# frozen_string_literal: true

module Karafka
  module Web
    module Tracking
      # Namespace for all the things related to tracking consumers and consuming processes
      module Consumers
        # Samples for fetching and storing metrics samples about the consumer process
        class Sampler
          include ::Karafka::Core::Helpers::Time

          attr_reader :counters, :consumer_groups, :errors, :times, :pauses, :jobs

          # 60 seconds window for time tracked window-based metrics
          TIMES_TTL = 60

          # Times ttl in ms
          TIMES_TTL_MS = TIMES_TTL * 1_000

          private_constant :TIMES_TTL, :TIMES_TTL_MS

          def initialize
            @counters = {
              batches: 0,
              messages: 0,
              errors: 0,
              retries: 0,
              dead: 0
            }
            @times = TtlHash.new(TIMES_TTL_MS)
            @consumer_groups = {}
            @errors = []
            @started_at = float_now
            @pauses = Set.new
            @jobs = {}
            @shell = MemoizedShell.new
          end

          # We cannot report and track the same time, that is why we use mutex here. To make sure
          # that samples aggregations and counting does not interact with reporter flushing.
          def track
            Reporter::MUTEX.synchronize do
              yield(self)
            end
          end

          # @return [Hash] report hash with all the details about consumer operations
          def to_report
            {
              schema_version: '1.0.0',
              type: 'consumer',
              dispatched_at: float_now,

              process: {
                started_at: @started_at,
                name: process_name,
                status: ::Karafka::App.config.internal.status.to_s,
                listeners: Karafka::Server.listeners.count,
                concurrency: concurrency,
                memory_usage: memory_usage,
                memory_total_usage: memory_total_usage,
                memory_size: memory_size,
                cpu_count: cpu_count,
                cpu_usage: cpu_usage
              },

              versions: {
                ruby: ruby_version,
                karafka: ::Karafka::VERSION,
                waterdrop: ::WaterDrop::VERSION
              },

              stats: Karafka::Server.jobs_queue.statistics.merge(
                utilization: utilization
              ).merge(total: @counters),

              consumer_groups: @consumer_groups,
              jobs: jobs.values
            }
          end

          # Clears counters and errors.
          # Used after data is reported by reported to start collecting new samples
          # @note We do not clear processing or pauses or other things like this because we track
          #   their states and not values, so they need to be tracked between flushes.
          def clear
            @counters.each { |k, _| @counters[k] = 0 }

            @errors.clear
          end

          private

          # @return [Numeric] % utilization of all the threads. 100% means all the threads are
          #   utilized all the time within the given time window. 0% means, nothing is happening
          #   most if not all the time.
          def utilization
            return 0 if times[:total].empty?

            # Max times ttl
            timefactor = float_now - @started_at
            timefactor = timefactor > TIMES_TTL ? TIMES_TTL : timefactor

            # We divide by 1_000 to convert from milliseconds
            # We multiply by 100 to have it in % scale
            times[:total].sum / 1_000 / concurrency / timefactor * 100
          end

          # @return [String] Unique process name
          def process_name
            @process_name ||= "#{Socket.gethostname}:#{::Process.pid}:#{SecureRandom.hex(6)}"
          end

          # @return [Integer] memory used by this process in kilobytes
          def memory_usage
            pid = ::Process.pid

            case RUBY_PLATFORM
            # Reading this that way is cheaper than running a shell command
            when /linux/
              IO.readlines("/proc/#{pid}/status").each do |line|
                next unless line.start_with?('VmRSS:')

                break line.split[1].to_i
              end
            when /darwin|bsd/
              @shell
                .call("ps -o pid,rss -p #{pid}")
                .lines
                .last
                .split
                .last
                .to_i
            else
              0
            end
          end

          # Total memory used in the OS
          def memory_total_usage
            case RUBY_PLATFORM
            when /darwin|bsd|linux/
              @shell
                .call('ps -A -o rss=')
                .split("\n")
                .inject { |a, e| a.to_i + e.strip.to_i }
            else
              0
            end
          end

          # @return [Integer] total amount of memory
          def memory_size
            @memory_size ||= case RUBY_PLATFORM
                             when /linux/
                               @shell
                                 .call('grep MemTotal /proc/meminfo')
                                 .match(/(\d+)/)
                                 .to_s
                                 .to_i
                             when /darwin|bsd/
                               @shell
                                 .call('sysctl -a')
                                 .split("\n")
                                 .find { |line| line.start_with?('hw.memsize:') }
                                 .to_s
                                 .split(' ')
                                 .last
                                 .to_i
                             else
                               0
                             end
          end

          # @return [Array<Float>] load averages for last 1, 5 and 15 minutes
          def cpu_usage
            case RUBY_PLATFORM
            when /darwin|bsd|linux/
              @shell
                .call('w | head -1')
                .strip
                .split(' ')
                .map(&:to_f)
                .last(3)
            else
              [-1, -1, -1]
            end
          end

          # @return [Integer] CPU count
          def cpu_count
            @cpu_count ||= Etc.nprocessors
          end

          # @return [String] currently used ruby version with details
          def ruby_version
            if defined?(JRUBY_VERSION)
              revision = JRUBY_REVISION.to_s
              version = JRUBY_VERSION
            else
              revision = RUBY_REVISION.to_s
              version = RUBY_ENGINE_VERSION
            end

            "#{RUBY_ENGINE} #{version}-#{RUBY_PATCHLEVEL} #{revision[0..5]}"
          end

          # @return [Integer] number of threads that process work
          def concurrency
            @concurrency ||= Karafka::App.config.concurrency
          end
        end
      end
    end
  end
end