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

    DEFAULT_TIMEOUT = 10.freeze

    attr_reader :uri

    class << self
      def instance
        @instance ||= new(Configuration.endpoint_uri)
      end

      # For test purpose only.
      def reset_instance!
        @instance = nil
      end

      def request(uri, request, timeout = nil)
        instance_for(uri).request(request, timeout)
      end

      # For test purpose only.
      def clear_cache!
        @instances = nil
        @cert_store = nil
      end

      def cert_store
        @cert_store ||= OpenSSL::X509::Store.new.tap do |store|
          store.set_default_paths
          store.add_file(Configuration.ca_file)
        end
      end

      private

      def instance_for(uri)
        endpoint_url = "#{uri.scheme}://#{uri.host}:#{uri.port}"
        instances.fetch(endpoint_url) do
          instances[endpoint_url] = new(URI.parse(endpoint_url))
        end
      end

      def instances
        @instances ||= {}
      end
    end

    def initialize(uri)
      @uri = uri
    end

    def request(request, timeout=DEFAULT_TIMEOUT)
      request['User-Agent'] = user_agent
      ensure_started(timeout)

      begin
        connection.request(request)
      rescue *SOCKET_ERRORS => e
        ensure_finished
        raise NetworkError.from_socket_error(e)
      end
    end

    private

    attr_accessor :connection

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

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

    def retry_twice_on_socket_error
      attempt = 0
      begin
        yield
      rescue *SOCKET_ERRORS => e
        raise NetworkError.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

    def user_agent
      @user_agent ||= "#{GemInfo.name}-#{GemInfo.version}"
    end
  end
end