# `Capstan.Binlog.Event`
[🔗](https://github.com/baselabs/capstan/blob/v1.3.1/lib/capstan/binlog/event.ex#L1)

Binlog event header parse + CRC32 integrity check — the first decode layer.

Every binlog event is a 19-byte header followed by a body:

    <<timestamp::32-little, type::8, server_id::32-little, event_size::32-little,
      log_pos::32-little, flags::16-little, body::binary>>

## CRC32 posture

The C1 substrate runs with `binlog_checksum=CRC32` and the dump negotiates it
(`SET @master_binlog_checksum`), so this module assumes **every** event carries
a trailing 4-byte CRC32 checksum over the whole event minus those 4 bytes. A
`FORMAT_DESCRIPTION` event declares the checksum algorithm on the wire, but C1
does not need to read that byte — the precondition + negotiation already
guarantee CRC32.

`parse/1` verifies the trailer and, on success, returns the header fields plus
the CRC-stripped body. A mismatch fails **loudly**: `{:error, :crc_mismatch}`,
never a usable event — an integrity failure must never be silently swallowed
into something that looks valid. A too-short input returns
`{:error, :truncated}`.

This module does not interpret the body or map `type` to a name — that is
the decoder's job (`Capstan.Binlog.Decoder`), which owns the type-byte → name map and
per-type body decode. `type` here is the raw event-type byte (0..255).

The artificial `ROTATE` that opens every dump (`timestamp=0`, `log_pos=0`) is
a normal, CRC-valid event and parses like any other — callers decide what to
do with it.

# `t`

```elixir
@type t() :: %Capstan.Binlog.Event{
  body: binary(),
  event_size: non_neg_integer(),
  flags: non_neg_integer(),
  log_pos: non_neg_integer(),
  server_id: non_neg_integer(),
  timestamp: non_neg_integer(),
  type: 0..255
}
```

Binlog event header fields plus the CRC-verified, CRC-stripped body.

# `parse`

```elixir
@spec parse(binary()) :: {:ok, t()} | {:error, :truncated | :crc_mismatch}
```

Parses one binlog event: the 19-byte header, splits off the trailing 4-byte
CRC32 checksum, and verifies it against the header + body.

Returns `{:ok, %Event{}}` with the CRC-stripped body on a verified event,
`{:error, :crc_mismatch}` on a checksum mismatch (fail closed), or
`{:error, :truncated}` when `event` is too short to hold a header and
checksum.

---

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