.dump(payload)
      request
    end

    def handle_response(response)
      if response.code.first == '2'
        retry_after = response["Retry-After"]
        @next_request_not_before = retry_after ? Time.now + retry_after.to_f : nil
        MultiJson.load(response.body)
      elsif response.code == "429"
        raise RateLimitExceeded.new(response["Retry-After"])
      else
        raise BackendNotAvailable.new("Server responded with status code #{response.code}", response.code)
      end
    end

    def uri
      url = configuration.url
      url = "#{DEFAULT_PROTOCOL}://#{url}" unless url.match /^http/
      URI.parse(url)
    end

    def request_headers
      headers = {
        'Content-Type' => 'application/json',
        'Accept' => 'application/json',
        'User-Agent' => user_agent,
      }
      if configuration.http_host
        headers['Host'] = configuration.http_host
      end
      headers
    end

    def user_agent
      @user_agent ||= (
        gem_info = Gem.loaded_specs["infopark_cloud_connector"]
        "#{gem_info.name}-#{gem_info.version}"
      )
    end
  end

  module ConnectionManager
    def self.connection(timeout=DEFAULT_TIMEOUT)
      configure_timeout(@connection, timeout) if @connection
      @connection
    end

    def self.connection=(conn)
      @connection = conn
    end

    def self.ensure_started(uri, timeout=DEFAULT_TIMEOUT)
      return if @connection && @connection.started?
      conn = Net::HTTP.new(uri.host, uri.port)
      if uri.scheme == 'https'
        conn.use_ssl = true
        conn.verify_mode = OpenSSL::SSL::VERIFY_PEER
        conn.ca_file = RailsConnector::Configuration.ca_file
      end
      configure_timeout(conn, timeout)
      retry_twice_on_socket_error do
        conn.start
      end
      @connection = conn
    end

    def self.ensure_finished
      @connection.finish if @connection && @connection.started?
      @connection = nil
    end

    class << self
      private

      def retry_twice_on_socket_error
        attempt = 0
        begin
          yield
        rescue *ContentService::SOCKET_ERRORS => e
          raise BackendNotAvailable.from_socket_error(e) if attempt == 2
          attempt += 1
          retry
        end
      end

      def configure_timeout(connection, timeout)
        connection.open_timeout = timeout
        connection.read_timeout = timeout
        connection.ssl_timeout = timeout
      end

    end
  end
end
end