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+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.RichMedia.Parser do
+  require Logger
+
+  @cachex Pleroma.Config.get([:cachex, :provider], Cachex)
+
+  defp parsers do
+    Pleroma.Config.get([:rich_media, :parsers])
+  end
+
+  def parse(nil), do: {:error, "No URL provided"}
+
+  if Pleroma.Config.get(:env) == :test do
+    @spec parse(String.t()) :: {:ok, map()} | {:error, any()}
+    def parse(url), do: parse_url(url)
+  else
+    @spec parse(String.t()) :: {:ok, map()} | {:error, any()}
+    def parse(url) do
+      with {:ok, data} <- get_cached_or_parse(url),
+           {:ok, _} <- set_ttl_based_on_image(data, url) do
+        {:ok, data}
+      end
+    end
+
+    defp get_cached_or_parse(url) do
+      case @cachex.fetch(:rich_media_cache, url, fn ->
+             case parse_url(url) do
+               {:ok, _} = res ->
+                 {:commit, res}
+
+               {:error, reason} = e ->
+                 # Unfortunately we have to log errors here, instead of doing that
+                 # along with ttl setting at the bottom. Otherwise we can get log spam
+                 # if more than one process was waiting for the rich media card
+                 # while it was generated. Ideally we would set ttl here as well,
+                 # so we don't override it number_of_waiters_on_generation
+                 # times, but one, obviously, can't set ttl for not-yet-created entry
+                 # and Cachex doesn't support returning ttl from the fetch callback.
+                 log_error(url, reason)
+                 {:commit, e}
+             end
+           end) do
+        {action, res} when action in [:commit, :ok] ->
+          case res do
+            {:ok, _data} = res ->
+              res
+
+            {:error, reason} = e ->
+              if action == :commit, do: set_error_ttl(url, reason)
+              e
+          end
+
+        {:error, e} ->
+          {:error, {:cachex_error, e}}
+      end
+    end
+
+    defp set_error_ttl(_url, :body_too_large), do: :ok
+    defp set_error_ttl(_url, {:content_type, _}), do: :ok
+
+    # The TTL is not set for the errors above, since they are unlikely to change
+    # with time
+
+    defp set_error_ttl(url, _reason) do
+      ttl = Pleroma.Config.get([:rich_media, :failure_backoff], 60_000)
+      @cachex.expire(:rich_media_cache, url, ttl)
+      :ok
+    end
+
+    defp log_error(url, {:invalid_metadata, data}) do
+      Logger.debug(fn -> "Incomplete or invalid metadata for #{url}: #{inspect(data)}" end)
+    end
+
+    defp log_error(url, reason) do
+      Logger.warn(fn -> "Rich media error for #{url}: #{inspect(reason)}" end)
+    end
+  end
+
+  @doc """
+  Set the rich media cache based on the expiration time of image.
+
+  Adopt behaviour `Pleroma.Web.RichMedia.Parser.TTL`
+
+  ## Example
+
+      defmodule MyModule do
+        @behaviour Pleroma.Web.RichMedia.Parser.TTL
+        def ttl(data, url) do
+          image_url = Map.get(data, :image)
+          # do some parsing in the url and get the ttl of the image
+          # and return ttl is unix time
+          parse_ttl_from_url(image_url)
+        end
+      end
+
+  Define the module in the config
+
+      config :pleroma, :rich_media,
+        ttl_setters: [MyModule]
+  """
+  @spec set_ttl_based_on_image(map(), String.t()) ::
+          {:ok, Integer.t() | :noop} | {:error, :no_key}
+  def set_ttl_based_on_image(data, url) do
+    case get_ttl_from_image(data, url) do
+      {:ok, ttl} when is_number(ttl) ->
+        ttl = ttl * 1000
+
+        case @cachex.expire_at(:rich_media_cache, url, ttl) do
+          {:ok, true} -> {:ok, ttl}
+          {:ok, false} -> {:error, :no_key}
+        end
+
+      _ ->
+        {:ok, :noop}
+    end
+  end
+
+  defp get_ttl_from_image(data, url) do
+    [:rich_media, :ttl_setters]
+    |> Pleroma.Config.get()
+    |> Enum.reduce({:ok, nil}, fn
+      module, {:ok, _ttl} ->
+        module.ttl(data, url)
+
+      _, error ->
+        error
+    end)
+  end
+
+  def parse_url(url) do
+    with {:ok, %Tesla.Env{body: html}} <- Pleroma.Web.RichMedia.Helpers.rich_media_get(url),
+         {:ok, html} <- Floki.parse_document(html) do
+      html
+      |> maybe_parse()
+      |> Map.put("url", url)
+      |> clean_parsed_data()
+      |> check_parsed_data()
+    end
+  end
+
+  defp maybe_parse(html) do
+    Enum.reduce_while(parsers(), %{}, fn parser, acc ->
+      case parser.parse(html, acc) do
+        data when data != %{} -> {:halt, data}
+        _ -> {:cont, acc}
+      end
+    end)
+  end
+
+  defp check_parsed_data(%{"title" => title} = data)
+       when is_binary(title) and title != "" do
+    {:ok, data}
+  end
+
+  defp check_parsed_data(data) do
+    {:error, {:invalid_metadata, data}}
+  end
+
+  defp clean_parsed_data(data) do
+    data
+    |> Enum.reject(fn {key, val} ->
+      not match?({:ok, _}, Jason.encode(%{key => val}))
+    end)
+    |> Map.new()
+  end
+end