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"]
)