local Util = require('util')

local NFT = { }

-- largely copied from http://www.computercraft.info/forums2/index.php?/topic/5029-145-npaintpro/

local tColourLookup = { }
for n = 1, 16 do
  tColourLookup[string.byte("0123456789abcdef", n, n)] = 2 ^ (n - 1)
end

local function getColourOf(hex)
  return tColourLookup[hex:byte()]
end

function NFT.parse(imageText)
  local image = {
    fg   = { },
    bg   = { },
    text = { },
  }

  local num = 1
  for _,sLine in ipairs(Util.split(imageText)) do
    table.insert(image.fg, { })
    table.insert(image.bg, { })
    table.insert(image.text, { })

    --As we're no longer 1-1, we keep track of what index to write to
    local writeIndex = 1
    --Tells us if we've hit a 30 or 31 (BG and FG respectively)- next char specifies the curr colour
    local bgNext, fgNext = false, false
    --The current background and foreground colours
    local currBG, currFG = nil,nil
    for i = 1, #sLine do
      local nextChar = string.sub(sLine, i, i)
      if nextChar:byte() == 30 then
        bgNext = true
      elseif nextChar:byte() == 31 then
        fgNext = true
      elseif bgNext then
        currBG = getColourOf(nextChar)
        bgNext = false
      elseif fgNext then
        currFG = getColourOf(nextChar)
        fgNext = false
      else
        if nextChar ~= " " and currFG == nil then
          currFG = _G.colors.white
        end
        image.bg[num][writeIndex] = currBG
        image.fg[num][writeIndex] = currFG
        image.text[num][writeIndex] = nextChar
        writeIndex = writeIndex + 1
      end
    end
    image.height = num
    if not image.width or writeIndex - 1 > image.width then
      image.width = writeIndex - 1
    end
    num = num+1
  end
  return image
end

function NFT.load(path)

  local imageText = Util.readFile(path)
  if not imageText then
    error('Unable to read image file')
  end
  return NFT.parse(imageText)
end

return NFT