mdns_lite

defmodule MdnsLite do
  @moduledoc """
  A simple implementation of an mDNS (multicast DNS (Domain Name Server))
  server.  mDNS uses multicast UDP rather than TCP. Its primary use is to
  provide DNS support for the `local` domain. `MdnsLite` listens on a
  well-known ip address/port. If a request arrives that it recognizes, it
  constructs the appropriate DNS response.

  `MdnsLite` responds to a limited number of DNS requests; they are all handled
  in the `MdnsLite.Query` module. Of particular note is the SRV request. The
  response will be a list of known services and how to contact them (domain and
  port) as described in the configuration file.

  `MdnsLite` uses a "network monitor", a module that listens for changes in a
  network.  Its purpose is to ensure that the network interfaces are up to
  date. The current version of `MdnsLite` has an `MdnsLite.InetMonitor` which
  periodically checks, via `inet:getifaddrs()`, for changes in the network. For
  example, a change could be the re-assignment of IP addresses.

  This module is initialized, at runtime, with host information and service
  descriptions found in the `config.exs` file.  The descriptions will be used
  by `MdnsLite` to construct a response to a query.

  Please refer to the `README.md` for further information.
  """

  @doc """
  Set the list of host names

  `host` can have the value of  `:hostname` in which case the value will be
  replaced with the value of `:inet.gethostname()`, otherwise you can provide a
  string value. You can specify an alias hostname in which case `host` will be
  `["hostname", "alias-example"]`. The second value must be a string. When you
  use an alias, an "A" query can be made to  `alias-example.local` as well as
  to `hostname.local`. This can also be configured at runtime via
  `MdnsLite.set_host/1`:

  ```elixir
  iex> MdnsLite.set_host([:hostname, "nerves"])
  :ok
  ```
  """
  defdelegate set_host(host), to: MdnsLite.Configuration

  @doc """
  Add services for mdns_lite to advertise

  The `services` section lists the services that the host offers, such as
  providing an HTTP server. You must supply the `protocol`, `transport` and
  `port` values for each service. You may also specify `weight` and/or `host`.
  They each default to a zero value. Please consult the RFC for an explanation
  of these values. Services can be configured in `config.exs` as shown above,
  or at runtime:

  ```elixir
  iex> services = [
    # service type: _http._tcp.local - used in match
    %{
      name: "Web Server",
      protocol: "http",
      transport: "tcp",
      port: 80,
    },
    # service_type: _ssh._tcp.local - used in match
    %{
      name: "Secure Socket",
      protocol: "ssh",
      transport: "tcp",
      port: 22,
    }
  ]

  iex> MdnsLite.add_mds_services(services)
  :ok
  ```
  """
  defdelegate add_mdns_services(services), to: MdnsLite.Configuration

  @doc """
  Remove services

  Services can also be removed at runtime via `remove_mdns_services/1` with the
  service name to remove:

  ```elixir
  iex> service_names = ["Web Server", "Secure Socket"]
  iex> MdnsLite.remove_mdns_services(services)
  :ok

  # Remove just a single service
  iex> MdnsLite.remove_mdns_services("Secure Socket")
  :ok
  ```
  """
  defdelegate remove_mdns_services(service_names), to: MdnsLite.Configuration
end