# `HL7v2.Ack`
[🔗](https://github.com/Balneario-de-Cofrentes/hl7v2/blob/v3.10.1/lib/hl7v2/ack.ex#L1)

Builds HL7v2 ACK/NAK response messages.

Given an original message's MSH segment, generates an acknowledgment message
with properly swapped sender/receiver fields and a matching message control ID
in the MSA segment.

## Examples

    iex> msh = %HL7v2.Segment.MSH{
    ...>   field_separator: "|",
    ...>   encoding_characters: "^~\\&",
    ...>   sending_application: %HL7v2.Type.HD{namespace_id: "SENDER"},
    ...>   receiving_application: %HL7v2.Type.HD{namespace_id: "RECEIVER"},
    ...>   message_type: %HL7v2.Type.MSG{message_code: "ADT", trigger_event: "A01"},
    ...>   message_control_id: "MSG001",
    ...>   processing_id: %HL7v2.Type.PT{processing_id: "P"},
    ...>   version_id: %HL7v2.Type.VID{version_id: "2.5.1"}
    ...> }
    iex> {ack_msh, msa} = HL7v2.Ack.accept(msh)
    iex> msa.acknowledgment_code
    "AA"
    iex> msa.message_control_id
    "MSG001"
    iex> ack_msh.sending_application.namespace_id
    "RECEIVER"

# `accept`

```elixir
@spec accept(
  HL7v2.Segment.MSH.t(),
  keyword()
) :: {HL7v2.Segment.MSH.t(), HL7v2.Segment.MSA.t()}
```

Builds an AA (Application Accept) acknowledgment.

Returns `{ack_msh, msa}`.

## Options

  * `:text` — optional text message for MSA-3
  * `:message_control_id` — override the generated ACK message control ID

# `encode`

```elixir
@spec encode(
  {HL7v2.Segment.MSH.t(), HL7v2.Segment.MSA.t()}
  | {HL7v2.Segment.MSH.t(), HL7v2.Segment.MSA.t(), HL7v2.Segment.ERR.t()}
) :: binary()
```

Encodes an ACK response to wire format.

Accepts the tuple returned by `accept/2`, `error/2`, or `reject/2`.

## Examples

    iex> msh = %HL7v2.Segment.MSH{
    ...>   field_separator: "|",
    ...>   encoding_characters: "^~\\&",
    ...>   sending_application: %HL7v2.Type.HD{namespace_id: "SENDER"},
    ...>   message_type: %HL7v2.Type.MSG{message_code: "ADT", trigger_event: "A01"},
    ...>   message_control_id: "MSG001",
    ...>   processing_id: %HL7v2.Type.PT{processing_id: "P"},
    ...>   version_id: %HL7v2.Type.VID{version_id: "2.5.1"}
    ...> }
    iex> ack = HL7v2.Ack.accept(msh)
    iex> wire = HL7v2.Ack.encode(ack)
    iex> String.starts_with?(wire, "MSH|^~\\&|")
    true

# `error`

```elixir
@spec error(
  HL7v2.Segment.MSH.t(),
  keyword()
) ::
  {HL7v2.Segment.MSH.t(), HL7v2.Segment.MSA.t()}
  | {HL7v2.Segment.MSH.t(), HL7v2.Segment.MSA.t(), HL7v2.Segment.ERR.t()}
```

Builds an AE (Application Error) acknowledgment.

Returns `{ack_msh, msa}` or `{ack_msh, msa, err}` when `:error_code` is provided.

## Options

  * `:text` — optional text message for MSA-3
  * `:error_code` — HL7 error code identifier (e.g., "207"); triggers ERR segment
  * `:error_text` — descriptive text for the error code
  * `:severity` — error severity: "E" (error), "W" (warning), "I" (information); defaults to "E"
  * `:message_control_id` — override the generated ACK message control ID

# `reject`

```elixir
@spec reject(
  HL7v2.Segment.MSH.t(),
  keyword()
) ::
  {HL7v2.Segment.MSH.t(), HL7v2.Segment.MSA.t()}
  | {HL7v2.Segment.MSH.t(), HL7v2.Segment.MSA.t(), HL7v2.Segment.ERR.t()}
```

Builds an AR (Application Reject) acknowledgment.

Returns `{ack_msh, msa}` or `{ack_msh, msa, err}` when `:error_code` is provided.

## Options

  * `:text` — optional text message for MSA-3
  * `:error_code` — HL7 error code identifier (e.g., "207"); triggers ERR segment
  * `:error_text` — descriptive text for the error code
  * `:severity` — error severity: "E" (error), "W" (warning), "I" (information); defaults to "E"
  * `:message_control_id` — override the generated ACK message control ID

---

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