# `Kombu.Transport.Virtual.Channel`
[🔗](https://github.com/hacktobeer/kombu/blob/v0.1.0/lib/kombu/transport/virtual/channel.ex#L1)

Shared virtual channel operations (`kombu.transport.virtual.base.Channel`).

Provides message envelope preparation, base64 body encoding/decoding, priority clamping,
exchange/queue/binding state transitions, and routing table lookup.

# `augment_message`

```elixir
@spec augment_message(map(), String.t() | nil, String.t() | nil, keyword()) :: map()
```

Augments a prepared message envelope with `body_encoding`, `delivery_tag`,
and `delivery_info` (`exchange`, `routing_key`).

# `decode_body`

```elixir
@spec decode_body(term(), String.t() | nil) :: term()
```

Decodes `body` using `encoding` (`"base64"` or `"utf-8"` / `nil`).

# `encode_body`

```elixir
@spec encode_body(term(), String.t() | nil) :: {term(), String.t() | nil}
```

Encodes `body` using `encoding` (`"base64"` or `"utf-8"` / `nil`).
Returns `{encoded_body, encoding}`.

# `exchange_declare`

```elixir
@spec exchange_declare(
  Kombu.Transport.Virtual.BrokerState.t(),
  String.t() | nil,
  keyword()
) ::
  {:ok, Kombu.Transport.Virtual.BrokerState.t()}
```

Declares an exchange in `%BrokerState{}`.
Raises `Kombu.ChannelError` if `passive: true` and the exchange does not exist,
or `Kombu.NotEquivalentError` if redeclared with incompatible attributes.

# `flow`

Raises `Kombu.NotImplementedError` for unsupported `flow/1` on virtual channels.

# `get_message_priority`

```elixir
@spec get_message_priority(map(), keyword()) :: integer()
```

Extracts and clamps the integer priority (`0..9`) from `message["properties"]["priority"]`.
If `reverse: true`, returns `max_priority - priority` (so priority 9 becomes 0 for Redis keys).

# `list_bindings`

```elixir
@spec list_bindings(Kombu.Transport.Virtual.BrokerState.t()) :: [
  {String.t(), String.t(), String.t()}
]
```

Lists all `{queue, exchange, routing_key}` bindings in `%BrokerState{}`.

# `lookup`

```elixir
@spec lookup(
  Kombu.Transport.Virtual.BrokerState.t(),
  String.t() | nil,
  String.t() | nil,
  String.t() | nil
) :: [String.t()]
```

Looks up all queues matching `routing_key` for `exchange` in `%BrokerState{}`.

# `message_to_python`

```elixir
@spec message_to_python(map() | Kombu.Message.t(), term()) :: Kombu.Message.t()
```

Converts a raw message map into a `%Kombu.Message{}` bound to `channel`.

# `prepare_message`

```elixir
@spec prepare_message(term(), keyword()) :: map()
```

Prepares a message envelope map before publishing (`Channel.prepare_message`).

# `queue_bind`

```elixir
@spec queue_bind(
  Kombu.Transport.Virtual.BrokerState.t(),
  String.t(),
  String.t() | nil,
  String.t() | nil,
  keyword()
) ::
  {{String.t(), String.t(), String.t()},
   Kombu.Transport.Virtual.BrokerState.t()}
```

Binds `queue` to `exchange` with `routing_key` in `%BrokerState{}`.
Returns `{meta_tuple, updated_broker_state}`.

# `queue_unbind`

```elixir
@spec queue_unbind(
  Kombu.Transport.Virtual.BrokerState.t(),
  String.t(),
  String.t() | nil,
  String.t() | nil,
  keyword()
) :: Kombu.Transport.Virtual.BrokerState.t()
```

Unbinds `queue` from `exchange` with `routing_key` in `%BrokerState{}`.

---

*Consult [api-reference.md](api-reference.md) for complete listing*