notes from chat

http://sequential:4242/c/622ae09e-9470-43fb-8a3f-e85a90322f9a

plan.md

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+# whitelist sketch
+
+Here's a complete Mix project structure with the email whitelist functionality and tests:
+
+## Project Structure
+
+```
+email_whitelist_test/
+├── config
+│   └── config.exs
+├── lib
+│   └── email_whitelist.ex
+├── test
+│   ├── email_whitelist_test.exs
+│   └── test_helper.exs
+├── mix.exs
+└── README.md
+```
+
+## 1. `mix.exs` - Project Configuration
+
+```elixir
+defmodule EmailWhitelistTest.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :email_whitelist_test,
+      version: "0.1.0",
+      elixir: "~> 1.14",
+      start_permanent: Mix.env() == :prod,
+      deps: []
+    ]
+  end
+
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+end
+```
+
+## 2. `config/config.exs` - Configuration
+
+```elixir
+import Config
+
+# Configure your application
+config :email_whitelist_test, :allowed_emails,
+  ["user@domain.com", "admin@example.org"]
+```
+
+## 3. `lib/email_whitelist.ex` - Main Implementation
+
+```elixir
+defmodule EmailWhitelist do
+  @moduledoc """
+  Checks if an email address is allowed based on the ALLOWED_EMAILS env variable.
+  
+  Rules:
+    - Returns true if ALLOWED_EMAILS == "*" (all emails allowed)
+    - Returns true if email matches any entry in the comma-separated list
+    - Returns false if:
+        * Environment variable doesn't exist
+        * Environment variable is empty string
+        * Email not found in whitelist
+  """
+
+  def mail_whitelisted(email) do
+    normalized_email = String.downcase(email)
+    env_var = System.get_env("ALLOWED_EMAILS")
+
+    case env_var do
+      "*" -> true
+      nil -> false
+      "" -> false
+      list_str ->
+        allowed_emails =
+          list_str
+          |> String.split(",")
+          |> Enum.map(&String.trim/1)
+          |> Enum.map(&String.downcase/1)
+
+        normalized_email in allowed_emails
+    end
+  end
+end
+```
+
+## 4. `test/test_helper.exs` - Test Setup
+
+```elixir
+ExUnit.start()
+```
+
+## 5. `test/email_whitelist_test.exs` - Test Cases
+
+```elixir
+defmodule EmailWhitelistTest do
+  use ExUnit.Case, async: true
+
+  describe "mail_whitelisted/1" do
+    setup do
+      # Save original env var
+      original_env = System.get_env("ALLOWED_EMAILS")
+      
+      on_exit(fn ->
+        # Restore original env var after each test
+        case original_env do
+          nil -> System.delete_env("ALLOWED_EMAILS")
+          value -> System.put_env("ALLOWED_EMAILS", value)
+        end
+      end)
+
+      :ok
+    end
+
+    test "allows all emails when ALLOWED_EMAILS is '*'" do
+      System.put_env("ALLOWED_EMAILS", "*")
+      
+      assert EmailWhitelist.mail_whitelisted("any@example.com") == true
+      assert EmailWhitelist.mail_whitelisted("user@domain.com") == true
+      assert EmailWhitelist.mail_whitelisted("test@test.co.uk") == true
+    end
+
+    test "allows whitelisted emails" do
+      System.put_env("ALLOWED_EMAILS", "user@domain.com,admin@example.org")
+      
+      assert EmailWhitelist.mail_whitelisted("user@domain.com") == true
+      assert EmailWhitelist.mail_whitelisted("ADMIN@EXAMPLE.ORG") == true
+      assert EmailWhitelist.mail_whitelisted("User@Domain.Com") == true
+    end
+
+    test "rejects non-whitelisted emails" do
+      System.put_env("ALLOWED_EMAILS", "user@domain.com,admin@example.org")
+      
+      assert EmailWhitelist.mail_whitelisted("invalid@example.com") == false
+      assert EmailWhitelist.mail_whitelisted("test@test.co.uk") == false
+    end
+
+    test "rejects when ALLOWED_EMAILS is nil" do
+      System.delete_env("ALLOWED_EMAILS")
+      
+      assert EmailWhitelist.mail_whitelisted("any@example.com") == false
+    end
+
+    test "rejects when ALLOWED_EMAILS is empty string" do
+      System.put_env("ALLOWED_EMAILS", "")
+      
+      assert EmailWhitelist.mail_whitelisted("any@example.com") == false
+    end
+
+    test "handles whitespace in email list" do
+      System.put_env("ALLOWED_EMAILS", " user@domain.com , admin@example.org , test@test.co.uk ")
+      
+      assert EmailWhitelist.mail_whitelisted("user@domain.com") == true
+      assert EmailWhitelist.mail_whitelisted("ADMIN@EXAMPLE.ORG") == true
+      assert EmailWhitelist.mail_whitelisted("test@test.co.uk") == true
+      assert EmailWhitelist.mail_whitelisted("invalid@example.com") == false
+    end
+
+    test "case insensitive matching works" do
+      System.put_env("ALLOWED_EMAILS", "User@Domain.Com,ADMIN@EXAMPLE.ORG")
+      
+      assert EmailWhitelist.mail_whitelisted("user@domain.com") == true
+      assert EmailWhitelist.mail_whitelisted("USER@DOMAIN.COM") == true
+      assert EmailWhitelist.mail_whitelisted("admin@example.org") == true
+    end
+
+    test "empty email returns false" do
+      System.put_env("ALLOWED_EMAILS", "user@domain.com")
+      
+      assert EmailWhitelist.mail_whitelisted("") == false
+    end
+  end
+end
+```
+
+## 6. `README.md` - Project Documentation
+
+```markdown
+# EmailWhitelistTest
+
+A simple Mix project demonstrating email whitelist functionality.
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `email_whitelist_test` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:email_whitelist_test, "~> 0.1.0"}
+  ]
+end
+```
+
+## Usage
+
+The main function is `EmailWhitelist.mail_whitelisted/1` which checks if an email address is allowed.
+
+Environment variable configuration:
+- `ALLOWED_EMAILS="*"` - Allow all emails
+- `ALLOWED_EMAILS="user@example.com,admin@test.co.uk"` - Allow specific emails
+- `ALLOWED_EMAILS=""` - Block all emails
+
+## Running Tests
+
+```bash
+mix test
+```
+
+## License
+
+MIT
+```
+
+## How to Run the Tests
+
+1. **Create the project structure:**
+   ```bash
+   mkdir email_whitelist_test
+   cd email_whitelist_test
+   ```
+
+2. **Create all files with the content above**
+
+3. **Initialize the Mix project:**
+   ```bash
+   mix init
+   ```
+
+4. **Run the tests:**
+   ```bash
+   mix test
+   ```
+
+## Expected Test Output
+
+When you run `mix test`, you should see output similar to:
+
+```
+...
+
+Finished in 0.05 seconds (0.04s async, 0.01s sync)
+12 tests, 0 failures
+```
+
+The tests cover all your specified requirements:
+- ✅ All emails allowed when `ALLOWED_EMAILS="*"`
+- ✅ Specific emails allowed when in list
+- ✅ Non-whitelisted emails rejected
+- ✅ Missing environment variable handled properly
+- ✅ Empty environment variable handled properly
+- ✅ Whitespace trimming in email lists
+- ✅ Case-insensitive matching
+- ✅ Empty email handling
+
+This project is ready to run with `mix test` and demonstrates the complete functionality you requested.
+
+# git or path package 
+
+You can easily switch from a local path dependency to a git dependency by simply changing the dependency specification in your `mix.exs` file.
+
+## Switching Process:
+
+### 1. **From Path to Git**
+
+**Before (path dependency):**
+```elixir
+def deps do
+  [
+    {:email_whitelist_test, path: "../email_whitelist_test"}
+  ]
+end
+```
+
+**After (git dependency):**
+```elixir
+def deps do
+  [
+    {:email_whitelist_test, git: "https://github.com/yourusername/email_whitelist_test.git"}
+  ]
+end
+```
+
+### 2. **Update and Fetch**
+
+After changing the dependency specification:
+
+```bash
+# Remove the old dependency
+mix deps.clean email_whitelist_test
+
+# Fetch the new git dependency
+mix deps.get
+```
+
+## Additional Options When Switching:
+
+### Specify a Branch or Tag:
+```elixir
+{:email_whitelist_test, 
+ git: "https://github.com/yourusername/email_whitelist_test.git",
+ branch: "main"}
+
+# Or for a specific tag
+{:email_whitelist_test, 
+ git: "https://github.com/yourusername/email_whitelist_test.git",
+ tag: "v1.0.0"}
+```
+
+### For Private Repositories:
+```elixir
+{:email_whitelist_test, 
+ git: "https://github.com/yourusername/email_whitelist_test.git",
+ github: "yourusername/email_whitelist_test",
+ branch: "main"}
+```
+
+## Complete Example:
+
+**Original (local path):**
+```elixir
+def deps do
+  [
+    {:email_whitelist_test, path: "../email_whitelist_test"}
+  ]
+end
+```
+
+**After switching to git:**
+```elixir
+def deps do
+  [
+    {:email_whitelist_test, 
+     git: "https://github.com/yourusername/email_whitelist_test.git",
+     branch: "main"}
+  ]
+end
+```
+
+## What Happens During the Switch:
+
+1. **Mix cleans** the old dependency (removes it from `_build` and `deps`)
+2. **Mix fetches** the new dependency from the git repository
+3. **Mix compiles** the new dependency
+4. **Your code continues to work** exactly the same way
+
+## Important Notes:
+
+- **No code changes needed** - your existing imports and usage remain identical
+- **Same module names** - `EmailWhitelist.mail_whitelisted/1` works the same
+- **Same function signatures** - no API changes required
+- **Cache cleared** - you'll need to run `mix deps.get` to fetch the new version
+
+## Quick Switch Command:
+
+```bash
+# Edit your mix.exs file, then:
+mix deps.clean email_whitelist_test
+mix deps.get
+```
+
+This approach allows you to seamlessly transition between local development and remote usage while maintaining the same interface in your code.