ToDo

-- Get args
-- local arg1, arg2, arg3 = ...

-- local w, h = term.getSize()
local todoList = {}

-- monitorSideInput = arg1
-- if monitor == nil then
--    print("Monitor null")
-- end

-- Monitor Settings
monitor = peripheral.wrap('right')
local maxX,maxY = monitor.getSize()
monitor.setTextScale(1.5)
monitor.setBackgroundColor(colors.black)
term.setCursorBlink(false)

function GetUserInput()
    print('Todo: 1. Add, 2. Update, 3. Remove, 4. List, 5. Clear, 6. Exit')
    local choice = read()
    if choice == "1" then
        print('Todo: ')
        local newItem = read()
        AddTodoItem(newItem)
    elseif choice == "2" then
        print('To update: (index) ')
        local itemToUpdateKey = read()
        print('To update: (text) ')
        local itemToUpdateString = read()
        UpdateTodoItem(itemToUpdateKey, itemToUpdateString)
    elseif choice == "3" then
        print('To remove: (index) ')
        local itemToRemoveKey = read()
        RemoveTodoItem(itemToRemoveKey)
    elseif choice == "4" then
        print('List: ', dump(todoList))
    elseif choice == "5" then
        print('Clear list? (y/n) ')
        local clear = read()
        if clear == "y" then
            print('Clear db? (y/n) ')
            local cleardb = read()
            if cleardb == "y" then
                ClearDb()
            end
            todoList = {}
        end
    elseif choice == "6" then
        error("Quitting...")
    end
end

-- Main Function
function main()
    while true do
        -- monitor.clear()
        -- monitor.setCursorPos(1,1)
        -- monitor.setTextColor(colors.white)
        GetUserInput()
        ShowOnMonitor(todoList)
        sleep(1)
    end
end

-- Table
function AddTodoItem(string)
    table.insert(todoList, string)
    UpdateDb()
end

function UpdateTodoItem(key, string)
    todoList[tonumber(key)] = string
    UpdateDb()
end

function RemoveTodoItem(key)
    table.remove(todoList, tonumber(key))
    UpdateDb()
end

-- Helpers
function dump(o)
   if type(o) == 'table' then
      local s = '{ '
      for k,v in pairs(o) do
         if type(k) ~= 'number' then k = '"'..k..'"' end
         s = s .. '['..k..'] = ' .. dump(v) .. ','
      end
      return s .. '} '
   else
      return tostring(o)
   end
end

-- Monitor

function ShowOnMonitor(o)
    monitor.clear()
    monitor.setCursorPos(maxX / 2 - 3, 1)
    monitor.setTextColor(colors.yellow)

    monitor.write('Todo List')
   if type(o) == 'table' then
    monitor.setTextColor(colors.blue)
      local s = '{ '
      for k,v in pairs(o) do
          monitor.setCursorPos(1, k + 1)
          monitor.write(k..') '..dump(v))
      end
   end
end

-- Local Db
function UpdateDb()
    local file = fs.open('.todolist','w') -- the period in front of the name to make it hidden, just a habit i guess
    file.write(textutils.serialize(todoList))
    file.close()
end

function ReadDb()
    local file = fs.open('.todolist','r')
    local database = textutils.unserialize(file.readAll())
    file.close()
end

function InitDb()
    local file = fs.open('.todolist','r')
    if file ~= nil then
        local readData = textutils.unserialize(file.readAll())
        if readData ~= nil then
            todoList = readData
        else
            todoList = {}
        end
        file.close()
    else
        todoList = {}
        local file = fs.open('.todolist','w')
        file.write(textutils.serialize(todoList))
        file.close()
    end
end

function ClearDb()
    local file = fs.open('.todolist','w')
    local clear = {}
    file.write(clear)
    file.close()
end

-- Init
InitDb()
main()