handle weirdly-formatted friendica peers

CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Added ON DELETE to `most_recent_crawl` table, such that it can handle previously-crawled but now-dead instances.
 - You can now login to the admin view by clicking, not just by pressing enter.
+- Add handling for weirdly-formatted Friendica peers
 
 ## [2.7.0 - 2018-08-18]
 

backend/lib/backend/crawler/crawlers/friendica.ex

@@ -76,13 +76,15 @@ defmodule Backend.Crawler.Crawlers.Friendica do
   end
 
   defp to_domain(url) do
-    url =
-      cond do
-        String.starts_with?(url, "https://") -> String.slice(url, 8..-1)
-        String.starts_with?(url, "http://") -> String.slice(url, 7..-1)
-        true -> url
-      end
-
     url
+    |> strip_prefix("http://")
+    |> strip_prefix("https://")
+    |> strip_username()
+  end
+
+  # Sometimes a url at the poco/@server endpoint has the form username@domain.tld, in which case we only want domain.tld
+  defp strip_username(string) do
+    [_match, _username, domain] = Regex.run(~r/([\w-_]+@)?([\w.-_]+)/, string)
+    domain
   end
 end

backend/lib/backend/crawler/crawlers/misskey.ex

@@ -205,7 +205,7 @@ defmodule Backend.Crawler.Crawlers.Misskey do
   defp extract_mentions_from_status(status) do
     status_content = Map.get(status, "text")
 
-    Regex.scan(~r/@\w+@([\w.-]+)/, status_content)
+    Regex.scan(~r/@\w+@([\w._-]+)/, status_content)
     |> Enum.map(fn [_match, domain] -> domain end)
     |> Enum.reduce(%{}, fn domain, acc ->
       Map.update(acc, domain, 1, &(&1 + 1))

backend/lib/backend/crawler/util.ex

@@ -9,7 +9,7 @@ defmodule Backend.Crawler.Util do
   # (e.g. https://mastodon.social/@demouser or https://pleroma.site/users/demouser)
   @spec get_domain(String.t()) :: String.t()
   def get_domain(url) do
-    [_match, domain] = Regex.run(~r/https?:\/\/([\w.-]+)\/.*/, url)
+    [_match, domain] = Regex.run(~r/https?:\/\/([\w.-_]+)\/.*/, url)
     domain
   end
 

backend/lib/backend/util.ex

@@ -202,4 +202,22 @@ defmodule Backend.Util do
       {:error, error} -> raise error
     end
   end
+
+  @doc """
+  Strips `prefix` from `string`. If it doesn't start with that prefix, just returns the string.
+  """
+  @spec strip_prefix(String.t(), String.t()) :: String.t()
+  def strip_prefix(string, prefix) do
+    if String.starts_with?(string, prefix) do
+      prefix_length = String.length(prefix)
+      String.slice(string, prefix_length..-1)
+    else
+      string
+    end
+  end
+
+  @spec is_valid_domain?(String.t()) :: boolean
+  def is_valid_domain?(domain) do
+    Regex.match?(~r/[\w.-_]+/, domain)
+  end
 end

backend/lib/backend_web/controllers/instance_controller.ex

@@ -1,7 +1,5 @@
 defmodule BackendWeb.InstanceController do
   use BackendWeb, :controller
-
-  import Backend.Util
   alias Graph.Cache
 
   action_fallback(BackendWeb.FallbackController)