local normalize_ip = require("kong.tools.ip").normalize_ip
local dns_client


--- Load and setup the DNS client according to the provided configuration.
-- @param conf (table) Kong configuration
-- @return the initialized `resty.dns.client` module, or an error
local setup_client = function(conf)
  if not dns_client then
    dns_client = require "kong.resty.dns.client"
  end

  conf = conf or {}
  local servers = {}

  -- servers must be reformatted as name/port sub-arrays
  if conf.dns_resolver then
    for i, server in ipairs(conf.dns_resolver) do
      local s = normalize_ip(server)
      servers[i] = { s.host, s.port or 53 }   -- inserting port if omitted
    end
  end

  local opts = {
    hosts = conf.dns_hostsfile,
    resolvConf = nil,                  -- defaults to system resolv.conf
    nameservers = servers,             -- provided list or taken from resolv.conf
    enable_ipv6 = true,                -- allow for ipv6 nameserver addresses
    retrans = nil,                     -- taken from system resolv.conf; attempts
    timeout = nil,                     -- taken from system resolv.conf; timeout
    validTtl = conf.dns_valid_ttl,     -- ttl in seconds overriding ttl of valid records
    badTtl = conf.dns_error_ttl,       -- ttl in seconds for dns error responses (except 3 - name error)
    emptyTtl = conf.dns_not_found_ttl, -- ttl in seconds for empty and "(3) name error" dns responses
    staleTtl = conf.dns_stale_ttl,     -- ttl in seconds for records once they become stale
    cacheSize = conf.dns_cache_size,   -- maximum number of records cached in memory
    order = conf.dns_order,            -- order of trying record types
    noSynchronisation = conf.dns_no_sync,
  }

  -- new dns client
  if ngx.shared.kong_dns_cache and _G.busted_new_dns_client ~= false then

    servers = {}

    if conf.resolver_address then
      for i, server in ipairs(conf.resolver_address) do
        local s = normalize_ip(server)
        servers[i] = { s.host, s.port or 53 }   -- inserting port if omitted
      end
    end

    opts = {
      nameservers = servers,
      hosts = conf.resolver_hosts_file,
      family = conf.resolver_family,
      valid_ttl = conf.resolver_valid_ttl,
      error_ttl = conf.resolver_error_ttl,
      stale_ttl = conf.resolver_stale_ttl,
      cache_size = conf.resolver_lru_cache_size,
      enable_ipv6 = true, -- allow for IPv6 nameserver addresses
    }
  end

  assert(dns_client.init(opts))

  return dns_client
end


return setup_client