class Redis::Cluster::Command

def determine_first_key_position(command)
  case command.first.to_s.downcase
  when 'eval', 'evalsha', 'migrate', 'zinterstore', 'zunionstore' then 3
  when 'object' then 2
  when 'memory'
    command[1].to_s.casecmp('usage').zero? ? 2 : 0
  when 'xread', 'xreadgroup'
    determine_optional_key_position(command, 'streams')
  else
    dig_details(command, :first_key_position).to_i
  end
end

def determine_optional_key_position(command, option_name)
  idx = command.map(&:to_s).map(&:downcase).index(option_name)
  idx.nil? ? 0 : idx + 1
end

def dig_details(command, key)
  name = command.first.to_s
  return unless @details.key?(name)
  @details.fetch(name).fetch(key)
end

def extract_first_key(command)
  i = determine_first_key_position(command)
  return '' if i == 0
  key = command[i].to_s
  hash_tag = extract_hash_tag(key)
  hash_tag.empty? ? key : hash_tag
end

def extract_hash_tag(key)
  s = key.index('{')
  e = key.index('}', s.to_i + 1)
  return '' if s.nil? || e.nil?
  key[s + 1..e - 1]
end

def initialize(details)
  @details = pick_details(details)
end

def pick_details(details)
  details.transform_values do |detail|
    {
      first_key_position: detail[:first],
      write: detail[:flags].include?('write'),
      readonly: detail[:flags].include?('readonly')
    }
  end
end

def should_send_to_master?(command)
  dig_details(command, :write)
end

def should_send_to_slave?(command)
  dig_details(command, :readonly)
end