require 'tmpdir'
require 'rqrcode'

DPI = 203
SRC_PDF = ARGV[0] || '/home/randy/EPH266757312_adresne_stitky_a6.pdf'
OUT_PS  = ARGV[1] || '/tmp/test-label-v2.ps'

# barcode crop region in the source label, in native pixels at 203dpi
BARCODE_BOX = { x0: 388, y0: 222, x1: 772, y1: 322 }

def read_pbm(path)
  bytes = File.binread(path)
  header = /\AP4\s+(?:#[^\n]*\n\s*)*(\d+)\s+(\d+)\s/.match(bytes)
  raise "bad pbm #{path}" unless header

  width, height = header[1].to_i, header[2].to_i
  bytes_per_row = (width + 7) / 8
  body = bytes.byteslice(header.end(0), bytes_per_row * height)
  { width: width, height: height, bytes_per_row: bytes_per_row, body: body }
end

def pbm_bit(pbm, x, y)
  byte = pbm[:body].getbyte(y * pbm[:bytes_per_row] + (x / 8))
  (byte >> (7 - (x % 8))) & 1
end

# Packs a [x,y] => 0/1 (1 = black) pixel getter into row-padded, bit-inverted
# (PostScript DeviceGray 1bpc: 0=black) bytes ready for the `image` operator.
def pack_for_ps_image(width, height)
  bytes_per_row = (width + 7) / 8
  rows = Array.new(height) { "\x00".b * bytes_per_row }
  height.times do |y|
    row = rows[y].dup.b
    width.times do |x|
      next unless yield(x, y) == 1

      byte_index = x / 8
      bit = 0x80 >> (x % 8)
      row.setbyte(byte_index, row.getbyte(byte_index) | bit)
    end
    rows[y] = row
  end
  packed = rows.join
  inverted = packed.bytes.map { |b| (~b) & 0xFF }.pack('C*')
  { width: width, height: height, hex: inverted.unpack1('H*').upcase }
end

def ps_image_block(x_pt, y_pt, w_pt, h_pt, img)
  <<~PS
    gsave
    #{x_pt} #{y_pt} translate
    #{w_pt} #{h_pt} scale
    #{img[:width]} #{img[:height]} 1
    [#{img[:width]} 0 0 -#{img[:height]} 0 #{img[:height]}]
    { <#{img[:hex]}> } image
    grestore
  PS
end

Dir.mktmpdir do |dir|
  pbm_path = File.join(dir, 'label.pbm')
  system('gs', '-q', '-dNOPAUSE', '-dBATCH', '-dSAFER',
         '-sDEVICE=pbmraw', "-r#{DPI}", '-dFirstPage=1', '-dLastPage=1',
         "-sOutputFile=#{pbm_path}", SRC_PDF) or raise 'gs failed'

  pbm = read_pbm(pbm_path)
  bw = BARCODE_BOX[:x1] - BARCODE_BOX[:x0]
  bh = BARCODE_BOX[:y1] - BARCODE_BOX[:y0]
  barcode_img = pack_for_ps_image(bw, bh) do |x, y|
    pbm_bit(pbm, BARCODE_BOX[:x0] + x, BARCODE_BOX[:y0] + y)
  end

  qr = RQRCode::QRCode.new('TEST-LABEL-PRINTSERVER')
  modules = qr.modules
  quiet = 4
  qsize = modules.size + quiet * 2
  qr_img = pack_for_ps_image(qsize, qsize) do |x, y|
    mx, my = x - quiet, y - quiet
    next 0 if mx.negative? || my.negative? || mx >= modules.size || my >= modules.size

    modules[my][mx] ? 1 : 0
  end

  # physical sizes on the A6 (298x420pt) page
  barcode_pt_w = 220
  barcode_pt_h = barcode_pt_w * bh / bw
  qr_pt = 100

  ps = <<~PS
    %!PS
    << /PageSize [298 420] >> setpagedevice
    1 setlinewidth
    10 10 278 400 rectstroke
    /Helvetica-Bold findfont 24 scalefont setfont
    30 380 moveto (TEST LABEL) show
    /Helvetica findfont 9 scalefont setfont
    30 362 moveto (Generic print-quality test page - safe to reprint anytime) show
    /Helvetica-Bold findfont 13 scalefont setfont
    30 330 moveto (Odosielatel: Test Sender, BA) show
    30 312 moveto (Adresat: Test Recipient, KE) show
    /Helvetica findfont 8 scalefont setfont
    30 292 moveto (Fine print 8pt: quick brown fox 0123456789) show
    #{ps_image_block(30, 210, barcode_pt_w, barcode_pt_h, barcode_img)}
    /Helvetica findfont 8 scalefont setfont
    30 198 moveto (1D: reused known-good Code128 from a real courier label) show
    #{ps_image_block(30, 60, qr_pt, qr_pt, qr_img)}
    /Helvetica findfont 8 scalefont setfont
    140 100 moveto (QR: TEST-LABEL-PRINTSERVER) show
    140 88 moveto (rendered natively via rqrcode) show
    showpage
  PS

  File.write(OUT_PS, ps)
  puts "wrote #{OUT_PS}"
end