Move obsidian-related imports under Obsidian

lib/obsidian/parser.ex

@@ -0,0 +1,51 @@
+defmodule Obsidian.Parser do
+  alias Obsidian.Entry
+
+  def from_file_contents(file_contents) do
+    with {:ok, [meta]} <- parse_frontmatter(file_contents) do
+      {:ok,
+       %Entry{
+         type: parse_subtype(meta["subType"]),
+         musicbrainz_id: meta["id"],
+         title: meta["title"],
+         year: meta["year"] |> maybe_parse_year(),
+         image_url: meta["image"],
+         genres: meta["genres"]
+       }}
+    end
+  end
+
+  defp parse_frontmatter(file_contents) do
+    case file_contents do
+      "---\n" <> rest ->
+        case String.split(rest, "\n---\n") do
+          [frontmatter, _] ->
+            case YamlElixir.read_all_from_string(frontmatter) do
+              {:ok, meta} -> {:ok, meta}
+              {:error, _} -> {:error, "Invalid frontmatter"}
+            end
+
+          _ ->
+            {:error, "Invalid frontmatter"}
+        end
+
+      _ ->
+        {:error, "Invalid frontmatter"}
+    end
+  end
+
+  defp parse_subtype("Album"), do: :album
+  defp parse_subtype("ep"), do: :ep
+  defp parse_subtype("Live"), do: :live
+  defp parse_subtype("Compilation"), do: :compilation
+  defp parse_subtype("Single"), do: :single
+  defp parse_subtype(_), do: :other
+
+  defp maybe_parse_year(nil), do: nil
+  defp maybe_parse_year(year) when is_integer(year), do: year
+
+  defp maybe_parse_year(year) when is_binary(year) do
+    {integer, _remainder} = Integer.parse(year, 10)
+    integer
+  end
+end