Fix edge cases with parser

- Remove front_matter dependency, and use a hand-rolled simpler parser
  which is suitable for the data to parse (which is well-formed).
- Fix a couple of edge cases with years and titles with commas

lib/music_library/records/parser.ex

@@ -1,24 +1,49 @@
 defmodule MusicLibrary.Records.Parser do
-  alias MusicLibrary.Records.Record
-
   def from_entry_contents(entry_contents) do
-    with {:ok, meta, _body} <- FrontMatter.parse(entry_contents) do
+    with {:ok, [meta]} <- parse_frontmatter(entry_contents) do
       {:ok,
-       %Record{
+       %{
          type: parse_subtype(meta["subType"]),
          musicbrainz_id: meta["id"],
          title: meta["title"],
-         year: meta["year"],
+         year: meta["year"] |> maybe_parse_year(),
          image: meta["image"],
          genres: meta["genres"]
        }}
     end
   end
 
+  defp parse_frontmatter(entry_contents) do
+    case entry_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