class Holidays::Definition::Context::FunctionProcessor

def calculate(input, id, args, modifier)
  result = @proc_result_cache_repo.lookup(id, *args)
  if result.kind_of?(Date)
    if modifier
      result = result + modifier # NOTE: This could be a positive OR negative number.
    end
  elsif result.is_a?(Integer)
    begin
      result = Date.civil(input[:year], input[:month], result)
    rescue ArgumentError
      raise Holidays::InvalidFunctionResponse.new("invalid day response from custom method call resulting in invalid date. Result: '#{result}'")
    end
  elsif result.nil?
    # Do nothing. This is because some functions can return 'nil' today.
    # I want to change this and so rather than come up with a clean
    # implementation I'll do this so we don't throw an error in this specific
    # situation. This should be removed once we have changed the existing
    # custom definition functions. See https://github.com/holidays/holidays/issues/204
  else
    raise Holidays::InvalidFunctionResponse.new("invalid response from custom method call, must be a 'date' or 'integer' representing the day. Result: '#{result}'")
  end
  result
end

def call(input, func_id, desired_func_args, func_modifier = nil)
  validate!(input, func_id, desired_func_args)
  function = @custom_methods_repo.find(func_id)
  raise Holidays::FunctionNotFound.new("Unable to find function with id '#{func_id}'") if function.nil?
  calculate(input, function, parse_arguments(input, desired_func_args), func_modifier)
end

def initialize(custom_methods_repo, proc_result_cache_repo)
  @custom_methods_repo = custom_methods_repo
  @proc_result_cache_repo = proc_result_cache_repo
end

def parse_arguments(input, target_args)
  args = []
  if target_args.include?(:year)
    args << input[:year]
  end
  if target_args.include?(:month)
    args << input[:month]
  end
  if target_args.include?(:day)
    args << input[:day]
  end
  if target_args.include?(:date)
    args << Date.civil(input[:year], input[:month], input[:day])
  end
  if target_args.include?(:region)
    args << input[:region]
  end
  args
end

def validate!(input, func_id, desired_func_args)
  raise ArgumentError if desired_func_args.nil? || desired_func_args.empty?
  desired_func_args.each do |name|
    raise ArgumentError unless VALID_ARGUMENTS.include?(name)
  end
  raise ArgumentError if desired_func_args.include?(:year) && !input[:year].is_a?(Integer)
  raise ArgumentError if desired_func_args.include?(:month) && (input[:month] < 0 || input[:month] > 12)
  raise ArgumentError if desired_func_args.include?(:day) && (input[:day] < 1 || input[:day] > 31)
  raise ArgumentError if desired_func_args.include?(:region) && !input[:region].is_a?(Symbol)
end