require "rmagick"
require "digest"

class ImageUtils
  @@magickImg = nil

  @@password = ""
  @@message = ""

  @@hash = nil

  @@width = 0
  @@height = 0

  @@pixel_arr = []

  def initialize(pass, msg, uri)
    @@password = pass
    @@message  = msg
    @@salt     = 0

    @@magickImg = Magick::Image.read(uri).first

    @@width = @@magickImg.columns
    @@height = @@magickImg.rows

    @@pixel_arr = @@magickImg.get_pixels(0, 0, @@width, @@height)

    if msg.length > 1024 then
      puts "Maximum length exceeded.  Exiting."
      exit
    end

    self.generateHash
  end

  def getPixel(x, y)
    loc = (y*@@width) + x

    return @@pixel_arr[loc]
  end

  def getSalt
    for x in 0..@@width-1
      for y in 0..@@height-1
        pix = self.getPixel(x, y)

        @@salt = @@salt + (pix.red/512)
        @@salt = @@salt + (pix.green/512)
        @@salt = @@salt + (pix.blue/512)
      end
    end

    h = Digest::SHA512.hexdigest(@@salt.to_s(16))

    return h
  end

  def generateHash
    pass_h = Digest::SHA512.hexdigest(@@password)

    @@hash = Digest::SHA512.hexdigest(pass_h + @@salt.to_s)
  end

  def generateLookupTable
    tbl = []

    hash_bits = @@pixelImg.getBits(@@hash)
    msg_bits = @@pixelImg.getBits(@@message)

    # gross, but pad in the 24 bits that will become the msg length
    # and padding bits...
    msg_bits = msg_bits << 24

    while msg_bits > 0 do
      loc = nil

      loop do
        x = (hash_bits.to_i % @@pixelImg.getSize[:width])
        y = (hash_bits.to_i % @@pixelImg.getSize[:height])

        loc = {"x": x, "y": y}

      break if !tbl.include?(loc)
        hash_bits = hash_bits >> 1

        if hash_bits <= 0 then
          puts
          puts "wow too much data"
          puts "leftover bits: " + msg_bits.to_s(36)
          exit
        end
      end

      hash_bits = hash_bits >> 1

      tbl.push(loc)

      msg_bits = msg_bits >> 6
    end

    return tbl
  end

  def getBits(o)
    msg_bytes = o.unpack("c*")

    msg_bits = 0

    for b in msg_bytes
      msg_bits = (msg_bits << 8) | b
    end

    return msg_bits
  end
end