feat: custom field deletion

lib/membership/custom_field.ex

@@ -28,7 +28,10 @@ defmodule Mv.Membership.CustomField do
   ## Constraints
   - Name must be unique across all custom fields
   - Name maximum length: 100 characters
-  - Cannot delete a custom field that has existing custom field values (RESTRICT)
+  - Deleting a custom field will cascade delete all associated custom field values
+
+  ## Calculations
+  - `assigned_members_count` - Returns the number of distinct members with values for this custom field
 
   ## Examples
       # Create a new custom field
@@ -55,7 +58,7 @@ defmodule Mv.Membership.CustomField do
   end
 
   actions do
-    defaults [:read, :update, :destroy]
+    defaults [:read, :update]
     default_accept [:name, :value_type, :description, :immutable, :required]
 
     create :create do
@@ -63,6 +66,17 @@ defmodule Mv.Membership.CustomField do
       change Mv.Membership.CustomField.Changes.GenerateSlug
       validate string_length(:slug, min: 1)
     end
+
+    destroy :destroy_with_values do
+      primary? true
+    end
+
+    read :prepare_deletion do
+      argument :id, :uuid, allow_nil?: false
+
+      filter expr(id == ^arg(:id))
+      prepare build(load: [:assigned_members_count])
+    end
   end
 
   attributes do
@@ -111,6 +125,17 @@ defmodule Mv.Membership.CustomField do
     has_many :custom_field_values, Mv.Membership.CustomFieldValue
   end
 
+  calculations do
+    calculate :assigned_members_count,
+              :integer,
+              expr(
+                fragment(
+                  "(SELECT COUNT(DISTINCT member_id) FROM custom_field_values WHERE custom_field_id = ?)",
+                  id
+                )
+              )
+  end
+
   identities do
     identity :unique_name, [:name]
     identity :unique_slug, [:slug]

lib/membership/custom_field_value.ex

@@ -25,11 +25,12 @@ defmodule Mv.Membership.CustomFieldValue do
 
   ## Relationships
   - `belongs_to :member` - The member this custom field value belongs to (CASCADE delete)
-  - `belongs_to :custom_field` - The custom field definition
+  - `belongs_to :custom_field` - The custom field definition (CASCADE delete)
 
   ## Constraints
   - Each member can have only one custom field value per custom field (unique composite index)
   - Custom field values are deleted when the associated member is deleted (CASCADE)
+  - Custom field values are deleted when the associated custom field is deleted (CASCADE)
   - String values maximum length: 10,000 characters
   - Email values maximum length: 254 characters (RFC 5321)
 
@@ -46,12 +47,19 @@ defmodule Mv.Membership.CustomFieldValue do
 
     references do
       reference :member, on_delete: :delete
+      reference :custom_field, on_delete: :delete
     end
   end
 
   actions do
     defaults [:create, :read, :update, :destroy]
     default_accept [:value, :member_id, :custom_field_id]
+
+    read :by_custom_field_id do
+      argument :custom_field_id, :uuid, allow_nil?: false
+
+      filter expr(custom_field_id == ^arg(:custom_field_id))
+    end
   end
 
   attributes do

lib/membership/membership.ex

@@ -42,7 +42,8 @@ defmodule Mv.Membership do
       define :create_custom_field, action: :create
       define :list_custom_fields, action: :read
       define :update_custom_field, action: :update
-      define :destroy_custom_field, action: :destroy
+      define :destroy_custom_field, action: :destroy_with_values
+      define :prepare_custom_field_deletion, action: :prepare_deletion, args: [:id]
     end
   end
 end