refactor opengraph to a different module with a behaviour

lib/pleroma/web/metadata.ex

@@ -1,65 +1,18 @@
 defmodule Pleroma.Web.Metadata do
   alias Phoenix.HTML
-  alias Pleroma.{Formatter, User}
-  alias Pleroma.Web.MediaProxy
 
+  @parsers Pleroma.Config.get([:metadata, :providers], [])
   def build_tags(params) do
-    if(meta_enabled?(:opengraph), do: opengraph_tags(params), else: [])
-    |> Enum.map(&to_tag/1)
-    |> Enum.map(&HTML.safe_to_string/1)
-    |> Enum.join()
-  end
+    Enum.reduce(@parsers, "", fn parser, acc ->
+      rendered_html =
+        params
+        |> parser.build_tags()
+        |> Enum.map(&to_tag/1)
+        |> Enum.map(&HTML.safe_to_string/1)
+        |> Enum.join()
 
-  def meta_enabled?(type) do
-    Pleroma.Config.get([:metadata, type], false)
-  end
-
-  # opengraph for single status
-  defp opengraph_tags(%{activity: activity, user: user}) do
-    with truncated_content = scrub_html_and_truncate(activity.data["object"]["content"]) do
-      [
-        {:meta,
-         [
-           property: "og:title",
-           content:
-             "#{user.name}" <>
-               if user.local do
-                 "(@#{user.nickname}@{pleroma_domain})"
-               else
-                 "(@#{user.nickname})"
-               end
-         ], []},
-        {:meta, [property: "og:url", content: activity.data["id"]], []},
-        {:meta, [property: "og:description", content: truncated_content], []},
-        {:meta, [property: "og:image", content: user_avatar_url(user)], []},
-        {:meta, [property: "og:image:width", content: 120], []},
-        {:meta, [property: "og:image:height", content: 120], []},
-        {:meta, [property: "twitter:card", content: "summary"], []}
-      ]
-    end
-  end
-
-  # opengraph for user card
-  defp opengraph_tags(%{user: user}) do
-    with truncated_bio = scrub_html_and_truncate(user.bio || "") do
-      [
-        {:meta,
-         [
-           property: "og:title",
-           content: "#{user.name} (@#{user.nickname}@#{pleroma_domain()}) profile"
-         ], []},
-        {:meta, [property: "og:url", content: User.profile_url(user)], []},
-        {:meta, [property: "og:description", content: truncated_bio], []},
-        {:meta, [property: "og:image", content: user_avatar_url(user)], []},
-        {:meta, [property: "og:image:width", content: 120], []},
-        {:meta, [property: "og:image:height", content: 120], []},
-        {:meta, [property: "twitter:card", content: "summary"], []}
-      ]
-    end
-  end
-
-  defp opengraph_tags(_) do
-    []
+      acc <> rendered_html
+    end)
   end
 
   def to_tag(data) do
@@ -73,20 +26,4 @@ defmodule Pleroma.Web.Metadata do
         raise ArgumentError, message: "make_tag invalid args"
     end
   end
-
-  defp scrub_html_and_truncate(content) do
-    content
-    # html content comes from DB already encoded, decode first and scrub after
-    |> HtmlEntities.decode()
-    |> Pleroma.HTML.strip_tags()
-    |> Formatter.truncate()
-  end
-
-  defp user_avatar_url(user) do
-    User.avatar_url(user) |> MediaProxy.url()
-  end
-
-  def pleroma_domain do
-    Pleroma.Web.Endpoint.host()
-  end
 end

lib/pleroma/web/metadata/opengraph.ex

@@ -0,0 +1,66 @@
+defmodule Pleroma.Web.Metadata.Providers.OpenGraph do
+  alias Pleroma.Web.Metadata.Providers.Provider
+  alias Pleroma.{HTML, Formatter, User}
+  alias Pleroma.Web.MediaProxy
+
+  @behaviour Provider
+
+  @impl Provider
+  def build_tags(%{activity: activity, user: user}) do
+    with truncated_content = scrub_html_and_truncate(activity.data["object"]["content"]) do
+      [
+        {:meta,
+         [
+           property: "og:title",
+           content: user_name_string(user)
+         ], []},
+        {:meta, [property: "og:url", content: activity.data["id"]], []},
+        {:meta, [property: "og:description", content: truncated_content], []},
+        {:meta, [property: "og:image", content: user_avatar_url(user)], []},
+        {:meta, [property: "og:image:width", content: 120], []},
+        {:meta, [property: "og:image:height", content: 120], []},
+        {:meta, [property: "twitter:card", content: "summary"], []}
+      ]
+    end
+  end
+
+  @impl Provider
+  def build_tags(%{user: user}) do
+    with truncated_bio = scrub_html_and_truncate(user.bio || "") do
+      [
+        {:meta,
+         [
+           property: "og:title",
+           content: user_name_string(user)
+         ], []},
+        {:meta, [property: "og:url", content: User.profile_url(user)], []},
+        {:meta, [property: "og:description", content: truncated_bio], []},
+        {:meta, [property: "og:image", content: user_avatar_url(user)], []},
+        {:meta, [property: "og:image:width", content: 120], []},
+        {:meta, [property: "og:image:height", content: 120], []},
+        {:meta, [property: "twitter:card", content: "summary"], []}
+      ]
+    end
+  end
+
+  defp scrub_html_and_truncate(content) do
+    content
+    # html content comes from DB already encoded, decode first and scrub after
+    |> HtmlEntities.decode()
+    |> HTML.strip_tags()
+    |> Formatter.truncate()
+  end
+
+  defp user_avatar_url(user) do
+    User.avatar_url(user) |> MediaProxy.url()
+  end
+
+  defp user_name_string(user) do
+    "#{user.name}" <>
+      if user.local do
+        "(@#{user.nickname}@#{Pleroma.Web.Endpoint.host()})"
+      else
+        "(@#{user.nickname})"
+      end
+  end
+end

lib/pleroma/web/metadata/provider.ex

@@ -0,0 +1,3 @@
+defmodule Pleroma.Web.Metadata.Providers.Provider do
+  @callback build_tags(map()) :: list()
+end