From c6e3a490d2f32c7edad598c82b98272f0c9771f3 Mon Sep 17 00:00:00 2001
From: Your Name <you@example.com>
Date: Tue, 16 Sep 2025 09:34:03 +0000
Subject: [PATCH] add forgotten files

---
 CLAUDE.md                                     | 33 +++++++++++++++
 lib/fun_core/basic_signup_allowlist.ex        | 19 +++++++++
 test/fun_core/basic_signup_allowlist_test.exs | 40 +++++++++++++++++++
 3 files changed, 92 insertions(+)
 create mode 100644 CLAUDE.md
 create mode 100644 lib/fun_core/basic_signup_allowlist.ex
 create mode 100644 test/fun_core/basic_signup_allowlist_test.exs

diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 0000000..e05257f
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,33 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Commands
+
+- `mix compile` - Compile source files
+- `mix test` - Run all tests
+- `mix test test/path/to/test.exs` - Run a specific test file
+- `mix test test/path/to/test.exs:LINE` - Run a specific test at a line number
+- `mix deps.get` - Install dependencies
+- `mix clean` - Clean build artifacts
+
+## Architecture
+
+This is an Elixir library that provides email allowlist functionality for restricting account creation. The library consists of two main modules:
+
+1. **BasicSignupAllowlist** (lib/basic_signup_allowlist.ex) - Public API module that reads the `SIGNUP_ALLOWLIST_EMAILS` environment variable and delegates to the functional core
+2. **FunCore.BasicSignupAllowlist** (lib/fun_core/basic_signup_allowlist.ex) - Pure functional core that handles the allowlist logic without side effects
+
+The architecture follows a functional core/imperative shell pattern where:
+- The functional core contains pure functions for email normalization and allowlist checking
+- The outer module handles environment variable reading and provides the public interface
+
+## Environment Variables
+
+- `SIGNUP_ALLOWLIST_EMAILS` - Comma-separated list of allowed email addresses, or "*" to allow all emails
+
+## Project Configuration
+
+- Elixir version: ~> 1.18 (managed via mise)
+- No external dependencies currently
+- Test framework: ExUnit with async: false for integration tests that modify environment variables
\ No newline at end of file
diff --git a/lib/fun_core/basic_signup_allowlist.ex b/lib/fun_core/basic_signup_allowlist.ex
new file mode 100644
index 0000000..33dc034
--- /dev/null
+++ b/lib/fun_core/basic_signup_allowlist.ex
@@ -0,0 +1,19 @@
+defmodule FunCore.BasicSignupAllowlist do
+  def normalize(email) do
+    email |> String.trim() |> String.downcase()
+  end
+
+  def addresses_as_list(addresses_str) do
+    addresses_str
+    |> String.split(",")
+    |> Enum.map(&normalize/1)
+  end
+
+  def mail_allowlisted_fun(signups_allowed, email_received) do
+    case signups_allowed do
+      nil -> false
+      "*" -> true
+      list_str -> normalize(email_received) in addresses_as_list(list_str)
+    end
+  end
+end
diff --git a/test/fun_core/basic_signup_allowlist_test.exs b/test/fun_core/basic_signup_allowlist_test.exs
new file mode 100644
index 0000000..9f364b5
--- /dev/null
+++ b/test/fun_core/basic_signup_allowlist_test.exs
@@ -0,0 +1,40 @@
+defmodule FunCore.BasicSignupAllowlistTest do
+  use ExUnit.Case
+  import FunCore.BasicSignupAllowlist
+
+  test "addresses_as_list" do
+    assert addresses_as_list("joe@example.com, jane@example.com") == [
+             "joe@example.com",
+             "jane@example.com"
+           ]
+  end
+
+  test "jane in list" do
+    lst = addresses_as_list("joe@example.com, jane@example.com")
+    assert "jane@example.com" in lst
+  end
+
+  describe "Not allowlisted when allowed list is" do
+    test "not set" do
+      refute(mail_allowlisted_fun(nil, "joe@example.com"))
+    end
+
+    test "empty" do
+      refute(mail_allowlisted_fun("j", "joe@example.com"))
+    end
+  end
+
+  describe "Allowlisted when" do
+    test "*" do
+      assert(mail_allowlisted_fun("*", "jane@example.com"))
+    end
+
+    test "Multiple set and one match" do
+      assert(mail_allowlisted_fun("joe@example.com, jane@example.com", "jane@example.com"))
+    end
+
+    test "Matches with different casings" do
+      assert(mail_allowlisted_fun("joe@Example.com, jane@example.com", "Joe@example.com"))
+    end
+  end
+end