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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Web.RichMedia.Parser do
   6   @hackney_options [
   7     pool: :media,
   8     recv_timeout: 2_000,
   9     max_body: 2_000_000,
  10     with_body: true
  11   ]
  12
  13   defp parsers do
  14     Pleroma.Config.get([:rich_media, :parsers])
  15   end
  16
  17   def parse(nil), do: {:error, "No URL provided"}
  18
  19   if Pleroma.Config.get(:env) == :test do
  20     def parse(url), do: parse_url(url)
  21   else
  22     def parse(url) do
  23       try do
  24         Cachex.fetch!(:rich_media_cache, url, fn _ ->
  25           {:commit, parse_url(url)}
  26         end)
  27         |> set_ttl_based_on_image(url)
  28       rescue
  29         e ->
  30           {:error, "Cachex error: #{inspect(e)}"}
  31       end
  32     end
  33   end
  34
  35   @doc """
  36   Set the rich media cache based on the expiration time of image.
  37
  38   Adopt behaviour `Pleroma.Web.RichMedia.Parser.TTL`
  39
  40   ## Example
  41
  42       defmodule MyModule do
  43         @behaviour Pleroma.Web.RichMedia.Parser.TTL
  44         def ttl(data, url) do
  45           image_url = Map.get(data, :image)
  46           # do some parsing in the url and get the ttl of the image
  47           # and return ttl is unix time
  48           parse_ttl_from_url(image_url)
  49         end
  50       end
  51
  52   Define the module in the config
  53
  54       config :pleroma, :rich_media,
  55         ttl_setters: [MyModule]
  56   """
  57   def set_ttl_based_on_image({:ok, data}, url) do
  58     with {:ok, nil} <- Cachex.ttl(:rich_media_cache, url),
  59          ttl when is_number(ttl) <- get_ttl_from_image(data, url) do
  60       Cachex.expire_at(:rich_media_cache, url, ttl * 1000)
  61       {:ok, data}
  62     else
  63       _ ->
  64         {:ok, data}
  65     end
  66   end
  67
  68   defp get_ttl_from_image(data, url) do
  69     Pleroma.Config.get([:rich_media, :ttl_setters])
  70     |> Enum.reduce({:ok, nil}, fn
  71       module, {:ok, _ttl} ->
  72         module.ttl(data, url)
  73
  74       _, error ->
  75         error
  76     end)
  77   end
  78
  79   defp parse_url(url) do
  80     try do
  81       {:ok, %Tesla.Env{body: html}} = Pleroma.HTTP.get(url, [], adapter: @hackney_options)
  82
  83       html
  84       |> parse_html()
  85       |> maybe_parse()
  86       |> Map.put(:url, url)
  87       |> clean_parsed_data()
  88       |> check_parsed_data()
  89     rescue
  90       e ->
  91         {:error, "Parsing error: #{inspect(e)} #{inspect(__STACKTRACE__)}"}
  92     end
  93   end
  94
  95   defp parse_html(html), do: Floki.parse_document!(html)
  96
  97   defp maybe_parse(html) do
  98     Enum.reduce_while(parsers(), %{}, fn parser, acc ->
  99       case parser.parse(html, acc) do
 100         {:ok, data} -> {:halt, data}
 101         {:error, _msg} -> {:cont, acc}
 102       end
 103     end)
 104   end
 105
 106   defp check_parsed_data(%{title: title} = data)
 107        when is_binary(title) and byte_size(title) > 0 do
 108     {:ok, data}
 109   end
 110
 111   defp check_parsed_data(data) do
 112     {:error, "Found metadata was invalid or incomplete: #{inspect(data)}"}
 113   end
 114
 115   defp clean_parsed_data(data) do
 116     data
 117     |> Enum.reject(fn {key, val} ->
 118       with {:ok, _} <- Jason.encode(%{key => val}) do
 119         false
 120       else
 121         _ -> true
 122       end
 123     end)
 124     |> Map.new()
 125   end
 126 end