refactor opengraph to a different module with a behaviour

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