    # 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 = {})
      stream = nil
      begin
        response = connection(opts).public_send(http_method.to_sym.downcase) do |req|
          request = build_request(http_method, path, req, opts)
          stream = download_file(request) if opts[:return_type] == 'File' || opts[:return_type] == 'Binary'
        end

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

        unless response.success?
          if response.status == 0 && response.respond_to?(:return_message)
            # Errors from libcurl will be made visible here
            fail ApiError.new(code: 0,
                              message: response.return_message)
          else
            fail ApiError.new(code: response.status,
                              response_headers: response.headers,
                              response_body: response.body),
                 response.reason_phrase
          end
        end
      rescue Faraday::TimeoutError
        fail ApiError.new('Connection timed out')
      rescue Faraday::ConnectionFailed
        fail ApiError.new('Connection failed')
      end

      if opts[:return_type] == 'File' || opts[:return_type] == 'Binary'
        data = deserialize_file(response, stream)
      elsif opts[:return_type]
        data = deserialize(response, opts[:return_type])
      else
        data = nil
      end
      return data, response.status, 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 [Faraday::Request] A Faraday Request
    def build_request(http_method, path, request, 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] || {}

      update_params_for_auth! header_params, query_params, opts[:auth_names]

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

      # Overload default options only if provided
      request.options.params_encoder = config.params_encoder if config.params_encoder
      request.options.timeout        = config.timeout        if config.timeout

      request.url url
      request.params = query_params
      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'
        data = URI.encode_www_form(form_params)
      elsif header_params['Content-Type'] == 'multipart/form-data'
        data = {}
        form_params.each do |key, value|
          case value
          when ::File, ::Tempfile
            data[key] = Faraday::FilePart.new(value.path, Marcel::MimeType.for(Pathname.new(value.path)))
          when ::Array, nil
            # let Faraday handle 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

    def download_file(request)
      stream = []

      # handle streaming Responses
      request.options.on_data = Proc.new do |chunk, overall_received_bytes|
        stream << chunk
      end
      stream
    end

    def deserialize_file(response, stream)
      body = response.body
      if @config.return_binary_data == true
        # return byte stream
        encoding = body.encoding
        stream.join.force_encoding(encoding)
      else
        # return file instead of binary data
        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 = body.encoding
        tempfile = Tempfile.open(prefix, @config.temp_folder_path, encoding: encoding)
        tempfile.write(stream.join.force_encoding(encoding))
        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`"
        tempfile
      end
    end

    def connection(opts)
      opts[:header_params]['Content-Type'] == 'multipart/form-data' ? connection_multipart : connection_regular
    end

    def connection_multipart
      @connection_multipart ||= build_connection do |conn|
        conn.request :multipart
        conn.request :url_encoded
      end
    end

    def connection_regular
      @connection_regular ||= build_connection
    end

    def build_connection
      Faraday.new(url: config.base_url, ssl: ssl_options, proxy: config.proxy) do |conn|
        basic_auth(conn)
        config.configure_middleware(conn)
        yield(conn) if block_given?
        conn.adapter(Faraday.default_adapter)
        config.configure_connection(conn)
      end
    end

    def ssl_options
      {
        ca_file: config.ssl_ca_file,
        verify: config.ssl_verify,
        verify_mode: config.ssl_verify_mode,
        client_cert: config.ssl_client_cert,
        client_key: config.ssl_client_key
      }
    end

    def basic_auth(conn)
      if config.username && config.password
        if Gem::Version.new(Faraday::VERSION) >= Gem::Version.new('2.0')
          conn.request(:authorization, :basic, config.username, config.password)
        else
          conn.request(:basic_auth, config.username, config.password)
        end
      end
    end
