input

class DatePickerInput < SimpleForm::Inputs::StringInput
  def display_pattern
    I18n.t('datepicker.dformat', default: '%d/%m/%Y')
  end

  def picker_pattern
    I18n.t('datepicker.pformat', default: 'dd/MM/yyyy')
  end

  def wrapper_classes
    'input-append date datepicker'
  end

  def input_value
    object.send(attribute_name) if object.respond_to? attribute_name
  end

  def set_display_pattern
    value = input_value
    input_html_options[:value] ||= I18n.localize(value, format: display_pattern) if value.present?
  end

  def set_picker_pattern
    input_html_options[:type] = 'text'
    input_html_options[:data] ||= {}
    input_html_options[:data].merge!(format: picker_pattern, language: I18n.locale.to_s,
                                       date_weekstart: I18n.t('datepicker.weekstart', default: 0))
  end

  def input
    set_display_pattern
    set_picker_pattern
    template.content_tag :div, class: wrapper_classes do
      input = super
      input += template.content_tag :span, class: 'add-on' do
        template.content_tag :i, '', class: 'icon-calendar',
                              data: { 'time-icon' => 'icon-time', 'date-icon' => 'icon-calendar' }
      end
      input
    end
  end
end

spec

require "spec_helper"

RSpec.describe DatePickerInput do
  before { I18n.locale = I18n.default_locale }
  # Prevent warnings about already initialized constant
  after { Object.send(:remove_const, :Dummy) }
  let!(:dummy) do
    Dummy = Class.new do
      include Mongoid::Document
      field :date, type: Date
    end
  end
  let(:foo) { dummy.new(date: Date.parse('05.03.2015')) }
  let(:body) { Nokogiri::HTML(input_for(foo, :date, as: :date_picker)) }

  subject { body.at_css('input#dummy_date') }

  it 'sets data-format attribute to dd/MM/yyyy' do
    expect(subject.attr('data-format')).to eq 'dd/MM/yyyy'
  end

  it 'formats the inputs value' do
    expect(subject.attr('value')).to eq '05/03/2015'
  end

  it 'sets the data-language attribute to en' do
    expect(subject.attr('data-language')).to eq 'en'
  end

  it 'sets the data-date-weekstart attribute to 0' do
    expect(subject.attr('data-date-weekstart')).to eq '0'
  end
end