1 files changed, 42 insertions, 0 deletions
diff --git a/lib/meme.ex b/lib/meme.ex
new file mode 100644
index 0000000..36048f8
--- /dev/null
+++ b/lib/meme.ex
@@ -0,0 +1,42 @@
+import Ecto.Query
+
+alias Thulani.Schema.Meme
+
+defmodule Thulani.Meme do
+  @type kind :: :audio | :text | :image
+
+  def any, do: [:audio, :text, :image] |> MapSet.new()
+  def silent, do: [:text, :image] |> MapSet.new()
+
+  @spec random(MapSet.t(kind) | kind) :: {:ok, Meme} | {:err, term()}
+  def random(allowed_kinds \\ any())
+
+  def random(allowed_kinds) when is_struct(allowed_kinds) do
+    from(m in Meme,
+      where: ^random_predicates(allowed_kinds),
+      order_by: fragment("random()"),
+      limit: 1
+    )
+  end
+
+  def random(kind) when is_atom(kind) do
+    [kind] |> MapSet.new() |> random
+  end
+
+  defp random_predicates(allowed_kinds) do
+    not_permitted = any() |> MapSet.difference(allowed_kinds)
+
+    not_permitted
+    |> Enum.map(fn x -> require_nil(x) end)
+    |> Enum.reduce(true, fn acc, x -> dynamic([], ^acc and ^x) end)
+  end
+
+  defp require_nil(:audio), do: dynamic([m], is_nil(m.audio_id))
+  defp require_nil(:image), do: dynamic([m], is_nil(m.image_id))
+  defp require_nil(:text), do: dynamic([m], is_nil(m.content))
+
+  @spec by_name(String.t()) :: Meme
+  def by_name(name) when is_bitstring(name) do
+    from(m in Meme, where: m.title == ^name)
+  end
+end