module Sane
  class << self
    def init
      version_code = FFI::MemoryPointer.new(:int)
      check_status!(API.sane_init(version_code, FFI::Pointer::NULL))
      version_code.read_int
    end

    def exit
      API.sane_exit
    end

    def get_devices
      devices_pointer = FFI::MemoryPointer.new(:pointer)
      check_status!(API.sane_get_devices(devices_pointer, 0))
      devices = devices_pointer.read_pointer
      [].tap do |result|
        until devices.read_pointer.null?
          result << API::Device.new(devices.read_pointer)
          devices += FFI.type_size(:pointer)
        end
      end
    end

    def open(device_name)
      device_handle_pointer = FFI::MemoryPointer.new(:pointer)
      check_status!(API.sane_open(device_name.to_s, device_handle_pointer))
      device_handle_pointer.read_pointer
    end

    def close(device_handle)
      API.sane_close(device_handle)
    end

    def check_status!(status)
      raise Error.new(API.sane_strstatus(status), status) if status != :good
    end
  end
end