class Devise::ParameterFilter

def filter(conditions)
  conditions = stringify_params(conditions.dup)
  conditions.merge!(filtered_hash_by_method_for_given_keys(conditions.dup, :downcase, @case_insensitive_keys))
  conditions.merge!(filtered_hash_by_method_for_given_keys(conditions.dup, :strip, @strip_whitespace_keys))
  conditions
end

def filtered_hash_by_method_for_given_keys(conditions, method, condition_keys)
  condition_keys.each do |k|
    next unless conditions.key?(k)
    value = conditions[k]
    conditions[k] = value.send(method) if value.respond_to?(method)
  end
  conditions
end

def initialize(case_insensitive_keys, strip_whitespace_keys)
  @case_insensitive_keys = case_insensitive_keys || []
  @strip_whitespace_keys = strip_whitespace_keys || []
end

def param_requires_string_conversion?(value)
  true
end

def stringify_params(conditions)
  return conditions unless conditions.is_a?(Hash)
  conditions.each do |k, v|
    conditions[k] = v.to_s if param_requires_string_conversion?(v)
  end
end