-------------------------------------------------------------
-- COMMANDS
-------------------------------------------------------------

local command = {}
command.new = function()
    local self = {}
    self.name = "default"

    function self:execute()
        table.insert(Tu.commandStack, self)
        print(string.format("execute: %s", self.name))
    end

    function self:undo()
        print(string.format("undo: %s", self.name))
    end

    return self
end

-- command forward
local com_forward = {}
com_forward.new = function ()
    local self = command.new()
    self.name = "forward"

    local super_execute = self.execute
    function self:execute()
        local valid = turtle.forward()
        if valid == false then
            return false
        end
        super_execute(self)
        return true
    end

    local super_undo = self.undo
    function self:undo()
        local valid = turtle.back()
        if valid == false then
            return false
        end
        super_undo(self)
        return true
    end

    return self
end

-- command back
local com_back = {}
com_back.new = function ()
    local self = command.new()
    self.name = "back"

    local super_execute = self.execute
    function self:execute()
        local valid = turtle.back()
        if valid == false then
            return false
        end
        super_execute(self)
        return true
    end

    local super_undo = self.undo
    function self:undo()
        local valid = turtle.forward()
        if valid == false then
            return false
        end
        super_undo(self)
        return true
    end

    return self
end

-- command up
local com_up = {}
com_up.new = function ()
    local self = command.new()
    self.name = "up"

    local super_execute = self.execute
    function self:execute()
        local valid = turtle.up()
        if valid == false then
            return false
        end
        super_execute(self)
        return true
    end

    local super_undo = self.undo
    function self:undo()
        local valid = turtle.down()
        if valid == false then
            return false
        end
        super_undo(self)
        return true
    end

    return self
end

-- command down
local com_down = {}
com_down.new = function ()
    local self = command.new()
    self.name = "down"

    local super_execute = self.execute
    function self:execute()
        local valid = turtle.down()
        if valid == false then
            return false
        end
        super_execute(self)
        return true
    end

    local super_undo = self.undo
    function self:undo()
        local valid = turtle.up()
        if valid == false then
            return false
        end
        super_undo(self)
        return true
    end

    return self
end

-- command turnLeft
local com_turnLeft = {}
com_turnLeft.new = function ()
    local self = command.new()
    self.name = "down"

    local super_execute = self.execute
    function self:execute()
        local valid = turtle.turnLeft()
        if valid == false then
            return false
        end
        super_execute(self)
        return true
    end

    local super_undo = self.undo
    function self:undo()
        local valid = turtle.turnRight()
        if valid == false then
            return false
        end
        super_undo(self)
        return true
    end

    return self
end

-- command turnRight
local com_turnRight = {}
com_turnRight.new = function ()
    local self = command.new()
    self.name = "down"

    local super_execute = self.execute
    function self:execute()
        local valid = turtle.turnRight()
        if valid == false then
            return false
        end
        super_execute(self)
        return true
    end

    local super_undo = self.undo
    function self:undo()
        local valid = turtle.turnLeft()
        if valid == false then
            return false
        end
        super_undo(self)
        return true
    end

    return self
end


-------------------------------------------------------------
-- INSTANCE
-------------------------------------------------------------

-- instance
Tu = {}
Tu.active = false
Tu.updateTime = 1.0
Tu.elapsedTime = 0.0

-- commands
Tu.commandStack = {}
Tu.forward = com_forward.new()
Tu.back = com_back.new()
Tu.up = com_up.new()
Tu.down = com_down.new()
Tu.turnLeft = com_turnLeft.new()
Tu.turnRight = com_turnRight.new()

function Tu.undoStack()
    for i = 1, #Tu.commandStack, 1 do
        Tu.commandStack[i]:undo()
    end
end

function Tu.getLastCommand()
    if #Tu.commandStack == 0 then
        return nil
    end
    return Tu.commandStack[#Tu.commandStack]
end

function Tu.start()
    print("start")
    Tu.turnRight:execute()
    Tu.turnLeft:execute()
    for i = 1, 20, 1 do
        turtle.digDown()
        Tu.down:execute()
    end
    Tu.undoStack()
end

function Tu.update()
    if turtle.getFuelLevel() > 0 then

    end
end

Tu.start()
while Tu.active == true do
    Tu.elapsedTime = os.clock()

    if Tu.updateTime == 0.0 then
        Tu.update()
        return
    end

    local currentTime = Tu.elapsedTime % Tu.updateTime
    if currentTime == 0.0 then
        Tu.update()
    end
end