From 6f9ee3e9b63d238e7d7156f64e828e57c4885cc6 Mon Sep 17 00:00:00 2001
From: Johanna Larsson <johanna.a.m.larsson@gmail.com>
Date: Wed, 29 Jul 2026 08:33:16 +0100
Subject: [PATCH] Adds record key validation

Just a little module with a regex, some docs, and a test. All from the spec
---
 lib/latch/record_key.ex        | 22 ++++++++++++++++++++++
 test/latch/record_key_test.exs | 30 ++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)
 create mode 100644 lib/latch/record_key.ex
 create mode 100644 test/latch/record_key_test.exs

diff --git a/lib/latch/record_key.ex b/lib/latch/record_key.ex
new file mode 100644
index 0000000..d7eef49
--- /dev/null
+++ b/lib/latch/record_key.ex
@@ -0,0 +1,22 @@
+defmodule Latch.RecordKey do
+  @moduledoc """
+  Record keys have a defined set of allowed shapes: TID, NSID, `literal:<value>`, and `any`.
+
+  https://atproto.com/specs/record-key
+  """
+
+  @regex ~r/^[A-Za-z0-9._:~-]{1,512}$/
+
+  @doc """
+  Validates record key syntax according to the spec.
+
+  From the spec:
+  * the allowed characters are alphanumeric (A-Za-z0-9), period, dash, underscore, colon, or tilde (.-_:~)
+  * must have at least 1 and at most 512 characters
+  * the specific record key values . and .. are not allowed
+  """
+  @spec valid?(String.t()) :: boolean()
+  def valid?(key) when is_binary(key) do
+    key not in [".", ".."] and String.match?(key, @regex)
+  end
+end
diff --git a/test/latch/record_key_test.exs b/test/latch/record_key_test.exs
new file mode 100644
index 0000000..2752ee3
--- /dev/null
+++ b/test/latch/record_key_test.exs
@@ -0,0 +1,30 @@
+defmodule Latch.RecordKeyTest do
+  use ExUnit.Case, async: true
+
+  alias Latch.RecordKey
+
+  describe "valid?/1" do
+    test "validates" do
+      # Examples taken from https://atproto.com/specs/record-key#usage-and-implementation-guidelines
+      assert RecordKey.valid?("3jui7kd54zh2y")
+      assert RecordKey.valid?("self")
+      assert RecordKey.valid?("example.com")
+      assert RecordKey.valid?("~1.2-3_")
+      assert RecordKey.valid?("dHJ1ZQ")
+      assert RecordKey.valid?("pre:fix")
+      assert RecordKey.valid?("_")
+
+      refute RecordKey.valid?("alpha/beta")
+      refute RecordKey.valid?(".")
+      refute RecordKey.valid?("..")
+      refute RecordKey.valid?("#extra")
+      refute RecordKey.valid?("@handle")
+      refute RecordKey.valid?("any space")
+      refute RecordKey.valid?("any+space")
+      refute RecordKey.valid?("number[3]")
+      refute RecordKey.valid?("number(3)")
+      refute RecordKey.valid?("\"quote\"")
+      refute RecordKey.valid?("dHJ1ZQ==")
+    end
+  end
+end
-- 
2.51.2