[Computer Craft] multi tasking

--[[
        simple kernal
        with FS permitions / enviromant control
        by BigSHinyToys

    notes: extentions that will be suported
    .lnk < shourcuts
    .txt < text files
    .lua < executible lua script
    .cnf < configur file
]]--
local ver = "0.2" -- curretn vershion

function deepcopy(orig) -- modified deep copy function from
    local copy
    if type(orig) == 'table' then
        copy = {}
        for orig_key, orig_value in next, orig, nil do
            if orig_key ~= "_G" then
                copy[deepcopy(orig_key)] = deepcopy(orig_value)
            end
        end
        setmetatable(copy, deepcopy(getmetatable(orig)))
    else -- number, string, boolean, etc
        copy = orig
    end
    return copy
end

local oldG = deepcopy(_G) -- makes copy of the _G table
local logFile = "sysErrorLog" -- file for errors to be loged
local tThreads = {} -- this table stored all the threads coroutienes
local focused = 1 -- curretnly not used will be for focuesed routine

--[[
the bellow functions make clones of the original function
returning a modified ver hat has permituions enforced
]]--
local function customFileSystem(root)
    local newFS = {}
    local backUpFS = fs
    for k,v in pairs(fs) do
        newFS[k] = function(path,...)
            return backUpFS[k](root..path,...)
        end
    end
    return newFS
end

local function customFileSystemIO(root)
    local newFS = {}
    local backUpFS = io
    for k,v in pairs(io) do
        newFS[k] = function(path,...)
            return backUpFS[k](root..path,...)
        end
    end
    return newFS
end

local function customRun(root)
    local old = os.run
    return function(env,path,...)
        old(env,root..path,...)
    end
end

-- sysLog saves the string it is sent to a file
-- this saves the reason why a thread crashed
local function sysLog(sDATA)
    file = fs.open(logFile,"a")
    if file then
        file.write(sDATA.."\n")
        file:close()
        return true
    else
        return false
    end
end


-- this returns a list of running threads
local function listThread()
    local list = {}
    for i = 1,#tThreads do
        table.insert(list,tThreads[i].parth)
    end
    return list
end

-- this function makes a new thread
local function newThread(...)
    sysLog("Thread Request :") -- saves a message to the log file
    local input = {...} -- puts sent arguments in table
    local tEnv = deepcopy(oldG) -- makes a local copy of the global table
    local root = "SYS_MOUSE/users/admin" -- for fs permitons this is the
    if input[1] == false then -- checks if fs permitions are granted false for limmited permitions
        -- this section modifies the copy of the _G table adding custom replacments for certin functions
        tEnv.fs = customFileSystem(root)
        tEnv.shell = {}
        tEnv.shell.resolve = function(path) return path end
        tEnv.shell.getRuningProgram = function() return root end
        tEnv.io = customFileSystemIO(root)
        tEnv.os.run = customRun(root)
    end
    -- this allows a program to creat a new thread
    tEnv.os.newThread = newThread
    -- this allows a program to get a list of running programs
    tEnv.os.listThread = listThread
    -- removes the first value
    table.remove(input,1)
    -- this section checks for the existance of the program
    if input[1] and fs.exists(input[1]) then
        sysLog("New Thread : "..tostring(input[1])) -- logs that a new thread was requested
        local program = input[1]
        table.remove(input,1)
        -- adds the new thread to the thread table
        table.insert(
            tThreads,{
                parth = tostring(program),
                env = deepcopy(tEnv), -- copys the newly modified copy of the _G
                main = coroutine.create(function(...) return os.run(tThreads[#tThreads].env,program,...) end)
            }
        )
        sysLog("Thread Made : ") -- logs if it worked or not
        sysLog("Input : "..#input)
        local data = {}

        for i = 1,#input do
            table.insert(data,tostring(input[i]))
        end
        sysLog(table.concat(data,"\n"))
        -- sends in the argmetns to the program
        local test = {coroutine.resume(tThreads[#tThreads].main,unpack(input))}
        sysLog("First Output : ")
        data = {}
        for i = 1,#test do
            table.insert(data,tostring(test[i]))
        end
        sysLog(table.concat(data," "))
        sysLog("-- end Thread request --")
    end
end

sysLog("---- New log ----") -- logs that the program started

newThread(true,"SYS_MOUSE/desk_top.lua") -- calls the creation of a new thread running the program specified

while true do -- main loop
    local event = {coroutine.yield()} -- non terminataible this is basicly os.pullEvent() and it is put into a tbale
    local pos = 1
    while pos <= #tThreads do -- go thorught the list of threads
        local test , req = coroutine.resume(tThreads[pos].main,unpack(event)) -- execute the thread with the event
        if coroutine.status(tThreads[pos].main) ~= "dead" and test then -- if thread not dead then go to the next thread
            pos = pos + 1
        else -- else remove the thread from the table and log the error
            sysLog("Thread Crash "..#tThreads.." : "..coroutine.status(tThreads[pos].main).." "..tostring(tThreads[pos].parth).." "..tostring(req))
            table.remove(tThreads,pos)
            if #tThreads == 0 then -- if everthing crashes then go back to shell after pressing enter
                local evnt,rand -- tempo values for testing
                while rand ~= 28 do
                    evnt,rand = os.pullEvent("key")
                end
                term.setBackgroundColor(colors.black)
                term.setTextColor(colors.white)
                term.clear()
                term.setCursorPos(1,1)
                print("System Crash loading old Shell")
                return
            end
        end
    end
end