mt-api

local mtTasks = {}
local activeTask = nil
local tEnv = nil
local cos = {}
local activeRestrictedEvents = { "key", "char", "terminate" }
local removeTasks = {}

local function injectCoroutine(name,co,...)
    cos[name] = co
end

local function queueTaskRemoval(k)
    log("Queueing removal of task "..k)
    table.insert(removeTasks,k)
end

local function processTaskRemoval()
    log("Processing Task removals")
    for k,v in pairs( removeTasks ) do
        log("Removing task "..v)
        cos[v] = nil
        screens.removeScreen("mt_"..v)
        mtTasks[v]=nil
        if activeTask == v then
            switchTask("mtshell")
        end
    end
    log("Task removel over")
    removeTasks = {}
end

local function isActiveRestrictedEvent(ev)
    for k,v in pairs(activeRestrictedEvents) do
        if ev == v then return true end
    end
    return false
end

local function process()
    while true do
        local ev,p1,p2,p3,p4,p5,p6 = os.pullEventRaw()
        if ev == "key" and p1 == 197 then
            switchTask("mttaskswitcher")
        end
        log("Processing ev: "..ev.."(AT:"..activeTask..")")
        if isActiveRestrictedEvent(ev) then
            if cos[activeTask] ~= nil and coroutine.status(cos[activeTask]) == "dead" then
                log("Active task died or is nil." .. coroutine.status(cos[activeTask]) )
                queueTaskRemoval(activeTask)
            else
                if cos[activeTask] then
                    screens.setActiveScreen("mt_"..activeTask)
                    log("Active task pre status: "..coroutine.status(cos[activeTask]))
                    coroutine.resume(cos[activeTask],ev,p1,p2,p3,p4,p5,p6)
                    log("Active task post status: "..coroutine.status(cos[activeTask]))
                    if coroutine.status(cos[activeTask]) == "dead" then
                        log("Active task died")
                        queueTaskRemoval(activeTask)
                    end
                else
                    if activeTask == "mtshell" then error("CRITICAL FAILURE: mtshell died") end
                end
            end
        else

            for k,v in pairs(cos) do
                if coroutine.status(v) == "dead" then
                    queueTaskRemoval(k)
                else
                    screens.setActiveScreen("mt_"..k)
                    coroutine.resume(v,ev,p1,p2,p3,p4,p5,p6)
                    if coroutine.status(v) == "dead" then
                        queueTaskRemoval(k)
                    end
                end
            end
        end
        processTaskRemoval()
    end
end

local function taskHost(path,...)
    log("New taskhost running:" ..path.. " (Exists: "..tostring(fs.exists(path))..") Args: "..textutils.serialize(arg))
    local p1,p2=os.run( tEnv, path, unpack(arg) )
    log("Taskhost "..path.. " / Execution ended")
--  if activeTask == n then switchTask("mtshell") end
end

function switchTask(str)
    if mtTasks[str] and activeTask ~= str then
        log("Switched task to "..str)
        activeTask = str

        screens.setActiveAndDisplayScreen("mt_"..str)
        return true
    else
        log("Failed to switch tasks. Task "..str.." not found")
        return false
    end
end

function getActiveTask()
    return activeTask
end

function getTaskList()
    local l = {}
    for k,v in pairs(mtTasks) do
        table.insert(l,k)
    end
    return l
end

function newTask(n,str,...)
    mtTasks[n] = {}
    mtTasks[n].taskHost = coroutine.create(taskHost)
    mtTasks[n].screen = screens.newScreen("mt_"..n)
    activeTask = n
    log("Created new task: "..n .. " // CO Status: "..coroutine.status(mtTasks[n].taskHost))
    screens.setActiveAndDisplayScreen("mt_"..n)

    injectCoroutine(n,mtTasks[n].taskHost,unpack(arg))
    coroutine.resume(mtTasks[n].taskHost,str,unpack(arg))
    if coroutine.status(mtTasks[n].taskHost) == "dead" then
        queueTaskRemoval(n)
        processTaskRemoval()
    end
end

function init(cShell)
    tEnv = {}
    setmetatable(tEnv,{__index=_G})
    tEnv.shell = cShell
    --print(tostring(tEnv.print))
    --read()
    newTask("mtshell","/mtshell")
    newTask("mttaskswitcher","/mt_taskswitcher")
    switchTask("mtshell")
    --print("running")
    --read()
    process()
end