# Minimal chainable ESC/POS builder for the Epson TM-T20II.
#
# Written instead of pulling in the `escpos` gem: the gem's diacritics
# handling needed the same manual UTF-8->CP852 `.encode` call anyway, and a
# couple of its helpers didn't behave as documented against this printer --
# fewer moving parts doing it directly.
class ReceiptBuilder
  INIT       = "\x1B\x40".freeze
  CP852      = "\x1B\x74\x12".freeze # code page for Slovak diacritics

  ALIGN_LEFT = "\x1B\x61\x00".freeze
  ALIGN_CENT = "\x1B\x61\x01".freeze
  ALIGN_RIGH = "\x1B\x61\x02".freeze

  BOLD_ON    = "\x1B\x45\x01".freeze
  BOLD_OFF   = "\x1B\x45\x00".freeze
  UNDER_ON   = "\x1B\x2D\x01".freeze
  UNDER_OFF  = "\x1B\x2D\x00".freeze

  TXT_NORM   = "\x1D\x21\x00".freeze
  TXT_BIG    = "\x1D\x21\x11".freeze # double height and width
  TXT_HIGH   = "\x1D\x21\x01".freeze # double height
  TXT_WIDE   = "\x1D\x21\x10".freeze # double width

  CUT        = "\x1D\x56\x00".freeze

  def initialize
    @buffer = "".b
    init
  end

  def init
    @buffer << INIT << CP852
    self
  end

  def text(str)
    @buffer << str.encode('CP852', invalid: :replace, undef: :replace, replace: '?')
    self
  end

  # Appends already-encoded/raw bytes as-is (e.g. pre-parsed ESC/POS command
  # sequences), bypassing the CP852 text encoding `text` applies.
  def raw(bytes)
    @buffer << bytes
    self
  end

  def align(mode)
    @buffer << case mode
               when :center then ALIGN_CENT
               when :right  then ALIGN_RIGH
               else ALIGN_LEFT
               end
    self
  end

  def bold(enable = true)
    @buffer << (enable ? BOLD_ON : BOLD_OFF)
    self
  end

  def underline(enable = true)
    @buffer << (enable ? UNDER_ON : UNDER_OFF)
    self
  end

  def size(mode)
    @buffer << case mode
               when :big  then TXT_BIG
               when :high then TXT_HIGH
               when :wide then TXT_WIDE
               else TXT_NORM
               end
    self
  end

  # Native ESC/POS QR code
  def qr(data, size: 6)
    qr_data = data.b
    store_len = qr_data.bytesize + 3

    @buffer << "\x1D\x28\x6B\x03\x00\x31\x43" << size.chr
    @buffer << "\x1D\x28\x6B\x03\x00\x31\x45\x30" # error correction L
    @buffer << "\x1D\x28\x6B" << [store_len % 256, store_len / 256].pack('CC') << "\x31\x50\x30" << qr_data
    @buffer << "\x1D\x28\x6B\x03\x00\x31\x51\x30" # print
    self
  end

  # Native ESC/POS EAN-13
  def ean13(code)
    @buffer << "\x1D\x6B\x02" << code.b << "\x00"
    self
  end

  # Raster bit image (GS v 0) -- bytes must already be packed 1bpp,
  # row-major, (width_px/8 rounded up) bytes per row, MSB-first, 1=black.
  def image(width_px, height_px, bytes)
    width_bytes = (width_px + 7) / 8
    @buffer << "\x1D\x76\x30\x00"
    @buffer << [width_bytes % 256, width_bytes / 256, height_px % 256, height_px / 256].pack('C4')
    @buffer << bytes
    self
  end

  def feed(lines = 3)
    @buffer << ("\n" * lines)
    self
  end

  def cut
    @buffer << CUT
    self
  end

  def render
    @buffer
  end

  def print!(device)
    File.open(device, 'wb') { |f| f.write(@buffer) }
  end
end