Copy code from app

This was extracted from use in an existing application. For now, I'll
copy the code as-is and go from there.

lib/boolean_timestamp.rb

@@ -1,5 +1,47 @@
 require "boolean_timestamp/version"
 
 module BooleanTimestamp
-  # Your code goes here...
+  def self.included(base)
+    base.extend ClassMethods
+  end
+
+  module ClassMethods
+    def boolean_timestamp(method_name)
+      method_name = String(method_name)
+      column_name = "#{method_name}_at"
+      fully_qualified_column_name = "#{table_name}.#{column_name}"
+
+      unless column_names.include?(column_name)
+        raise(
+          ArgumentError,
+          "Can't build methods from unknown column '#{fully_qualified_column_name}'",
+        )
+      end
+
+      define_singleton_method(method_name) do
+        where("#{fully_qualified_column_name} <= ?", Time.current)
+      end
+
+      define_singleton_method("not_#{method_name}") do
+        where(
+          "#{fully_qualified_column_name} IS NULL OR #{fully_qualified_column_name} > ?",
+          Time.current,
+        )
+      end
+
+      define_method method_name do
+        public_send(column_name).present? && !public_send(column_name).future?
+      end
+
+      alias_method "#{method_name}?", method_name
+
+      define_method "#{method_name}=" do |value|
+        if ActiveModel::Type::Boolean::FALSE_VALUES.include?(value)
+          public_send("#{column_name}=", nil)
+        elsif !public_send(method_name)
+          public_send("#{column_name}=", Time.current)
+        end
+      end
+    end
+  end
 end