demarches-normaliennes/app/models/champs/date_champ.rb

class Champs::DateChamp < Champ
  before_validation :convert_to_iso8601, unless: -> { validation_context == :prefill }
  validate :iso_8601

  def search_terms
    # Text search is pretty useless for dates so we’re not including these champs
  end

  private

  def convert_to_iso8601
    return if likely_iso8601_format? && parsable_iso8601?

    self.value = if /^\d{2}\/\d{2}\/\d{4}$/.match?(value)
      Date.parse(value).iso8601
    else
      nil
    end
  end

  def iso_8601
    return if parsable_iso8601? || value.blank?
    # i18n-tasks-use t('errors.messages.not_a_date')
    errors.add :date, :not_a_date
  end

  def likely_iso8601_format?
    /^\d{4}-\d{2}-\d{2}$/.match?(value)
  end

  def parsable_iso8601?
    Date.parse(value)
    true
  rescue ArgumentError, # case 2023-27-02, out of range
         TypeError # nil
    false
  end
end