class Sass::Script::Functions::EvaluationContext

def assert_integer(number, name = nil)
  assert_type number, :Number, name
  return if number.int?
  if name
    raise ArgumentError.new("Expected $#{name} to be an integer but got #{number}")
  else
    raise ArgumentError.new("Expected #{number} to be an integer")
  end
end

def assert_type(value, type, name = nil)
  valid_types = Array(type)
  found_type = valid_types.find do |t|
    value.is_a?(Sass::Script::Value.const_get(t)) ||
      t == :Map && value.is_a?(Sass::Script::Value::List) && value.value.empty?
  end
  if found_type
    value.check_deprecated_interp if found_type == :String
    return
  end
  err = if valid_types.size == 1
          "#{value.inspect} is not a #{TYPE_NAMES[type] || type.to_s.downcase}"
        else
          type_names = valid_types.map {|t| TYPE_NAMES[t] || t.to_s.downcase}
          "#{value.inspect} is not any of #{type_names.join(', ')}"
        end
  err = "$#{name.to_s.tr('_', '-')}: " + err if name
  raise ArgumentError.new(err)
end

def assert_unit(number, unit, name = nil)
  assert_type number, :Number, name
  return if number.is_unit?(unit)
  expectation = unit ? "have a unit of #{unit}" : "be unitless"
  if name
    raise ArgumentError.new("Expected $#{name} to #{expectation} but got #{number}")
  else
    raise ArgumentError.new("Expected #{number} to #{expectation}")
  end
end

def initialize(environment)
  @environment = environment
  @options = environment.options
end

def perform(node, env = environment.caller)
  if node.is_a?(Sass::Script::Value::Base)
    node
  else
    node.perform(env)
  end
end