[Pleroma.Formatter]: Add support for non-HTTP schemes in URIs

The call to the regex in add_links is there just to be sure it’s a legal URI, it can be removed if you want to get more performance.

The URI Schemes list is sorted, but with http(s) at the start (in case it might make it faster for common links).

Closes: https://git.pleroma.social/pleroma/pleroma/issues/127

lib/pleroma/formatter.ex

@@ -165,8 +165,29 @@ defmodule Pleroma.Formatter do
     @emoji
   end
 
-  @link_regex ~r/https?:\/\/[\w\.\/?=\-#\+%&@~'\(\):]+[\w\/]/u
+  @link_regex ~r/[0-9a-z+\-\.]+:[0-9a-z$-_.+!*'(),]+/ui
 
+  # IANA got a list https://www.iana.org/assignments/uri-schemes/ but
+  # Stuff like ipfs isn’t in it
+  # There is very niche stuff
+  @uri_schemes [
+    "https://",
+    "http://",
+    "dat://",
+    "dweb://",
+    "gopher://",
+    "ipfs://",
+    "ipns://",
+    "irc:",
+    "ircs:",
+    "magnet:",
+    "mailto:",
+    "mumble:",
+    "ssb://",
+    "xmpp:"
+  ]
+
+  # TODO: make it use something other than @link_regex
   def html_escape(text) do
     Regex.split(@link_regex, text, include_captures: true)
     |> Enum.map_every(2, fn chunk ->
@@ -176,11 +197,14 @@ defmodule Pleroma.Formatter do
     |> Enum.join("")
   end
 
-  @doc "changes http:... links to html links"
+  @doc "changes scheme:... urls to html links"
   def add_links({subs, text}) do
     links =
-      Regex.scan(@link_regex, text)
+      text
-      |> Enum.map(fn [url] -> {Ecto.UUID.generate(), url} end)
+      |> String.split([" ", "\t", "<br>"])
+      |> Enum.filter(fn word -> String.starts_with?(word, @uri_schemes) end)
+      |> Enum.filter(fn word -> Regex.match?(@link_regex, word) end)
+      |> Enum.map(fn url -> {Ecto.UUID.generate(), url} end)
       |> Enum.sort_by(fn {_, url} -> -String.length(url) end)
 
     uuid_text =