feat: prevent join requests with equal mail

lib/membership/membership.ex

@@ -29,7 +29,11 @@ defmodule Mv.Membership do
   require Ash.Query
   import Ash.Expr
   alias Ash.Error.Query.NotFound, as: NotFoundError
+  alias Mv.Helpers.SystemActor
   alias Mv.Membership.JoinRequest
+  alias Mv.Membership.Member
+  alias MvWeb.Emails.JoinAlreadyMemberEmail
+  alias MvWeb.Emails.JoinAlreadyPendingEmail
   alias MvWeb.Emails.JoinConfirmationEmail
   require Logger
 
@@ -365,15 +369,130 @@ defmodule Mv.Membership do
 
   ## Returns
     - `{:ok, request}` - Created JoinRequest in status pending_confirmation, email sent
+    - `{:ok, :notified_already_member}` - Email already a member; notice sent by email only (no request created)
+    - `{:ok, :notified_already_pending}` - Email already has pending/submitted request; notice or resend sent by email only
     - `{:error, :email_delivery_failed}` - Request created but confirmation email could not be sent (logged)
     - `{:error, error}` - Validation or authorization error
   """
   def submit_join_request(attrs, opts \\ []) do
     actor = Keyword.get(opts, :actor)
-    token = Map.get(attrs, :confirmation_token) || generate_confirmation_token()
+    email = normalize_submit_email(attrs)
 
-    # Raw token is passed to the submit action; JoinRequest.Changes.SetConfirmationToken
-    # hashes it before persist. Only the hash is stored; the raw token is sent in the email link.
+    pending =
+      if email != nil and email != "", do: pending_join_request_with_email(email), else: nil
+
+    cond do
+      email != nil and email != "" and member_exists_with_email?(email) ->
+        send_already_member_and_return(email)
+
+      pending != nil ->
+        handle_already_pending(email, pending)
+
+      true ->
+        do_create_join_request(attrs, actor)
+    end
+  end
+
+  defp normalize_submit_email(attrs) do
+    raw = attrs["email"] || attrs[:email]
+    if is_binary(raw), do: String.trim(raw), else: nil
+  end
+
+  defp member_exists_with_email?(email) when is_binary(email) do
+    system_actor = SystemActor.get_system_actor()
+    opts = [actor: system_actor, domain: __MODULE__]
+
+    case Ash.get(Member, %{email: email}, opts) do
+      {:ok, _member} -> true
+      _ -> false
+    end
+  end
+
+  defp member_exists_with_email?(_), do: false
+
+  defp pending_join_request_with_email(email) when is_binary(email) do
+    system_actor = SystemActor.get_system_actor()
+
+    query =
+      JoinRequest
+      |> Ash.Query.filter(expr(email == ^email and status in [:pending_confirmation, :submitted]))
+      |> Ash.Query.sort(inserted_at: :desc)
+      |> Ash.Query.limit(1)
+
+    case Ash.read_one(query, actor: system_actor, domain: __MODULE__) do
+      {:ok, request} -> request
+      _ -> nil
+    end
+  end
+
+  defp pending_join_request_with_email(_), do: nil
+
+  defp apply_anti_enumeration_delay do
+    Process.sleep(100 + :rand.uniform(200))
+  end
+
+  defp send_already_member_and_return(email) do
+    case JoinAlreadyMemberEmail.send(email) do
+      {:ok, _} ->
+        :ok
+
+      {:error, reason} ->
+        Logger.error("Join already-member email failed for #{email}: #{inspect(reason)}")
+    end
+
+    apply_anti_enumeration_delay()
+    {:ok, :notified_already_member}
+  end
+
+  defp handle_already_pending(email, existing) do
+    if existing.status == :pending_confirmation do
+      resend_confirmation_to_pending(email, existing)
+    else
+      send_already_pending_and_return(email)
+    end
+  end
+
+  defp resend_confirmation_to_pending(email, request) do
+    new_token = generate_confirmation_token()
+
+    case request
+         |> Ash.Changeset.for_update(:regenerate_confirmation_token, %{
+           confirmation_token: new_token
+         })
+         |> Ash.update(domain: __MODULE__, authorize?: false) do
+      {:ok, _updated} ->
+        case JoinConfirmationEmail.send(email, new_token, resend: true) do
+          {:ok, _} ->
+            :ok
+
+          {:error, reason} ->
+            Logger.error("Join resend confirmation email failed for #{email}: #{inspect(reason)}")
+        end
+
+        apply_anti_enumeration_delay()
+        {:ok, :notified_already_pending}
+
+      {:error, _} ->
+        # Fallback: do not create duplicate; send generic pending email
+        send_already_pending_and_return(email)
+    end
+  end
+
+  defp send_already_pending_and_return(email) do
+    case JoinAlreadyPendingEmail.send(email) do
+      {:ok, _} ->
+        :ok
+
+      {:error, reason} ->
+        Logger.error("Join already-pending email failed for #{email}: #{inspect(reason)}")
+    end
+
+    apply_anti_enumeration_delay()
+    {:ok, :notified_already_pending}
+  end
+
+  defp do_create_join_request(attrs, actor) do
+    token = Map.get(attrs, :confirmation_token) || generate_confirmation_token()
     attrs_with_token = Map.put(attrs, :confirmation_token, token)
 
     case Ash.create(JoinRequest, attrs_with_token,
@@ -384,6 +503,7 @@ defmodule Mv.Membership do
       {:ok, request} ->
         case JoinConfirmationEmail.send(request.email, token) do
           {:ok, _email} ->
+            apply_anti_enumeration_delay()
             {:ok, request}
 
           {:error, reason} ->