Timers

-- from https://www.lua.org/pil/11.4.html
local List = {}
function List.new ()
    return {first = 0, last = -1}
end

function List.pushleft (list, value)
    local first = list.first - 1
    list.first = first
    list[first] = value
end

function List.pushright (list, value)
    local last = list.last + 1
    list.last = last
    list[last] = value
end

function List.popleft (list)
    local first = list.first
    if first > list.last then
        return nil
    end
    local value = list[first]
    list[first] = nil        -- to allow garbage collection
    list.first = first + 1
    return value
end

function List.popright (list)
    local last = list.last
    if list.first > last then
        return nil
    end
    local value = list[last]
    list[last] = nil         -- to allow garbage collection
    list.last = last - 1
    return value
end

-- the lib
local timerList = {}
local timersPool = List.new()

function addTimer(callback, ms, loops, label, ...)
    local id = List.popleft(timersPool)
    if id then
        local timer = timerList[id]
        timer.callback = callback
        timer.label = label
        timer.arguments = {...}
        timer.time = ms
        timer.currentTime = 0
        timer.currentLoop = 0
        timer.loops = loops or 1
        timer.isComplete = false
        timer.isPaused = false
        timer.isEnabled = true
    else
        id = #timerList+1
        timerList[id] = {
            callback = callback,
            label = label,
            arguments = {...},
            time = ms,
            currentTime = 0,
            currentLoop = 0,
            loops = loops or 1,
            isComplete = false,
            isPaused = false,
            isEnabled = true,
        }
    end
    return id
end

function getTimerId(label)
    local found
    for id = 1, #timerList do
        local timer = timerList[id]
        if timer.label == label then
            found = id
            break
        end
    end
    return found
end

function pauseTimer(id)
    if type(id) == 'string' then
        id = getTimerId(id)
    end

    if timerList[id] and timerList[id].isEnabled then
        timerList[id].isPaused = true
        return true
    end
    return false
end

function resumeTimer(id)
    if type(id) == 'string' then
        id = getTimerId(id)
    end

    if timerList[id] and timerList[id].isPaused then
        timerList[id].isPaused = false
        return true
    end
    return false
end

function removeTimer(id)
    if type(id) == 'string' then
        id = getTimerId(id)
    end

    if timerList[id] and timerList[id].isEnabled then
        timerList[id].isEnabled = false
        List.pushright(timersPool, id)
        return true
    end
    return false
end

function clearTimers()
    local timer
    repeat
        timer = List.popleft(timersPool)
        if timer then
            table.remove(timerList, timer)
        end
    until timer == nil
end

function timersLoop()
    for id = 1, #timerList do
        local timer = timerList[id]
        if timer.isEnabled and timer.isPaused == false then
            if not timer.isComplete then
                timer.currentTime = timer.currentTime + 500
                if timer.currentTime >= timer.time then
                    timer.currentTime = 0
                    timer.currentLoop = timer.currentLoop + 1
                    if timer.loops > 0 then
                        if timer.currentLoop >= timer.loops then
                            timer.isComplete = true
                            if eventTimerComplete ~= nil then
                                eventTimerComplete(id, timer.label)
                            end
                            removeTimer(id)
                        end
                    end
                    if timer.callback ~= nil then
                        timer.callback(timer.currentLoop, table.unpack(timer.arguments))
                    end
                end
            end
        end
    end
end