Add convenience to store images

lib/music_library/assets.ex

@@ -2,9 +2,22 @@ defmodule MusicLibrary.Assets do
   alias MusicLibrary.Assets.Asset
   alias MusicLibrary.Repo
 
+  @doc """
+  Store any file type - the responsibility to correctly populate format and
+  properties is left to the caller.
+  """
   def store(params) do
     %Asset{}
     |> Asset.changeset(params)
     |> Repo.insert()
   end
+
+  @doc """
+  Store image files - properties will be computed automatically.
+  """
+  def store_image(params) do
+    %Asset{}
+    |> Asset.image_changeset(params)
+    |> Repo.insert()
+  end
 end

lib/music_library/assets/asset.ex

@@ -3,6 +3,8 @@ defmodule MusicLibrary.Assets.Asset do
 
   import Ecto.Changeset
 
+  alias Vix.Vips.Image
+
   @primary_key {:hash, :string, autogenerate: false}
   schema "assets" do
     field :content, :binary
@@ -20,6 +22,15 @@ defmodule MusicLibrary.Assets.Asset do
     |> unique_constraint(:hash)
   end
 
+  def image_changeset(asset, attrs) do
+    asset
+    |> cast(attrs, [:content, :format])
+    |> validate_required([:content, :format])
+    |> generate_hash()
+    |> generate_properties()
+    |> unique_constraint(:hash)
+  end
+
   defp generate_hash(changeset) do
     case get_change(changeset, :content) do
       nil ->
@@ -30,6 +41,25 @@ defmodule MusicLibrary.Assets.Asset do
     end
   end
 
+  defp generate_properties(changeset) do
+    case get_change(changeset, :content) do
+      nil ->
+        changeset
+
+      content ->
+        put_change(changeset, :properties, get_image_properties(content))
+    end
+  end
+
+  defp get_image_properties(content) do
+    {:ok, image} = Image.new_from_buffer(content)
+
+    %{
+      "width" => Image.width(image),
+      "height" => Image.height(image)
+    }
+  end
+
   defp hash(content) do
     :crypto.hash(:sha256, content) |> Base.encode16()
   end

test/music_library/assets_test.exs

@@ -2,6 +2,7 @@ defmodule MusicLibrary.AssetsTest do
   use MusicLibrary.DataCase
 
   alias MusicLibrary.Assets
+  alias MusicLibrary.Fixtures
 
   describe "store/1" do
     test "stores using the hash as key" do
@@ -31,4 +32,19 @@ defmodule MusicLibrary.AssetsTest do
       assert [hash: {"has already been taken", _}] = changeset.errors
     end
   end
+
+  describe "store_image/1" do
+    test "computes properties automatically" do
+      params = %{
+        content: Fixtures.Records.marbles_cover_data(),
+        format: "image/jpeg"
+      }
+
+      assert {:ok, asset} = Assets.store_image(params)
+      assert asset.hash == "599407DDF69907D4A60FE13CCAA824D25CF08DC124FD6AA3E8E7ECD98C885FFE"
+      assert asset.properties == %{"width" => 400, "height" => 396}
+      assert asset.content == Fixtures.Records.marbles_cover_data()
+      assert asset.format == "image/jpeg"
+    end
+  end
 end