# `Tessera.Storage`
[🔗](https://github.com/alexdont/tessera/blob/v0.1.0/lib/tessera/storage.ex#L1)

Write-only storage abstraction for tile output.

Tessera generates a tile (or manifest) into a temporary local file and
hands it off to a storage adapter via `put/3`. The adapter is responsible
for moving / copying / uploading the file to its permanent home. Tessera
cleans up the temp file after `put/3` returns.

## Why write-only

Reads, existence checks, and deletes are the consumer's job. Tessera
never reads back what it wrote: it produces output, hands it off, and
forgets. Caching, eviction, cleanup, and serving live entirely in the
consumer (e.g., PhoenixKit's `FileController`).

## Default implementation

`Tessera.Storage.Local` writes to a caller-supplied `:root` directory on
the local filesystem. Used unless `opts[:storage]` says otherwise.

## Custom adapters

Implement the behaviour and pass the module via `opts[:storage]`:

    defmodule MyApp.S3TileStorage do
      @behaviour Tessera.Storage

      def put(content_path, key, opts) do
        bucket = Keyword.fetch!(opts, :bucket)
        ExAws.S3.put_object(bucket, key, File.read!(content_path))
        |> ExAws.request()
        |> case do
          {:ok, _} -> :ok
          {:error, reason} -> {:error, reason}
        end
      end
    end

    Tessera.generate_tile(input, {1, 0, 0}, "my-image",
      image_width: 4032,
      image_height: 3024,
      storage: MyApp.S3TileStorage,
      storage_opts: [bucket: "my-tiles"]
    )

# `put`

```elixir
@callback put(content_path :: Path.t(), key :: String.t(), opts :: keyword()) ::
  :ok | {:error, term()}
```

Persist a freshly-generated tile or manifest from `content_path` under
the given relative `key` (e.g. `"my-image.dzi"` or
`"my-image_files/3/0_0.jpg"`).

Return `:ok` on success, `{:error, reason}` otherwise. The implementation
may assume `content_path` exists and is readable.

---

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