# frozen_string_literal: true

class RedisClient
  class SentinelConfig
    include Config::Common

    SENTINEL_DELAY = 0.25
    DEFAULT_RECONNECT_ATTEMPTS = 2

    attr_reader :name

    def initialize(
      sentinels:,
      sentinel_password: nil,
      sentinel_username: nil,
      role: :master,
      name: nil,
      url: nil,
      **client_config
    )
      unless %i(master replica slave).include?(role.to_sym)
        raise ArgumentError, "Expected role to be either :master or :replica, got: #{role.inspect}"
      end

      if url
        url_config = URLConfig.new(url)
        client_config = {
          username: url_config.username,
          password: url_config.password,
          db: url_config.db,
        }.compact.merge(client_config)
        name ||= url_config.host
      end

      @name = name
      unless @name
        raise ArgumentError, "RedisClient::SentinelConfig requires either a name or an url with a host"
      end

      @to_list_of_hash = @to_hash = nil
      @extra_config = {
        username: sentinel_username,
        password: sentinel_password,
        db: nil,
      }
      if client_config[:protocol] == 2
        @extra_config[:protocol] = client_config[:protocol]
        @to_list_of_hash = lambda do |may_be_a_list|
          if may_be_a_list.is_a?(Array)
            may_be_a_list.map { |l| l.each_slice(2).to_h }
          else
            may_be_a_list
          end
        end
      end

      @sentinels = {}.compare_by_identity
      @role = role.to_sym
      @mutex = Mutex.new
      @config = nil

      client_config[:reconnect_attempts] ||= DEFAULT_RECONNECT_ATTEMPTS
      @client_config = client_config || {}
      super(**client_config)
      @sentinel_configs = sentinels_to_configs(sentinels)
    end

    def sentinels
      @mutex.synchronize do
        @sentinel_configs.dup
      end
    end

    def reset
      @mutex.synchronize do
        @config = nil
      end
    end

    def host
      config.host
    end

    def port
      config.port
    end

    def path
      nil
    end

    def retry_connecting?(attempt, error)
      reset unless error.is_a?(TimeoutError)
      super
    end

    def sentinel?
      true
    end

    def check_role!(role)
      if @role == :master
        unless role == "master"
          sleep SENTINEL_DELAY
          raise FailoverError, "Expected to connect to a master, but the server is a replica"
        end
      else
        unless role == "slave"
          sleep SENTINEL_DELAY
          raise FailoverError, "Expected to connect to a replica, but the server is a master"
        end
      end
    end

    def resolved?
      @mutex.synchronize do
        !!@config
      end
    end

    private

    def sentinels_to_configs(sentinels)
      sentinels.map do |sentinel|
        case sentinel
        when String
          Config.new(**@client_config, **@extra_config, url: sentinel)
        else
          Config.new(**@client_config, **@extra_config, **sentinel)
        end
      end
    end

    def config
      @mutex.synchronize do
        @config ||= if @role == :master
          resolve_master
        else
          resolve_replica
        end
      end
    end

    def resolve_master
      each_sentinel do |sentinel_client|
        host, port = sentinel_client.call("SENTINEL", "get-master-addr-by-name", @name)
        next unless host && port

        refresh_sentinels(sentinel_client)

        return Config.new(host: host, port: Integer(port), **@client_config)
      end
    rescue ConnectionError
      raise ConnectionError, "No sentinels available"
    else
      raise ConnectionError, "Couldn't locate a replica for role: #{@name}"
    end

    def sentinel_client(sentinel_config)
      @sentinels[sentinel_config] ||= sentinel_config.new_client
    end

    def resolve_replica
      each_sentinel do |sentinel_client|
        replicas = sentinel_client.call("SENTINEL", "replicas", @name, &@to_list_of_hash)
        replicas.reject! do |r|
          flags = r["flags"].to_s.split(",")
          flags.include?("s_down") || flags.include?("o_down")
        end
        next if replicas.empty?

        replica = replicas.sample
        return Config.new(host: replica["ip"], port: Integer(replica["port"]), **@client_config)
      end
    rescue ConnectionError
      raise ConnectionError, "No sentinels available"
    else
      raise ConnectionError, "Couldn't locate a replica for role: #{@name}"
    end

    def each_sentinel
      last_error = nil

      @sentinel_configs.dup.each do |sentinel_config|
        sentinel_client = sentinel_client(sentinel_config)
        success = true
        begin
          yield sentinel_client
        rescue RedisClient::Error => error
          last_error = error
          success = false
          sleep SENTINEL_DELAY
        ensure
          if success
            @sentinel_configs.unshift(@sentinel_configs.delete(sentinel_config))
          end
          # Redis Sentinels may be configured to have a lower maxclients setting than
          # the Redis nodes. Close the connection to the Sentinel node to avoid using
          # a connection.
          sentinel_client.close
        end
      end

      raise last_error if last_error
    end

    def refresh_sentinels(sentinel_client)
      sentinel_response = sentinel_client.call("SENTINEL", "sentinels", @name, &@to_list_of_hash)
      sentinels = sentinel_response.map do |sentinel|
        { host: sentinel.fetch("ip"), port: Integer(sentinel.fetch("port")) }
      end
      new_sentinels = sentinels.select do |sentinel|
        @sentinel_configs.none? do |sentinel_config|
          sentinel_config.host == sentinel.fetch(:host) && sentinel_config.port == sentinel.fetch(:port)
        end
      end

      @sentinel_configs.concat sentinels_to_configs(new_sentinels)
    end
  end
end