uOS Startup

-- UOS STARTUP IS _startup

--[[
    Author of original code: NeverCast
]]--

--[[
    Project info:

    Name: uOS
    Creator: Jesusthekiller
    Language: Lua (CC)
    Website: None
    License: GNU GPL
        License file can be fount at www.jesusthekiller.com/license-gpl.html

    Version: 1.0
]]--

--[[
    Changelog:
      1.0:
        Initial Release
]]--

--[[
    LICENSE:

    uOS
    Copyright (c) 2013 Jesusthekiller

    This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

    See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.
]]--

if not fs.exists("uos") then
    shell.run("pastebin", "get", "7jGYum4B", "uos")
end

if os.myEnv then
    return
end

local prevState = {}

table.size = function(tbl)
    local count = 0
    for _,__ in pairs(tbl) do
        count = count + 1
    end
    return count
end

local function getParentShell()
  local at=0
  while true do
    at=at+1
    local ok,env = pcall(function() return getfenv(at) end)
    if not ok then break end
    if table.size(env) == 1 then
          local i,v = next(env) -- Grab first
          if i == "shell" then
            return v
          end
    end
  end
  return nil
end

local function recover()
    -- Set flag
    os.myEnv = true
    -- Put back the trampled environment
    os.startTimer = prevState.startTimer
    os.shutdown = prevState.shutdown
    os.pullEvent = prevState.pullEvent
    --

    prevState = nil
    -- start rednet
    os.unloadAPI("rednet")
    os.loadAPI("rednet")

    -- start uos shell
    os.run({}, "uos")
end

os.stage = {}

local function setStage(stage)
    os.stage.currentStage = stage
end

local function getStage()
    return os.stage.currentStage
end

local function _os_pullEvent(_filter)
    _filter = _filter or ""
    if _filter == "key" then
        setStage("bioswait")
        return "key", 0
    elseif _filter == "timer" then
        setStage("shutdown")
        return "timer", 0
    end
end

local function _replSleep(dur)
    local timer = prevState.startTimer( dur )
    repeat
        local sEvent, param = prevState.pullEvent( "timer" )
    until param == timer
end

local function _os_shutdown()
    if getStage() == "shutdown" then
        setStage("jstincse")
    elseif getStage() == "bioswait" then
        setStage("biosexit")
    end
    if getStage() == "biosexit" then
        recover()
    end
end

local function _os_startTimer(seconds)
    return 0
end

local function inject()
    prevState.startTimer = os.startTimer
    prevState.shutdown = os.shutdown
    prevState.pullEvent = os.pullEvent
    os.shutdown = _os_shutdown
    os.pullEvent = _os_pullEvent
    os.startTimer = _os_startTimer
    setStage("injected")
    local shellImpl = getParentShell()
    shellImpl.exit()
end

inject()