transform-templated-string.rb

def transform_templated_string(template, replacements)
  # Ensure replacements keys are valid
  replacements.each_key do |key|
    unless /^[a-z_]+$/i.match?(key.to_s)
      raise ArgumentError, 'keys may only consist of letters and underscores'
    end
  end

  # Perform the replacements
  replacements.reduce(template) do |transformed_string, (key, value)|
    key_pattern = /%\{#{key}\}/
    transformed_string.gsub(key_pattern, value.to_s)
  end
end

result = transform_templated_string(
  'Cannot have insurance score less than %{minimum_insurance_score} and insurance lapse of %{minimum_days_for_lapse} or more days',
  {minimum_insurance_score: '100', minimum_days_for_lapse: 5, foo: 'bar'}
)

puts result