DOGGY BOOTLOADER for opencompuer

local function main()
  local ci = component.invoke
  local computer = computer or require("computer")

  local bi = function(a, m, ...)
    local r = table.pack(pcall(ci, a, m, ...))
    if not r[1] then return nil, r[2] else return table.unpack(r, 2, r.n) end
  end

  local e = component.list("eeprom")()
  computer.getBootAddress = function() return bi(e, "getData") end
  computer.setBootAddress = function(a) return bi(e, "setData", a) end

  do
    local s, g = component.list("screen")(), component.list("gpu")()
    if g and s then bi(g, "bind", s) end
  end

  local function tryLoad(a)
    local h, r = bi(a, "open", "/init.lua")
    if not h then return nil, "Failed to open /init.lua: " .. tostring(r) end
    local b = ""
    repeat
      local d, r = bi(a, "read", h, math.maxinteger or math.huge)
      if not d and r then
        bi(a, "close", h)
        return nil, "Failed to read /init.lua: " .. tostring(r)
      end
      b = b .. (d or "")
    until not d
    bi(a, "close", h)
    local i, l = load(b, "=init")
    if not i then return nil, "Failed to load /init.lua: " .. tostring(l) end
    return i
  end

  local l = {}
  for a in component.list("filesystem") do
    local b = bi(a, "getLabel") or "Unnamed Drive"
    if b ~= "tmpfs" then
      table.insert(l, { address = a, label = b })
    end
  end

  local function displayError(errorMessage)
    local g = component.list("gpu")()
    local w, h = bi(g, "getResolution")
    local boxWidth, boxHeight = 60, 4
    local boxX, boxY = math.floor((w - boxWidth) / 2), math.floor((h - boxHeight) / 2)
    bi(g, "setBackground", 0x0000FF) -- Light blue background
    bi(g, "fill", boxX, boxY, boxWidth, boxHeight, " ")
    bi(g, "setForeground", 0xFF0000) -- Red text
    bi(g, "setBackground", 0x0000FF) -- Light blue background
    local textX = math.floor((boxWidth - #errorMessage) / 2) + boxX
    local textY = math.floor((boxHeight - 1) / 2) + boxY
    bi(g, "set", textX, textY, errorMessage)

    computer.beep(800, 1) -- 1 second beep
    computer.beep(800, 0.5) -- Half-second beep
    computer.beep(800, 0.5) -- Half-second beep
  end

  local function displayMenu(sI)
    local g = component.list("gpu")()
    local w, h = bi(g, "getResolution")
    local boxWidth, boxHeight = 60, #l + 4
    local boxX, boxY = math.floor((w - boxWidth) / 2), math.floor((h - boxHeight) / 2)
    local filteredList = {}
    for _, o in ipairs(l) do
      if o.label ~= "tmpfs" then
        table.insert(filteredList, o)
      end
    end
    if #filteredList == 0 then
      displayError("No bootable medium found!")
      return
    end
    bi(g, "setBackground", 0x0000FF) -- Light blue background
    bi(g, "fill", boxX, boxY, boxWidth, boxHeight, " ")
    bi(g, "setForeground", 0xFFFFFF)
    bi(g, "setBackground", 0x0000FF) -- Light blue background
    bi(g, "set", boxX + 2, boxY + 1, "Select OS to boot:")
    for i, o in ipairs(filteredList) do
      local lN = boxY + i + 2
      local tC = i == sI and 0xFF0000 or 0xFFFFFF
      bi(g, "setForeground", tC)
      bi(g, "set", boxX + 2, lN, o.label .. " (" .. o.address .. ")")
    end
    computer.beep(800, 0.1) -- Shorter beep
  end

  local sI = math.ceil(#l / 2)
  displayMenu(sI)
  while true do
    local e = { computer.pullSignal() }
    if e[1] == "key_down" then
      if e[4] == 200 and sI > 1 then
        sI = sI - 1
        displayMenu(sI)
      elseif e[4] == 208 and sI < #l then
        sI = sI + 1
        displayMenu(sI)
      elseif e[4] == 28 then
        local o = l[sI]
        local i, r = tryLoad(o.address)
        if i then
          computer.setBootAddress(o.address)
          computer.beep(800, 0.2)
          computer.beep(800, 0.6)
          computer.beep(800, 0.2)
          return i()
        else
          displayError("Unable to boot device!")
          computer.beep(800, 0.1)
          computer.beep(800, 0.1)
          computer.beep(800, 0.1)
        end
      end
    end
  end
end

main()