defmodule LSG.IRC.LinkPlugin do
@moduledoc """
# Link Previewer
An extensible link previewer for IRC.
To extend the supported sites, create a new handler implementing the callbacks.
See `link_plugin/` directory for examples. The first in list handler that returns true to the `match/2` callback will be used,
and if the handler returns `:error` or crashes, will fallback to the default preview.
Unsupported websites will use the default link preview method, which is for html document the title, otherwise it'll use
the mimetype and size.
## Configuration:
```
config :lsg, LSG.IRC.LinkPlugin,
handlers: [
LSG.IRC.LinkPlugin.Youtube: [
invidious: true
],
LSG.IRC.LinkPlugin.Twitter: [],
LSG.IRC.LinkPlugin.Imgur: [],
]
```
"""
@ircdoc """
# Link preview
Previews links (just post a link!).
Announces real URL after redirections and provides extended support for YouTube, Twitter and Imgur.
"""
def short_irc_doc, do: false
def irc_doc, do: @ircdoc
require Logger
def start_link() do
GenServer.start_link(__MODULE__, [], name: __MODULE__)
end
@callback match(uri :: URI.t, options :: Keyword.t) :: {true, params :: Map.t} | false
@callback expand(uri :: URI.t, params :: Map.t, options :: Keyword.t) :: {:ok, lines :: [] | String.t} | :error
@callback post_match(uri :: URI.t, content_type :: binary, headers :: [], opts :: Keyword.t) :: {:body | :file, params :: Map.t} | false
@callback post_expand(uri :: URI.t, body :: binary() | Path.t, params :: Map.t, options :: Keyword.t) :: {:ok, lines :: [] | String.t} | :error
@optional_callbacks [expand: 3, post_expand: 4]
defstruct [:client]
def init([]) do
{:ok, _} = Registry.register(IRC.PubSub, "messages", [plugin: __MODULE__])
#{:ok, _} = Registry.register(IRC.PubSub, "messages:telegram", [plugin: __MODULE__])
Logger.info("Link handler started")
{:ok, %__MODULE__{}}
end
def handle_info({:irc, :text, message = %{text: text}}, state) do
String.split(text)
|> Enum.map(fn(word) ->
if String.starts_with?(word, "http://") || String.starts_with?(word, "https://") do
uri = URI.parse(word)
if uri.scheme && uri.host do
spawn(fn() ->
:timer.kill_after(:timer.seconds(30))
case expand_link([uri]) do
{:ok, uris, text} ->
text = case uris do
[uri] -> text
[luri | _] ->
if luri.host == uri.host && luri.path == luri.path do
text
else
["-> #{URI.to_string(luri)}", text]
end
end
if is_list(text) do
for line <- text, do: message.replyfun.(line)
else
message.replyfun.(text)
end
_ -> nil
end
end)
end
end
end)
{:noreply, state}
end
def handle_info(msg, state) do
{:noreply, state}
end
def terminate(_reason, state) do
:ok
end
# 1. Match the first valid handler
# 2. Try to run the handler
# 3. If :error or crash, default link.
# If :skip, nothing
# 4. ?
# Over five redirections: cancel.
def expand_link(acc = [_, _, _, _, _ | _]) do
{:ok, acc, "link redirects more than five times"}
end
def expand_link(acc=[uri | _]) do
Logger.debug("link: expanding: #{inspect uri}")
handlers = Keyword.get(Application.get_env(:lsg, __MODULE__, [handlers: []]), :handlers)
handler = Enum.reduce_while(handlers, nil, fn({module, opts}, acc) ->
Logger.debug("link: attempt expanding: #{inspect module} for #{inspect uri}")
module = Module.concat([module])
case module.match(uri, opts) do
{true, params} -> {:halt, {module, params, opts}}
false -> {:cont, acc}
end
end)
run_expand(acc, handler)
end
def run_expand(acc, nil) do
expand_default(acc)
end
def run_expand(acc=[uri|_], {module, params, opts}) do
Logger.debug("link: expanding #{inspect uri} with #{inspect module}")
case module.expand(uri, params, opts) do
{:ok, data} -> {:ok, acc, data}
:error -> expand_default(acc)
:skip -> nil
end
rescue
e ->
Logger.error("link: rescued #{inspect uri} with #{inspect module}: #{inspect e}")
Logger.error(Exception.format(:error, e, __STACKTRACE__))
expand_default(acc)
catch
e, b ->
Logger.error("link: catched #{inspect uri} with #{inspect module}: #{inspect {e, b}}")
expand_default(acc)
end
defp get(url, headers \\ [], options \\ []) do
get_req(url, :hackney.get(url, headers, <<>>, options))
end
defp get_req(_, {:error, reason}) do
{:error, reason}
end
defp get_req(url, {:ok, 200, headers, client}) do
headers = Enum.reduce(headers, %{}, fn({key, value}, acc) ->
Map.put(acc, String.downcase(key), value)
end)
content_type = Map.get(headers, "content-type", "application/octect-stream")
length = Map.get(headers, "content-length", "0")
{length, _} = Integer.parse(length)
handlers = Keyword.get(Application.get_env(:lsg, __MODULE__, [handlers: []]), :handlers)
handler = Enum.reduce_while(handlers, false, fn({module, opts}, acc) ->
module = Module.concat([module])
try do
case module.post_match(url, content_type, headers, opts) do
{mode, params} when mode in [:body, :file] -> {:halt, {module, params, opts, mode}}
false -> {:cont, acc}
end
rescue
e ->
Logger.error(inspect(e))
{:cont, false}
catch
e, b ->
Logger.error(inspect({b}))
{:cont, false}
end
end)
cond do
handler != false and length <= 30_000_000 ->
case get_body(url, 30_000_000, client, handler, <<>>) do
{:ok, _} = ok -> ok
:error ->
{:ok, "file: #{content_type}, size: #{human_size(length)}"}
end
#String.starts_with?(content_type, "text/html") && length <= 30_000_000 ->
# get_body(url, 30_000_000, client, <<>>)
true ->
:hackney.close(client)
{:ok, "file: #{content_type}, size: #{human_size(length)}"}
end
end
defp get_req(_, {:ok, redirect, headers, client}) when redirect in 300..399 do
headers = Enum.reduce(headers, %{}, fn({key, value}, acc) ->
Map.put(acc, String.downcase(key), value)
end)
location = Map.get(headers, "location")
:hackney.close(client)
{:redirect, location}
end
defp get_req(_, {:ok, status, headers, client}) do
:hackney.close(client)
{:error, status, headers}
end
defp get_body(url, len, client, {handler, params, opts, mode} = h, acc) when len >= byte_size(acc) do
case :hackney.stream_body(client) do
{:ok, data} ->
get_body(url, len, client, h, << acc::binary, data::binary >>)
:done ->
body = case mode do
:body -> acc
:file ->
{:ok, tmpfile} = Plug.Upload.random_file("linkplugin")
File.write!(tmpfile, acc)
tmpfile
end
handler.post_expand(url, body, params, opts)
{:error, reason} ->
{:ok, "failed to fetch body: #{inspect reason}"}
end
end
defp get_body(_, len, client, h, _acc) do
:hackney.close(client)
IO.inspect(h)
{:ok, "Error: file over 30"}
end
def expand_default(acc = [uri = %URI{scheme: scheme} | _]) when scheme in ["http", "https"] do
Logger.debug("link: expanding #{uri} with default")
headers = [{"user-agent", "DmzBot (like TwitterBot)"}]
options = [follow_redirect: false, max_body_length: 30_000_000]
case get(URI.to_string(uri), headers, options) do
{:ok, text} ->
{:ok, acc, text}
{:redirect, link} ->
new_uri = URI.parse(link)
#new_uri = %URI{new_uri | scheme: scheme, authority: uri.authority, host: uri.host, port: uri.port}
expand_link([new_uri | acc])
{:error, status, _headers} ->
text = Plug.Conn.Status.reason_phrase(status)
{:ok, acc, "Error: HTTP #{text} (#{status})"}
{:error, {:tls_alert, {:handshake_failure, err}}} ->
{:ok, acc, "TLS Error: #{to_string(err)}"}
{:error, reason} ->
{:ok, acc, "Error: #{to_string(reason)}"}
end
end
# Unsupported scheme, came from a redirect.
def expand_default(acc = [uri | _]) do
{:ok, [uri], "-> #{URI.to_string(uri)}"}
end
defp human_size(bytes) do
bytes
|> FileSize.new(:b)
|> FileSize.scale()
|> FileSize.format()
end
end
