    require 'securerandom'
    
    # Call an API with given options.
    #
    # @return [Array<(Object, Integer, Hash)>] an array of 3 elements:
    #   the data deserialized from response body (could be nil), response status code and response headers.
    def call_api(http_method, path, opts = {})
      opts[:'header_params'][:'svix-req-id'] = SecureRandom.random_number(2**32).to_s
      request = build_request(http_method, path, opts)
      response = request.run

      # retry on 5XX and general network errors
      sleep_time = 0.05
      retry_count = 0
      (0..1).each do |n|
        break if response.success? || (response.code < 500 && response.code > 0)
        retry_count += 1
        sleep(sleep_time)
        sleep_time = sleep_time * 2
        opts[:'header_params'][:'svix-retry-count'] = retry_count.to_s
        request = build_request(http_method, path, opts)
        response = request.run
      end

      if @config.debugging
        @config.logger.debug "HTTP response body ~BEGIN~\n#{response.body}\n~END~\n"
      end

      unless response.success?
        if response.timed_out?
          fail ApiError.new('Connection timed out')
        elsif response.code == 0
          # Errors from libcurl will be made visible here
          fail ApiError.new(:code => 0,
                            :message => response.return_message)
        else
          fail ApiError.new(:code => response.code,
                            :response_headers => response.headers,
                            :response_body => response.body),
               response.status_message
        end
      end

      if opts[:return_type]
        data = deserialize(response, opts[:return_type])
      else
        data = nil
      end
      return data, response.code, response.headers
    end

    # Builds the HTTP request
    #
    # @param [String] http_method HTTP method/verb (e.g. POST)
    # @param [String] path URL path (e.g. /account/new)
    # @option opts [Hash] :header_params Header parameters
    # @option opts [Hash] :query_params Query parameters
    # @option opts [Hash] :form_params Query parameters
    # @option opts [Object] :body HTTP body (JSON/XML)
    # @return [Typhoeus::Request] A Typhoeus Request
    def build_request(http_method, path, opts = {})
      url = build_request_url(path, opts)
      http_method = http_method.to_sym.downcase

      header_params = @default_headers.merge(opts[:header_params] || {})
      query_params = opts[:query_params] || {}
      form_params = opts[:form_params] || {}

      {{#hasAuthMethods}}
      update_params_for_auth! header_params, query_params, opts[:auth_names]
      {{/hasAuthMethods}}

      # set ssl_verifyhosts option based on @config.verify_ssl_host (true/false)
      _verify_ssl_host = @config.verify_ssl_host ? 2 : 0

      req_opts = {
        :method => http_method,
        :headers => header_params,
        :params => query_params,
        :params_encoding => @config.params_encoding,
        :timeout => @config.timeout,
        :ssl_verifypeer => @config.verify_ssl,
        :ssl_verifyhost => _verify_ssl_host,
        :sslcert => @config.cert_file,
        :sslkey => @config.key_file,
        :verbose => @config.debugging
      }

      # set custom cert, if provided
      req_opts[:cainfo] = @config.ssl_ca_cert if @config.ssl_ca_cert

      if [:post, :patch, :put, :delete].include?(http_method)
        req_body = build_request_body(header_params, form_params, opts[:body])
        req_opts.update :body => req_body
        if @config.debugging
          @config.logger.debug "HTTP request body param ~BEGIN~\n#{req_body}\n~END~\n"
        end
      end

      request = Typhoeus::Request.new(url, req_opts)
      download_file(request) if opts[:return_type] == 'File'
      request
    end

    # Builds the HTTP request body
    #
    # @param [Hash] header_params Header parameters
    # @param [Hash] form_params Query parameters
    # @param [Object] body HTTP body (JSON/XML)
    # @return [String] HTTP body data in the form of string
    def build_request_body(header_params, form_params, body)
      # http form
      if header_params['Content-Type'] == 'application/x-www-form-urlencoded' ||
          header_params['Content-Type'] == 'multipart/form-data'
        data = {}
        form_params.each do |key, value|
          case value
          when ::File, ::Array, nil
            # let typhoeus handle File, Array and nil parameters
            data[key] = value
          else
            data[key] = value.to_s
          end
        end
      elsif body
        data = body.is_a?(String) ? body : body.to_json
      else
        data = nil
      end
      data
    end

    # Save response body into a file in (the defined) temporary folder, using the filename
    # from the "Content-Disposition" header if provided, otherwise a random filename.
    # The response body is written to the file in chunks in order to handle files which
    # size is larger than maximum Ruby String or even larger than the maximum memory a Ruby
    # process can use.
    #
    # @see Configuration#temp_folder_path
    def download_file(request)
      tempfile = nil
      encoding = nil
      request.on_headers do |response|
        content_disposition = response.headers['Content-Disposition']
        if content_disposition && content_disposition =~ /filename=/i
          filename = content_disposition[/filename=['"]?([^'"\s]+)['"]?/, 1]
          prefix = sanitize_filename(filename)
        else
          prefix = 'download-'
        end
        prefix = prefix + '-' unless prefix.end_with?('-')
        encoding = response.body.encoding
        tempfile = Tempfile.open(prefix, @config.temp_folder_path, encoding: encoding)
        @tempfile = tempfile
      end
      request.on_body do |chunk|
        chunk.force_encoding(encoding)
        tempfile.write(chunk)
      end
      request.on_complete do |response|
        if tempfile
          tempfile.close
          @config.logger.info "Temp file written to #{tempfile.path}, please copy the file to a proper folder "\
                              "with e.g. `FileUtils.cp(tempfile.path, '/new/file/path')` otherwise the temp file "\
                              "will be deleted automatically with GC. It's also recommended to delete the temp file "\
                              "explicitly with `tempfile.delete`"
        end
      end
    end
