exchange.ex

defmodule AMQP.Exchange do
  @moduledoc """
  Functions to operate on Exchanges.
  """

  import AMQP.Core

  alias AMQP.{Basic, Channel}

  @doc """
  Declares an Exchange. The default Exchange type is `direct`.

  AMQP 0-9-1 brokers provide four pre-declared exchanges:

  *   Direct exchange: (empty string) or `amq.direct`
  *   Fanout exchange: `amq.fanout`
  *   Topic exchange: `amq.topic`
  *   Headers exchange: `amq.match` (and `amq.headers` in RabbitMQ)

  Besides the exchange name and type, the following options can be used:

  # Options

    * `:durable`: If set, keeps the Exchange between restarts of the broker;
    * `:auto_delete`: If set, deletes the Exchange once all queues unbind from it;
    * `:passive`: If set, returns an error if the Exchange does not already exist;
    * `:internal:` If set, the exchange may not be used directly by publishers, but only when bound to other exchanges. Internal exchanges are used to construct wiring that is not visible to applications.

  """
  @spec declare(Channel.t, String.t, atom, keyword) :: :ok | Basic.error
  def declare(%Channel{pid: pid}, exchange, type \\ :direct, options \\ []) do
    exchange_declare =
      exchange_declare(exchange:    exchange,
                       type:        Atom.to_string(type),
                       passive:     Keyword.get(options, :passive,     false),
                       durable:     Keyword.get(options, :durable,     false),
                       auto_delete: Keyword.get(options, :auto_delete, false),
                       internal:    Keyword.get(options, :internal,    false),
                       nowait:      Keyword.get(options, :no_wait,     false),
                       arguments:   Keyword.get(options, :arguments,   []))

    case :amqp_channel.call(pid, exchange_declare) do
      exchange_declare_ok() -> :ok
      error -> {:error, error}
    end
  end

  @doc """
  Deletes an Exchange by name. When an Exchange is deleted all bindings to it are
  also deleted
  """
  @spec delete(Channel.t, String.t, keyword) :: :ok | Basic.error
  def delete(%Channel{pid: pid}, exchange, options \\ []) do
    exchange_delete =
      exchange_delete(exchange:  exchange,
                      if_unused: Keyword.get(options, :if_unused, false),
                      nowait:    Keyword.get(options, :no_wait,   false))

    case :amqp_channel.call(pid, exchange_delete) do
      exchange_delete_ok() -> :ok
      error -> {:error, error}
    end
  end

  @doc """
  Binds an Exchange to another Exchange or a Queue using the
  exchange.bind AMQP method (a RabbitMQ-specific extension)
  """
  @spec bind(Channel.t, String.t, String.t, keyword) :: :ok | Basic.error
  def bind(%Channel{pid: pid}, destination, source, options \\ []) do
    exchange_bind =
      exchange_bind(destination: destination,
                    source:      source,
                    routing_key: Keyword.get(options, :routing_key, ""),
                    nowait:      Keyword.get(options, :no_wait,     false),
                    arguments:   Keyword.get(options, :arguments,   []))

    case :amqp_channel.call(pid, exchange_bind) do
      exchange_bind_ok() -> :ok
      error -> {:error, error}
    end
  end

  @doc """
  Unbinds an Exchange from another Exchange or a Queue using the
  exchange.unbind AMQP method (a RabbitMQ-specific extension)
  """
  @spec unbind(Channel.t, String.t, String.t, keyword) :: :ok | Basic.error
  def unbind(%Channel{pid: pid}, destination, source, options \\ []) do
    exchange_unbind =
      exchange_unbind(destination: destination,
                      source:      source,
                      routing_key: Keyword.get(options, :routing_key, ""),
                      nowait:      Keyword.get(options, :no_wait,     false),
                      arguments:   Keyword.get(options, :arguments,   []))

    case :amqp_channel.call(pid, exchange_unbind) do
      exchange_unbind_ok() -> :ok
      error -> {:error, error}
    end
  end

  @doc """
  Convenience function to declare an Exchange of type `direct`.
  """
  @spec direct(Channel.t, String.t, keyword) :: :ok | Basic.error
  def direct(%Channel{} = channel, exchange, options \\ []) do
    declare(channel, exchange, :direct, options)
  end

  @doc """
  Convenience function to declare an Exchange of type `fanout`.
  """
  @spec fanout(Channel.t, String.t, keyword) :: :ok | Basic.error
  def fanout(%Channel{} = channel, exchange, options \\ []) do
    declare(channel, exchange, :fanout, options)
  end

  @doc """
  Convenience function to declare an Exchange of type `topic`.
  """
  @spec topic(Channel.t, String.t, keyword) :: :ok | Basic.error
  def topic(%Channel{} = channel, exchange, options \\ []) do
    declare(channel, exchange, :topic, options)
  end
end