From 1a39c1bb336753092860fc5eb4a5b6522fa814a6 Mon Sep 17 00:00:00 2001
From: byGalax <dennis@landmann.dev>
Date: Sat, 16 May 2026 17:55:20 +0200
Subject: [PATCH] feat(shared): parseMentionUsernames + insertMentions helpers

---
 packages/shared/src/chat/index.ts         |  1 +
 packages/shared/src/chat/mentions.test.ts | 27 ++++++++++
 packages/shared/src/chat/mentions.ts      | 60 +++++++++++++++++++++++
 3 files changed, 88 insertions(+)
 create mode 100644 packages/shared/src/chat/mentions.test.ts
 create mode 100644 packages/shared/src/chat/mentions.ts

diff --git a/packages/shared/src/chat/index.ts b/packages/shared/src/chat/index.ts
index 2172065..5ca0053 100644
--- a/packages/shared/src/chat/index.ts
+++ b/packages/shared/src/chat/index.ts
@@ -8,6 +8,7 @@ export * from './messages';
 export * from './types';
 export * from './userKeyMigration';
 export * from './pinnedMessages';
+export * from './mentions';
 
 // ----- RPC wrappers ---------------------------------------------------------
 
diff --git a/packages/shared/src/chat/mentions.test.ts b/packages/shared/src/chat/mentions.test.ts
new file mode 100644
index 0000000..5730a46
--- /dev/null
+++ b/packages/shared/src/chat/mentions.test.ts
@@ -0,0 +1,27 @@
+import { describe, expect, it } from 'vitest';
+
+import { parseMentionUsernames } from './mentions';
+
+describe('parseMentionUsernames', () => {
+  it('extracts a leading mention', () => {
+    expect(parseMentionUsernames('@anna hi')).toEqual(['anna']);
+  });
+  it('extracts mid-sentence', () => {
+    expect(parseMentionUsernames('hey @ben_c what do you think')).toEqual(['ben_c']);
+  });
+  it('lowercases usernames', () => {
+    expect(parseMentionUsernames('hi @Anna')).toEqual(['anna']);
+  });
+  it('deduplicates', () => {
+    expect(parseMentionUsernames('@xx and @xx again')).toEqual(['xx']);
+  });
+  it('ignores emails (no preceding boundary)', () => {
+    expect(parseMentionUsernames('mail me at foo@bar.com')).toEqual([]);
+  });
+  it('rejects 1-char names', () => {
+    expect(parseMentionUsernames('@a')).toEqual([]);
+  });
+  it('handles multiple in one message', () => {
+    expect(parseMentionUsernames('@anna, @ben and @cara')).toEqual(['anna', 'ben', 'cara']);
+  });
+});
diff --git a/packages/shared/src/chat/mentions.ts b/packages/shared/src/chat/mentions.ts
new file mode 100644
index 0000000..5fb6aff
--- /dev/null
+++ b/packages/shared/src/chat/mentions.ts
@@ -0,0 +1,60 @@
+import type { AppSupabaseClient } from '../supabase/client';
+
+// `@anna_b` style — letters, digits, underscore, dot, dash, 2-32 chars.
+// Conservative on purpose: false negatives (a real username we don't match)
+// are recoverable (no notification fires); false positives (matching a
+// non-username) just become an INSERT that the FK check rejects.
+const MENTION_RE = /(?:^|[\s,;:!?(])@([a-zA-Z0-9_.-]{2,32})/g;
+
+export function parseMentionUsernames(plaintext: string): string[] {
+  const out = new Set<string>();
+  for (const m of plaintext.matchAll(MENTION_RE)) {
+    if (m[1]) out.add(m[1].toLowerCase());
+  }
+  return [...out];
+}
+
+export interface MentionResolver {
+  // Resolves an array of @usernames in this conversation to user-ids.
+  // Returns only memberships that exist + are accepted.
+  resolveUsernames(conversationId: string, usernames: string[]): Promise<Map<string, string>>;
+}
+
+export function makeMentionResolver(client: AppSupabaseClient): MentionResolver {
+  return {
+    async resolveUsernames(conversationId, usernames) {
+      if (usernames.length === 0) return new Map();
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      const { data, error } = await (client as any)
+        .from('conversation_members')
+        .select('user_id, accepted, profiles!inner(username)')
+        .eq('conversation_id', conversationId)
+        .eq('accepted', true)
+        .in('profiles.username', usernames);
+      if (error) throw error;
+      const out = new Map<string, string>();
+      for (const row of (data ?? []) as Array<{ user_id: string; profiles: { username: string } }>) {
+        out.set(row.profiles.username.toLowerCase(), row.user_id);
+      }
+      return out;
+    },
+  };
+}
+
+export async function insertMentions(
+  client: AppSupabaseClient,
+  messageId: string,
+  conversationId: string,
+  mentionedUserIds: string[],
+): Promise<void> {
+  if (mentionedUserIds.length === 0) return;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  const { error } = await (client as any).from('message_mentions').insert(
+    mentionedUserIds.map((uid) => ({
+      message_id: messageId,
+      mentioned_user_id: uid,
+      conversation_id: conversationId,
+    })),
+  );
+  if (error) throw error;
+}