feat(orm): add belongs_to and has_many associations

lib/prism/orm/associable.rb

@@ -0,0 +1,44 @@
+module Prism
+  module Orm
+    module Associable
+      def self.included(base)
+        base.extend(ClassMethods)
+      end
+
+      module ClassMethods
+        def associations
+          @associations ||= {}
+        end
+
+        def belongs_to(name, class_name: nil, foreign_key: nil)
+          target = class_name || Inflector.camelize(name.to_s)
+          key = (foreign_key || "#{name}_id").to_s
+          associations[name.to_sym] = { type: :belongs_to, class_name: target, foreign_key: key }
+
+          define_method(name) do
+            value = self[key]
+            next nil if value.nil?
+            @association_cache ||= {}
+            @association_cache[name] ||= Object.const_get(target).find(value)
+          end
+
+          define_method("#{name}=") do |record|
+            self[key] = record&.id
+            @association_cache ||= {}
+            @association_cache[name] = record
+          end
+        end
+
+        def has_many(name, class_name: nil, foreign_key: nil)
+          target = class_name || Inflector.classify(name.to_s)
+          key = (foreign_key || "#{Inflector.underscore(self.name)}_id").to_s
+          associations[name.to_sym] = { type: :has_many, class_name: target, foreign_key: key }
+
+          define_method(name) do
+            Object.const_get(target).where(key => id)
+          end
+        end
+      end
+    end
+  end
+end