From 3de985ccc5f1de646406a6da660f285c43221f32 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonatan=20M=C3=A4nnchen?= <jonatan@maennchen.ch>
Date: Fri, 26 Jul 2024 13:57:23 +0200
Subject: [PATCH] feat: Add Ash.Type.File (#1337)

---
 lib/ash/type/file.ex                | 123 ++++++++++++++++++++++
 lib/ash/type/file/implementation.ex |  38 +++++++
 lib/ash/type/file/io.ex             |   8 ++
 lib/ash/type/file/path.ex           |  11 ++
 lib/ash/type/file/plug_upload.ex    |  17 ++++
 lib/ash/type/file/source.ex         |  42 ++++++++
 lib/ash/type/type.ex                |   1 +
 test/type/file_test.exs             | 153 ++++++++++++++++++++++++++++
 8 files changed, 393 insertions(+)
 create mode 100644 lib/ash/type/file.ex
 create mode 100644 lib/ash/type/file/implementation.ex
 create mode 100644 lib/ash/type/file/io.ex
 create mode 100644 lib/ash/type/file/path.ex
 create mode 100644 lib/ash/type/file/plug_upload.ex
 create mode 100644 lib/ash/type/file/source.ex
 create mode 100644 test/type/file_test.exs

diff --git a/lib/ash/type/file.ex b/lib/ash/type/file.ex
new file mode 100644
index 00000000..d99befbc
--- /dev/null
+++ b/lib/ash/type/file.ex
@@ -0,0 +1,123 @@
+defmodule Ash.Type.File do
+  @moduledoc """
+  A type that represents a file on the filesystem.
+
+  > #### Persistence {: .warning}
+  >
+  > This type does not support persisting via `Ash.DataLayer`.
+  >
+  > It is mainly intended to be used in
+  > [arguments](dsl-ash-resource.html#actions-action-argument).
+
+  ## Valid values to cast
+
+  This type can cast multiple types of values:
+
+  * itself
+  * `Plug.Upload`
+  * Any value that implements the `Ash.Type.File.Source` protocol.
+  """
+
+  use Ash.Type
+
+  alias Ash.Type.File.Implementation
+  alias Ash.Type.File.IO, as: IOImplementation
+  alias Ash.Type.File.Path, as: PathImplementation
+  alias Ash.Type.File.Source
+
+  @enforce_keys [:source, :implementation]
+  defstruct [:source, :implementation]
+  @type t() :: %__MODULE__{source: Implementation.source(), implementation: Implementation.t()}
+
+  @impl Ash.Type
+  def storage_type(_constraints), do: :error
+
+  @impl Ash.Type
+  def cast_input(nil, _constraints), do: {:ok, nil}
+  def cast_input(%__MODULE__{} = file, _constraints), do: {:ok, file}
+
+  def cast_input(source, _constraints) do
+    with {:ok, implementation} <- Source.implementation(source) do
+      {:ok, %__MODULE__{source: source, implementation: implementation}}
+    end
+  end
+
+  @impl Ash.Type
+  def cast_stored(_file, _constraints), do: :error
+
+  @impl Ash.Type
+  def dump_to_native(_file, _constraints), do: :error
+
+  @doc """
+  Returns the path to the file.
+
+  Not every implementation will support this operation. If the implementation
+  does not support this operation, then `{:error, :not_supported}` will be
+  returned. In this case, use the `open/2` function to access the file.
+
+  ## Example
+
+      iex> path = "README.md"
+      ...> file = Ash.Type.File.from_path(path)
+      ...> Ash.Type.File.path(file)
+      {:ok, "README.md"}
+
+  """
+  @spec path(file :: t()) :: {:ok, Path.t()} | {:error, :not_supported | Implementation.error()}
+  def path(%__MODULE__{implementation: implementation, source: source}) do
+    Code.ensure_loaded!(implementation)
+
+    if function_exported?(implementation, :path, 1) do
+      implementation.path(source)
+    else
+      {:error, :not_supported}
+    end
+  end
+
+  @doc """
+  Open the file with the given `modes`.
+
+  This function will delegate to the `open/2` function on the `implementation`.
+
+  For details on the `modes` argument, see the `File.open/2` documentation.
+
+  ## Example
+
+      iex> path = "README.md"
+      ...> file = Ash.Type.File.from_path(path)
+      ...> Ash.Type.File.open(file, [:read])
+      ...> # => {:ok, #PID<0.109.0>}
+
+  """
+  @spec open(file :: t(), modes: [File.mode()]) ::
+          {:ok, IO.device()} | {:error, Implementation.error()}
+  def open(%__MODULE__{implementation: implementation, source: source}, modes \\ []),
+    do: implementation.open(source, modes)
+
+  @doc """
+  Create a file from a path.
+
+  ## Example
+
+      iex> path = "README.md"
+      ...> Ash.Type.File.from_path(path)
+      %Ash.Type.File{source: "README.md", implementation: Ash.Type.File.Path}
+
+  """
+  @spec from_path(path :: Path.t()) :: t()
+  def from_path(path), do: %__MODULE__{source: path, implementation: PathImplementation}
+
+  @doc """
+  Create a file from an `IO.device()`
+
+  ## Example
+
+      iex> path = "README.md"
+      ...> {:ok, device} = File.open(path)
+      ...> Ash.Type.File.from_io(device)
+      %Ash.Type.File{source: device, implementation: Ash.Type.File.IO}
+
+  """
+  @spec from_io(device :: IO.device()) :: t()
+  def from_io(device), do: %__MODULE__{source: device, implementation: IOImplementation}
+end
diff --git a/lib/ash/type/file/implementation.ex b/lib/ash/type/file/implementation.ex
new file mode 100644
index 00000000..1041a87c
--- /dev/null
+++ b/lib/ash/type/file/implementation.ex
@@ -0,0 +1,38 @@
+defmodule Ash.Type.File.Implementation do
+  @moduledoc """
+  Behaviour for file implementations that are compatible with `Ash.Type.File`.
+  """
+
+  @typedoc "Any `module()` implementing the `Ash.Type.File.Implementation` behaviour."
+  @type t() :: module()
+
+  @typedoc "The source of the file the implementation operates on."
+  @type source() :: term()
+
+  @typedoc "Errors returned by the implementation."
+  @type error() :: term()
+
+  @doc """
+  Return path of the file on disk.
+
+  See: `Ash.Type.File.path/1`
+
+  This callback is optional. If the file is not stored on disk, this callback
+  can be omitted.
+  """
+  @callback path(file :: source()) :: {:ok, Path.t()} | {:error, error()}
+
+  @doc """
+  Open `IO.device()` for the file.
+
+  See `Ash.Type.File.open/2`
+
+  The return pid must point to a process following the
+  [Erlang I/O Protocol](https://www.erlang.org/doc/apps/stdlib/io_protocol.html)
+  like `StringIO` or `File`.
+  """
+  @callback open(file :: source(), modes :: [File.mode()]) ::
+              {:ok, IO.device()} | {:error, error()}
+
+  @optional_callbacks [path: 1]
+end
diff --git a/lib/ash/type/file/io.ex b/lib/ash/type/file/io.ex
new file mode 100644
index 00000000..df7de1cc
--- /dev/null
+++ b/lib/ash/type/file/io.ex
@@ -0,0 +1,8 @@
+defmodule Ash.Type.File.IO do
+  @moduledoc false
+
+  @behaviour Ash.Type.File.Implementation
+
+  @impl Ash.Type.File.Implementation
+  def open(device, _modes), do: {:ok, device}
+end
diff --git a/lib/ash/type/file/path.ex b/lib/ash/type/file/path.ex
new file mode 100644
index 00000000..67b7e63e
--- /dev/null
+++ b/lib/ash/type/file/path.ex
@@ -0,0 +1,11 @@
+defmodule Ash.Type.File.Path do
+  @moduledoc false
+
+  @behaviour Ash.Type.File.Implementation
+
+  @impl Ash.Type.File.Implementation
+  def path(path), do: {:ok, path}
+
+  @impl Ash.Type.File.Implementation
+  def open(path, modes), do: File.open(path, modes)
+end
diff --git a/lib/ash/type/file/plug_upload.ex b/lib/ash/type/file/plug_upload.ex
new file mode 100644
index 00000000..55428b6d
--- /dev/null
+++ b/lib/ash/type/file/plug_upload.ex
@@ -0,0 +1,17 @@
+if Code.ensure_loaded?(Plug.Upload) do
+  defmodule Ash.Type.File.PlugUpload do
+    @moduledoc false
+
+    @behaviour Ash.Type.File.Implementation
+
+    @impl Ash.Type.File.Implementation
+    def path(%Plug.Upload{path: path}), do: {:ok, path}
+
+    @impl Ash.Type.File.Implementation
+    def open(%Plug.Upload{path: path}, options), do: File.open(path, options)
+  end
+
+  defimpl Ash.Type.File.Source, for: Plug.Upload do
+    def implementation(%Plug.Upload{}), do: {:ok, Ash.Type.File.PlugUpload}
+  end
+end
diff --git a/lib/ash/type/file/source.ex b/lib/ash/type/file/source.ex
new file mode 100644
index 00000000..2c8db907
--- /dev/null
+++ b/lib/ash/type/file/source.ex
@@ -0,0 +1,42 @@
+defprotocol Ash.Type.File.Source do
+  @moduledoc """
+  Protocol for allowing the casting of something into an `Ash.Type.File`.
+
+  ## Usage
+
+  ```elixir
+  defmodule MyStruct do
+    defstruct [:path]
+
+    @behavior Ash.Type.File.Implementation
+
+    @impl Ash.Type.File.Implementation
+    def path(%__MODULE__{path: path}), do: {:ok, path}
+
+    @impl Ash.Type.File.Implementation
+    def open(%__MODULE__{path: path}, modes), do: File.open(path, modes)
+
+    defimpl Ash.Type.File.Source do
+      def implementation(%MyStruct{} = struct), do: {:ok, MyStruct}
+    end
+  end
+  ```
+  """
+
+  @fallback_to_any true
+
+  alias Ash.Type.File.Implementation
+
+  @doc """
+  Detect Implementation of the file.
+
+  Returns an `:ok` tuple with the implementation module if the file is supported
+  and `:error` otherwise.
+  """
+  @spec implementation(t()) :: {:ok, Implementation.t()} | :error
+  def implementation(file)
+end
+
+defimpl Ash.Type.File.Source, for: Any do
+  def implementation(_file), do: :error
+end
diff --git a/lib/ash/type/type.ex b/lib/ash/type/type.ex
index 75356dfe..f394d6fd 100644
--- a/lib/ash/type/type.ex
+++ b/lib/ash/type/type.ex
@@ -36,6 +36,7 @@ defmodule Ash.Type do
     atom: Ash.Type.Atom,
     string: Ash.Type.String,
     integer: Ash.Type.Integer,
+    file: Ash.Type.File,
     float: Ash.Type.Float,
     duration_name: Ash.Type.DurationName,
     function: Ash.Type.Function,
diff --git a/test/type/file_test.exs b/test/type/file_test.exs
new file mode 100644
index 00000000..68c0807b
--- /dev/null
+++ b/test/type/file_test.exs
@@ -0,0 +1,153 @@
+defmodule Ash.Type.FileTest do
+  use ExUnit.Case
+
+  alias Ash.Test.Domain, as: Domain
+  alias Ash.Type.File, as: FileType
+
+  doctest FileType
+
+  defmodule MyFile do
+    defstruct [:path]
+
+    @behaviour FileType.Implementation
+
+    @impl FileType.Implementation
+    def path(%MyFile{path: path}), do: {:ok, path}
+
+    @impl FileType.Implementation
+    def open(%MyFile{path: path}, options), do: File.open(path, options)
+
+    defimpl FileType.Source do
+      def implementation(%MyFile{}), do: {:ok, MyFile}
+    end
+  end
+
+  defmodule StringImpl do
+    @behaviour FileType.Implementation
+
+    @impl FileType.Implementation
+    def open(string, _options), do: StringIO.open(string, [])
+  end
+
+  defmodule Post do
+    @moduledoc false
+    use Ash.Resource, domain: Domain, data_layer: Ash.DataLayer.Ets
+
+    ets do
+      private?(true)
+    end
+
+    actions do
+      defaults []
+    end
+
+    attributes do
+      uuid_primary_key :id
+    end
+
+    actions do
+      action :import, :file do
+        argument :file, :file, allow_nil?: false
+
+        run fn %Ash.ActionInput{arguments: %{file: file}}, _context ->
+          {:ok, file}
+        end
+      end
+    end
+  end
+
+  describe inspect(&FileType.cast_input/2) do
+    test "can cast itself" do
+      file = %FileType{source: __ENV__.file, implementation: FileType.Path}
+
+      assert {:ok, ^file} =
+               Post
+               |> Ash.ActionInput.for_action(:import, %{file: file})
+               |> Ash.run_action()
+    end
+
+    test "can cast protocol implementation" do
+      file = %MyFile{path: __ENV__.file}
+
+      assert {:ok, %FileType{implementation: MyFile, source: ^file}} =
+               Post
+               |> Ash.ActionInput.for_action(:import, %{file: file})
+               |> Ash.run_action()
+    end
+
+    test "can cast Plug.Upload" do
+      file = %Plug.Upload{path: __ENV__.file}
+
+      assert {:ok, %FileType{implementation: FileType.PlugUpload, source: ^file}} =
+               Post
+               |> Ash.ActionInput.for_action(:import, %{file: file})
+               |> Ash.run_action()
+    end
+
+    test "can't cast any other value" do
+      file = DateTime.utc_now()
+
+      assert {:error,
+              %Ash.Error.Invalid{
+                errors: [%Ash.Error.Action.InvalidArgument{field: :file, class: :invalid}]
+              }} =
+               Post
+               |> Ash.ActionInput.for_action(:import, %{file: file})
+               |> Ash.run_action()
+    end
+  end
+
+  describe inspect(&FileType.open/2) do
+    test "can open path" do
+      file = FileType.from_path(__ENV__.file)
+
+      assert {:ok, handle} = FileType.open(file, [:read])
+
+      assert IO.read(handle, 9) == "defmodule"
+    end
+
+    test "can open IO device" do
+      {:ok, device} = StringIO.open("Test")
+      file = FileType.from_io(device)
+
+      assert {:ok, handle} = FileType.open(file, [:read])
+
+      assert IO.read(handle, 4) == "Test"
+    end
+
+    test "can open Plug.Upload" do
+      file = %FileType{
+        source: %Plug.Upload{path: __ENV__.file},
+        implementation: FileType.PlugUpload
+      }
+
+      assert {:ok, handle} = FileType.open(file, [:read])
+
+      assert IO.read(handle, 9) == "defmodule"
+    end
+  end
+
+  describe inspect(&FileType.path/1) do
+    test "results in path if supported" do
+      file = FileType.from_path(__ENV__.file)
+
+      assert FileType.path(file) == {:ok, __ENV__.file}
+    end
+
+    test "results in path for Plug.Upload" do
+      file = %FileType{
+        source: %Plug.Upload{path: __ENV__.file},
+        implementation: FileType.PlugUpload
+      }
+
+      assert FileType.path(file) == {:ok, __ENV__.file}
+    end
+
+    test "errors if not supported" do
+      {:ok, device} = StringIO.open("Test")
+      file = FileType.from_io(device)
+
+      assert FileType.path(file) == {:error, :not_supported}
+    end
+  end
+end