module Redis::Config
  DEFAULT_SENTINEL_PORT = '26379'.freeze
  SIDEKIQ_SIZE = 25

  class << self
    def app
      config
    end

    def sidekiq
      app.merge(size: SIDEKIQ_SIZE)
    end

    def config
      @config ||= sentinel? ? sentinel_config : base_config
    end

    def base_config
      {
        url: ENV.fetch('REDIS_URL', 'redis://127.0.0.1:6379'),
        password: ENV.fetch('REDIS_PASSWORD', nil).presence,
        reconnect_attempts: 2,
        network_timeout: 5
      }
    end

    def sentinel?
      ENV.fetch('REDIS_SENTINELS', nil).presence
    end

    def sentinel_config
      redis_sentinels = ENV.fetch('REDIS_SENTINELS', nil)

      # expected format for REDIS_SENTINELS url string is host1:port1, host2:port2
      sentinels = redis_sentinels.split(',').map do |sentinel_url|
        host, port = sentinel_url.split(':').map(&:strip)
        { host: host, port: port.presence || DEFAULT_SENTINEL_PORT, password: base_config[:password] }
      end

      # over-write redis url as redis://:<your-redis-password>@<master-name>/ when using sentinel
      # more at https://github.com/redis/redis-rb/issues/531#issuecomment-263501322
      master = "redis://#{ENV.fetch('REDIS_SENTINEL_MASTER_NAME', 'mymaster')}"

      base_config.merge({ url: master, sentinels: sentinels })
    end
  end
end