class Facter::Resolvers::Memory

def build_facts_list(result)
  @fact_list[:total_bytes] = result[:total_bytes]
  @fact_list[:available_bytes] = result[:available_bytes]
  @fact_list[:used_bytes] = result[:used_bytes]
  @fact_list[:capacity] = format('%<capacity>.2f',
                                 capacity: (result[:used_bytes] / result[:total_bytes].to_f * 100)) + '%'
end

def calculate_memory
  state = read_performance_information
  return unless state
  total_bytes = state[:PhysicalTotal] * state[:PageSize]
  available_bytes = state[:PhysicalAvailable] * state[:PageSize]
  if total_bytes.zero? || available_bytes.zero?
    @log.debug 'Available or Total bytes are zero could not proceed further'
    return
  end
  { total_bytes: total_bytes, available_bytes: available_bytes, used_bytes: total_bytes - available_bytes }
end

def post_resolve(fact_name, _options)
  @fact_list.fetch(fact_name) { validate_info(fact_name) }
end

def read_performance_information
  require 'facter/resolvers/windows/ffi/memory_ffi'
  state_ptr = FFI::MemoryPointer.new(PerformanceInformation.size)
  if MemoryFFI::GetPerformanceInfo(state_ptr, state_ptr.size) == FFI::WIN32FALSE
    @log.debug 'Resolving memory facts failed'
    return
  end
  # we need to enlarge the scope of this pointer so that Ruby GC will not free the memory.
  # If the pointer if freed, Lifreq structures will contain garbage from memory.
  @long_living_pointer = state_ptr
  PerformanceInformation.new(state_ptr)
end

def validate_info(fact_name)
  result = calculate_memory
  return unless result
  build_facts_list(result)
  @fact_list[fact_name]
end