class Redis::Client::Connector::Sentinel

def check(client)
  # Check the instance is really of the role we are looking for.
  # We can't assume the command is supported since it was introduced
  # recently and this client should work with old stuff.
  begin
    role = client.call([:role])[0]
  rescue Redis::CommandError
    # Assume the test is passed if we can't get a reply from ROLE...
    role = @role
  end
  if role != @role
    client.disconnect
    raise ConnectionError, "Instance role mismatch. Expected #{@role}, got #{role}."
  end
end

def initialize(options)
  super(options)
  @options[:password] = DEFAULTS.fetch(:password)
  @options[:db] = DEFAULTS.fetch(:db)
  @sentinels = @options.delete(:sentinels).dup
  @role = @options.fetch(:role, "master").to_s
  @master = @options[:host]
end

def resolve
  result = case @role
           when "master"
             resolve_master
           when "slave"
             resolve_slave
           else
             raise ArgumentError, "Unknown instance role #{@role}"
           end
  result || (raise ConnectionError, "Unable to fetch #{@role} via Sentinel.")
end

def resolve_master
  sentinel_detect do |client|
    if reply = client.call(["sentinel", "get-master-addr-by-name", @master])
      {:host => reply[0], :port => reply[1]}
    end
  end
end

def resolve_slave
  sentinel_detect do |client|
    if reply = client.call(["sentinel", "slaves", @master])
      slave = Hash[*reply.sample]
      {:host => slave.fetch("ip"), :port => slave.fetch("port")}
    end
  end
end

def sentinel_detect
  @sentinels.each do |sentinel|
    client = Client.new(@options.merge({
      :host => sentinel[:host],
      :port => sentinel[:port],
      :reconnect_attempts => 0,
    }))
    begin
      if result = yield(client)
        # This sentinel responded. Make sure we ask it first next time.
        @sentinels.delete(sentinel)
        @sentinels.unshift(sentinel)
        return result
      end
    rescue BaseConnectionError
    ensure
      client.disconnect
    end
  end
  raise CannotConnectError, "No sentinels available."
end