local args = {...}
local tasks = {}
local currentTask = "tasks"
local running = true
local state = "list"
local timer
local lastclicked = 1
local line = 0
local w, h = term.getSize()

if #args > 0 then
    currentTask = args[1]
end

function loadTasks(fileName)
    if fs.exists(fileName) then
        local file = fs.open(fileName,"r")
        local data = file.readAll()
        file.close()
        return textutils.unserialize(data)
    end
    return {}
end
function saveTasks(fileName, taskTable)
    for i = 2, #taskTable do
        taskTable[i].checked = false
    end
    local file = fs.open(fileName,"w")
    file.write(textutils.serialize(taskTable))
    file.close()
end

function printTasks(taskTable, line2)
    local padding = 2
    term.clear()
    if #taskTable > 0 then
    for i=1+line2, 13+line2 do
        term.setCursorPos(padding, padding+i-line2-1)
        if taskTable[i].checked == true then
            term.setBackgroundColor(colors.white)
            term.setTextColor(colors.black)
        end
        if taskTable[i].completed == "x" then
            term.write("[X] "..taskTable[i].name)
        else
            term.write("[_] "..taskTable[i].name)
        end
        term.setBackgroundColor(colors.black)
        term.setTextColor(colors.white)
    end
    else
        term.setCursorPos(padding, padding)
        term.write("No tasks found.")
    end
    term.setCursorPos(math.ceil((w / 2) - (11 / 2)), h - 3)
    term.write("<<<     >>>")
    term.setCursorPos(2, h - 1)
    term.write("[A]dd - [D]elete - [Q]uit")

end

local currentMessage = {}
function displayAddItem()
    local padding = 6
    term.clear()
    term.setBackgroundColor(colors.black)
    term.setTextColor(colors.white)
term.setCursorPos(padding, padding)
    term.write("Add Task")
term.setCursorPos(padding, padding+1)
    term.write("-----------------------")
    term.setCursorPos(2, h - 2)
    term.write("Press [ENTER] to insert new item")
term.setCursorPos(2, h - 1)
    term.write("Enter nothing (blank string) to cancel")

    --we have to draw the whole screen first!
    term.setCursorPos(padding, padding+3)
    term.write("Task Name: ")
    local newTask = read()
    if newTask ~= "" then
        table.insert(tasks, {name = newTask, completed = "_", checked = false})
    end
state = "list" --return our state back to the main list
end

tasks = loadTasks(currentTask)

timer = os.startTimer(0)
while running do
    local event, p1, p2, p3 = os.pullEvent()
    if event == "key" and state == "list" then
        if p1 == keys.q then
            running = false
        elseif p1 == keys.a then
            state = "additem"
        elseif p1 == keys.d then
            table.remove(tasks, lastclicked)
        end
    end
    if event == "mouse_click" and state == "list" then
        if p3-1 <= (line + 13 < #tasks and line + 13 or #tasks) and p3-1 >= 1 then
            if p2 >= 2 and p2 <= 4 then
                if tasks[p3-1].completed == "x" then
                    tasks[p3-1].completed = "_"
                else
                    tasks[p3-1].completed = "x"
                end
            end
            if p2 >= 5 then
                tasks[lastclicked].checked = false
                tasks[p3-1+line].checked = true
                lastclicked = p3-1+line
            end
        end
        if p3 == h-3 then
            if p2 >= 20 and p2 <= 22 then
                if line >= 13 then
                    line = line - 13
                elseif line - 13 < 0 then
                    line = 0
                end
            end
            if p2 >= 28 and p2 <= 30 then
                if line + 13 < #tasks then
                    line = line + 13
                else
                    line = #tasks
                end
            end
        end
    end
    if event == "timer" and p1 == timer then
        if state == "list" then
            printTasks(tasks, line)
        elseif state == "additem" then
            displayAddItem()
        end
        timer = os.startTimer(0.1)
    end
end

saveTasks(currentTask, tasks)
term.setCursorPos(1,1)
term.clear()