require 'rcs-common/trace'

require_release 'rcs-db/db_layer'
require_release 'rcs-db/shard'

require_relative 'mailer'

module RCS
  module Monitor
    class ComponentChecker
      include RCS::Tracer

      attr_reader :mailer

      CACHE_TIMEOUT = 3600 * 3 #3h

      def initialize
        @mailer = Mailer.new
        reset_cache

        reset

        raise "Invalid cn: #{hostname}" if hostname.to_s.empty?
      end

      def check_all
        no_raise do
          reset

          check_mongo("mongoDB router", "#{hostname}:27017")
          check_mongo("mongoDB shard", "#{hostname}:27018")
          check_mongo("mongoDB config", "#{hostname}:27019")

          if @failed.empty? # If there are no errors with mongoDB
            RCS::DB::Shard.sorted.each do |shard|
              address = shard['host'].split(':').first
              check_mongo(shard['_id'], "#{address}:27017")
              check_mongo(shard['_id'], "#{address}:27018")
            end
          end

          if @failed.empty? # If there are no errors with mongoDB in any shard
            ::Status.all.each { |status| check_component(status) }
          end

          if @failed.any?
            subject = "Some errors were reported"
            short_message = subject + ": " + @failed.map { |hash| hash[:name] }.join(", ")

            mailer.alert(subject, :component_failed, binding: binding, short_message: short_message)
          end

          if @restored.any?
            subject = "Components restored"
            short_message = subject + ": " + @restored.map { |hash| hash[:name] }.join(", ")

            mailer.alert(subject, :component_restored, binding: binding, short_message: short_message)
          end
        end
      end

      private

      def reset_cache
        @cache = {}
        @cache_at = Time.now
      end

      def reset
        @failed = []
        @restored = []

        reset_cache if Time.now - @cache_at > CACHE_TIMEOUT
      end

      def no_raise(&block)
        yield
      rescue Moped::Errors::ConnectionFailure, Moped::Errors::QueryFailure => error
        trace(:error, "There was a problem querying mongoDB")
      rescue Exception => error
        # TODO: try to send a mail with the error
        trace(:fatal, "[#{error.class}] #{error.message} #{error.backtrace}")
      end

      def hostname
        @hostname ||= RCS::DB::Config.instance.global['CN']
      end

      def check_connection(host, port)
        build_info = nil
        RCS::DB::DB.instance.open(host, port, 'admin', raise: false) do |session|
          build_info = session.command(buildInfo: 1)
        end
        build_info
      end

      def check_mongo(name, address)
        host, port = *address.split(':')

        trace(:debug, "Checking mongoDB connection to #{address}")
        connection_available = check_connection(host, port)
        hash = {name: "#{name} @ #{address}"}

        if @cache[address] != :error and !connection_available
          trace(:error, "#{name} @ #{host} has failed")
          @failed << hash.merge(message: "Unable to connect (attempted from #{hostname})")
        elsif @cache[address] == :error and connection_available
          trace(:info, "#{name} @ #{host} is healthy again")
          @restored << hash
        end

        @cache[address] = connection_available ? :ok : :error
      end

      def check_component(status)
        trace(:debug, "Checking component #{status.name}")

        status.check

        hash = {name: " #{status.name} (ver. #{status.version}) @ #{status.address}", message: status.info, time: status.time}

        if @cache[status.id] != :error and status.error?
          trace(:error, "Component #{status.name} #{status.version} has failed: #{status.info}")
          @failed << hash
        elsif @cache[status.id] == :error and !status.error?
          trace(:info, "Component #{status.name} #{status.version} is healthy again")
          @restored << hash
        end

        @cache[status.id] = status.error? ? :error : :ok
      end
    end
  end
end