module Devise::Mailers::Helpers

def devise_mail(record, action, opts = {}, &block)
  initialize_from_record(record)
  mail headers_for(action, opts), &block
end

def devise_mapping
  @devise_mapping ||= Devise.mappings[scope_name]
end

def headers_for(action, opts)
  headers = {
    subject: subject_for(action),
    to: resource.email,
    from: mailer_sender(devise_mapping),
    reply_to: mailer_reply_to(devise_mapping),
    template_path: template_paths,
    template_name: action
  }.merge(opts)
  @email = headers[:to]
  headers
end

def initialize_from_record(record)
  @scope_name = Devise::Mapping.find_scope!(record)
  @resource   = instance_variable_set("@#{devise_mapping.name}", record)
end

def mailer_from(mapping)
  mailer_sender(mapping, :from)
end

def mailer_reply_to(mapping)
  mailer_sender(mapping, :reply_to)
end

def mailer_sender(mapping, sender = :from)
  default_sender = default_params[sender]
  if default_sender.present?
    default_sender.respond_to?(:to_proc) ? instance_eval(&default_sender) : default_sender
  elsif Devise.mailer_sender.is_a?(Proc)
    Devise.mailer_sender.call(mapping.name)
  else
    Devise.mailer_sender
  end
end

def subject_for(key)
  I18n.t(:"#{devise_mapping.name}_subject", scope: [:devise, :mailer, key],
    default: [:subject, key.to_s.humanize])
end

def template_paths
  template_path = _prefixes.dup
  template_path.unshift "#{@devise_mapping.scoped_path}/mailer" if self.class.scoped_views?
  template_path
end