From 077160157123455375ee386847d1637af036fdb9 Mon Sep 17 00:00:00 2001
From: Danijel Martinek <danijel@fraqtal.xyz>
Date: Fri, 8 May 2026 21:13:18 +0200
Subject: [PATCH] feat(core-realtime): channel-template matcher (placeholder
 extraction)

---
 .../src/channel-template.test.ts              | 33 +++++++++++++++++++
 .../core-realtime/src/channel-template.ts     | 28 ++++++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 packages/core-realtime/src/channel-template.test.ts
 create mode 100644 packages/core-realtime/src/channel-template.ts

diff --git a/packages/core-realtime/src/channel-template.test.ts b/packages/core-realtime/src/channel-template.test.ts
new file mode 100644
index 0000000..39ff016
--- /dev/null
+++ b/packages/core-realtime/src/channel-template.test.ts
@@ -0,0 +1,33 @@
+import { describe, it, expect } from "vitest";
+import { matchChannelTemplate } from "@/channel-template";
+
+describe("matchChannelTemplate", () => {
+  it("matches a plain channel name exactly", () => {
+    expect(matchChannelTemplate("blog.feed", "blog.feed")).toEqual({ params: {} });
+    expect(matchChannelTemplate("blog.feed", "blog.other")).toBeNull();
+  });
+
+  it("matches a templated channel and extracts params", () => {
+    expect(
+      matchChannelTemplate("notifications.user.{userId}", "notifications.user.user_42"),
+    ).toEqual({ params: { userId: "user_42" } });
+  });
+
+  it("returns null when a templated channel doesn't match the shape", () => {
+    expect(
+      matchChannelTemplate("notifications.user.{userId}", "notifications.user"),
+    ).toBeNull();
+    expect(
+      matchChannelTemplate("notifications.user.{userId}", "blog.feed"),
+    ).toBeNull();
+  });
+
+  it("supports multiple placeholders", () => {
+    expect(
+      matchChannelTemplate(
+        "rooms.{roomId}.user.{userId}",
+        "rooms.r1.user.u1",
+      ),
+    ).toEqual({ params: { roomId: "r1", userId: "u1" } });
+  });
+});
diff --git a/packages/core-realtime/src/channel-template.ts b/packages/core-realtime/src/channel-template.ts
new file mode 100644
index 0000000..7247a3d
--- /dev/null
+++ b/packages/core-realtime/src/channel-template.ts
@@ -0,0 +1,28 @@
+const PLACEHOLDER = /\{([a-zA-Z_][a-zA-Z0-9_]*)\}/g;
+
+export function matchChannelTemplate(
+  template: string,
+  candidate: string,
+): { params: Record<string, string> } | null {
+  // No placeholders: exact match.
+  if (!template.includes("{")) {
+    return template === candidate ? { params: {} } : null;
+  }
+
+  // Build a regex from the template, replacing {name} with named groups.
+  const names: string[] = [];
+  const escaped = template.replace(/[.+?^${}()|[\]\\]/g, "\\$&"); // escape regex specials
+  // The above escapes `{` and `}` too — restore them around placeholders.
+  const pattern = escaped.replace(/\\\{([a-zA-Z_][a-zA-Z0-9_]*)\\\}/g, (_m, name) => {
+    names.push(name);
+    return `([^.]+)`;
+  });
+  const re = new RegExp(`^${pattern}$`);
+  const match = candidate.match(re);
+  if (!match) return null;
+  const params: Record<string, string> = {};
+  names.forEach((name, i) => {
+    params[name] = match[i + 1]!;
+  });
+  return { params };
+}