require 'ffi'

class Serial
  def initialize(address, baude_rate=9600, data_bits=8)
    file_opts = RubySerial::Win32::GENERIC_READ | RubySerial::Win32::GENERIC_WRITE
    @fd = RubySerial::Win32.CreateFileA(address, file_opts, 0, nil, RubySerial::Win32::OPEN_EXISTING, 0, nil)
    err = FFI.errno
    if err != 0
      raise RubySerial::Exception, RubySerial::Win32::ERROR_CODES[err]
    else
      @open = true
    end

    RubySerial::Win32::DCB.new.tap do |dcb|
      dcb[:dcblength] = RubySerial::Win32::DCB::Sizeof
      err = RubySerial::Win32.GetCommState @fd, dcb
      if err == 0
        raise RubySerial::Exception, RubySerial::Win32::ERROR_CODES[FFI.errno]
      end 
      dcb[:baudrate] = baude_rate
      dcb[:bytesize] = data_bits
      dcb[:stopbits] = RubySerial::Win32::DCB::ONESTOPBIT
      dcb[:parity]   = RubySerial::Win32::DCB::NOPARITY
      err = RubySerial::Win32.SetCommState @fd, dcb
      if err == 0
        raise RubySerial::Exception, RubySerial::Win32::ERROR_CODES[FFI.errno]
      end 
    end

    RubySerial::Win32::CommTimeouts.new.tap do |timeouts|
      timeouts[:read_interval_timeout]          = 50
      timeouts[:read_total_timeout_multiplier]  = 50
      timeouts[:read_total_timeout_constant]    = 10
      timeouts[:write_total_timeout_multiplier] = 50
      timeouts[:write_total_timeout_constant]   = 10
      err = RubySerial::Win32.SetCommTimeouts @fd, timeouts
      if err == 0
        raise RubySerial::Exception, RubySerial::Win32::ERROR_CODES[FFI.errno]
      end 
    end
  end

  def read(size)
    buff = FFI::MemoryPointer.new :char, size
    count = FFI::MemoryPointer.new :uint32, 1
    err = RubySerial::Win32.ReadFile(@fd, buff, size, count, nil)
    if err == 0
      raise RubySerial::Exception, RubySerial::Win32::ERROR_CODES[FFI.errno]
    end
    buff.get_bytes(0, count.read_string.unpack('H4').join().to_i(16))
  end

  def getbyte
    buff = FFI::MemoryPointer.new :char, 1
    count = FFI::MemoryPointer.new :uint32, 1
    err = RubySerial::Win32.ReadFile(@fd, buff, 1, count, nil)
    if err == 0
      raise RubySerial::Exception, RubySerial::Win32::ERROR_CODES[FFI.errno]
    end

    if count.read_string.unpack('H4').join().to_i(16) == 0
      nil
    else
      buff.read_string.unpack('C').first
    end
  end

  def write(data)
    buff = FFI::MemoryPointer.from_string(data.to_s)
    count = FFI::MemoryPointer.new :uint32, 1
    err = RubySerial::Win32.WriteFile(@fd, buff, buff.size, count, nil)
    if err == 0
      raise RubySerial::Exception, RubySerial::Win32::ERROR_CODES[FFI.errno]
    end 
  end

  def close
    err = RubySerial::Win32.CloseHandle(@fd)
    if err == 0
      raise RubySerial::Exception, RubySerial::Win32::ERROR_CODES[FFI.errno]
    else
      @open = false
    end 
  end

  def closed?
    !@open
  end
end