[chat] updates to privacy and filters

apps/api/src/sanitize.ts

@@ -0,0 +1,49 @@
+import { Profanity } from '@2toad/profanity'
+
+/**
+ * The profanity filter behind `POST /api/sanitize/v1/isPure`.
+ *
+ * The word list is `@2toad/profanity`'s rather than one of ours: the hard part of this is
+ * not naming swears, it's not flagging ordinary text — a filter that rejects "Grape
+ * Escape" or "Title Screen" as a room name is worse than no filter, because the player is
+ * told their name is unacceptable and can't see why. It matches whole words, so `grape`,
+ * `analysis`, `assassin`, `class` and `Scunthorpe` come out clean, while leetspeak
+ * (`sh1t`, `a$$hole`) and letters spaced apart (`f u c k`) do not.
+ *
+ * Two knobs below adjust the list for this server; the matching itself is the library's.
+ */
+
+/**
+ * Words to filter on top of the library's list — the ones it doesn't carry but a room
+ * full of players will find. Matched as whole words like everything else, so `kys` here
+ * doesn't flag `skyscraper`.
+ */
+const EXTRA_WORDS: string[] = ['kys', 'molest']
+
+/**
+ * Innocent words that the list reads a swear inside of. Empty today — the whole-word
+ * matching means the usual victims (`shiitake`, `Scunthorpe`, `analysis`) already pass —
+ * and this is where one goes if a player ever turns up with a name it gets wrong, rather
+ * than a change to how matching works.
+ */
+const ALLOWED_WORDS: string[] = []
+
+/**
+ * Built once per isolate, not per request: the constructor compiles the word list into a
+ * regex, which is the whole reason a check costs microseconds at request time. Module
+ * scope is where that cost belongs.
+ */
+const filter = new Profanity({ wholeWord: true })
+filter.addWords(EXTRA_WORDS)
+filter.whitelist.addWords(ALLOWED_WORDS)
+
+/**
+ * Whether `value` contains a swear. Mirrors the reference server's
+ * `Sanitize.ContainsSwears`, which is the whole of what `isPure` reports.
+ *
+ * An empty value is clean — the client checks a field as it's being typed, and an empty
+ * box is not something to refuse.
+ */
+export function containsSwears(value: string): boolean {
+	return value !== '' && filter.exists(value)
+}