feat: add member fuzzy search for linking (#168)

lib/membership/member.ex

@@ -152,7 +152,8 @@ defmodule Mv.Membership.Member do
       prepare fn query, _ctx ->
         q = Ash.Query.get_argument(query, :query) || ""
 
-        # 0.2 as similarity threshold (recommended) - lower value can lead to more results but also to more unspecific results
+        # 0.2 as similarity threshold (recommended)
+        # Lower value can lead to more results but also to more unspecific results
         threshold = Ash.Query.get_argument(query, :similarity_threshold) || 0.2
 
         if is_binary(q) and String.trim(q) != "" do
@@ -187,7 +188,81 @@ defmodule Mv.Membership.Member do
         end
       end
     end
+
+    # Action to find members available for linking to a user account
+    # Returns only unlinked members (user_id == nil), limited to 10 results
+    #
+    # Special behavior for email matching:
+    # - When user_email AND search_query are both provided: filter by email (email takes precedence)
+    # - When only user_email provided: return all unlinked members (caller should use filter_by_email_match helper)
+    # - When only search_query provided: filter by search terms
+    read :available_for_linking do
+      argument :user_email, :string, allow_nil?: true
+      argument :search_query, :string, allow_nil?: true
+
+      prepare fn query, _ctx ->
+        user_email = Ash.Query.get_argument(query, :user_email)
+        search_query = Ash.Query.get_argument(query, :search_query)
+
+        # Start with base filter: only unlinked members
+        base_query = Ash.Query.filter(query, is_nil(user))
+
+        # Determine filtering strategy
+        # Priority: search_query (if present) > no filters
+        # user_email is used for POST-filtering via filter_by_email_match helper
+        if not is_nil(search_query) and String.trim(search_query) != "" do
+          # Search query present: Use fuzzy search (regardless of user_email)
+          trimmed = String.trim(search_query)
+
+          # Use same fuzzy search as :search action (PostgreSQL Trigram + FTS)
+          base_query
+          |> Ash.Query.filter(
+            expr(
+              # Full-text search
+              # Trigram similarity for names
+              # Exact substring match for email
+              fragment("search_vector @@ websearch_to_tsquery('simple', ?)", ^trimmed) or
+                fragment("search_vector @@ plainto_tsquery('simple', ?)", ^trimmed) or
+                fragment("? % first_name", ^trimmed) or
+                fragment("? % last_name", ^trimmed) or
+                fragment("word_similarity(?, first_name) > 0.2", ^trimmed) or
+                fragment("word_similarity(?, last_name) > 0.2", ^trimmed) or
+                fragment("similarity(first_name, ?) > 0.2", ^trimmed) or
+                fragment("similarity(last_name, ?) > 0.2", ^trimmed) or
+                contains(email, ^trimmed)
+            )
+          )
+          |> Ash.Query.limit(10)
+        else
+          # No search query: return all unlinked members
+          # Caller should use filter_by_email_match helper for email match logic
+          base_query
+          |> Ash.Query.limit(10)
         end
+      end
+    end
+  end
+
+  # Public helper function to apply email match logic after query execution
+  # This should be called after using :available_for_linking with user_email argument
+  #
+  # If a member with matching email exists, returns only that member
+  # Otherwise returns all members (no filtering)
+  def filter_by_email_match(members, user_email)
+      when is_list(members) and is_binary(user_email) do
+    # Check if any member matches the email
+    email_match = Enum.find(members, &(&1.email == user_email))
+
+    if email_match do
+      # Return only the email-matched member
+      [email_match]
+    else
+      # No email match, return all members
+      members
+    end
+  end
+
+  def filter_by_email_match(members, _user_email), do: members
 
   validations do
     # Required fields are covered by allow_nil? false