Screenshare program

--[[
Screenshare program by @MKlegoman357

This is a program you which mirrors computer's screen
onto a monitor. This program automatically adapts to
both, terminal and monitor for the best user experience.
It also auto-adapts to monitor and screen size changes,
as well as notices when a monitor gets disconnected.

Usage:

screenshare <side> [text scale] [program] [arguments]

side - this is the side or network name the monitor is connected to
text scale - this is the text scale of the monitor (default: 1)
program, arguments - this is the program you want to run (default: shell or multishell, depends if advanced computer or not)

Notes:
* only works with CC 1.6 and above
* all arguments, except side, are optional
* uses default 'window' API, which is pretty laggy
]]

local args = {...}
local side = args[1]
local textScale = tonumber(args[2]) or 1
local program = {select(3, ...)}
local name = shell and shell.getRunningProgram and fs.getName(shell.getRunningProgram()) or "screenshare"

if #args == 0 or args[1] == "?" or args[1] == "help" then
  print("Usage:")
  print(name, " <side> [text scale] [program] [arguments] ...")

  error("", 0)
end

if peripheral.getType(side) ~= "monitor" then
  error("No monitor on \"" .. side .. "\" side!", 0)
end

local function clamp (n, min, max)
  return n > max and max or n < min and min or n
end

local function clear (t, bc)
  t = t or term

  t.setBackgroundColor(bc or colors.black)
  t.setTextColor(colors.white)
  t.clear()
  t.setCursorPos(1, 1)
end

local prevTerm = term.current()
local mon = peripheral.wrap(side)

textScale = clamp(textScale, 0.5, 5)

mon.setTextScale(textScale)

local termW, termH, monW, monH, termX, termY, monX, monY, width, height

local function updateVariables ()
  termW, termH = prevTerm.getSize()
  monW, monH = mon.getSize()

  width = termW < monW and termW or monW
  height = termH < monH and termH or monH

  termX, termY = clamp(math.ceil((termW - width) / 2), 1, termW), clamp(math.ceil((termH - height) / 2), 1, termH)
  monX, monY = clamp(math.ceil((monW - width) / 2), 1, monW), clamp(math.ceil((monH - height) / 2), 1, monH)
end

updateVariables()

local termWin = window.create(prevTerm, termX, termY, width, height, true)
local monWin = window.create(mon, monX, monY, width, height, true)

local redirect = {}

for name in pairs(term.native()) do
  redirect[name] = function (...)
    termWin[name](...)

    return monWin[name](...)
  end
end

redirect.isColor = function ()
  return term.native().isColor() and mon.isColor()
end

redirect.isColour = function ()
  return term.native().isColour() and mon.isColour()
end

local function updateDisplays ()
  mon.setTextScale(textScale)
  updateVariables()

  termWin.reposition(termX, termY, width, height)
  monWin.reposition(monX, monY, width, height)

  clear(prevTerm, colors.white)
  clear(mon, colors.white)

  termWin.redraw()
  monWin.redraw()
end

clear(prevTerm, colors.white)
clear(mon, colors.white)

term.redirect(redirect)
clear()

if not program[1] then
  if term.isColor() then
    program[1] = "/rom/programs/advanced/multishell.lua"
  else
    program[1] = "/rom/programs/shell.lua"
  end
end

local env = setmetatable({shell = shell, multishell = multishell}, {__index = _G})

local co

do
  local func, err = loadfile(program[1])

  if not func then
    printError("Error loading file:")
    error(err, 0)
  end

  setfenv(func, env)

  co = coroutine.create(func)
end

local ok, filter = coroutine.resume(co, unpack(program, 2))

while ok and coroutine.status(co) ~= "dead" do
  local event = {coroutine.yield(filter)}

  if event[1] == "mouse_click" or event[1] == "mouse_drag" or event[1] == "mouse_scroll" then
    event[3] = event[3] - termX + 1
    event[4] = event[4] - termY + 1
  elseif event[1] == "monitor_resize" and event[2] == side then
    updateDisplays()

    os.queueEvent("term_resize", "monitor")
  elseif event[1] == "term_resize" then
    updateDisplays()
  elseif event[1] == "peripheral_detach" and event[2] == side then
    term.redirect(prevTerm)
    clear()
    printError("Monitor was disconnected! Please attach the monitor on \"" .. side .. "\" side or press [E] to exit.")
    term.setCursorBlink(false)

    repeat
      local event, k = os.pullEvent()

      if event == "key" and k == keys.e then
        clear()
        print("Screenshare stopped!")

        error("", 0)
      end
    until peripheral.getType(side) == "monitor"

    updateDisplays()
  end

  ok, filter = coroutine.resume(co, unpack(event))
end

if not ok then
  error(filter, 0)
end

term.redirect(prevTerm)

clear(prevTerm)
clear(mon)

print("Screenshare stopped!")