require "rack/common_logger"
require "logstash/event"

module Rack
  module Logstasher
    class Logger < Rack::CommonLogger
      def initialize(app, logger, opts = {})
        super(app, logger)
        @extra_request_headers = opts[:extra_request_headers] || {}
        @extra_response_headers = opts[:extra_response_headers] || {}
      end

    private

      def log(env, status, response_headers, began_at)
        now = Utils.clock_time

        data = {
          method: env["REQUEST_METHOD"],
          path: env["PATH_INFO"],
          query_string: env["QUERY_STRING"],
          status: status.to_i,
          duration: duration_in_ms(began_at, now).round(2),
          remote_addr: env["REMOTE_ADDR"],
          request: request_line(env),
          length: extract_content_length(response_headers),
        }

        @extra_request_headers.each do |header, log_key|
          env_key = "HTTP_#{header.upcase.gsub('-', '_')}"
          if env[env_key]
            data[log_key] = env[env_key]
          end
        end

        @extra_response_headers.each do |header, log_key|
          if response_headers[header]
            data[log_key] = response_headers[header]
          end
        end

        event = LogStash::Event.new(data.merge("tags" => %w[request]))
        msg = "#{event.to_json}\n"
        if @logger.respond_to?(:write)
          @logger.write(msg)
        else
          @logger << msg
        end
      end

      def duration_in_ms(began, ended)
        (ended - began) * 1000
      end

      def request_line(env)
        line = "#{env['REQUEST_METHOD']} #{env['SCRIPT_NAME']}#{env['PATH_INFO']}"
        line << "?#{env['QUERY_STRING']}" if env["QUERY_STRING"] && !env["QUERY_STRING"].empty?
        line << " #{env['SERVER_PROTOCOL']}"
        line
      end
    end
  end
end