[CC][0.1][BETA] Buffer API

--[[
HPWebcamAble Presents...
Buffer

--------------------------------
/!\ Warning /!\
The program is in BETA
It is not officially stable yet!
--------------------------------

=== Description ====
This is an API that lets you efficiently draw to the screen


==== Documentation ====
Coming soon


==== Installation and Use ====
Pastebin Code: LVmgReu6

pastebin get <code> buffer

Then run 'buffer' (Or what you called it)


==== Update History ====
Pastebin will always have the most recent version

|0.1| <- This program
  First BETA release
]]

local toHex = {
    [ colors.white ] = "0",
    [ colors.orange ] = "1",
    [ colors.magenta ] = "2",
    [ colors.lightBlue ] = "3",
    [ colors.yellow ] = "4",
    [ colors.lime ] = "5",
    [ colors.pink ] = "6",
    [ colors.gray ] = "7",
    [ colors.lightGray ] = "8",
    [ colors.cyan ] = "9",
    [ colors.purple ] = "a",
    [ colors.blue ] = "b",
    [ colors.brown ] = "c",
    [ colors.green ] = "d",
    [ colors.red ] = "e",
    [ colors.black ] = "f",
}

local function checkArgs(tCheckArgs,tExpectedArgs) -- This function isn't used. I know ;)
  local err = "expected "..tExpectedArgs[1]
  local got = ", got "..type(tCheckArgs[1])
  local shouldErr = type(tCheckArgs[1]) ~= tExpectedArgs[1]
  for i = 2, #tExpectedArgs do
    err = err..","..tExpectedArgs[i]
    got = got..","..type(tCheckArgs[i])
    shouldErr = (shouldErr or type(tCheckArgs[i]) ~= tExpectedArgs[i])
  end
  if shouldErr then
    error( err..got , 3 )
  end
  return true
end


function create()

  local string_rep = string.rep
  local string_sub = string.sub

  local function createLine(backgroundColor)
    local w,h = term.getSize()
    local line = {
      text = string_rep(" " , w),
      backColor = string_rep( toHex[backgroundColor] , w ),
      textColor = string_rep( toHex[colors.white] , w )
    }

    return line
  end

  local screen = {} -- Stores each line of the computer's screen
  local w,h = term.getSize()
  for i = 1, h do
    screen[i] = createLine(colors.black)
  end
  local buffer -- Stores which lines have been updated and need redrawing

  local api = {} -- Returned for the program implementing this API to use

  function api.buffer(text)
    if not buffer then buffer = {} end
    local curX,curY = term.getCursorPos()
    local maxX = curX + #text
    local minX = curX - 1

    screen[curY].text = screen[curY].text:sub(1,minX)..text..screen[curY].text:sub(maxX)
    screen[curY].textColor = screen[curY].textColor:sub(1,minX)..string_rep( toHex[term.getTextColor()] ,#text)..screen[curY].textColor:sub(maxX)
    screen[curY].backColor = screen[curY].backColor:sub(1,minX)..string_rep( toHex[term.getBackgroundColor()] ,#text)..screen[curY].backColor:sub(maxX)

    buffer[curY] = true
    term.setCursorPos(maxX-1,curY)
  end

  function api.writeToScreen()
    local startX,startY = term.getCursorPos()
    local w,h = term.getSize()
    if not buffer then return end
    for i = 1, h do
      if buffer[i] then
        term.setCursorPos(1,i)
        local line = screen[i]
        term.blit(line.text,line.textColor,line.backColor)
      end
    end
    buffer = nil
    term.setCursorPos(startX,startY)
  end

  function api.clearScreen()
    local w,h = term.getSize()
    local curBack = term.getBackgroundColor()
    if not buffer then buffer = {} end
    for i = 1, h do
      screen[i] = createLine(curBack)
      buffer[i] = true
    end
  end

  function api.focreRedraw()
    local startX,startY = term.getCursorPos()
    local w,h = term.getSize()
    for i = 1, h do
      term.setCursorPos(1,i)
      local line = screen[i]
      term.blit(line.text,line.textColor,line.backColor)
    end
    term.setCursorPos(startX,startY)
  end

  return api

end