ComputerCraft Color Picker

local params = {...}
local colorFile = params[1] .. ".col"

term.setBackgroundColor(colors.black)
term.clear()
term.setTextColor(colors.white)

local color = {}
local palette = {
  text = colors.black,
  background = colors.black,
  header = colors.black
}

function fileExists(filename)
  local file = fs.open(filename, "r")

  if file then
    file.close()

    return true
  end

  return false
end

local function loadColors ()
  local palette = {
    text = colors.black,
    background = colors.black,
    header = colors.black
  }

  local file = fs.open("/" .. colorFile, "r")

  if not file then
    error("Could not open " .. colorFile)
  end

  local index = 1

  repeat
    line = file.readLine()

    if line then
      if index == 1 then
        palette.text = tonumber(line)
      elseif index == 2 then
        palette.background = tonumber(line)
      elseif index == 3 then
        palette.header = tonumber(line)
      end

      index = index + 1
    end
  until line == nil

  file.close()

  return palette
end

local function saveColors (palette)
  local file = fs.open("/" .. colorFile, "w")

  file.writeLine(palette.text .. "")
  file.writeLine(palette.background .. "")
  file.writeLine(palette.header .. "")

  file.close()
end

local function setColor (mouseButton, colorIndex)
  if mouseButton == 1 then
    palette.text = colorIndex
  elseif mouseButton == 2 then
    palette.background = colorIndex
  elseif mouseButton == 3 then
    palette.header = colorIndex
  end
end

local function colorsChosen ()
  if not palette.header
    or not palette.background
    or not palette.text
  then
    return false
  end

  return true
end

local function colorText (backgroundColor)
  if backgroundColor == colors.white
    or backgroundColor == colors.yellow
  then
    term.setTextColor(colors.black)
  else
    term.setTextColor(colors.white)
  end
end

local function displayColors (palette)
  term.setCursorPos(10, #color + 1)

  term.setBackgroundColor(
    palette.text
  )

  colorText(palette.text)
  term.write("Text")

  term.setCursorPos(10, #color + 2)

  term.setBackgroundColor(
    palette.background
  )

  colorText(palette.background)
  term.write("Background")

  term.setCursorPos(10, #color + 3)

  term.setBackgroundColor(
    palette.header
  )

  colorText(palette.header)
  term.write("Header")
end

--Main program
if not fileExists(colorFile) then
  local file = fs.open(colorFile, "w")

  for i = 1, 3 do
    file.writeLine(colors.black .. "")
  end

  file.close()
end

palette = loadColors()

local index = 1

for key, value in pairs(colors) do
  term.setCursorPos(1, index)

  if type(value) ~= "function" then
    color[index] = value

    if key == "white" or key == "yellow" then
      term.setTextColor(colors.black)
    else
      term.setTextColor(colors.white)
    end

    term.setBackgroundColor(value)

    term.write(key)

    index = index + 1
  end
end

repeat
  displayColors(palette)

  local event, button, x, y
    = os.pullEvent("mouse_click")

  if y <= #color then
    setColor(button, color[y])
  end
until y > #color

saveColors(palette)

term.setTextColor(colors.white)
term.setBackgroundColor(colors.black)
term.clear()
displayColors(palette)
term.setCursorPos(1, 1)