# `Sftpd.Backends.S3`
[🔗](https://github.com/elixir-ssh/sftpd/blob/v0.1.1/lib/sftpd/backends/s3.ex#L1)

S3 storage backend for the SFTP server.

This backend supports efficient directory listings and optional streaming read
and write callbacks for large file transfers.

S3 support is optional at the package level. Applications that use this
backend must also depend on `:ex_aws`, `:ex_aws_s3`, `:hackney`,
`:sweet_xml`, `:jason`, and `:configparser_ex`. When those dependencies are
absent, `init/1` returns `{:error, :missing_s3_dependency}`.

See the `Backends` extra in HexDocs for package-level backend guidance and
`Telemetry` for the event reference emitted around S3-backed operations.

# `prefix`

```elixir
@type prefix() :: String.t() | {:session, atom()}
```

S3 backend state containing bucket name, optional prefix, and AWS client module

# `state`

```elixir
@type state() :: %{bucket: String.t(), prefix: prefix(), aws_client: module()}
```

# `writer_handle`

```elixir
@type writer_handle() :: %{
  bucket: String.t(),
  key: String.t(),
  upload_id: String.t() | nil,
  next_offset: non_neg_integer(),
  next_part_number: pos_integer(),
  pending_chunks: :queue.queue(binary()),
  pending_size: non_neg_integer(),
  uploaded_parts: [{pos_integer(), binary()}]
}
```

# `init`

```elixir
@spec init(keyword()) :: {:ok, state()} | {:error, atom()}
```

Initialize the S3 backend.

Requires the `:bucket` option. `:prefix` scopes all object keys under a
prefix, and `:aws_client` can override the ExAws-compatible request module.

Returns `{:error, :missing_bucket}` when `:bucket` is not provided.
Returns `{:error, :missing_s3_dependency}` when `ExAws.S3` is unavailable,
which lets core-only applications compile and handle accidental S3
configuration without adding ExAws.

# `parse_http_date`

```elixir
@spec parse_http_date(String.t()) :: :calendar.datetime()
```

Parse an HTTP date string (RFC 1123 format) into an Erlang datetime tuple.

Returns the current time if parsing fails.

## Examples

    iex> Sftpd.Backends.S3.parse_http_date("Sun, 06 Nov 1994 08:49:37 GMT")
    {{1994, 11, 6}, {8, 49, 37}}

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